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S1.1 Alterations in cell cycle regulation in tumor cells
45
Symposia
Symposium 1. Frontiers in molecular biology
•
Alterations in cell cycle regulation in tumor cells
W.S. Saunders. USA Many cancer cells are characterized by increased genomlc mstablhty and chromosome segregatlonal defects, often associated with hyperamphficatlon o f the mlcrotubule-organlzmg centrosome and tile fornlatlon of multlpolar spindles. Hyperanlphficatlon of tile centrosome has been observed m nlany tumor tissues and is ln~ked with both aneuploldy and turnorlgenesls. Centrosomal aberrations occur exclusively m aneuplold tumors, while diploid cells always have normal centrosomes. Centrosome amphficatlon is also more pronounced m recurrent tumors, and m cell lines that show more aggressive mahgnaslt phenotypes. However, tile presence of extra centrosomes does not always result m a multlpolar spindle. It has been proposed that cells have a mechanasm to regulate supernumerary centrosomes for normal bipolar division, but little evidence exists to support the competing models. We show that the oral cancer cells use spindle pole components to coalesce supernumerary centrosomes into two fialctlonal poles. We demonstrate that the mlcrotubule motor, cytoplasmic dynem 1s a critical part of tins regulatory machinery, and that m oral cancer cells, overexpresslon of the spindle protein NuMA is sufficient to interfere with dynem localization. We also show that overexpresslon o f NuMA or lntnbltlon o f dynem is sufficient to cause nlultlpolarlty m cells with hyperanlphfied centrosomes.
~.~
Predictive and prognostic biomarkers in oral cancers
D. Saranath. Indm
Globally, over a quarter mllhon new cases of cancers o f the oral cavity were diagnosed m the year 2000, with 80,000 (30°,5) being Indian oral cancer patients and 47,000 oral cancer related deaths m hldla. Tile poor survival and high mortality rates are clue to presentation m advanced stages, recurrence of tile prm:ary and development of second prm~ary tumors. Hence, efforts to understand the mechamsm of oral carcinogenesis and the biology of oral cancer are imperative, and may define the pathology and processes revolved m mlt:atlon and progression of the disease, as also indicate biological behavlour of tile cancer cells. Development of predictive blomarkers of high oral cancer risk individuals, as well as blon~arkers of radiochemo resistance, may result m better patient management. Hence, we investigated molecular genetic and eplgenetlc events m oral carcinogenesis. In our studies, traslscrlptlonal silencing of multiple regulatory genes - p16, MGMT, DAPK and GSTP1, by hypermethylatlon at the promoter regions, was observed as an early event occurring in 88°,; o f the tumor tissue samples and 75% corresponding tumor adjacent mucosa. Further, nlult:ple genes were hypernlethylated m 560,5 malignant cancers and 46% tunlor adjacent mucosa. It was mteres/mg to note that a majority of buccal scrapmgs from premalignant oral
lesions and long term tobacco users were also hypermethylated in the genes. On the other hand, hypermethylatlon was not observed in buccal scrapings of normal healthy individuals with no tobacco/alcohol habits. Additional blomarkers including p53 and H.ras mutahons and consequent over-expression, EGF-R amphficahon and overexpression, microsatellite instability and loss of heterozygosity on chromosomes 3 and 9, were observed as early events occurring m a certain proportion of premahgnant oral lemons. Telonlerase activity was observed m 88% oral cancer samples and 25% premahgnaslt oral lesions. Our data indicates that a judicious selection of a panel o f blomarkers may indicate useful predictive blomarkers m individuals with higher risk o f progressing to oral cancers. These would constitute Irnportant objective markers m selection of high risk individuals for preventive chenlotherapeutlc trials, and objechve assessment o f the efficacy of the chemo- and radio- therapy. Molecular aberrations including activation of oncogenes by amplification, point mutations and restriction fragment length polymorphtsms o f c.myc/N.myc, K.ras/N.ras, Bcl-2/Bax, erbB-1 and ERK3, were observed m oral cancer tissues. Several o f these blomarkers VlZ p53, H.ras and BclXL, may indicate inherent res:stance o f the cancer cells to chemo-radloreslstance. The specific alterations m an individual would also be useful m objechve momtormg of efficacy of therapy, using buccal scrapmgs of the individual, post therapy, leading to aggressive follow-up protocols. The aberrant expression of specific genes m oral cancers and premahgnant oral lesions, would be useful m determtmng novel therapeutic targets m prevention and treatment of oral cancers.
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3
[
Molecular predictors of neck metastasis
N.G. NLkltakls. USA Metastasis of oral cancer to regional lymph nodes is accepted as tile single most important adverse prognostic factor mid indicator o f survival. Therefore, preoperative nodal status assessment is crucial for the selection of tile optm~al therapeutic approach. Nonetheless, reliable detection o f regional metastasis by means o f chmcal examination asld/or tmagmg techmques remains challenging, especially when considering early mlcrometastasls. Predictive paranleters that coukl propoint patients at risk for neck nletastasls are tnghly desirable. Currently, the ability to predict clHncally undetectable neck disease is hrmted and based solely on chmcal (e.g. tumor size) and hlstopathologlcal (e.g. depth of invasion) character:st:cs o f the prmlary tumor. In recent years, advanced knowledge of the molecular basis o f oral cancer has allowed the discovery and investigation of a number of blomarkers as possible indicators o f mmor progression and metastasis. A wide array of molecules that participate m diverse cancer-related biologic processes, such as cell prohferatlon, differentiation, apoptosls, adhesion, invasion, signaling, angiogenesis and lymphanglogenesis, have been intensively investigated. The advent of new molecular assays (e.g. cDNA and tissue microarrays) that complement existing methods (e.g. mamunohlstochennstry and polynlerase chain reaction - PCR) has resulted m the generat:on of an expanding body of knowledge. Despite tile prom:stag results o f several studies, which have established significant correlations
Symposia
Symposium 1. Frontiers in molecular biology
•
Alterations in cell cycle regulation in tumor cells
W.S. Saunders. USA Many cancer cells are characterized by increased genomlc mstablhty and chromosome segregatlonal defects, often associated with hyperamphficatlon o f the mlcrotubule-organlzmg centrosome and tile fornlatlon of multlpolar spindles. Hyperanlphficatlon of tile centrosome has been observed m nlany tumor tissues and is ln~ked with both aneuploldy and turnorlgenesls. Centrosomal aberrations occur exclusively m aneuplold tumors, while diploid cells always have normal centrosomes. Centrosome amphficatlon is also more pronounced m recurrent tumors, and m cell lines that show more aggressive mahgnaslt phenotypes. However, tile presence of extra centrosomes does not always result m a multlpolar spindle. It has been proposed that cells have a mechanasm to regulate supernumerary centrosomes for normal bipolar division, but little evidence exists to support the competing models. We show that the oral cancer cells use spindle pole components to coalesce supernumerary centrosomes into two fialctlonal poles. We demonstrate that the mlcrotubule motor, cytoplasmic dynem 1s a critical part of tins regulatory machinery, and that m oral cancer cells, overexpresslon of the spindle protein NuMA is sufficient to interfere with dynem localization. We also show that overexpresslon o f NuMA or lntnbltlon o f dynem is sufficient to cause nlultlpolarlty m cells with hyperanlphfied centrosomes.
~.~
Predictive and prognostic biomarkers in oral cancers
D. Saranath. Indm
Globally, over a quarter mllhon new cases of cancers o f the oral cavity were diagnosed m the year 2000, with 80,000 (30°,5) being Indian oral cancer patients and 47,000 oral cancer related deaths m hldla. Tile poor survival and high mortality rates are clue to presentation m advanced stages, recurrence of tile prm:ary and development of second prm~ary tumors. Hence, efforts to understand the mechamsm of oral carcinogenesis and the biology of oral cancer are imperative, and may define the pathology and processes revolved m mlt:atlon and progression of the disease, as also indicate biological behavlour of tile cancer cells. Development of predictive blomarkers of high oral cancer risk individuals, as well as blon~arkers of radiochemo resistance, may result m better patient management. Hence, we investigated molecular genetic and eplgenetlc events m oral carcinogenesis. In our studies, traslscrlptlonal silencing of multiple regulatory genes - p16, MGMT, DAPK and GSTP1, by hypermethylatlon at the promoter regions, was observed as an early event occurring in 88°,; o f the tumor tissue samples and 75% corresponding tumor adjacent mucosa. Further, nlult:ple genes were hypernlethylated m 560,5 malignant cancers and 46% tunlor adjacent mucosa. It was mteres/mg to note that a majority of buccal scrapmgs from premalignant oral
lesions and long term tobacco users were also hypermethylated in the genes. On the other hand, hypermethylatlon was not observed in buccal scrapings of normal healthy individuals with no tobacco/alcohol habits. Additional blomarkers including p53 and H.ras mutahons and consequent over-expression, EGF-R amphficahon and overexpression, microsatellite instability and loss of heterozygosity on chromosomes 3 and 9, were observed as early events occurring m a certain proportion of premahgnant oral lemons. Telonlerase activity was observed m 88% oral cancer samples and 25% premahgnaslt oral lesions. Our data indicates that a judicious selection of a panel o f blomarkers may indicate useful predictive blomarkers m individuals with higher risk o f progressing to oral cancers. These would constitute Irnportant objective markers m selection of high risk individuals for preventive chenlotherapeutlc trials, and objechve assessment o f the efficacy of the chemo- and radio- therapy. Molecular aberrations including activation of oncogenes by amplification, point mutations and restriction fragment length polymorphtsms o f c.myc/N.myc, K.ras/N.ras, Bcl-2/Bax, erbB-1 and ERK3, were observed m oral cancer tissues. Several o f these blomarkers VlZ p53, H.ras and BclXL, may indicate inherent res:stance o f the cancer cells to chemo-radloreslstance. The specific alterations m an individual would also be useful m objechve momtormg of efficacy of therapy, using buccal scrapmgs of the individual, post therapy, leading to aggressive follow-up protocols. The aberrant expression of specific genes m oral cancers and premahgnant oral lesions, would be useful m determtmng novel therapeutic targets m prevention and treatment of oral cancers.
•
3
[
Molecular predictors of neck metastasis
N.G. NLkltakls. USA Metastasis of oral cancer to regional lymph nodes is accepted as tile single most important adverse prognostic factor mid indicator o f survival. Therefore, preoperative nodal status assessment is crucial for the selection of tile optm~al therapeutic approach. Nonetheless, reliable detection o f regional metastasis by means o f chmcal examination asld/or tmagmg techmques remains challenging, especially when considering early mlcrometastasls. Predictive paranleters that coukl propoint patients at risk for neck nletastasls are tnghly desirable. Currently, the ability to predict clHncally undetectable neck disease is hrmted and based solely on chmcal (e.g. tumor size) and hlstopathologlcal (e.g. depth of invasion) character:st:cs o f the prmlary tumor. In recent years, advanced knowledge of the molecular basis o f oral cancer has allowed the discovery and investigation of a number of blomarkers as possible indicators o f mmor progression and metastasis. A wide array of molecules that participate m diverse cancer-related biologic processes, such as cell prohferatlon, differentiation, apoptosls, adhesion, invasion, signaling, angiogenesis and lymphanglogenesis, have been intensively investigated. The advent of new molecular assays (e.g. cDNA and tissue microarrays) that complement existing methods (e.g. mamunohlstochennstry and polynlerase chain reaction - PCR) has resulted m the generat:on of an expanding body of knowledge. Despite tile prom:stag results o f several studies, which have established significant correlations