Forty-two cases of squamous cell carcinoma arising in the upper aerodigestive tract were examined to determine the incidence and type of point mutation in codon 12 of the c-K-ras gene by using the polymerase chain reaction and oligonucleotide hybridization techniques on DNA extracted from paraffin blocks.
The results indicated that all three NIH 3T3 transformants, 11 of 24 (46%) SCCs, and 5 of 16 (31%) BCCs contained mutations at the second position of Ha-ras codon 12 (GGC----GTC), predicting a glycine-to-valine amino acid substitution, whereas only 1 of 40 skin cancers (an SCC) displayed a mutation in the first position of Ki-ras codon 12 (GGT----AGT), predicting a glycine-to-serine amino acid change.
This investigation of oral squamous carcinoma in five individuals revealed that four of the patients were constitutionally heterozygous at the c-Ha-ras-1 locus and that the tumour from one patient had lost that heterozygosity.
By NIH3T3 transfection assay in conjunction with in vitro transient neomycin selection, activated c-H-ras-1 oncogenes were detected in two squamous cell carcinoma cell lines, ZA and HOC-313, newly established from human oral cancer patients.
Interestingly, DNA from both primary and secondary transformants of one particular human squamous cell carcinoma contained highly amplified copies of the Ha-ras oncogene.
Mutated ras genes have been found to be conspicuously absent from primary tumors of the esophagus, although high expression of ras p21 oncoprotein in some esophageal squamous cell carcinomas and mutations of the Ki- and Ha-ras genes in esophageal carcinoma cell lines have been reported.
Topographic genotyping with subsequent polymerase chain reaction (PCR) and sequence analysis of K-ras-2 showed mutations in significantly fewer cases of PC (9%, 2 of 22 cases) than in AdC (36%, 35 of 97 cases) or SqC (0%, 0 of 42 cases) (P < .001).
Characteristic codon 61 mutations in the Ha-ras gene were found in most of the papillomas and SCCs induced by DMBA and TPA in transgenic as well as nontransgenic mice.
Our previous reports have shown that two thirds of 4-nitroquinoline-1-oxide (4NQO)-induced murine oral squamous cell carcinomas (SCC) have Hras1 mutations.
We have utilized an in vitro correlate of squamous cell carcinogenesis, in which progression stages from normal squamous epithelium to dysplastic lesions and to SCC are represented by primary cultures of normal keratinocytes, by human papilloma virus-immortalized keratinocytes (UP) and by HPVimmortalized/v-Ha-ras transfected tumorigenic keratinocytes (UPR).
Point mutations in codon 61 of the human Ha-ras gene were detected in the SCC, five of six analyzed actinic keratoses and in non-lesional epidermis of DMBA- and UVB-treated grafts, indicating that DMBA as well as UVB alone can induce these mutations in human skin.
Squamous cell carcinomas in psoralen-plus-ultraviolet A (PUVA) treated patients frequently exhibit p53 tumor suppressor genes and Ha-ras protooncogenes that are mutated at dipyrimidine sites and carry the ultraviolet fingerprint (i.e., C-to-T or CC-to-TT transitions).
The aim of the study was to assess the frequency of Ha-ras oncogene mutations in cervical intraepithelial neoplasia (CIN) grade III and invasive squamous cell carcinomas and to examine this genetic factor in relation to HPV infection and the clinical evolution of cervical lesions.
In the present studies, we investigated the correlation between RASSF1A promoter methylation status and Kras2 mutations in 65 primary non small cell lung cancer (NSCLC) including 33 adenocarcinomas, 12 large cell carcinomas, and 20 squamous cell carcinomas.