Immune Escape Mechanisms of Renal Cell Carcinoma

The potential of radiotherapy to enhance the efficacy of renal cell carcinoma therapy

Renal cell carcinoma (RCC) is an immunogenic tumor, but uses several immune-suppressive mechanisms to shift the balance from tumor immune response toward tumor growth. Although RCC has traditionally been considered to be radiation resistant, recent evidence suggests that hypofractionated radiotherapy contributes to systemic antitumor immunity. Because the efficacy of antitumor immune responses depends on the complex balance between diverse immune cells and progressing tumor cells, radiotherapy alone is unlikely to induce persistent antitumor immunity. Therefore, the combination of radiotherapy with drugs having synergistic immunomodulatory properties holds great promise with the optimal timing and sequence of modalities depending on the agent used. We highlight the immunomodulatory properties of targeted therapies, such as tyrosine kinase inhibitors, mammalian target of rapamycin (mTOR) inhibitors and vascular endothelial growth factor (VEGF) neutralizing antibodies, and will suggest a combination schedule with radiotherapy based on the available literature. We also address the combination of radiotherapy with innovative treatments in the field of immunotherapy.

Case-control study of HLA-G promoter methylation status, HPV infection and cervical neoplasia in Curitiba, Brazil: a pilot analysis

Background

The causal association between persistent human papillomavirus (HPV) infection and cervical cancer has been established, but the mechanisms that favor HPV persistence in cervical cells are still unknown. The diminished capability of the immune system to control and resolve HPV infection is one of several hypotheses. The tolerogenic protein HLA-G has shown aberrant expression in a variety of cancers, which has been suggested as a mechanism for tumor escape from immunosurveillance. In the present study we evaluate the role of epigenetic modification (promoter de-methylation) of the HLA-G gene on susceptibility to HPV infection and development of high-grade cervical lesions.

Methods

A case–control study was carried out in Curitiba, Brazil, between February and June 2010. A total of 789 women aged 15–47 years were recruited: 510 controls with normal cervical cytology, and 279 cases with histologically confirmed cervical intraepithelial neoplasia grade 2 (CIN2, N = 150) or grade 3 (CIN3, N = 129). All women were administered a questionnaire by interview, which collected information on demographic and lifestyle factors, and a cervical sample was collected. HPV DNA detection was performed by GP5+/GP6+ primer-mediated PCR. HPV-positive samples were genotyped by multiplex PCR. A pilot analysis of HLA-G promoter methylation was carried out in a subset of the study population (96 cases and 76 controls) by pyrosequencing. HLA-G methylation and HPV infection status of cases and controls were compared, and confounding factors were computed by t Student and non-parametric Wilcoxon tests. Comparison of HLA-G methylation between cases and controls was assessed by the Bonferroni correction. The association of HLA-G methylation with CIN2/3 was evaluated by logistic regression.

Results

HPV prevalence was 19.6% in controls and 94.3% in CIN2/3 cases. HPV16, 31, 33, 35 and 18 were the most prevalent types. Methylation analysis of seven CpGs in the HLA-G promoter did not reveal any spontaneous de-methylation events in CIN2/3 cases (mean proportion of methylation: 75.8%) with respect to controls (mean 73.7%; odds ratio 1.01, 95% confidence interval 0.96, 1.07).

Conclusions

This study did not support the hypothesis that spontaneous de-methylation events in the HLA-G promoter play a primary role in promoting escape from immunosurveillance in the development of precancerous cervical lesions.