Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide and has a high mortality rate due to limited treatment options. Hence, the response of HCC to different cancer immunotherapies is being intensively investigated in clinical trials. Immune checkpoint blockers (ICB) show promising results, albeit for a minority of HCC patients. Mouse models are commonly used to evaluate new therapeutic agents or regimens. However, to make clinical translation more successful, better characterized preclinical models are required. We therefore extensively investigated two immune-competent orthotopic HCC mouse models, namely transplanted Hep-55.1c and transgenic iAST, with respect to morphological, immunological and genetic traits and evaluated both models' responsiveness to immunotherapies. Hep-55.1c tumors were characterized by rich fibrous stroma, high mutational load and pronounced immune cell infiltrates, all of which are features of immune-responsive tumors. These characteristics were less distinct in iAST tumors, though these were highly vascularized. Cell depletion revealed that CD8+ T cells from iAST mice do not affect tumor growth and are tumor tolerant. This corresponds to the failure of single and combined ICB targeting PD-1 and CTLA-4. In contrast, combining anti-PD-1 and anti-CTLA-4 showed significant antitumor efficacy in the Hep-55.1c mouse model. Collectively, our data comprehensively characterize two immune-competent HCC mouse models representing ICB responsive and refractory characteristics. Our characterization confirms these models to be suitable for preclinical investigation of novel cancer immunotherapy approaches that aim to either deepen preexisting immune responses or generate de novo immunity against the tumor.

Immunotherapy of B-cell malignancies using CD19-targeted chimeric antigen receptor-transduced T cells or CD20-targeted therapeutic monoclonal antibodies has shown clinical efficacy. However, refractory disease and the emergence of antigen-loss tumor escape variants after treatment demonstrate the need to target additional antigens. Here we aimed to target the B-cell receptor-associated protein CD79b by a T-cell receptor (TCR)-based approach. Because thymic selection depletes high-avidity T cells recognizing CD79b-derived peptides presented in self-HLA molecules, we aimed to isolate T cells recognizing these peptides presented in allogeneic HLA. Peptide-HLA tetramers composed of CD79b peptides bound to either HLA-A2 or HLA-B7 were used to isolate T-cell clones from HLA-A*0201 and B*0702-negative individuals. For 3 distinct T-cell clones, CD79b specificity was confirmed through CD79b gene transduction and CD79b-specific shRNA knockdown. The CD79b-specific T-cell clones were highly reactive against CD79b-expressing primary B-cell malignancies, whereas no recognition of nonhematopoietic cells was observed. Although lacking CD79b-cell surface expression, intermediate reactivity toward monocytes, hematopoietic progenitor cells, and T-cells was observed. Quantitative reverse transcriptase polymerase chain reaction revealed low CD79b gene expression in these cell types. Therefore, aberrant gene expression must be taken into consideration when selecting common, apparently lineage-specific self-antigens as targets for TCR-based immunotherapies.
© 2015 by The American Society of Hematology.

Patients with BRAFV600E/K-driven melanoma respond to the BRAF inhibitor vemurafenib due to subsequent deactivation of the proliferative RAS/RAF/MEK/ERK pathway. In BRAF WT cells and those with mutations that activate or result in high levels of the BRAF activator RAS, BRAF inhibition can lead to ERK activation, resulting in tumorigenic transformation. We describe a patient with malignant melanoma who developed chronic lymphocytic leukemia (CLL) in the absence of RAS mutations during vemurafenib treatment. BRAF inhibition promoted patient CLL proliferation in culture and in murine xenografts and activated MEK/ERK in primary CLL cells from additional patients. BRAF inhibitor-driven ERK activity and CLL proliferation required B cell antigen receptor (BCR) activation, as inhibition of the BCR-proximal spleen tyrosine kinase (SYK) reversed ERK hyperactivation and proliferation of CLL cells from multiple patients, while inhibition of the BCR-distal Bruton tyrosine kinase had no effect. Additionally, the RAS-GTP/RAS ratio in primary CLL cells exposed to vemurafenib was reduced upon SYK inhibition. BRAF inhibition increased mortality and CLL expansion in mice harboring CLL xenografts; however, SYK or MEK inhibition prevented CLL proliferation and increased animal survival. Together, these results suggest that BRAF inhibitors promote B cell malignancies in the absence of obvious mutations in RAS or other receptor tyrosine kinases and provide a rationale for combined BRAF/MEK or BRAF/SYK inhibition.

Galectins, a family of structurally related beta-galactoside-binding proteins, are expressed by various cells of the immune systems and seem to be important for the regulation of immune responses and immune cell homeostasis. Since it has been demonstrated that galectin-2 regulates cell-mediated inflammatory bowel disease and colitis in mice, we intended to investigate the role of galectin-2 in inflammatory cutaneous T cell-mediated immune responses. To address this issue, groups of naive mice were sensitized to the contact allergen 2,4-dinitro-1-fluorobenzene and systemically treated with galectin-2 to analyze the effects of galectin-2 on contact allergy. Here we show that galectin-2 is expressed in murine skin and is up-regulated upon cutaneous inflammation. Interestingly, treatment of mice with galectin-2 significantly reduced the contact allergy response. This effect was long-lasting since rechallenge of galectin-2-treated mice after a 14-day interval still resulted in a decreased ear swelling. We were able to demonstrate that galectin-2 induced a reduction of MHC class I-restricted immune responses in the treated animals, which was mediated by the induction of apoptosis specifically in activated CD8(+) T cells. Additionally, we report that the galectin-2-binding protein CD29 is up-regulated on the surface of activated CD8(+) T cells compared with naive CD8(+) T cells or CD4(+) T cells, suggesting that increased galectin-2/CD29 signaling might be responsible for the proapoptotic effects of galectin-2 on activated CD8(+) T cells. Taken together, these data indicate that galectin-2 may represent a novel therapeutic alternative for the treatment of CD8-mediated inflammatory disorders such as contact allergy.