[Effectiveness of DNA repair and expression of MLH1, MSH2 and FASR in lymphocytes of patients with chemotherapy-responsive, disseminated cutaneous melanoma].

Patients with advanced malignant melanoma have poor prognosis as conventional chemotherapy induces complete response in a very small fraction (not more than 20%). One of research strategies aimed at raising its efficiency is the search for markers predicting individual response to chemotherapy. Our study was concerned with evaluation of the potential of DNA damage, repair (BER, MMR), expression of proteins MLH1, MSH2 and FasR as prognosticators of chemotherapy. These parameters were assessed in lymphocytes sampled from the blood of patients with metastatic cutaneous melanoma before and after one cycle of chemotherapy with lomustine, dacarbazine, cisplatin and interferon-gamma (LDCI). Clinical response was evaluated after a full course of therapy. We established that the major DNA damage induced by chemotherapy occurred on the levels of AP sites and single strand (SS) breaks. Despite the individual variations in BER efficacy, complete repair of SS breaks was reported in lymphocytes of all patients 30 days after the first cycle of chemotherapy. As a consequence, this type of damage and relevant BER efficacy did not correlate with clinical response. Conversely, the number of DNA double strand breaks detected in lymphocytes after the first cycle of chemotherapy was in good correlation with positive clinical response (p < 0.001). This parameter does not fully represent MMR function and, if coupled with cytotoxic effect of chemotherapy on lymphocytes, may be used as a predictive marker for clinical response to LDCI chemotherapy regimens for melanoma.