Development and immunophenotyping of squamous cell carcinoma xenografts: tools for translational immunology

Immune-relevant aspects of murine models of head and neck cancer

Head and neck cancers (HNCs) cause significant mortality and morbidity. There have been few advances in therapeutic management of HNC in the past 4 to 5 decades, which support the need for studies focusing on HNC biology. In recent years, increased recognition of the relevance of the host response in cancer progression has led to novel therapeutic strategies and putative biomarkers of tumor aggressiveness. However, tumor-immune interactions are highly complex and vary with cancer type. Pre-clinical, in vivo models represent an important and necessary step in understanding biological processes involved in development, progression and treatment of HNC. Rodents (mice, rats, hamsters) are the most frequently used animal models in HNC research. The relevance and utility of information generated by studies in murine models is unquestionable, but it is also limited in application to tumor-immune interactions. In this review, we present information regarding the immune-specific characteristics of the murine models most commonly used in HNC research, including immunocompromised and immunocompetent animals. The particular characteristics of xenograft, chemically induced, syngeneic, transgenic, and humanized models are discussed in order to provide context and insight for researchers interested in the in vivo study of tumor-immune interactions in HNC.

Expression of Ski can act as a negative feedback mechanism on retinoic acid signaling

BACKGROUND

Retinoic acid signaling is essential for many aspects of early development in vertebrates. To control the levels of signaling, several retinoic acid target genes have been identified that act to suppress retinoic acid signaling in a negative feedback loop. The nuclear protein Ski has been extensively studied for its ability to suppress transforming growth factor-beta (TGF-β) signaling but has also been implicated in the repression of retinoic acid signaling.

RESULTS

We demonstrate that ski expression is up-regulated in response to retinoic acid in both early Xenopus embryos and in human cell lines. Blocking retinoic acid signaling using a retinoic acid antagonist results in a corresponding decrease in the levels of ski mRNA. Finally, overexpression of SKI in human cells results in reduced levels of CYP26A1 mRNA, a known target of retinoic acid signaling.

CONCLUSIONS

Our results, coupled with the known ability of Ski to repress retinoic acid signaling, demonstrate that Ski expression is a novel negative feedback mechanism acting on retinoic acid signaling.

Induction of MAGE-A3 and HPV-16 immunity by Trojan vaccines in patients with head and neck carcinoma

BACKGROUND

We performed a pilot study using Trojan vaccines in patients with advanced squamous cell carcinoma of the head and neck (SCCHN). These vaccines are composed of HLA-I and HLA-II restricted melanoma antigen E (MAGE)-A3 or human papillomavirus (HPV)-16 derived peptides, joined by furin-cleavable linkers, and linked to a "penetrin" peptide sequence derived from HIV-TAT. Thirty-one patients with SCCHN were screened for the trial and 5 were enrolled.

METHODS

Enrolled patients were treated with 300 μg of Trojan peptide supplemented with Montanide and granulocyte-macrophage colony-stimulating factor (GM-CSF) at 4-week intervals for up to 4 injections.

RESULTS

Following vaccination, peripheral blood mononuclear cells (PBMCs) from 4 of 5 patients recognized both the full Trojan constructs and constituent HLA-II peptides, whereas responses to HLA-I restricted peptides were less pronounced.

CONCLUSION

This treatment regimen seems to have acceptable toxicity and elicits measurable systemic immune responses against HLA-II restricted epitopes in a subset of patients with advanced SCCHN.