cis-Diamminedichloroplatinum(II) (CDDP), which is mostly referred to as cisplatin, is a widely used antineoplastic. The efficacy of cisplatin can be improved by combining it with the vitamin B6 precursor pyridoxine. Here, we evaluated the putative synergistic interaction of CDDP with pyridoxine in the treatment of an orthotopic mouse model of non-small-cell lung cancer (NSCLC). CDDP and pyridoxine exhibited hyperadditive therapeutic effects. However, this synergy was only observed in the context of an intact immune system and disappeared when the otherwise successful drug combination was applied to the same NSCLC cancer implanted in the lungs of athymic mice (which lack T lymphocytes). Immunocompetent mice that had been cured from NSCLC by the combined regimen of CDDP plus pyridoxine became resistant against subcutaneous rechallenge with the same (but not with an unrelated) cancer cell line. In vitro, CDDP and pyridoxine did not only cause synergistic killing of NSCLC cells but also elicited signs of immunogenic cell death including an endoplasmic reticulum stress response and exposure of calreticulin at the surface of the NSCLC cells. NSCLC cells treated with CDDP plus pyridoxine in vitro elicited a protective anticancer immune response upon their injection into immunocompetent mice. Altogether, these results suggest that the combined regimen of cisplatin plus pyridoxine mediates immune-dependent antineoplastic effects against NSCLC.

Catumaxomab (CatmAb), a trifunctional bispecific antibody directed against the epithelial cell adhesion molecule (EpCAM) and the T-cell antigen CD3, is approved as intraperitoneal therapy for the treatment of malignant ascites in patients with EpCAM-positive carcinomas. The immunomonitoring results of a phase II/III study using CatmAb revealed a tumoricidal effect associated with reduced VEGF levels, CD69-expressing T cells, and the release of T-helper cell (T H )-1 cytokines. We comprehensively dissected the immunomodulatory effects of the CatmAb on the major subsets of malignant ascites-infiltrating leukocytes and the molecular fingerprint of tumor cell death. Herein we show that in the presence of EpCAM-positive tumor targets, CatmAb markedly enhanced T-cell activation [CD69, CD107A (LAMP1), HLA-DR and PD-1(PDCD1) expression] and stimulated inflammatory CD4þ T H 1 and CD8 þ T H 1 to release IFN-g but failed to trigger T H 17 cells. Engagement of CD16-expressing cells caused upregulation of TRAIL (TNFSF10) and costimulatory CD40 and CD80 molecules. CatmAb promoted tumor cell death associated with ATP release and strongly synergized with oxaliplatin for the exposure of the three hallmarks of immunogenic cell death (calreticulin, HMGB1, and ATP). These findings warrant validation as potential biomarkers of efficacy of CatmAb. Cancer Res; 73(15); 4663-73. Ó2013 AACR.