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Signaling via oncogenic tyrosine kinases and phosphatases in human colon carcinoma cells
A524
AGA ABSTRACTS
GASTROENTEROLOGY, Vol. 108, No. 4
• COLORECTAL CANCER IN THE GERIATRIC PATIENT POPULATION OF A MUNICIPAL TEACHING HOSPITAL: A CASE FOR SCREENING FLEXIBLE SIGMOIDOSCOPY I Peleg. CM Wilcox. Department of Medicine, University of Iowa, Iowa City, Iowa, Emery University School of Medicine, and the Medical Service, Grady Memorial Hospital, Atlanta, Georgia. INTRODUCTION: Endoscopic screening is recognized as the most effective modality for the secondary prevention of colorectal cancer in populations at moderate or high risk for this malignancy. Although the risk of colorectal cancer increases with age, no policies for the screening of geriatric patients have been formulated. The aim Of this study is to investigate retrospectively the potential impact of screening flexible sigmoidoseopy in a geriatric patient population. METHODS: The study employed data from the tumor registry of Grady Memorial Hospital (GMH), a large municipal teaching hospital serving a population of approximately 300.000 largely indigent residents of the metropolitan Atlanta, Georgia, area. RESULTS: 506/529 (95.6%) consecutive patients who were diagnosed with colorectal cancer between 1/1/1986 and 8/1/1994 had complete data on the tumor site and were included in the analyses. 59.6% of those aged >75 years and 60.2% of those aged <75 years had a colorectal cancer diagnosed within the reach of the flexible sigmoidoscope. Table 1: Cancer detected within the reach of a sigmoidoscope >75 <75
84 I 220
80.5+4.5** ]
54.4
]
73.8
]
59.5-+11.6
53.4
I
71.3
U
I
Table 2: Cancer detected beyond the reach of a sigmoidoscope
~' ~-'7"5::"[ ~57"~ [ " "8"i.~419'~* : ::[..............62"i0 ........ ...................751~4......................
11<75 114 I 60.6_ ,.1
45.5,
71.7
I
*P<.05; **P<.01' CONCLUSION: These data'show that the proportion of colorectal cancers that are potentially preventable with screening sigmoidoscopy is similar between our general and geriatric patient populations. In contrast to other malignancies, advanced age is not related to advanced tumor stage and the majority of the geriatric patients with proximal and distal disease have a good prognosis. We suggest that geriatric patients with no previous invasive colorectal cancer screening undergo flexible sigmoidoscopy.
@ SIGNALING VIA ONCOGENIC TYROSINE KINASES A N D PHOSPHATASES IN H U M A N COLON CARCINOMA CELLS. Z-Y Peng and CA Cartwright~ Department of Medicine, Stanford University, Stanford, CA: Src protein-tyrosine kinase activity is elevated in most m a l i g n a n t a n d premalignant tumors of the colon. Moreover, Src activity decreases as intestinal ceils differentiate. Together the results indicate that downregulation of the Src kinase is important for differentiation, and upregulation for growth and transformation of intestinal cells. Association of Src with other cellular protein s is k n o w n to regulate its kinase activity. To isolate Src-binding proteins which m a y upregulate Src activity in h u m a n colon carcinoma cells, we are: 1) utilizing the yeast two-hybrid system to screen a colon carcinoma cDNA library for proteins which interact with specific regulatory domains of Src, 2) constructing recombinant glutathione S-transferase fusion proteins containing Src domains, and 3) screening a colon carcinoma ;~gtll expression library with purified, 32p-labeled Src. We find that one Src-binding protein is Syp, a cytoplasmic tyrosine phosphatase. Moreover, our in vitro studies s h o w that Syp dephosphorylated Src at Tyr 527, and the transforming F527 Src m u t a n t phosphorylates Syp. Both events are well-known mechanisms to upregulate enzymatic activity. Thus, Src and Syp appear to upregulate each other's activity in vitro. Others have s h o w n that overexpression of receptor tyrosine phosphatase a in rat embryo fibroblasts results in Src activation by dephosphorylation of Tyr 527, cell transformation a n d tumorigenesis. Thus, receptor tyrosine phosphatases m a y be involved in cell transformation, exerting at least some of their effects through activation of Src. TO the best of our knowledge, this is the first identification of a nonreceptor tyrosine phosphatase Which appears to activatel Src by a similar mechanism.
THE USE OF NONSTEROIDAL BUT NOT STEROIDAL ANTII N F L A M M A T O R Y DRUGS MODULATES THE RISK OF COLORECTAL ADENOMA AND ADENOCARCINOMA I Pele~. GA Cotsonis, WS Clark, CM Wilcox. The University of Iowa, Iowa City, Iowa, Emory University School of Medicine, Emory University School of Public Health and the Medical Service, Grady Memorial Hospital, Atlanta, Georgia. BACKGROUND: The ability of aspirin (ASA) and other nonsteroidal anti-inflammatory drugs (NSAID) to protect against the development of colorectal neoplasia is thought to result primarily from their inhibition of prostaglandin synthesis. If so, steroidal anti-inflammatory drugs (SAIDs) should also be protective. We tested this hypothesis by determining the quantity and cumulative dosage of NSAIDs and SAIDs dispensed to patients with colorectal adenoma or adenocarcinoma in the 4 year periods before their first diagnosed neoplasia. We compared this data with the use of these medications by a control population over the same time intervals. METHODS: The study employed the electronic medical record system of Grady Memorial Hospital (GMH), a large municipal hospital in Atlanta, Georgia. 95% of prescriptions written at GMH are also fiUed in the GMH pharmacies. The inclusion criterion for participants was a computerized patient record indicating at least four consecutive years use of the GMHpharmacies. 113 consecutive patients with incident colorectal adenoma and 93 consecutive patients with incident colorectal adenocarcinoma fulfilling the inclusion criterion were identified from the GMH Tumor Registry. 581 randomly selected GMH-outpatients who were alive, had no diagnosis of colorectal neoplasia at the censor time and fulfilled the inclusion criterion served as controls. Prescriptions for ASA, non aspirin NSAIDs (NaNSAIDs), SAIDs (Prednisone, prednisolone, dexamethasone) and acetaminophen (ACE) dispensed to the participants were electronically aggregated and summary statistics were calculated. RESULTS: The study had the power to detect differences at the P<0.05 level. We used proportional hazards models for retrospective data. In these models which included terms for age, sex and separately, cumulative dosage and days of exposure to the above mentioned medications, the only independent predictors for colorectal adenoma- and adenocarcinoma-free survival (at P<.05 level) were both the cumulative dosage and the days of exposure to aspirin and NaNSAID. The use of SAIDs and ACE afforded no reduction in risk. CONCLUSION: This is the first study to investigate the relationship between the use of SAIDs and the risk of colorectal neoplasia. The results suggest that the major chemopreventive effect of NSAIDs against the development of colorectal neoplasia may be independent of it's inhibition of prostaglandin synthesis.
GASTRIN AND ITS PRECURSORS IN HUMAN COLORECTAL CANCER. I.D. Penmeag LE.S. Ardill*, E. EI..Omax, J. McKenzie, K.E.L. MeCoI1. University Dept. of Medicine and Therapeutics, Western lnfn'mmy, Glasgow and *Dept. of Medicine, Queen's University, Belfast, U.K.. BACKGROUND: The role of gastrin in colorectai neoplasia remains unclear. We have shown that plasma gastrin is not elevated in patients with coloreetal neoplasia while others have proposed an autocrine/patacfine role. Recent studies suggest that gastrin processing intermediates may possess previously unsuspected biological activity including trophic properties for some cells. PURP(~E: To measure the content of gastrin and its precursors in human colorectal turnouts and normal colonic mucosa. METHODS: Samples of 15 turnouts and matching disease-free mucosa were obtained at surgery and rapidly frozen at -70°(2. After extraction by boiling in pbosphate-buffered saline, gastrin peptides were measured by redioimmunoassay using two region-specific antibodies. R98 detects C-terminal ¢arboxyamidated gaatrins whereas GPI68 recognises the N-terminal region and detects glyeineextended gaatrins and other precursors. Progasttin was measured indi~'tly using GPI68 after trypsin digestion of peptide extracts. Neither antibody cross-reacts with cholecystokinin. RESULTS(medians madranges, expressed as pmol.g "! wet weight):
Tumour Normal mace~t
R98 GPl6g GPItB (trypaln) !1.3(3.4-51.0) 12.9(I.4-141.0) 43.3(7.4-475.0) 10.4 (0 - 33.0)
17.5 (0 - 128.0)
20.5 (6.8 - 17510) 1
All 15 tumunrs contained measurable amounts of both carboxymnidated gas~ins and its p ~ whereas these were present in 14 and 13 samples of diseaseflee colon, respectively. Levels of carboxyamidated gastrins were closely correlated in both tissues (Ps = 0.624, P < 0.02) as were the concentrations of gastrin precursors'(ps = 0.605, P = 0.02). Only in tumunrs did trypsin digestion significantlyincrease the concentration of precursors (P = 0.00 I) consistent with
a relative lack of post-translationalprocessing in turnouts. CONCLUSIONS: Gastrin aud its processing-intermedintes occur at equivalent coneenlralious in almost all smaaples of normal and malignant colonic tissue. Turnouts may contain more progastrin, the pathuphysiohigie~l properties of which merit furtherinvestigation.
AGA ABSTRACTS
GASTROENTEROLOGY, Vol. 108, No. 4
• COLORECTAL CANCER IN THE GERIATRIC PATIENT POPULATION OF A MUNICIPAL TEACHING HOSPITAL: A CASE FOR SCREENING FLEXIBLE SIGMOIDOSCOPY I Peleg. CM Wilcox. Department of Medicine, University of Iowa, Iowa City, Iowa, Emery University School of Medicine, and the Medical Service, Grady Memorial Hospital, Atlanta, Georgia. INTRODUCTION: Endoscopic screening is recognized as the most effective modality for the secondary prevention of colorectal cancer in populations at moderate or high risk for this malignancy. Although the risk of colorectal cancer increases with age, no policies for the screening of geriatric patients have been formulated. The aim Of this study is to investigate retrospectively the potential impact of screening flexible sigmoidoseopy in a geriatric patient population. METHODS: The study employed data from the tumor registry of Grady Memorial Hospital (GMH), a large municipal teaching hospital serving a population of approximately 300.000 largely indigent residents of the metropolitan Atlanta, Georgia, area. RESULTS: 506/529 (95.6%) consecutive patients who were diagnosed with colorectal cancer between 1/1/1986 and 8/1/1994 had complete data on the tumor site and were included in the analyses. 59.6% of those aged >75 years and 60.2% of those aged <75 years had a colorectal cancer diagnosed within the reach of the flexible sigmoidoscope. Table 1: Cancer detected within the reach of a sigmoidoscope >75 <75
84 I 220
80.5+4.5** ]
54.4
]
73.8
]
59.5-+11.6
53.4
I
71.3
U
I
Table 2: Cancer detected beyond the reach of a sigmoidoscope
~' ~-'7"5::"[ ~57"~ [ " "8"i.~419'~* : ::[..............62"i0 ........ ...................751~4......................
11<75 114 I 60.6_ ,.1
45.5,
71.7
I
*P<.05; **P<.01' CONCLUSION: These data'show that the proportion of colorectal cancers that are potentially preventable with screening sigmoidoscopy is similar between our general and geriatric patient populations. In contrast to other malignancies, advanced age is not related to advanced tumor stage and the majority of the geriatric patients with proximal and distal disease have a good prognosis. We suggest that geriatric patients with no previous invasive colorectal cancer screening undergo flexible sigmoidoscopy.
@ SIGNALING VIA ONCOGENIC TYROSINE KINASES A N D PHOSPHATASES IN H U M A N COLON CARCINOMA CELLS. Z-Y Peng and CA Cartwright~ Department of Medicine, Stanford University, Stanford, CA: Src protein-tyrosine kinase activity is elevated in most m a l i g n a n t a n d premalignant tumors of the colon. Moreover, Src activity decreases as intestinal ceils differentiate. Together the results indicate that downregulation of the Src kinase is important for differentiation, and upregulation for growth and transformation of intestinal cells. Association of Src with other cellular protein s is k n o w n to regulate its kinase activity. To isolate Src-binding proteins which m a y upregulate Src activity in h u m a n colon carcinoma cells, we are: 1) utilizing the yeast two-hybrid system to screen a colon carcinoma cDNA library for proteins which interact with specific regulatory domains of Src, 2) constructing recombinant glutathione S-transferase fusion proteins containing Src domains, and 3) screening a colon carcinoma ;~gtll expression library with purified, 32p-labeled Src. We find that one Src-binding protein is Syp, a cytoplasmic tyrosine phosphatase. Moreover, our in vitro studies s h o w that Syp dephosphorylated Src at Tyr 527, and the transforming F527 Src m u t a n t phosphorylates Syp. Both events are well-known mechanisms to upregulate enzymatic activity. Thus, Src and Syp appear to upregulate each other's activity in vitro. Others have s h o w n that overexpression of receptor tyrosine phosphatase a in rat embryo fibroblasts results in Src activation by dephosphorylation of Tyr 527, cell transformation a n d tumorigenesis. Thus, receptor tyrosine phosphatases m a y be involved in cell transformation, exerting at least some of their effects through activation of Src. TO the best of our knowledge, this is the first identification of a nonreceptor tyrosine phosphatase Which appears to activatel Src by a similar mechanism.
THE USE OF NONSTEROIDAL BUT NOT STEROIDAL ANTII N F L A M M A T O R Y DRUGS MODULATES THE RISK OF COLORECTAL ADENOMA AND ADENOCARCINOMA I Pele~. GA Cotsonis, WS Clark, CM Wilcox. The University of Iowa, Iowa City, Iowa, Emory University School of Medicine, Emory University School of Public Health and the Medical Service, Grady Memorial Hospital, Atlanta, Georgia. BACKGROUND: The ability of aspirin (ASA) and other nonsteroidal anti-inflammatory drugs (NSAID) to protect against the development of colorectal neoplasia is thought to result primarily from their inhibition of prostaglandin synthesis. If so, steroidal anti-inflammatory drugs (SAIDs) should also be protective. We tested this hypothesis by determining the quantity and cumulative dosage of NSAIDs and SAIDs dispensed to patients with colorectal adenoma or adenocarcinoma in the 4 year periods before their first diagnosed neoplasia. We compared this data with the use of these medications by a control population over the same time intervals. METHODS: The study employed the electronic medical record system of Grady Memorial Hospital (GMH), a large municipal hospital in Atlanta, Georgia. 95% of prescriptions written at GMH are also fiUed in the GMH pharmacies. The inclusion criterion for participants was a computerized patient record indicating at least four consecutive years use of the GMHpharmacies. 113 consecutive patients with incident colorectal adenoma and 93 consecutive patients with incident colorectal adenocarcinoma fulfilling the inclusion criterion were identified from the GMH Tumor Registry. 581 randomly selected GMH-outpatients who were alive, had no diagnosis of colorectal neoplasia at the censor time and fulfilled the inclusion criterion served as controls. Prescriptions for ASA, non aspirin NSAIDs (NaNSAIDs), SAIDs (Prednisone, prednisolone, dexamethasone) and acetaminophen (ACE) dispensed to the participants were electronically aggregated and summary statistics were calculated. RESULTS: The study had the power to detect differences at the P<0.05 level. We used proportional hazards models for retrospective data. In these models which included terms for age, sex and separately, cumulative dosage and days of exposure to the above mentioned medications, the only independent predictors for colorectal adenoma- and adenocarcinoma-free survival (at P<.05 level) were both the cumulative dosage and the days of exposure to aspirin and NaNSAID. The use of SAIDs and ACE afforded no reduction in risk. CONCLUSION: This is the first study to investigate the relationship between the use of SAIDs and the risk of colorectal neoplasia. The results suggest that the major chemopreventive effect of NSAIDs against the development of colorectal neoplasia may be independent of it's inhibition of prostaglandin synthesis.
GASTRIN AND ITS PRECURSORS IN HUMAN COLORECTAL CANCER. I.D. Penmeag LE.S. Ardill*, E. EI..Omax, J. McKenzie, K.E.L. MeCoI1. University Dept. of Medicine and Therapeutics, Western lnfn'mmy, Glasgow and *Dept. of Medicine, Queen's University, Belfast, U.K.. BACKGROUND: The role of gastrin in colorectai neoplasia remains unclear. We have shown that plasma gastrin is not elevated in patients with coloreetal neoplasia while others have proposed an autocrine/patacfine role. Recent studies suggest that gastrin processing intermediates may possess previously unsuspected biological activity including trophic properties for some cells. PURP(~E: To measure the content of gastrin and its precursors in human colorectal turnouts and normal colonic mucosa. METHODS: Samples of 15 turnouts and matching disease-free mucosa were obtained at surgery and rapidly frozen at -70°(2. After extraction by boiling in pbosphate-buffered saline, gastrin peptides were measured by redioimmunoassay using two region-specific antibodies. R98 detects C-terminal ¢arboxyamidated gaatrins whereas GPI68 recognises the N-terminal region and detects glyeineextended gaatrins and other precursors. Progasttin was measured indi~'tly using GPI68 after trypsin digestion of peptide extracts. Neither antibody cross-reacts with cholecystokinin. RESULTS(medians madranges, expressed as pmol.g "! wet weight):
Tumour Normal mace~t
R98 GPl6g GPItB (trypaln) !1.3(3.4-51.0) 12.9(I.4-141.0) 43.3(7.4-475.0) 10.4 (0 - 33.0)
17.5 (0 - 128.0)
20.5 (6.8 - 17510) 1
All 15 tumunrs contained measurable amounts of both carboxymnidated gas~ins and its p ~ whereas these were present in 14 and 13 samples of diseaseflee colon, respectively. Levels of carboxyamidated gastrins were closely correlated in both tissues (Ps = 0.624, P < 0.02) as were the concentrations of gastrin precursors'(ps = 0.605, P = 0.02). Only in tumunrs did trypsin digestion significantlyincrease the concentration of precursors (P = 0.00 I) consistent with
a relative lack of post-translationalprocessing in turnouts. CONCLUSIONS: Gastrin aud its processing-intermedintes occur at equivalent coneenlralious in almost all smaaples of normal and malignant colonic tissue. Turnouts may contain more progastrin, the pathuphysiohigie~l properties of which merit furtherinvestigation.