TP53 mutation-mediated genomic instability induces the evolution of chemoresistance and recurrence in epithelial ovarian cancer

Abstract

Background: Genomic instability caused by mutation of the checkpoint molecule TP53 may endow cancer cells with the ability to undergo genomic evolution to survive stress and treatment. We attempted to gain insight into the potential contribution of ovarian cancer genomic instability resulted from TP53 mutation to the aberrant expression of multidrug resistance gene MDR1.

Methods: TP53 mutation status was assessed by performing nucleotide sequencing and immunohistochemistry. Ovarian cancer cell DNA ploidy was determined using Feulgen-stained smears or flow cytometry. DNA copy number was analyzed by performing fluorescence in situ hybridization (FISH).

Results: In addition to performing nucleotide sequencing for 5 cases of ovarian cancer, TP53 mutations were analyzed via immunohistochemical staining for P53. Both intensive P53 immunohistochemical staining and complete absence of signal were associated with the occurrence of TP53 mutations. HE staining and the quantification of DNA content indicated a significantly higher proportion of polyploidy and aneuploidy cells in the TP53 mutant group than in the wild-type group (p < 0.05). Moreover, in 161 epithelial ovarian cancer patients, multivariate logistic analysis identified late FIGO (International Federation of Gynecology and Obstetrics) stage, serous histotype, G3 grade and TP53 mutation as independent risk factors for ovarian cancer recurrence. In relapse patients, the proportion of chemoresistant cases in the TP53 wild-type group was significantly lower than in the mutant group (63.6% vs. 91.8%, p < 0.05). FISH results revealed a higher percentage of cells with >6 MDR1 copies and chromosome 7 amplication in the TP53 mutant group than in the wild-type group [11.7 ± 2.3% vs. 3.0 ± 0.7% and 2.1 ± 0.7% vs. 0.3 ± 0.05%, (p < 0.05), respectively]. And we observed a specific increase of MDR1 and chromosome 7 copy numbers in the TP53 mutant group upon disease regression (p < 0.01).

Conclusions: TP53 mutation-associated genomic instability may promote chromosome 7 accumulation and MDR1 amplification during ovarian cancer chemoresistance and recurrence. Our findings lay the foundation for the development of promising chemotherapeutic approaches to treat aggressive and recurrent ovarian cancer.

Keywords: Epithelial ovarian cancer; Genomic instability; MDR1 copy number; Recurrence; TP53 mutation.

Fig. 1

Immunohistochemistry results for 4 ovarian cancer samples harboring TP53 mutations. a: the patient with a TP53 nonsense mutation exhibited negative P53 staining; b: the patient with a low abundance (5.7%) of TP53 frameshift mutation exhibited faint P53 staining; c: the patient with a TP53 frameshift mutation exhibited moderate P53 staining; d: the patient with a TP53 missense mutation exhibited strong P53 staining. (×400)

Fig. 2

The relationship between the presence of TP53 mutation and ovarian cancer patient prognosis. a: proportional analysis of complete, partial and no remission after the first round of chemotherapy between the TP53 mutant and wild-type groups; b: Kaplan-Meier analysis of the TP53 mutant and wild-type groups (p < 0.05); c: the ratio of 5-year progression-free survival and subsequent chemoresistance after relapse between the TP53 mutant and wild-type groups. *p < 0.05

Fig. 3

Analysis of TP53 mutations and DNA abnormalities. a: HE staining of the TP53 wild-type and mutant ovarian cancer cells to investigate nucleus morphology; b: quantitative analysis of the ovarian cancer cell DNA index in the TP53 wild-type and mutant groups; c: cell cycle analysis of polyploid cell ratios in two groups by flow cytometry

Fig. 4

MDR1 and chromosome 7 copy numbers were detected via FISH in two group samples. a: MDR1-FISH revealed MDR1 copy numbers in the two groups, red indicates MDR1, and chromosome 7 centromeres are stained in green; b: the green-staining for chromosome 7 centromeres in the two groups

Fig. 5

Changes in MDR1 expression in primary and recurrent lesions between the TP53 wild-type and mutant groups detected by immunohistochemistry. First row: TP53 wild-type group, second row: TP53 mutant group. The first column indicates P53 expression, the second column indicates MDR1 expression in primary lesions, and the third column indicates MDR1 expression in relapse tissues. (×200)