It is evident from our study that HRAST81C SNP moderately increases bladder cancer risk, and rare allele is a predictive marker of advanced bladder tumors.
Analysis of HRAS gene TRR methylation showed that the methylation level of HRAS has clinical relevance (P = 0.0049, by unpaired Student's t test) with bladder cancer.
These results indicate that overactivation of Ha-ras is both necessary and sufficient to induce bladder tumors along a low-grade, noninvasive papillary pathway, and they shed light on the recent findings that ras activation, via point mutation, overexpression, or intensified signaling from FGF receptor 3, occurs in 70%-90% of these tumors in humans.
All together, co-existence of Aurora-A overexpression and Ha-ras mutation suggests a possible additively effect on the tumorigenesis of bladder cancer.
These results provide the first in vivo experimental evidence that p53 deficiency predisposes the urothelium to hyperproliferation, but is insufficient for bladder tumorigenesis; that the mere reduction of p53 dosage, as produced in transgenic mice expressing the dominant-negative p53 or in heterozygous p53 knockouts, is incapable of synergizing with Ha-ras to induce bladder tumors; and that the complete loss of p53 is a prerequisite for collaborating with activated Ha-ras to promote bladder tumorigenesis.
HRAS1 genotype may be related to the prognosis of bladder cancer, however, because incident cases, i.e., newly diagnosed cases had a higher frequency of rare alleles than did prevalent cases, i.e., cases already existing at the time of recruitment.
Our results also suggest that, whereas EGFr and Ha-ras, both of which act in the same signal transduction cascade, stimulated urothelial hyperplasia, they were not synergistic in urothelial tumorigenesis, and EGFr overexpression can cooperate with p53 and pRB dysfunction (as occurring in SV40T transgenic mice) to promote bladder tumor growth.
In this study, we reevaluated the frequency of Ha-ras codon 12 mutations in a series of 87 human bladder tumors using a combination of two different methods.
The c-Ha-ras-1 locus was studied by Southern blotting in white blood cells and tumor samples obtained from 126 patients with bladder cancer (74 Ta-T1 and 52 T2-T4).
On the other hand, deletion of one Ha-ras allele was observed in 1 of 5 cases of bladder cancer and in 2 of 3 cases of renal pelvic cancer, suggesting that that deletion may be important in the development of urothelial cancer.