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Proangiogenic factors in the development of HCC in alcoholic cirrhosis
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Proangiogenic factors in the development of HCC in alcoholic cirrhosis夽 Mariana V. Machado , Helena Cortez-Pinto ∗ Departamento de Gastrenterologia, Hospital Santa Maria, CHLN; Unidade de Nutric¸ão e Metabolismo, Faculdade de Medicina de Lisboa, Lisbon, Portugal
Summary Alcoholic liver disease, the most common cause of liver cirrhosis, is associated with an increased risk for hepatocellular carcinoma. Angiogenic factors have been implicated in pathophysiology of cirrhosis, and of hepatocellular carcinoma, and in particular of alcoholic liver cirrhosis, due to alcohol induced hypoxia associated with increased hepatic oxygen consumption. In one study, it was found that among genetic polymorphisms in proangiogenic factors, KDR and VEFGA may confer an increased risk of HCC, in patients with ALD. There is need of further studies of the proangiogenic factors in HCC, in order to help us define their use as prognostic markers and also as markers of response to treatment. © 2015 Elsevier Masson SAS. All rights reserved.
Alcoholic liver disease and hepatocellular carcinoma
Abbreviations: ALD, alcoholic liver disease; HIF, hypoxiainduced factor; VEGF, vascular endothelial growth factor; VEGFR, vascular endothelial growth factor receptor; HCC, hepatocellular carcinoma; NLD, non-liver disease; pVHL, Von Hippel-Lindau protein; HIFs, hypoxia-induced-factors. 夽 This article is part of the special issue ‘‘Alcohol, Virus and Steatosis evolving to cancer’’ featuring the conference papers of the 10th International Symposium organized by the Brazilian Society of Hepatology in São Paulo, Brazil, September 30th—October 1st, 2015. ∗ Corresponding author. Servic ¸o de Gastrenterologia, Hospital de Santa Maria, avenue Professeur Egas Moniz, 1649-035 Lisbon, Portugal. Tel.: +35 1217 985187; fax: +35 1217 985142. E-mail address: [email protected] (H. Cortez-Pinto).
Alcoholic liver disease (ALD) is the most common cause of liver cirrhosis in many countries of Europe and it is the second most frequent indication for liver transplantation in the United States and Europe [1]. The development of fatty liver among heavy drinkers is quite a constant event [2]; from those with fatty liver, about one third will progress to liver cirrhosis if they continue to use alcohol [3]. The risk of development of hepatocellular carcinoma (HCC) among patients with alcoholic cirrhosis has been calculated as an annual incidence of 1—2% [4]. There is also evidence that heavy alcohol consumption (>80 g/day) over a period of more than 10 years increases the risk for HCC approximately 5-fold [5]. It is also of interest that a recent study has shown that the large majority (92.1%) of patients with alcohol
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Please cite this article in press as: Machado MV, Cortez-Pinto H. Proangiogenic factors in the development of HCC in alcoholic cirrhosis. Clin Res Hepatol Gastroenterol (2015), http://dx.doi.org/10.1016/j.clinre.2015.06.001
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abuse and HCC were diagnosed with liver cirrhosis [6]. These data suggest that advanced fibrosis with cirrhosis is already present, when HCC develops in heavy alcohol consumers, in the majority of cases.
Angiogenesis and alcoholic liver cirrhosis Angiogenesis, the formation of new blood vessels, although a physiological mechanism, can get deregulated, and is one key mechanism in the pathogenesis of chronic liver disease [7] Angiogenesis increases during fibrosis progression and hepatocarcinogenesis. Liver hypoxia is a major driver of angiogenesis. Hypoxia induces activation of hypoxiainduced-factors (HIFs), which are transcription factors that promote expression of proangiogenic, profibrogenic [8] and prooncogenic genes [9]. Many mechanisms promote liver hypoxia in cirrhosis: compression of portal and central venules secondary to abnormal scaring with fibrotic tissue, intrahepatic shunts decreasing arterial oxygenation, as well as, hepatic sinusoids capillarization impairing oxygen exchange [7]. Activated HIF is a heterodimer with two subunits, ␣ and . Three ␣ subunits have been described, 1-3; HIF-1␣ and HIF-2␣ having already been demonstrated as important in angiogenesis. In a state of normoxia, HIF␣ is rapidly degraded in the proteasome after being targeted by
polyubiquitination. Polyubiquitination is enhanced by HIF␣ hydroxylation, which increases HIF␣ binding affinity to E3 ubiquitin ligase complex that contains von Hippel-Lindau protein (pVHL). During hypoxia, HIF␣ hydroxylation does not occur, allowing HIF␣ to dimerize with HIF. The HIF dimer can move to the nucleus and act as a transcriptional factor of several target genes [10], such as vascular endothelial growth factor (VEGF). The VEGF family has 5 genes, of which VEGFA is the main pro-angiogenic factor. VEGFs act through one of 3 receptors (VEGFR) 1-3. VEGFR1 and VEGFR2 are known players in angiogenesis [7] (Fig. 1). The role of proangiogenic factors in chronic liver disease has been suggested in different models. Concerning HIF-1␣, mouse deficient in HIF-1␣ are protected from liver fibrosis after bile duct ligation, an animal model of biliary cirrhosis [11,12]. In humans with chronic liver disease, HIF and VEGF levels are increased in early stages [12,13]. Regarding VEGF, in vitro studies have shown that it can directly stimulate proliferation and activation of hepatic stellate cells promoting procollagen-␣1 expression [14]. In mice chronically injected with tetrachloride carbon, a model that associates with severe fibrosis, administration of monoclonal antibodies anti-VEGFR1 or 2 abrogates the fibrogenic response, more efficiently with anti-VEGFR2. Furthermore, the simultaneous administration of both anti-VEGFR antibodies almost completely attenuated fibrosis development [14]. Lastly, the multiple receptor tyrosine kinase inhibitor,
Figure 1 HIF pathway. In conditions of normoxia, HIF-␣ undergoes hydroxylation in prolyl residues, which potentiates ubiquitination by increasing the binding affinity to the VHL-E3 ubiquitin ligase complex. Polyubiquitination targets HIF-␣ for proteasomal degradation. In conditions of hypoxia, hydroxylation does not occur, allowing HIF-␣ to heterodimerize with HIF-. The heterodimer translocates to the nucleus where it promotes transcription of several target genes, namely proangiogenic factors such as vascular endothelial growth factor (VEGF) and erythropoeitin and profibrogenic factors such as collagen 1, connective tissue growth factor (CTGF) and tissue-inhibitor of metalloproteinase-1 (TIMP-1).
Please cite this article in press as: Machado MV, Cortez-Pinto H. Proangiogenic factors in the development of HCC in alcoholic cirrhosis. Clin Res Hepatol Gastroenterol (2015), http://dx.doi.org/10.1016/j.clinre.2015.06.001
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Figure 2 Role of hypoxia angiogenic factors in the pathogenesis of alcoholic liver disease and progression to hepatocellular carcinoma. In susceptible subjects, alcohol induces steatohepatitis and pro-fibrogenic processes that can eventually progress to liver cirrhosis. Cirrhosis associates with abnormal scarring, which leads to compression of portal and central venules by fibrotic tissue, intra-hepatic shunts and sinusoidal capilarization. These phenomena induce hypoxia. Simultaneously, alcohol intake increases hepatic oxygen consumption, with sub-compensatory increase in oxygen delivery, promoting hypoxia in zone 3. Hypoxia can trigger the production of proangiogenic/profibrogenic factors, such as VEGF, CTGF, collagen 1 and TIMP-1. Those factors conduce to angiogenesis, modulate matrix remodelling. Furthermore, those factors are growth factors that may enhance proliferative responses and disturb apoptosis, all of which can further worsen cirrhosis and promote the development of hepatocellular carcinoma.
sorafenib, which is known to act on VEGFRs, improved portal hypertension and decreased fibrogenesis in animal models of liver cirrhosis [15,16]. Alcohol may promote liver hypoxia and modulate cellular response to it, predisposing alcoholic liver disease to even worse angiogenesis-related injury. In fact, alcohol intake increases hepatic oxygen consumption, with sub-compensatory increase in oxygen delivery, promoting hypoxia in zone 3 [17]. Chronic alcohol intake per se upregulates and activates HIF-1␣ in humans and experimental animal models [9]. Recently, it has been shown that plasmatic levels of angiogenic factors VEGF and angiopoietin-1 and -2 are increased in patients with alcoholic liver disease as compared to normal controls; and correlate with liver synthetic failure as well as end-stage liver disease complications such as hepatic encephalopathy and renal impairment [18] (Fig. 2).
Angiogenesis and hepatocellular carcinoma Hepatocellular carcinoma (HCC) is the fifth most common cancer in the world, and the third most common cause of cancer mortality [19]. The importance of angiogenesis in HCC translates the fact that HCC is a highly vascularized tumor dependent on neovascularization. Imaging diagnosis takes advantage of it, requiring the demonstration of contrast tumor enhancement in the arterial phase and rapid washout in the venous phase.
In different animal models of HCC, VEGF promotes HCC development and increases metastasis potential [20,21]. It has been shown a progressive increase in liver expression of VEGF from low-grade dysplasia, high-grade dysplasia, and early HCC [22]. Furthermore, hepatic expression of VEGF and its receptor, VEGFR2, correlated with HCC tumor grade, size, vascular invasion, and occurrence of metastasis [23—27]. Likewise, hepatic expression HIF-1␣ has been correlated with risk for HCC development and adverse prognosis [28]. Furthermore, VEGF and HIF plasmatic levels seem to correlate with stage, prognosis, treatment response and recurrence of HCC [21,28—31]. The only effective systemic palliative treatment for HCC is sorafenib, which has important anti-angiogenic effects. Interestingly, polymorphisms in VEGF and VEGF receptors associate with clinical outcome in patients with HCC treated with sorafenib [32].
Risk of HCC related with genetic polymorphisms of proangiogenic factors in alcoholic cirrhosis Given the aforementioned association of proangiogenic factors with an increased risk of fibrosis progression and HCC development, our group evaluated the possibility that having functional polymorphisms in HIF-1␣, VEGF and KDR (encoding for VEGFR2), could increase the risk of developing liver cirrhosis and hepatocellular carcinoma (HCC) in individuals considered as heavy drinkers [33]. In order
Please cite this article in press as: Machado MV, Cortez-Pinto H. Proangiogenic factors in the development of HCC in alcoholic cirrhosis. Clin Res Hepatol Gastroenterol (2015), http://dx.doi.org/10.1016/j.clinre.2015.06.001
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to evaluate that, the functional HIF-1˛ 1744C/T, VEGFA2578C/A and KDR 1416A/T single nucleotide polymorphisms were studied in 125 ALD patients and 88 heavy drinkers without liver disease (NLD). ALD patients were followed up for at least 5 years; 26 patients developed HCC. Interestingly, no differences were found between HIF-1␣, VEGFA or KDR allelic frequencies or genotypes, isolated or simultaneously, between ALD and NLD. However, when comparing patients who developed HCC with the other ALD patients, KDR 1416T allele frequency was significantly higher (36% vs. 15%, P = 0.004), OR 2.72 (95% CI 1.35—5.46). There was a progressive increase in genotypes with one or two T alleles in patients who developed HCC: AA 50% vs. 73%, AT 35% vs. 23% and TT 15% vs. 4%, P = 0.009. The simultaneous presence of KDR 1416T and VEGFA 2578A was associated with increased risk of HCC: OR 3.088 (95% CI 1.20—7.96). Although results lost significance when adjusted for age, it seems that the genetic polymorphisms KDR and VEFGA may confer an increased risk of HCC in patients with ALD [33]. Regarding the explanation of this association, there is evidence that these polymorphisms associate with an increase in function. VEGFA 2578C/A is a polymorphism in the promoter of VEGFA that is known to be associated with increased levels of VEGF [34]; KDR 1416A/T is a polymorphism in the gene of VEGFR2 that leads to the substitution of glutamine to histidine in position 472. This residue localizes in the fifth immunoglobulin-like (Ig-like) domain that contains structural features that inhibit VEGFR2 signaling in the absence of VEGF [35]. The p.Q472H polymorphism has been shown to lead to a 46% increase in receptor phosphorylation after binding to VEGF [36] and to cause a mild increase in the binding efficiency. Presumably, it should also increase autophosphorylation [37]. It was interesting to note that no influence was found from the presence of these polymorphisms on the risk of developing ALD among heavy drinkers. The attempts to identify polymorphisms that influence the risk of developing ALD among heavy drinkers have been quite frustrating with sometimes controversial results [38,39], what probably depends on the multifactorial nature of ALD and also of very different patterns of drinking, making standardization of these risk factors quite difficult. Differently, the possibility of identifying risk factors for developing HCC in alcoholic cirrhotics might be easier, and eventually more rewarding, since that could help us define which cirrhotics need to be more carefully followed and screened for HCC.
Summary and practical implications In summary, there is evidence of an important role of proangiogenic factors in the development and progression of liver cirrhosis and hepatocellular carcinoma. There are also reasons to believe that in alcohol-related disease these factors may be significant causal factors. Practical implications from these findings include the possibility of using these factors as prognostic markers, as shown by several authors [29,40] and recently reviewed [41]. Also, it has been suggested that serum levels of proangiogenic factors can be useful for monitoring treatment outcomes, but results from different studies yielded controversial results [41].
There are no studies evaluating the prognostic value of proangiogenic factors in HCC developing particularly in ALD patients, and it would be interesting to know if these factors, have different significances according to the etiology of HCC associated liver disease. We believe there is a large area of investigation to be done, since we are still lacking good treatments for HCC, and mostly we are lacking drugs that could prevent or diminish the risk of progression of alcoholic liver cirrhosis to HCC. Proangiogenic factors and their modulation are a line of investigation that needs further developments.
Disclosure of interest The authors declare that they have no conflicts of interest concerning this article.
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Please cite this article in press as: Machado MV, Cortez-Pinto H. Proangiogenic factors in the development of HCC in alcoholic cirrhosis. Clin Res Hepatol Gastroenterol (2015), http://dx.doi.org/10.1016/j.clinre.2015.06.001
ARTICLE IN PRESS
Clinics and Research in Hepatology and Gastroenterology (2015) xxx, xxx—xxx
Available online at
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MINI REVIEW
Proangiogenic factors in the development of HCC in alcoholic cirrhosis夽 Mariana V. Machado , Helena Cortez-Pinto ∗ Departamento de Gastrenterologia, Hospital Santa Maria, CHLN; Unidade de Nutric¸ão e Metabolismo, Faculdade de Medicina de Lisboa, Lisbon, Portugal
Summary Alcoholic liver disease, the most common cause of liver cirrhosis, is associated with an increased risk for hepatocellular carcinoma. Angiogenic factors have been implicated in pathophysiology of cirrhosis, and of hepatocellular carcinoma, and in particular of alcoholic liver cirrhosis, due to alcohol induced hypoxia associated with increased hepatic oxygen consumption. In one study, it was found that among genetic polymorphisms in proangiogenic factors, KDR and VEFGA may confer an increased risk of HCC, in patients with ALD. There is need of further studies of the proangiogenic factors in HCC, in order to help us define their use as prognostic markers and also as markers of response to treatment. © 2015 Elsevier Masson SAS. All rights reserved.
Alcoholic liver disease and hepatocellular carcinoma
Abbreviations: ALD, alcoholic liver disease; HIF, hypoxiainduced factor; VEGF, vascular endothelial growth factor; VEGFR, vascular endothelial growth factor receptor; HCC, hepatocellular carcinoma; NLD, non-liver disease; pVHL, Von Hippel-Lindau protein; HIFs, hypoxia-induced-factors. 夽 This article is part of the special issue ‘‘Alcohol, Virus and Steatosis evolving to cancer’’ featuring the conference papers of the 10th International Symposium organized by the Brazilian Society of Hepatology in São Paulo, Brazil, September 30th—October 1st, 2015. ∗ Corresponding author. Servic ¸o de Gastrenterologia, Hospital de Santa Maria, avenue Professeur Egas Moniz, 1649-035 Lisbon, Portugal. Tel.: +35 1217 985187; fax: +35 1217 985142. E-mail address: [email protected] (H. Cortez-Pinto).
Alcoholic liver disease (ALD) is the most common cause of liver cirrhosis in many countries of Europe and it is the second most frequent indication for liver transplantation in the United States and Europe [1]. The development of fatty liver among heavy drinkers is quite a constant event [2]; from those with fatty liver, about one third will progress to liver cirrhosis if they continue to use alcohol [3]. The risk of development of hepatocellular carcinoma (HCC) among patients with alcoholic cirrhosis has been calculated as an annual incidence of 1—2% [4]. There is also evidence that heavy alcohol consumption (>80 g/day) over a period of more than 10 years increases the risk for HCC approximately 5-fold [5]. It is also of interest that a recent study has shown that the large majority (92.1%) of patients with alcohol
http://dx.doi.org/10.1016/j.clinre.2015.06.001 2210-7401/© 2015 Elsevier Masson SAS. All rights reserved.
Please cite this article in press as: Machado MV, Cortez-Pinto H. Proangiogenic factors in the development of HCC in alcoholic cirrhosis. Clin Res Hepatol Gastroenterol (2015), http://dx.doi.org/10.1016/j.clinre.2015.06.001
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abuse and HCC were diagnosed with liver cirrhosis [6]. These data suggest that advanced fibrosis with cirrhosis is already present, when HCC develops in heavy alcohol consumers, in the majority of cases.
Angiogenesis and alcoholic liver cirrhosis Angiogenesis, the formation of new blood vessels, although a physiological mechanism, can get deregulated, and is one key mechanism in the pathogenesis of chronic liver disease [7] Angiogenesis increases during fibrosis progression and hepatocarcinogenesis. Liver hypoxia is a major driver of angiogenesis. Hypoxia induces activation of hypoxiainduced-factors (HIFs), which are transcription factors that promote expression of proangiogenic, profibrogenic [8] and prooncogenic genes [9]. Many mechanisms promote liver hypoxia in cirrhosis: compression of portal and central venules secondary to abnormal scaring with fibrotic tissue, intrahepatic shunts decreasing arterial oxygenation, as well as, hepatic sinusoids capillarization impairing oxygen exchange [7]. Activated HIF is a heterodimer with two subunits, ␣ and . Three ␣ subunits have been described, 1-3; HIF-1␣ and HIF-2␣ having already been demonstrated as important in angiogenesis. In a state of normoxia, HIF␣ is rapidly degraded in the proteasome after being targeted by
polyubiquitination. Polyubiquitination is enhanced by HIF␣ hydroxylation, which increases HIF␣ binding affinity to E3 ubiquitin ligase complex that contains von Hippel-Lindau protein (pVHL). During hypoxia, HIF␣ hydroxylation does not occur, allowing HIF␣ to dimerize with HIF. The HIF dimer can move to the nucleus and act as a transcriptional factor of several target genes [10], such as vascular endothelial growth factor (VEGF). The VEGF family has 5 genes, of which VEGFA is the main pro-angiogenic factor. VEGFs act through one of 3 receptors (VEGFR) 1-3. VEGFR1 and VEGFR2 are known players in angiogenesis [7] (Fig. 1). The role of proangiogenic factors in chronic liver disease has been suggested in different models. Concerning HIF-1␣, mouse deficient in HIF-1␣ are protected from liver fibrosis after bile duct ligation, an animal model of biliary cirrhosis [11,12]. In humans with chronic liver disease, HIF and VEGF levels are increased in early stages [12,13]. Regarding VEGF, in vitro studies have shown that it can directly stimulate proliferation and activation of hepatic stellate cells promoting procollagen-␣1 expression [14]. In mice chronically injected with tetrachloride carbon, a model that associates with severe fibrosis, administration of monoclonal antibodies anti-VEGFR1 or 2 abrogates the fibrogenic response, more efficiently with anti-VEGFR2. Furthermore, the simultaneous administration of both anti-VEGFR antibodies almost completely attenuated fibrosis development [14]. Lastly, the multiple receptor tyrosine kinase inhibitor,
Figure 1 HIF pathway. In conditions of normoxia, HIF-␣ undergoes hydroxylation in prolyl residues, which potentiates ubiquitination by increasing the binding affinity to the VHL-E3 ubiquitin ligase complex. Polyubiquitination targets HIF-␣ for proteasomal degradation. In conditions of hypoxia, hydroxylation does not occur, allowing HIF-␣ to heterodimerize with HIF-. The heterodimer translocates to the nucleus where it promotes transcription of several target genes, namely proangiogenic factors such as vascular endothelial growth factor (VEGF) and erythropoeitin and profibrogenic factors such as collagen 1, connective tissue growth factor (CTGF) and tissue-inhibitor of metalloproteinase-1 (TIMP-1).
Please cite this article in press as: Machado MV, Cortez-Pinto H. Proangiogenic factors in the development of HCC in alcoholic cirrhosis. Clin Res Hepatol Gastroenterol (2015), http://dx.doi.org/10.1016/j.clinre.2015.06.001
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Figure 2 Role of hypoxia angiogenic factors in the pathogenesis of alcoholic liver disease and progression to hepatocellular carcinoma. In susceptible subjects, alcohol induces steatohepatitis and pro-fibrogenic processes that can eventually progress to liver cirrhosis. Cirrhosis associates with abnormal scarring, which leads to compression of portal and central venules by fibrotic tissue, intra-hepatic shunts and sinusoidal capilarization. These phenomena induce hypoxia. Simultaneously, alcohol intake increases hepatic oxygen consumption, with sub-compensatory increase in oxygen delivery, promoting hypoxia in zone 3. Hypoxia can trigger the production of proangiogenic/profibrogenic factors, such as VEGF, CTGF, collagen 1 and TIMP-1. Those factors conduce to angiogenesis, modulate matrix remodelling. Furthermore, those factors are growth factors that may enhance proliferative responses and disturb apoptosis, all of which can further worsen cirrhosis and promote the development of hepatocellular carcinoma.
sorafenib, which is known to act on VEGFRs, improved portal hypertension and decreased fibrogenesis in animal models of liver cirrhosis [15,16]. Alcohol may promote liver hypoxia and modulate cellular response to it, predisposing alcoholic liver disease to even worse angiogenesis-related injury. In fact, alcohol intake increases hepatic oxygen consumption, with sub-compensatory increase in oxygen delivery, promoting hypoxia in zone 3 [17]. Chronic alcohol intake per se upregulates and activates HIF-1␣ in humans and experimental animal models [9]. Recently, it has been shown that plasmatic levels of angiogenic factors VEGF and angiopoietin-1 and -2 are increased in patients with alcoholic liver disease as compared to normal controls; and correlate with liver synthetic failure as well as end-stage liver disease complications such as hepatic encephalopathy and renal impairment [18] (Fig. 2).
Angiogenesis and hepatocellular carcinoma Hepatocellular carcinoma (HCC) is the fifth most common cancer in the world, and the third most common cause of cancer mortality [19]. The importance of angiogenesis in HCC translates the fact that HCC is a highly vascularized tumor dependent on neovascularization. Imaging diagnosis takes advantage of it, requiring the demonstration of contrast tumor enhancement in the arterial phase and rapid washout in the venous phase.
In different animal models of HCC, VEGF promotes HCC development and increases metastasis potential [20,21]. It has been shown a progressive increase in liver expression of VEGF from low-grade dysplasia, high-grade dysplasia, and early HCC [22]. Furthermore, hepatic expression of VEGF and its receptor, VEGFR2, correlated with HCC tumor grade, size, vascular invasion, and occurrence of metastasis [23—27]. Likewise, hepatic expression HIF-1␣ has been correlated with risk for HCC development and adverse prognosis [28]. Furthermore, VEGF and HIF plasmatic levels seem to correlate with stage, prognosis, treatment response and recurrence of HCC [21,28—31]. The only effective systemic palliative treatment for HCC is sorafenib, which has important anti-angiogenic effects. Interestingly, polymorphisms in VEGF and VEGF receptors associate with clinical outcome in patients with HCC treated with sorafenib [32].
Risk of HCC related with genetic polymorphisms of proangiogenic factors in alcoholic cirrhosis Given the aforementioned association of proangiogenic factors with an increased risk of fibrosis progression and HCC development, our group evaluated the possibility that having functional polymorphisms in HIF-1␣, VEGF and KDR (encoding for VEGFR2), could increase the risk of developing liver cirrhosis and hepatocellular carcinoma (HCC) in individuals considered as heavy drinkers [33]. In order
Please cite this article in press as: Machado MV, Cortez-Pinto H. Proangiogenic factors in the development of HCC in alcoholic cirrhosis. Clin Res Hepatol Gastroenterol (2015), http://dx.doi.org/10.1016/j.clinre.2015.06.001
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to evaluate that, the functional HIF-1˛ 1744C/T, VEGFA2578C/A and KDR 1416A/T single nucleotide polymorphisms were studied in 125 ALD patients and 88 heavy drinkers without liver disease (NLD). ALD patients were followed up for at least 5 years; 26 patients developed HCC. Interestingly, no differences were found between HIF-1␣, VEGFA or KDR allelic frequencies or genotypes, isolated or simultaneously, between ALD and NLD. However, when comparing patients who developed HCC with the other ALD patients, KDR 1416T allele frequency was significantly higher (36% vs. 15%, P = 0.004), OR 2.72 (95% CI 1.35—5.46). There was a progressive increase in genotypes with one or two T alleles in patients who developed HCC: AA 50% vs. 73%, AT 35% vs. 23% and TT 15% vs. 4%, P = 0.009. The simultaneous presence of KDR 1416T and VEGFA 2578A was associated with increased risk of HCC: OR 3.088 (95% CI 1.20—7.96). Although results lost significance when adjusted for age, it seems that the genetic polymorphisms KDR and VEFGA may confer an increased risk of HCC in patients with ALD [33]. Regarding the explanation of this association, there is evidence that these polymorphisms associate with an increase in function. VEGFA 2578C/A is a polymorphism in the promoter of VEGFA that is known to be associated with increased levels of VEGF [34]; KDR 1416A/T is a polymorphism in the gene of VEGFR2 that leads to the substitution of glutamine to histidine in position 472. This residue localizes in the fifth immunoglobulin-like (Ig-like) domain that contains structural features that inhibit VEGFR2 signaling in the absence of VEGF [35]. The p.Q472H polymorphism has been shown to lead to a 46% increase in receptor phosphorylation after binding to VEGF [36] and to cause a mild increase in the binding efficiency. Presumably, it should also increase autophosphorylation [37]. It was interesting to note that no influence was found from the presence of these polymorphisms on the risk of developing ALD among heavy drinkers. The attempts to identify polymorphisms that influence the risk of developing ALD among heavy drinkers have been quite frustrating with sometimes controversial results [38,39], what probably depends on the multifactorial nature of ALD and also of very different patterns of drinking, making standardization of these risk factors quite difficult. Differently, the possibility of identifying risk factors for developing HCC in alcoholic cirrhotics might be easier, and eventually more rewarding, since that could help us define which cirrhotics need to be more carefully followed and screened for HCC.
Summary and practical implications In summary, there is evidence of an important role of proangiogenic factors in the development and progression of liver cirrhosis and hepatocellular carcinoma. There are also reasons to believe that in alcohol-related disease these factors may be significant causal factors. Practical implications from these findings include the possibility of using these factors as prognostic markers, as shown by several authors [29,40] and recently reviewed [41]. Also, it has been suggested that serum levels of proangiogenic factors can be useful for monitoring treatment outcomes, but results from different studies yielded controversial results [41].
There are no studies evaluating the prognostic value of proangiogenic factors in HCC developing particularly in ALD patients, and it would be interesting to know if these factors, have different significances according to the etiology of HCC associated liver disease. We believe there is a large area of investigation to be done, since we are still lacking good treatments for HCC, and mostly we are lacking drugs that could prevent or diminish the risk of progression of alcoholic liver cirrhosis to HCC. Proangiogenic factors and their modulation are a line of investigation that needs further developments.
Disclosure of interest The authors declare that they have no conflicts of interest concerning this article.
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Please cite this article in press as: Machado MV, Cortez-Pinto H. Proangiogenic factors in the development of HCC in alcoholic cirrhosis. Clin Res Hepatol Gastroenterol (2015), http://dx.doi.org/10.1016/j.clinre.2015.06.001