Molecular Biology of Anal Cancer in HIV-Positive Patients

The molecular mechanisms involved in squamous cell carcinoma of the anus (SCCA) are poorly elucidated. HIV-positive and renal transplant patients are at high risk for developing SCCA, indicating that immune suppression plays a facilitating role. The investigators previously demonstrated that chromosomal instability (CIN) was more prevalent in SCCA of HIV-negative than HIV-positive patients. Hence, the investigators postulate that microsatellite instability (MSI), another molecular pathway, might be a feature of SCCA progression in the HIV-positive population.

Study Aims:

1. to determine the prevalence of MSI in paraffin-embedded tumor specimen of 15 patients from the Swiss HIV cohort who underwent surgical excision for SCCA; and
2. eventually, to test our hypothesis by assessing the MSI status of SCCA in 15 recently operated HIV-negative patients.

Study Design:

The study is designed in two steps:

1. Firstly, the investigators will retrieve tumor specimen from 15 HIV-positive patients, with a biopsy-confirmed diagnosis of SCCA, in three institutions. DNA from tumor and normal tissues will be extracted, and then amplified by PCR. Presence of MSI in tumors will be determined by assessing the microsatellite markers BAT25, BAT26, and CAT25.
2. Secondly, the results of molecular analysis will be compared with a population of HIV-negative patients, with the same tumors, using the same detection technique for MSI.