Expression hierarchy of T cell epitopes from melanoma differentiation antigens: unexpected high level presentation of tyrosinase-HLA-A2 Complexes revealed by peptide-specific, MHC-restricted, TCR-like antibodies.

Peptide Ags presented by class I MHC molecules on human melanomas and that are recognized by CD8(+) T cells are the subjects of many studies of antitumor immunity and represent attractive candidates for therapeutic approaches. However, no direct quantitative measurements exist to reveal their expression hierarchy on the cell surface. Using novel recombinant Abs which bind these Ags with a peptide-specific, MHC-restricted manner, we demonstrate a defined pattern of expression hierarchy of peptide-HLA-A2 complexes derived from three major differentiation Ags: gp100, Melan-A/Mart-1, and tyrosinase. Studying melanoma cell lines derived from multiple patients, we reveal a surprisingly high level of presentation of tyrosinase-derived complexes and moderate to very low expression of complexes derived from other Ags. No correlation between Ag presentation and mRNA expression was found; however, protein stability may play a major role. These results provide new insights into the characteristics of Ag presentation and are particularly important when such targets are being considered for immunotherapy. These results may shed new light on relationships between Ag presentation and immune response to cancer Ags.

p16(INK4A) is a surrogate biomarker for a subset of human papilloma virus-associated dysplasias of the uterine cervix as determined on the Pap smear.

Recently, p16(INK4A) has been identified as a biomarker for human papilloma virus (HPV)-induced dysplastic lesions of the cervix and it has been suggested that it may be a useful diagnostic aid for these lesions. This study therefore was performed to determine the utility of p16 expression in a series of Papanicolaou (Pap) smears collected in liquid medium and to determine its benefit, if any, over HPV testing. One hundred seven cases, including 23 negative cases, 34 with low-grade squamous intraepithelial lesion (LSIL), 16 with high-grade squamous intraepithelial lesion (HSIL), 29 with atypical squamous cells of uncertain significance (ASC-US), and 5 cases with ASC suspicious for HSIL (ASC-H), were evaluated for both p16 expression and HPV DNA. We observed p16 expression in only 36% of all cases with abnormal cytology (30/84) and in 40% of all cases associated with high-risk HPV. The highest rate of positivity (80%) and the highest levels of expression (more than three to five positive cells/10x field) were seen in HSIL. Similar results were observed with ASC-H cases. This suggests that in equivocal cases, p16 may be used for confirmation of the diagnosis. On the other hand, p16 positivity was noted in only 21% of LSIL and ASC-US cases. This raises the interesting possibility, given that only a minority of LSIL cases progress on to higher-grade lesions, that p16 might be useful for triaging these patients for closer follow-up and/or further evaluation. Additional studies are required for confirmation.

Lymph node-targeted immunotherapy mediates potent immunity resulting in regression of isolated or metastatic human papillomavirus-transformed tumors.

PURPOSE: The goal of this study was to investigate the therapeutic potential of a novel immunotherapy strategy resulting in immunity to localized or metastatic human papillomavirus 16-transformed murine tumors. EXPERIMENTAL DESIGN: Animals bearing E7-expressing tumors were coimmunized by lymph node injection with E7 49-57 antigen and TLR3-ligand (synthetic dsRNA). Immune responses were measured by flow cytometry and antitumor efficacy was evaluated by tumor size and survival. In situ cytotoxicity assays and identification of tumor-infiltrating lymphocytes and T regulatory cells were used to assess the mechanisms of treatment resistance in bulky disease. Chemotherapy with cyclophosphamide was explored to augment immunotherapy in late-stage disease. RESULTS: In therapeutic and prophylactic settings, immunization resulted in a considerable expansion of E7 49-57 antigen-specific T lymphocytes in the range of 1/10 CD8(+) T cells. The resulting immunity was effective in suppressing disease progression and mortality in a pulmonary metastatic disease model. Therapeutic immunization resulted in control of isolated tumors up to a certain volume, and correlated with antitumor immune responses measured in blood. In situ analysis showed that within bulky tumors, T-cell function was affected by negative regulatory mechanisms linked to an increase in T regulatory cells and could be overcome by cyclophosphamide treatment in conjunction with immunization. CONCLUSIONS: This study highlights a novel cancer immunotherapy platform with potential for translatability to the clinic and suggests its potential usefulness for controlling metastatic disease, solid tumors of limited size, or larger tumors when combined with cytotoxic agents that reduce the number of tumor-infiltrating T regulatory cells.