Small-molecule inhibitors of poly (ADP-ribose) polymerase (PARP) have shown considerable promise in the treatment of homologous recombination (HR)-defective tumors, such as BRCA1- and BRCA2-deficie...

Poly‐ADP ribose polymerase (PARP) inhibitors have shown promise in the treatment of human malignancies characterized by deficiencies in the DNA damage repair proteins BRCA1 and BRCA2 and preclinical studies have demonstrated the potential effectiveness of PARP inhibitors in targeting ataxia‐telangiectasia mutated (ATM)‐deficient tumours. Here, we show that mantle cell lymphoma (MCL) cells deficient in both ATM and p53 are more sensitive to the PARP inhibitor olaparib than cells lacking ATM function alone. In ATM‐deficient MCL cells, olaparib induced DNA‐PK‐dependent phosphorylation and stabilization of p53 as well as expression of p53‐responsive cell cycle checkpoint regulators, and inhibition of DNA‐PK reduced the toxicity of olaparib in ATM‐deficient MCL cells. Thus, both DNA‐PK and p53 regulate the response of ATM‐deficient MCL cells to olaparib. In addition, small molecule inhibition of both ATM and PARP was cytotoxic in normal human fibroblasts with disruption of p53, implying that the combination of ATM and PARP inhibitors may have utility in targeting p53‐deficient malignancies.

Immune checkpoint inhibitors (ICI) have revolutionized the treatment landscape of several solid tumor types. However, as patient outcomes are heterogeneous, clinical tools to aid in prognostication are needed. The Lung Immune Prognostic Index (LIPI) correlates with outcomes in patients with non-small cell lung cancer (NSCLC) treated with ICI, but its applicability beyond NSCLC is poorly defined. We sought to determine whether LIPI is associated with overall survival (OS), progression-free survival (PFS) and objective response rate (ORR) in a pooled, real-world, retrospective cohort of patients with solid tumors treated with ICI. Of the total pooled cohort (N = 578), 47.2%, 38.2% and 14.5% of patients were stratified into good, intermediate and poor LIPI group, respectively. Median OS were 22.8 (95% CI 17.4–29.5), 7.8 (95% CI 6.6–9.6), and 2.5 months (95% CI 1.4–3.4) (p < 0.0001). Median PFS were 9.9 (95% CI 7.2–11.5), 3.6 (95% CI 2.7–4.3), and 1.4 months (95% CI 1.2–2.2) (p < 0.0001). ORR was also associated with LIPI group (p < 0.001). Intermediate and poor LIPI were independently prognostic of OS compared to good LIPI, with hazard ratios (HR) of 1.8 (95% CI 1.4–2.3, p < 0.001) and 3.6 (95% CI 2.5–5.1, p < 0.001), respectively. These data are the first to suggest that in a real-world setting, the prognostic value of LIPI may be tumor agnostic.

Introduction: The serine/threonine protein kinase ataxia telangiectasia mutated (ATM) is critical in maintaining genomic integrity. Upon DNA double-strand breaks, ATM phosphorylates key downstream proteins including p53 and BRCA1/2, thereby orchestrating complex signaling pathways involved in cell cycle arrest, DNA repair, senescence and apoptosis. Although sporadic mutation of ATM occurs rarely in breast cancer, the status of its protein expression and its clinical significance in breast cancer remain not well established. Our study was designed to investigate the influence of ATM protein in both tumor and cancer-associated stroma on clinical outcome in hormone-positive (HPBC) and hormone-negative (HNBC) early-stage breast cancer (EBC). Methods: Tissue microarrays (TMAs), containing formalin-fixed, paraffin-embedded resected tumors from two cohorts of patients (HPBC cohort: n = 130; HNBC cohort: n = 168) diagnosed at the Tom Baker Cancer Centre, Calgary, Canada, were analyzed for ATM protein expression using fluorescence immunohistochemistry (IHC) and automated quantitative analysis (AQUA). ATM expression levels were measured within the tumor as a whole (tATM) as indicated by pan-cytokeratin expression, tumor nuclear compartment (nATM) as indicated by both DAPI and pan-cytokeratin-positive results, and cancer-associated stroma (csATM) as indicated by vimentin-positive and pan-cytokeratin-negative results. ATM expression levels within these compartments were correlated with clinical outcome. Results: While tATM and nATM were significantly lower in tumors compared to normal breast epithelial tissues, csATM was significantly higher than the corresponding normal tissue compartment. In addition, the median expression level of both tATM and nATM were two- to threefold lower (P <0.001) in HNBC than in HPBC. In both HNBC and HPBC cohorts, patients with low tATM, nATM and csATM tumors had significantly poorer survival outcomes than those with a high tATM, nATM and csATM, but this effect was more pronounced in HNBC. A multivariate analysis demonstrates that these biomarkers predict survival independent of tumor size and lymph node status, but only in the HNBC cohort (P <0.001). Conclusions: Low ATM protein expression in both malignant tumor and stromal compartments likely contributes to the aggressive nature of breast cancer and is an independent prognostic factor associated with worse survival in HNBC patients.