K-Ras and H-Ras Activation Promote Distinct Consequences on Endometrial Cell Survival

Abstract

A considerable amount of evidence indicates that Ras signaling contributes to the development of endometrial cancer. We previously demonstrated that endometrial cancer cells carrying oncogenic [12 Val]K-ras were susceptible to apoptosis. The present study examined the role of K-and H-Ras in the induction of apoptosis using rat endometrial cells (RENT4 cells). We found that constitutively activated K-Ras promoted apoptotic cell death, whereas the H-Ras mutant rescued rat endometrial cells from apoptosis. Expression of a constitutively active form of Raf-1 (Raf-CAAX) promoted apoptosis, whereas expression of a constitutively active catalytic subunit of phosphoinositide 3-kinase, p110K227E, allowed cells to escape from apoptosis. Moreover, inhibition of the MEK-MAPK pathway by the specific inhibitor, UO126, rescued the cells from apoptosis, whereas the inhibition of phosphoinositide 3-kinase by its specific inhibitor, LY294002, promoted apoptosis in RENT4 cells expressing activated K-Ras. However, both inhibitors promoted apoptosis in RENT4 cells expressing activated H-Ras. This difference in the regulation of apoptosis by the MEK inhibitor between K-Ras-and H-Ras-expressing cells depended on the interaction of effector proteins downstream of each Ras isoform. Finally, to elucidate the role of downstream K-Ras signal pathways, we generated K-Ras effector domain mutants (K12V35S, K12V40C). We examined the incidence of apoptotic cell death induced by the K-Ras effector domain mutants (K12V35S, K12V40C). The relative ratio of phospho-MAPK to phospho-Akt compared with that of mock cells was higher in K12V35S cells

Contributions of the Raf/MEK/ERK, PI3K/PTEN/Akt/mTOR and Jak/STAT pathways to leukemia

“…[246][247][248][249][250][251] Mutations at the p85 subunit of PI3K have been detected in Hodgkin's lymphoma cells. 252 The p110 subunit of PI3K is frequently mutated (B25%) in breast and some other cancers but it not believed to be frequently mutated in leukemia.…”

Endometrial Cancer Side-Population Cells Show Prominent Migration and Have a Potential to Differentiate into the Mesenchymal Cell Lineage

“…Stably transfected cells were selected and isolated in growth medium containing 400 g/ml Zeocin (Invitrogen) to establish cell lines expressing KRas protein, previously described elsewhere. 35 Pooled populations were used for the assay. Cells were cultured with Dulbecco's modified Eagle's medium (DMEM) (Nissui, Seika, Japan) supplemented with 20 g/ml Gly-HisLys, 2 mmol/L glutamine, 80 IU insulin (Sigma-Aldrich, St. Louis, MO), and 10% fetal calf serum (FCS) (Hyclone, Logan, UT).…”

Activation of Sterile20-Like Kinase 1 in Proteasome Inhibitor Bortezomib–Induced Apoptosis in Oncogenic K-ras-Transformed Cells

“…Recent reports showed that K-ras mutation increases the sensitivity of human cancer cells to genotoxic stresses, such as 5-fluorouracil, tumor necrosis factor (TNF)-related apoptosis-inducing ligand, and irradiation (16)(17)(18). In addition, it was also reported that endometrial cancer cells carrying K-ras 12V are more sensitive to apoptosis (19). Recently, the Ras-NORE1-mammalian sterile20-like kinase 1 (MST1) complex has been reported to be involved in mediating Ras-induced apoptosis in NIH3T3 and HEK293 cells treated with tamoxifen (20).…”