A Novel Indication for Panobinostat as a Senolytic Drug in NSCLC and HNSCC

Panobinostat (pano) is an FDA-approved histone deacetylase inhibitor. There is interest in evaluating alternate dosing schedules and novel combinations of pano for the treatment of upper aerodigestive and lung malignancies; thus we evaluated it in combination with Taxol, a chemotherapeutic with activity in both diseases. Dose-dependent synergy was observed in Non-Small Cell Lung Cancer (NSCLC) and Head and Neck Squamous Cell Carcinoma (HNSCC) cell lines and was due to senescence rather than potentiation of cell death. Senescence occurred following cisplatin- or Taxol-treatment in cell lines from both cancer types and was associated with decreased histone 3 (H3) acetylation and increased Bcl-xL expression: the latter a biomarker of senescence and target of anti-senescence therapeutics, or senolytics. Since H3 acetylation and Bcl-xL expression were altered in senescence, we subsequently evaluated pano as a senolytic in chemotherapy-treated cancer cells enriched for senescent cells. Pano caused cell death at significantly higher rates compared to repeat dosing with chemotherapy. This was associated with decreased expression of Bcl-xL and increased acetylated H3, reversing the expression patterns observed in senescence. These data support evaluating pano as a post-chemotherapy senolytic with the potential to kill persistent senescent cells that accumulate during standard chemotherapy in NSCLC and HNSCC.