Benefit of a combined treatment of cryotherapy and chemotherapy on tumour growth and late cryo-induced angiogenesis in a non-small-cell lung cancer model.

In the treatment of lung cancers, a local cryotherapy can be proposed as a palliative option for bronchial clearance. But this therapy can also be used as an adjuvant treatment, for instance in association with chemotherapy. We have already demonstrated differential biological effects of these therapies and the benefit to combine them. The aim of this study was to determine if this benefit observed at a molecular level was correlated with tumour growth. As vascular changes occur after cryotherapy, intratumoral angiogenesis was also studied. Cells from the A549 cell line were inoculated into SCID mice. Tumours were treated by cryotherapy (nitrous oxide cryoprobe), chemotherapy (injection of Vinorelbine) or both. Tumour growth was studied in each group and the T/C ratios were compared. Tumours treated by cryochemotherapy presented a significantly reduced volume and the lower T/C ratio, confirming the benefit of a combined treatment. Angiogenesis was assessed at variable time points after cryotherapy by immunohistochemical staining of VEGF and western blot analysis. A late cryo-induced angiogenesis was observed 8-15 days after treatment (expression of VEGF increased from 13% in untreated tumours to 77 and 70%, respectively). To determine if this hypervascularization could enhance the efficiency of chemotherapy, the drug was injected 15 days after cryotherapy and the induction of cell death was investigated (morphological study, immunohistochemical staining of cleaved caspase-3, TUNEL). Necrosis was increased but not apoptosis, suggesting that though a crucial parameter, intratumoral microvessel density is not the only factor to consider to reach an optimal efficiency of a combined treatment.