Induction of mitotic cell death by overriding G2/M checkpoint in endometrial cancer cells with non-functional p53

Abstract

Objective Endometrial tumors with non-functional p53, such as serous uterine endometrial carcinomas, are aggressive malignancies with a poor outcome, yet they have an Achilles’ heel: due to loss of p53 function, these tumors may be sensitive to treatments which abrogate the G2/M checkpoint. Our objective was to exploit this weakness to induce mitotic cell death using two strategies: (1) EGFR inhibitor gefitinib combined with paclitaxel to arrest cells at mitosis, or (2) BI2536, an inhibitor of polo-like kinase 1 (PLK1), to block PLK1 activity. Methods We examined the impact of combining gefitinib and paclitaxel or PLK1 inhibitor on expression of G2/M checkpoint controllers, cell viability, and cell cycle progression in endometrial cancer cells with mutant p53. Results In cells lacking normal p53 activity, each treatment activated CDC25C and inactivated Wee1, which in turn activated cdc2 and sent cells rapidly through the G2/M checkpoint and into mitosis. Live cell imaging demonstrated irreversible mitotic arrest and eventual cell death. Combinatorial therapy with paclitaxel and gefitinib was highly synergistic and resulted in a 10-fold reduction in the IC50 for paclitaxel, from 14 nM as a single agent to 1.3 nM in the presence of gefitinib. However, BI2536 alone at low concentrations (5 nM) was the most effective treatment and resulted in massive mitotic cell death. In a xenograft mouse model with p53-deficient cells, low dose BI2536 significantly inhibited tumor growth. Conclusions These findings reveal induction of mitotic cell death as a therapeutic strategy for endometrial tumors lacking functional p53.

The Consequence of Oncomorphic TP53 Mutations in Ovarian Cancer

“…The increased metastases in some of these animal models may be in part due to the activation of the EGFR/PI3K/AKT pathway [82,92]. These data are consistent with a previous study by our group in which inhibition of EGFR only synergized with chemotherapy in the absence of R175H p53 [91]. In addition to new protein interactions, the R175H mutant is capable of binding DNA and inducing direct transcriptional changes that can create a pro-survival and chemoresistant phenotype.…”

“…In experiments in lung cancer cells devoid of p53, overexpression of the oncomorph R175H p53 enhances resistance to both etoposide and cisplatin [40]. Furthermore, our studies indicate that expression of R175H p53 in endometrial cancer cells mediates resistance to paclitaxel in a mechanism that involves maintenance of the G2/M checkpoint [91]. …”

TP53 hot spot mutations in ovarian cancer: Selective resistance to microtubule stabilizers in vitro and differential survival outcomes from The Cancer Genome Atlas

“…Third in frequency, mutations at R175 have been shown to mediate resistance to etoposide and cisplatin in lung carcinoma cells and to paclitaxel in endometrial carcinoma cells [25,32]. We did not observe any significant in vitro results related to R175, and survival of TCGA patients with R175 mutations was not significantly different than the general cohort of patients with a TP53 mutation.…”

Comprehensive Profiling of EGFR/HER Receptors for Personalized Treatment of Gynecologic Cancers

“…Using p53-null endometrial tumors as a model system, we found that gefitinib produces a synergistic enhancement of the inhibitory action of paclitaxel in p53-inactivated endometrial cancer cells [97]. In p53-null cells, the G2/M checkpoint is maintained through an alternate pathway that includes activation of p38 MAPK/MK2, which results in inactivating phosphorylation of cdc2.…”

“…In p53-null cells, the G2/M checkpoint is maintained through an alternate pathway that includes activation of p38 MAPK/MK2, which results in inactivating phosphorylation of cdc2. Mechanistic studies revealed that treatment with gefitinib in combination with paclitaxel overcomes this checkpoint to reduce cdc2 phosphorylation [97]. All cells are shifted into M phase, where they are sensitive to paclitaxel and undergo mitotic catastrophe.…”