Effects of cryotherapy or chemotherapy on apoptosis in a non-small-cell lung cancer xenografted into SCID mice.

Lung cancers are among the most frequent and the most lethal tumours. They are mainly treated by surgery or by chemotherapy, but in the most advanced stages a local cryotherapy can be proposed as a palliative option for bronchial clearance. This therapy, based on the cytotoxic effects of low temperatures, acts by mechanisms which are not yet totally understood. The aim of this work was to investigate in vivo the biological effects of cryotherapy in a model of human non-small-cell lung cancer. We used a xenograft system: cells from the A549 cell line (adenocarcinoma) were injected subcutaneously into SCID mice. Cryotherapy was performed (three cycles, nitrous oxide cryoprobe). Chemotherapy (intravenous injection of Vinorelbine (Navelbine), 4.8 mg/kg) was used as a control treatment. Tumour nodes were excised at variable time points and studied morphologically. The induction of apoptosis was analysed by immunohistochemical staining of cleaved caspase-3 and by TUNEL. Results showed that cryotherapy was an efficient technique to induce cell death either by necrosis or by apoptosis. Necrosis was found near the cryoprobe impact site and was maximal 2 h after treatment (65%); a second peak was observed after 4 days (77%). Around this central necrotic area, apoptotic cells were found. Apoptosis was maximal after 8 h (47%). Chemotherapy induced apoptosis in a fewer number of cells and this effect was not time-dependent. Taken together, these results demonstrate the differential effects of cryotherapy and chemotherapy in vivo, suggesting different modes of action and the potential benefit to combine them.