Exploring the LDHC Interactome as Novel Candidate Therapeutic Targets to Advance Breast Cancer Precision Medicine

Breast cancer remains a major health burden worldwide, being the second most commonly diagnosed cancer, and accounting for the highest cancer-related mortality rate among women. Despite decades of advances in cancer care, the identification of therapeutic targets with higher tumor specificity and favorable safety profiles remains a challenge. Dr Decock and others have reported on the potential therapeutic value of the cancer testis antigen Lactate Dehydrogenase C (LDHC), which is highly tumor specific, inherently immunogenic, and exerts multiple pro-tumorigenic functions. Furthermore, Dr Decock’s team demonstrated that targeting LDHC strongly compromises tumor cellular fitness, and could be used to improve treatment response to common DNA damage-related drugs. Unfortunately, LDHC small molecule inhibitors or blocking antibodies are not available yet, hence, we aim to study the LDHC interactome for proxy targeting of LDHC as a novel therapeutic approach for breast cancer precision medicine. Immunoprecipitation (IP), followed by mass spectrometry (IP-MS) of LDHC stably silenced MDA-MB-468 breast cancer cells identified three potential LDHC binding partners with reported roles in genomic integrity and cancer: TUBA1B, PKM2 and hnRNPM. The expression and binding of these candidate binding partners was further assessed using qRT-PCR, western blotting, co-IP, and reverse co-IP, corroborating their likelihood of binding to LDHC. We focused further analysis on PKM2 and TUBA1B as promising candidate binding proteins based on reported experimental evidence and predicted interactions. Using recombinant proteins for co-IP, we found that both proteins form higher molecular weight complexes with LDHC. Although, we were not able to confirm binding of LDHC with individual candidate binding partners using isothermal titration calorimetry or in silico prediction and molecular docking, we cannot conclusively exclude the possibility of direct or indirect interaction due to experimental challenges.

Finally, silencing of PKM2 and TUBA1B in breast cancer cells increased DNA damage and decreased cancer cell survival, validating their role in genomic integrity and mimicking our previous observations following silencing of LDHC. In conclusion, our findings indicate that TUBA1B and PKM2 could potentially be targeted as LDHC proxy targets to mimic the effect of LDHC silencing on tumor cell survival and alleviate the need for specific LDHC targeting.