Inhibition Of Pro-Survival Pathways In Lung Cancer Cells With Functional Defects In The Fanconi Anemia Pathway

There is a growing appreciation that defects in homologous recombination repair may increase sensitivity of tumors to certain DNA-damaging agents, plausibly through a synthetic lethal interaction. The Fanconi Anemia (FA) pathway is a major mechanism of homologous recombination (HR) DNA repair. Deficiencies in FA pathway have been reported as a predictor of cisplatin, mitomycin C (MMC) or PARP inhibitor sensitivity in cancer cells. The novel PARP inhibitor BMN-673 has emerged from preclinical studies as a best in class PARP trapping agent. BMN-673 has also demonstrated single-agent cytotoxicity in BRCA mutant cells, and activity in cancer patients with BRCA germ line deficiency. To evaluate novel targeted agents in the background of FA deficiency we utilized RNAi technology to generate several lung cancer cell lines with FANCD2 deficiency. Successful FANCD2 knockdown was confirmed by reduction in the FANCD2 protein. Cell viability was evaluated with MTT assay. We treated the FA defective H1299D2-down and A549D2-down non-small cell lung cancer cells and their FA competent counterparts H1299E and A549E (empty vector controls) with the PARP inhibitors veliparib (ABT-888, 5μM) and BMN673 (0.5μM), as well as with the CHK1 inhibitor Arry-575 at a dose of 0.5μM. We also treated the BCL2 expressing small cell lung cancer cells H719D2-down, H792D2-down and their controls H719E and H792E with the BCL2/XL inhibitor navitoclax (ABT263) at a dose of 2μM. The treated cells were harvested at 24, 48 and 72 hours (h) post treatment. Cell viability analysis showed that H1299D2-down cells had 80% of viable cells compared to 100% viable cells in H1299E controls 72h post treatment with veliparib. The A549D2-down cells had 68% viable cells compared to 83% viable cells in the A549E cells 72 h post veliparib treatment. FA defective cells were also more sensitive to treatment of BMN-673 (25% for H1299D2-down vs 62% for H1299E; 29% for A549D2-down vs 46% for A549E) 72 h post BMN-673 treatment at dose of 0.5μM. BMN-673 was more potent compared to veliparib. FA defective cells were also more sensitive to the treatment of CHK1 or BCL2/XL inhibition. H1299D2-down cells had 38% of viable cells comparing to 60% viable cells in the H1299E cells post treatment of CHK1 inhibitor Arry-575 at a dose of 0.5 μM. In addition, MTT analysis showed that BCL2/XL inhibitor navitoclax was more cytotoxic to the H719D2-down (51%) as compared to H719E (85%) 48 h post treatment. Similarly, the H792D2-down cells were more sensitive to the treatment of navitoclax (58% viable cell) as compared to H792E cells (86% viable cell) 48 h post treatment at dose of 2μM. Given that FA pathway plays essential roles in response to DNA damage, our results suggest that a subset of lung cancer patients are likely to be more susceptible to treatments in which additional pathways (e.g PARP, CHK1 and BCL2/XL) are targeted. Clinical trials to evaluate this therapeutic concept are needed. Citation Format: Li Gao, Wenrui Duan, Kathleen Dotts, Arjun Kalvala, Brittany Aguila, Gregory A. Otterson, Miguel A. Villalona-Calero. Inhibition of pro-survival pathways in lung cancer cells with functional defects in the Fanconi Anemia pathway. [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 559. doi:10.1158/1538-7445.AM2015-559