Optimisation and molecular signalling of apoptosis in sequential cryotherapy and chemotherapy combination in human A549 lung cancer xenografts in SCID mice

Abstract

We define the optimal parameters for combination of cryotherapy (nitrous oxide) with chemotherapy (vinorelbine ditartrate, VNB) treatment and characterise some of the signals involved for apoptosis activation. No advantage appeared when cryotherapy and VNB were combined simultaneously compared to cryosurgery alone. In contrast, tumour volumes were reduced after a sequential treatment schedule, where each individual treatment was separated by 48 h. No significant benefit appeared when the sequential treatment was separated by 24 h, although some individual mice showed a good response. The sequence of treatment had no impact on the observed tumour growth inhibition in mice. The number of apoptotic cells was significantly augmented in the sequential treatment schedule where VNB was administered 48 h before cryotherapy. In this sequential treatment, the number of apoptotic cells correlated with heightened expression of the BH3-only Puma, Noxa and Bim-EL, at both the mRNA and protein levels. No significant change in Bax, Bcl-xL and Bcl-2 mRNA expression was apparent, whereas Mcl-1 expression increased only slightly to a much lower level than BH3-only mRNAs. Our data indicate that 48 h sequential rather than simultaneous cryotherapy with VNB in future cancer cryochemotherapy schedules will enhance the tumour response, and argue that VNB administration, 48 h before cryotherapy, will provoke apoptosis more efficiently.