Oncogenic KRAS sensitises colorectal tumour cells to chemotherapy by p53-dependent induction of Noxa

Abstract

BACKGROUND: Oxaliplatin and 5-fluorouracil (5-FU) currently form the backbone of conservative treatment in patients with metastatic colorectal cancer. Tumour responses to these agents are highly variable, but the underlying mechanisms are poorly understood. Our previous results have indicated that oncogenic KRAS in colorectal tumour cells sensitises these cells to chemotherapy. METHODS: FACS analysis was used to determine cell-cycle distribution and the percentage of apoptotic and mitotic cells. A multiplexed RT -PCR assay was used to identify KRAS-controlled apoptosis regulators after exposure to 5-FU or oxaliplatin. Lentiviral expression of short-hairpin RNAs was used to suppress p53 or Noxa. RESULTS: Oncogenic KRAS sensitised colorectal tumour cells to oxaliplatin and 5-FU in a p53-dependent manner and promoted p53 phosphorylation at Ser37 and Ser392, without affecting p53 stabilisation, p21 induction, or cell-cycle arrest. Chemotherapy-induced expression of the p53 target gene Noxa was selectively enhanced by oncogenic KRAS. Suppression of Noxa did not affect p21 induction or cell-cycle arrest, but reduced KRAS/p53-dependent apoptosis after exposure to chemotherapy in vitro and in tumour xenografts. Noxa suppression did not affect tumour growth per se, but strongly reduced the response of these tumours to chemotherapy. CONCLUSION: Oncogenic KRAS determines the cellular response to p53 activation by oxaliplatin or 5-FU, by facilitating apoptosis induction through Noxa.

The 1,2-Diaminocyclohexane Carrier Ligand in Oxaliplatin Induces p53-Dependent Transcriptional Repression of Factors Involved in Thymidylate Biosynthesis

“…p-p53(S15) was clearly detected when HCT116 p53 þ/þ or LoVo cells were treated with 5 mmol/ L oxaliplatin for 24 hours (Fig. 3A and C), consistent with previous reports (40,41). Under our experimental conditions, p53 accumulation was clearly detectable when HCT116 p53…”

Synergistic killing of colorectal cancer cells by oxaliplatin and ABT-737

“…Interestingly, ABT-737 is particularly effective in cells in which the Mcl-1 survival protein is neutralized by high Noxa levels [6,12,28]. Based on our previous study in which oxaliplatin caused apoptosis in a Noxa-dependent fashion [4], we tested whether ABT-737 could synergize with oxaliplatin in stimulating apoptosis in CRC cells. Furthermore, we tested the contribution of mutant KRAS and wild type TP53 to Noxa induction and sensitization to apoptosis.…”

“…In normal untransformed cells Noxa is not generally considered to be a potent inducer of cell death when compared to other members of the BH3-only proteins, like Puma and Bim. However, in tumor cells Noxa does play a major role in the induction of apoptosis [4,17]. The capacity of Noxa to induce apoptosis is strongly enhanced when anti-apoptotic proteins that are not bound by Noxa, such as Bcl-2, Bcl-X L and Bcl-w, are neutralized [2].…”

Expression Profiles of microRNAs in Drug-Resistant Non-Small Cell Lung Cancer Cell Lines Using microRNA Sequencing

“…The same change in trends among the dysregulated miRNAs involved in DDP or gefitinib resistance was identified. KEGG analysis revealed that both upregulated and downregulated miRNAs might be involved in the Ras signaling pathway, which plays an important role in drug resistance [15,16]. The expression levels, survival analysis, and ROC curve analysis of those dysregulated miRNAs in lung cancer based on data from the TCGA database showed that hsa-mir-192, hsa-mir-1293, hsa-mir-194, hsamir-561, hsa-mir-205, hsa-mir-30a, and hsa-mir-30c were related to lung cancer and might be effective biomarkers.…”

“…Among the predicted KEGG pathways, Ras signaling pathway is reportedly involved in drug resistance [15]. We predicted the miRNAs involved in the Ras signaling pathway, including 26 upregulated and 36 downregulated miRNAs.…”