Ras oncogene, expression

Metallothionein is also induced by a variety of nonmetals, and exposure to these agents often can cause tesistance to anticancer drugs such as cisplatin (Basu and Lazo 1991). Expression of v mos can attenuate the glucocorticoid-induced metallothionein expression and cisplatin resistance. Transcriptional activation of c-Ha-ras oncogene expression in murine NIH 3T3 cells with dexamethasone produces an increase in metallothionein content and a decrease in cisplatin accumulation (Isonishi et al. 1991). The ability of dexamethasone to affect the sensitivity of cells to electrophilic antineoplastic agents could be of some clinical interest because of its frequent usage as an antiemetic. 

Richmond, R.E., DeAngelo, A.B. Daniel. F.B. (1992) Immunohistochemical detection of ras and myc oncogene expression in regenerating rat liver. Toxicol. Lett., 60, 119-129... 

The frequency of active ras oncogenes in human bladder cancer (F6) associated with schistosomiasis was examined. Of nine squamous cell carcinomas of the bladder, none scored as positive in the regular DNA transfection assay. The restriction fragment polymorphism assay at codon 12 of the H-ras gene confirmed the absence of an activating mutation at this site in all samples. Western blotting analyses of the ras p21 proteins suggested a point mutation with codon 61 in one sample only. Enhanced expression of the ras p21 protein was demonstrated in four samples. 

The differential expression (F5) of the ras oncogene product p21 in the primary tumor, regional nodes, and distant metastatic sites in the patients with disseminated breast cancer was examined to define the biologic and clinical significance of the ras oncogene in the progression of breast cancer. 

We are only beginning to understand the regulation of the expression of sialyltransferase activity. The higher level of sialylation of many tumor cells and increased sialyltransferase activities are well known (see chapter 3 of Vol. 30 and section 10.5 below]. Transformation of FR3T3 cells with the c-Ha-ras oncogene resulted in a marked increase of the expression of 3-galactoside a-2,6-sialyltransferase activity and. 

For the expression of ras oncogene function, Ras must bind to GTP. In the metabolic pathway of GMP synthesis, IMP is converted to XMP by IMP dehydrogenase, and the XMP is converted to GMP by GMP synthetase. Oxanosine itself does not inhibit IMP dehydrogenase, but oxanosine 5 -monophosphate inhibits IMP dehydrogenase almost competitively with the substrate. Therefore, it is likely that... 

Y. Lu, W. Chaney, Induction of N-acetylglucosaminyltransferase V by elevated expression of activated or proto- Ha-ras oncogenes. Mol Cell Biochem, 1993, 122, 85-92. 

Tsao MS, LiuN, Nicklee T, Shepherd F, Viallet J. Angiogenesis correlates with vascular endothelial growth factor expression but not with Ki-ras oncogene activation in non-small cell lung carcinoma Clin Cancer Res 1997 3 1807 1814. 

---