Lactic acidosis is common to most solid tumors and has been found to affect infiltrating immune cells. Here we document effector phase inhibition of cytotoxic T cells (CTLs) involving complete blockage of cytokine production and partial impairment of lytic granule exocytosis. Lactic acidosis impaired TCR‐triggered phosphorylation of JNK, c‐Jun and p38, while not affecting MEK1 and ERK. The select targeting of signaling proteins involved in IFNγ production (JNK/c‐Jun, p38) without affecting those jointly used in cytokine regulation and granule exocytosis (MEK1/ERK) explains the observed split effect of lactic acidosis on the CTL responses. CTL inhibition by lactic acidosis showed fast dynamics with immediate onset and reversion. Functional recovery by neutralizing the extracellular pH despite continuous presence of lactate holds promise that CTL activity can be improved in the milieu of solid tumors with appropriate anti‐acidosis treatment, thereby increasing the efficacy of adoptive T cell therapy.

CD8+ tumor-infiltrating T cells (CD8-TILs) are found in many types of tumors including human renal cell carcinoma. However, tumor rejection rarely occurs, suggesting limited functional activity in the tumor microenvironment. In this study, we document that CD8-TILs are unresponsive to CD3 stimulation, showing neither lytic activity, nor lytic granule exocytosis, nor IFN-γ production. Mechanistically, no deficits in TCR proximal signaling molecules (lymphocyte-specific protein tyrosine kinase, phospholipase Cγ) were identified. In contrast, distal TCR signaling was suppressed, as T cells of TILs showed strongly reduced steady-state phosphorylation of the MAPK ERK and were unable to increase phosphorylation of ERK and JNK as well as AKT and AKT client proteins (IκB, GSK3) after stimulation. These deficits were tumor-specific as they were not observed in CD8+ T cells infiltrating non-tumor kidney areas (CD8+ non-tumor kidney-infiltrating lymphocytes; CD8-NILs). Diacylglycerol kinase-α (DGK-α) was more highly expressed in CD8-TILs compared with that in CD8-NILs, and its inhibition improved ERK phosphorylation and lytic granule exocytosis. Cultivation of TILs in low-dose IL-2 reduced DGK-α protein levels, increased steady-state phosphorylation of ERK, improved stimulation-induced phosphorylation of ERK and AKT, and allowed more CD8-TILs to degranulate and to produce IFN-γ. Additionally, the protein level of the AKT client molecule p27kip, an inhibitory cell cycle protein, was reduced, whereas cyclin E, which promotes G1–S phase transition, was increased. These results indicate that the tumor-inflicted deficits of TILs are reversible. DGK-α inhibition and provision of IL-2 signals could be strategies to recruit the natural CD8+ T cells to the anti-tumor response and may help prevent inactivation of adoptively transferred T cells thereby improving therapeutic efficacy.

Clear cell renal cell carcinoma (ccRCC) is an aggressive and difficult to manage cancer. Immunotherapy has the potential to induce long-lasting regression in a small group of patients. However, severe side effects limit broad application which highlights the need for a marker to distinguish responder from nonresponder. TNMG staging, referring to tumor size, lymph node involvement, presence of metastasis, and grade of tumor differentiation, represents an important prognostic system but is not useful for predicting responders to immunotherapy. NK cells are potent antitumor effector cells, and a role as prognostic marker in some solid tumors has been suggested. As NK cells are responsive to various immune modifiers, they may be important mediators of patient response to immunotherapies, in particular those including IL-2. We report that the NK cell percentage within RCC-infiltrating lymphocytes, as determined by flow cytometry, allows ccRCC subgrouping in NK(high)/NK(low) tissues independent of TNMG classification. Quantitative reverse transcriptase polymerase chain reaction using whole-tissue RNA identified four markers (NKp46, perforin, CX(3)CL1, and CX(3)CR1) whose transcript levels reproduced the NK(high)/NK(low) tissue distinction identified by flow cytometry with high selectivity and specificity. Combined in a multiplex profile and analyzed using neural network, the accuracy of predicting the NK(high)/NK(low) groups was 87.8%, surpassing that of each single marker. The tissue transcript signature, based on a robust high-throughput methodology, is easily amenable to archive material and clinical translation. This now allows the analysis of large patient cohorts to substantiate a role of NK cells in cancer progression or response to immunotherapy.

The mononuclear infiltrate in renal cell carcinoma (RCC) has been associated with the immunogenic nature of this tumor type and the clinical response rates achieved with immunotherapy.

Our study examined 166 patients with breast cancer with a mean age of 63 years. Each patient underwent mastectomy with the organ being investigated by histological giant sections and additional small sections from the nipple. Nipple involvement was found in 64 cases (38%). Multifocal carcinoma occurred in 76 patients. Further multicentric carcinomatous foci (36 cases) demonstrated a significant increase in affected nipples. Additional atypical ductal or lobular hyperplasia was observed in 53 cases and showed involvement in 34. Nine carcinomas of ductal origin were combined with lobular carcinoma in situ, all cases proved to have carcinomatous changes in the nipple. It is concluded that apart from the well-known influence of advanced tumor stages and tumor localization, nipple involvement correlates with multicentricity and multifocality of breast cancer as a disease of the whole organ.