Fanconi anemia repair pathway dysfunction, a potential therapeutic target in lung cancer

by Selleckchem | Jan 21 2024

The Fanconi anemia (FA) pathway is a major mechanism of homologous recombination DNA repair. The functional readout of the pathway is activation through mono-ubiquitination of FANCD2 leading to nuclear foci of repair. We have recently developed an FA triple-staining immunofluorescence based method (FATSI) to evaluate FANCD2 foci formation in formalin fixed paraffin-embedded (FFPE) tumor samples. DNA-repair deficiencies have been considered of interest in lung cancer prevention, given the persistence of damage produced by cigarette smoke in this setting, as well as in treatment, given potential increased efficacy of DNA-damaging drugs. We screened 139 non-small cell lung cancer (NSCLC) FFPE tumors for FANCD2 foci formation by FATSI analysis. Among 104 evaluable tumors, 23 (22%) were FANCD2 foci negative, thus repair deficient. To evaluate and compare novel-targeted agents in the background of FA deficiency, we utilized RNAi technology to render several lung cancer cell lines FANCD2 deficient. Successful FANCD2 knockdown was confirmed by reduction in the FANCD2 protein. Subsequently, we treated the FA defective H1299D2-down and A549D2-down NSCLC cells and their FA competent counterparts (empty vector controls) with the PARP inhibitors veliparib (ABT-888) (5 μM) and BMN673 (0.5 μM), as well as the CHK1 inhibitor Arry-575 at a dose of 0.5 μM. We also treated the FA defective small cell lung cancer cell lines H719D2-down and H792D2-down and their controls with the BCL-2/XL inhibitor ABT-263 at a dose of 2 μM. The treated cells were harvested at 24, 48, and 72 h post treatment. MTT cell viability analysis showed that each agent was more cytotoxic to the FANCD2 knock-down cells. In all tests, the FA defective lung cancer cells had less viable cells as comparing to controls 72 h post treatment. Both MTT and clonogenic analyses comparing the two PARP inhibitors, showed that BMN673 was more potent compared to veliparib. 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 DNA cross-link based therapy, or to treatments in which additional repair mechanisms are targeted. These subjects can be identified through FATSI analysis. Clinical trials to evaluate this therapeutic concept are needed.

Comments:

Your research sounds incredibly promising! Identifying DNA repair deficiencies in lung cancer through the FATSI method seems like a crucial step toward understanding potential vulnerabilities in these tumors. It's fascinating how you've linked the FA pathway's role in DNA repair to susceptibility to certain targeted therapies. Your findings suggest that lung cancer patients with FA deficiencies might respond more favorably to treatments targeting DNA damage or other repair mechanisms.

The utilization of RNAi to render lung cancer cell lines FANCD2 deficient and then subjecting them to various inhibitors like PARP and CHK1 inhibitors, as well as BCL-2/XL inhibitors, is a clever way to investigate the response of these cells to specific agents. The observed increased cytotoxicity in the FA defective lung cancer cells post-treatment indicates a potential avenue for more effective therapies in this subset of patients.

It's notable that BMN673 showed greater potency compared to veliparib in your assays, emphasizing the importance of choosing the right inhibitors for targeting specific pathways in these repair-deficient tumors.

The idea of using FATSI analysis to identify patients who might benefit from these therapies is innovative. Clinical trials to validate these concepts in actual patient cohorts could potentially revolutionize treatment strategies for lung cancer.

Your work could significantly impact personalized medicine in lung cancer treatment, tailoring therapies based on the DNA repair profile of individual tumors. Do you plan to explore these findings further in clinical settings?