D. Saranath et al., MOLECULAR LESIONS IN HUMAN ORAL-CANCER - THE INDIAN SCENE, European journal of cancer. Part B, Oral oncology, 29B(2), 1993, pp. 107-112
Carcinogenesis is a multi-step process including aberrant expression o
f two interacting classes of genes oncogenes and tumour suppressor gen
es. With recent technological advances, it is feasible to identify the
various molecular lesions underlying the different stages of neoplasi
a. Squamous cell carcinomas of the head and neck, although representin
g 2-4% of the malignancies in the West, comprise a large fraction (40%
) of total cancers in India, posing a major health problem. Further, e
pidemiological and experimental evidence unequivocally confirms a caus
al association between tobacco chewing habit, highly prevalent in Indi
a, and oral cancers. Thus, the oral cancers offer an excellent in vivo
system for the study of the environmental tobacco-carcinogen induced
molecular alterations in the malignancy, and associated premalignant l
esions such as leukoplakia. With a view to elucidating the molecular l
esions involving oncogenes in oral carcinogenesis, we have investigate
d myc/ras/EGF-R activation by amplification, point mutation, gene rear
rangement and allelic losses. Further, a functionally activated potent
transforming gene was detected in a NIH3T3 transfection/tumorigenicit
y assay, unrelated to myc/ras/EGF-R. Studies on the involvement of p53
gene in oral cancer, indicates p53 allelic loss as an event observed
in leukoplakia and tumour tissues. Advanced oral cancer stages demonst
rate cumulative molecular aberrations, with greater than 95% samples s
howing oncogene involvement, thus indicating a multi-step process of o
ral carcinogenesis. The review presents a comparative picture of the o
ral malignancies seen in Western countries and India, significance of
molecular lesions and future perspectives of oncogenes and tumour supp
ressor gene involvement in oral cancer.