Abstract 5457: MAD2γ, a new MAD2 isoform, is ubiquitously expressed in distinct cell lines, reduces mitotic arrest, and associates with resistance to cisplatin-based chemotherapy in testicular germ cell tumors

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Abstract The mitotic spindle assembly checkpoint (SAC) signaling has been emerging as an important promising mechanism in cancer therapy. A prolonged mitotic arrest in response to cancer chemotherapy induces apoptosis, mitotic catastrophe, mitotic slippage and senescence, depending on what cell line and/or inhibitor is studied. In consequence, a weakened or disturbed SAC signaling in human cancers might contribute to drug resistance both to spindle inhibitors and to DNA damaging agents. In several studies the mitotic arrest deficient 2 (MAD2α) has been implicated in the association between failure in the SAC signaling and chemotherapy response. In this study, we identified a novel splicing variant of MAD2, designated as MAD2γ. This isoform was ubiquitously expressed in several cancer cell lines and non-cancerous primary foreskin fibroblasts. When it was ectopically expressed, MAD2γ localized in the nucleus. Its overexpression in a fully functional SAC-competent cancer cell line, HCT116, reduced the mitotic index, suggesting SAC impairment. Furthermore, the endogenous overexpression of MAD2γ in testicular germ cell tumor patients was associated with a resistant response to cisplatin-based chemotherapy, whereas expression of MAD2α was not significantly different between resistant and sensitive patients. In addition, HCT116 raised significantly its endogenous expression of MAD2γ only in response to cisplatin, but not that of MAD2α. Our data suggest that MAD2γ may have an opposing role to MAD2α in the activation of the SAC signaling, and that its expression is associated to a resistant response to DNA-damaging agents, such as cisplatin-based chemotherapy. This highlight the importance to study alternative splicing that may compromise the SAC function, which has been regarded as a promise for cancer therapy. Citation Format: Alejandro Lopez-Saavedra, Rodrigo Caceres, Fernando Luna, Irwin Hernandez, Luis Alonso Herrera. MAD2γ, a new MAD2 isoform, is ubiquitously expressed in distinct cell lines, reduces mitotic arrest, and associates with resistance to cisplatin-based chemotherapy in testicular germ cell tumors. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5457. doi:10.1158/1538-7445.AM2015-5457

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