Immunotherapeutic strategies: the melanoma example

Anticancer properties of peptide fragments of hair proteins

The primary function of hair and fur covering mammalian skin is to provide mechanical and thermal protection for the body. The proteins that constitute hair are extremely resistant to degradation by environmental factors. However, even durable materials can be slowly broken down by mechanical stresses, biodegradation mediated by endogenous enzymes in the skin or host microbes. We hypothesised that the biodegradation products of hair may possess bioprotective properties, which supplement their physical protective properties. Although evolutionary processes have led to a reduction in the amount of hair on the human body, it is possible that the bioprotective properties of hair biodegradation products have persisted. The human skin is exposed to various environmental carcinogenic factors. Therefore, we hypothesised that the potential bioprotective mechanisms of hair degradation products affect melanoma growth. We used pepsin to partially digest hair enzymatically, and this process produced a water-soluble lysate containing a mixture of peptides, including fragments of keratin and keratin-associated proteins. We found out that the mixtures of soluble peptides obtained from human hair inhibited the proliferation of human melanoma cells in vitro. Moreover, the hair-derived peptide mixtures also inhibited the proliferation of B lymphoma cells and urinary bladder cancer cells. Normal human cells varied in their susceptibility to the effects of the lysate; the hair-derived peptide mixtures modulated the proliferation of normal human fibroblasts but did not inhibit the proliferation of human mesenchymal cells derived from umbilical cord stromal cells. These results suggest that hair-derived peptides may represent a new class of anti-proliferative factors derived from basically structural proteins. Identification of active regulatory compounds and recognition of the mechanism of their action might pave the way to elaboration of new anticancer drugs.

T cells in gastric cancer: friends or foes

Gastric cancer is the second cause of cancer-related deaths worldwide. Helicobacter pylori is the major risk factor for gastric cancer. As for any type of cancer, T cells are crucial for recognition and elimination of gastric tumor cells. Unfortunately T cells, instead of protecting from the onset of cancer, can contribute to oncogenesis. Herein we review the different types, “friend or foe”, of T-cell response in gastric cancer.

BRAF(V600) inhibitor GSK2118436 targeted inhibition of mutant BRAF in cancer patients does not impair overall immune competency

PURPOSE

An intact immune system likely contributes to the outcome of treatment and may be important for clearance of drug-resistant tumor cells and for prevention of recurrence. Although pharmacologic inhibition of BRAF(V600E) in melanoma patients, which is linked to immune suppression, results in an initial response rate, these responses are typically of limited duration. Combining immunotherapeutic drugs with kinase-targeted agents is an attractive strategy to increase clinical efficacy. Evidence suggesting that mitogen-activated protein kinase pathway activation in tumor cells contributes to immune suppression suggests that the two approaches may be synergistic, provided that BRAF(V600E) inhibitors are nontoxic to immune cells.

METHODS

To assess effects of mutant BRAF inhibition on systemic immunity, we studied 13 patients with tumors carrying a BRAF mutation who underwent treatment with GSK2118436, a V600 mutant BRAF-specific inhibitor. We carried out peripheral blood immunomonitoring before and following one or two 28-day cycles of treatment.

RESULTS

GSK2118436 treatment had no detectable impact on most immune parameters tested, including serum cytokine levels, peripheral blood cell counts, leukocyte subset frequencies, and memory CD4(+) and CD8(+) T-cell recall responses. A slight increase in serum TNF-α over the course of treatment was observed. In addition, three of the four human leukocyte antigen-A2-positive patients experienced a modest increase in circulating tumor antigen-specific CD8(+) T cells following BRAF(V600) inhibitor therapy.

CONCLUSIONS

GSK2118436 treatment results in no detectable negative impact on existing systemic immunity or the de novo generation of tumor-specific T cells. These findings suggest that future trials combining specific BRAF(V600E) inhibition with immunotherapy should not impair immune response.

On the selectivity and efficacy of defense peptides with respect to cancer cells

Here, we review potential determinants of the anticancer efficacy of innate immune peptides (ACPs) for cancer cells. These determinants include membrane-based factors, such as receptors, phosphatidylserine, sialic acid residues, and sulfated glycans, and peptide-based factors, such as residue composition, sequence length, net charge, hydrophobic arc size, hydrophobicity, and amphiphilicity. Each of these factors may contribute to the anticancer action of ACPs, but no single factor(s) makes an overriding contribution to their overall selectivity and toxicity. Differences between the anticancer actions of ACPs seem to relate to different levels of interplay between these peptide and membrane-based factors.

Development of genetically engineered CD4+ and CD8+ T cells expressing TCRs specific for a M. tuberculosis 38-kDa antigen

Cell-mediated immunity is critical to the clearance of Mycobacterium tuberculosis due to the primarily intracellular niche of this pathogen. Adoptive transfer of M. tuberculosis-specific effector T cells has been shown to confer immunity to M. tuberculosis-infected recipients resulting in M. tuberculosis clearance. However, it is difficult to generate sufficient numbers of M. tuberculosis antigen-specific T cells in a short time. Recent studies have developed T cell receptor (TCR) gene-modified T cells that allow for the rapid generation of large numbers of antigen-specific T cells. Many TCRs that target various tumor and viral antigens have now been isolated and shown to have functional activity. Nevertheless, TCRs specific for intracellular bacterial antigens (including M. tuberculosis antigens) have yet to be isolated and their functionality confirmed. We isolated M. tuberculosis 38-kDa antigen-specific HLA class I and class II-restricted TCRs and modified the TCR gene C regions by substituting nine amino acids with their murine TCR homologs (minimal murinization). Results showed that both wild-type and minimal murinized TCR genes were successfully cloned into retroviral vectors and transduced into primary CD4(+) and CD8(+) T cells and displayed anti-M. tuberculosis activity. As expected, minimal murinized TCRs displayed higher cell surface expression levels and stronger anti-M. tuberculosis activity than wild-type TCRs. To the best of our knowledge, this is the first report describing TCRs targeting M. tuberculosis antigens and this investigation provides the basis for future TCR gene-based immunotherapies that can be designed for the treatment of immunocompromised M. tuberculosis-infected patients.