Acidosis-induced metabolic reprogramming in tumor cells enhances the anti-proliferative activity of the PDK inhibitor dichloroacetate

Altered metabolic pathways in cancer such as exacerbated glycolytic flux and increased glutamine metabolism are promising targets for anti-cancer therapies. While commonly observed in glycolytic tumors, extracellular acidosis has never been considered as a potential modulator of anti-metabolic drug activity such as dichloroacetate (DCA). Using cancer cells from various origins selected for their ability to proliferate under acidic conditions, we found that DCA exerts greater inhibitory effects on the growth of these acid-adapted cells than in parental cells. Moreover, daily DCA administration to mice led to a significant decrease in tumor growth from acid-adapted cells but not from parental cells. 13C-tracer studies revealed that DCA induced a double metabolic shift, diminishing glycolysis and increasing intracellular glutamine in acid-adapted cells. As a consequence, DCA reduced the pentose phosphate pathway activity more extensively and increased apoptosis in acid-adapted cells. Finally, the combination of DCA with a glutaminase inhibitor significantly enhanced the cytotoxic effects of DCA. Overall, the interplay between acidosis and DCA exposure leads to metabolic reprogramming that considerably alters cellular fitness.

Apoptic Renal Carcinoma Cells are Better Inducers of Cross-Presenting Activity than Their Primary Necrotic Counterpart

Vaccination with tumor-loaded dendritic cells (DC) is a promising treatment strategy for patients with renal cell carcinoma (RCC). Cells undergoing cell death proved useful as a source of tumor antigen for DC loading. Both apoptotic and necrotic tumor cells have been shown to efficiently load RCC-tumor antigens on DC. However, no direct comparison of these two kinds of death has been attempted in the same RCC. We compared DC pulsed with apoptotic cells, whole cell lysates or their supernatants of the cell line K1, derived from a patient with clear cell RCC, to determine their ability to activate T cells. Monocyte-derived DCs were pulsed with the different sources of tumor antigen, matured and co-cultured with autologouos peripheral blood lymphocytes. After three weekly re-stimulations with DCs, generation of cytotoxic T lymphocytes CTL was assessed by IFN-γ release in an ELISpot assay in the presence of the sensitizing target. By comparison with lysate, apoptotic tumor cells induced a higher frequency of MHC class I-restricted IFN-γ releasing lymphocytes. A higher CTL response was induced by pulsing DCs with cell lysate supernatant compared with whole cell lysate. These results indicate that, although necrotic death has been regarded as highly permissive when compared to apoptotic death, the immunogenicity of the death treatment may vary from one tumor to another.

PD-L1 marks a subset of melanomas with a shorter overall survival and distinct genetic and morphological characteristics

BACKGROUND

Programmed cell death ligand 1 (PD-L1) is a cell surface molecule that plays a critical role in suppressing immune responses, mainly through binding of the PD-1 receptor on T lymphocytes. PD-L1 may be expressed by metastatic melanoma (MM). However, its clinical and biological significance remains unclear. Here, we investigated whether expression of PD-L1 in MM identifies a biologically more aggressive form of the disease, carrying prognostic relevance.

PATIENTS AND METHODS

PD-L1 expression was analyzed by immunohistochemistry using two different antibodies in primary tumors and paired metastases from 81 melanoma patients treated at a single institution. Protein expression levels were correlated with PD-L1 mRNA, BRAF mutational status and clinical outcome. PD-L1(+) and PD-L1(-) subsets of the A375 cell line were stabilized in vitro and compared using gene expression profiling and functional assays. Results were confirmed using xenograft models.

RESULTS

PD-L1 membrane positivity was detected in 30/81 (37%) of patients. By multivariate analysis, Breslow thickness and PD-L1 membrane positivity were independent risk factors for melanoma-specific death {PD-L1 5% cutoff [hazard ratio (HR) 3.92, confidence interval (CI) 95% 1.61-9.55 P < 0.003], PD-L1 as continuous variable (HR 1.03, 95% CI 1.02-1.04 P < 0.002)}. PD-L1 expression defined a subset of the BRAF-mutated A375 cell line characterized by a highly invasive phenotype and by enhanced ability to grow in xenograft models.

CONCLUSIONS

PD-L1 is an independent prognostic marker in melanoma. If confirmed, our clinical and experimental data suggest that PD-L1(+) melanomas should be considered a disease subset with distinct genetic and morpho-phenotypic features, leading to enhanced aggressiveness and invasiveness.

Usefulness of chest physiotherapy with positive expiratory pressure (PEP)-mask in HIV-infected children with recurrent pulmonary infections

Eight children with human immunodeficiency virus (HIV) and recurrent bacterial pulmonary infections were treated using a Positive Expiratory Pressure (PEP)-mask twice a day for 12 months. At the end of the study, a reduction in the number of pulmonary infections [mean (SD) 2.1 (0.9) vs 4.5 (1) p < 0.0001] and antibiotic courses [mean (SD) 1.5 (0.7) vs 2.4 (0.9) p < 0.021] was noted. The PEP-mask is a chest physiotherapy technique for removing infected secretions and optimizing airway functions that is also useful in HIV-infected children.