Reduction of mitomycin C resistance in human bladder cancer T24 cells by knocking-down ras oncogene

Abstract

Aim: Mitomycin C (MMC) is a commonly used as intravesical treatment for superficial bladder cancer. However, its role in combination with ras inhibition has not been investigated. The aim of this study was to explore the role of ras in MMCinduced apoptosis in T24 bladder cancer cells and to determine the efficacy of combination therapy in vitro . Methods:We measured the effects of various doses of MMC on apoptosis induction as well as on ras, ERK and Ki-67 protein expression by T24 cell line using immunocytochemistry, flow cytometry and Western blotting. We also tested the effect of siRNA on ras employed singly or in combination with MMC. Results: T24 cells expressed high level of ras protein. MMC treatment increased the level of ras and ERK protein expressionafter 24 h, and decreased these levels after 72 h. Ras siRNA (100 nmol/L) caused massive apoptosis associated with a marked decrease in ras expression in T24 cells. When combined with low doses of MMC, ras siRNA (50 nmol/L) sensitized T24 cells to apoptosis and decreased their expression of ras. The effect of combined therapy was higher than that of either compound used alone. Expression levels of ERK, a downstream target of ras, declined following combination therapy. Conclusion:Ras siRNA in combination with low dose MMC is a possible treatment strategy for patients with ras-positive bladder tumors.

Curcumin Enhances Chemosensitivity and Apoptosis in T24 Bladder Cancer Cells through Inhibition of the Ras/ MAPK Signaling Pathway

“…The activated Ras/Raf/ERK-signaling pathway creates a robust proliferative stimulus that leads to uncontrolled cell division [25][26]. In a previous study [18],…”

“…In our previous study [18], we used MMC in low and high concentrations (up to 100 μg/ml) in combination with two different concentrations of Ras siRNA, and we found that Ras siRNA sensitized T24 cells to apoptosis induced by…”

“…Recent observation has also shown that modulation of cell signaling pathways through the pleiotropic effects of curcumin likely activate cell death signals and induce apoptosis predominantly in Ras-activated tumour cells [17]. On the other hand, we have recently shown that silencing the RAS oncogene by small interfering RNA (siRNA) reversed the resistance of T24 bladder cancer cells to MMC and induced apoptosis when exposed to small doses of MMC (0.3 to 10 µg/ml) [18]. Based on this finding and other related experiments demonstrating that inhibition of Ras decreased resistance and invasiveness of cancer cells in vitro, if curcumin can disrupt the Ras/Raf/MEK/ERK signaling pathway, it should reverse Ras-dependent resistance of cancer cells to chemotherapeutic agents.…”

Magnetic Nanoparticles Used in Oncology

“…Some studies [111,112], in the case of bladder cancer, have shown that the treatment with mitomicyn-C decreased the recurrence rate after 10 years by 40%.…”

Cancer drug resistance: a new perspective

“…Treatment often induces repair mechanism in the cell. The paper by Sharaf Eldin et al [17] describes the role of apoptosis in resistance to another alkylating drug, but surprisingly RAS expression is also involved in resistance. They describe a novel approach to reverse resistance by the use of siRNA, which suppresses the survival pathway in which RAS plays a role.…”