Modifications in tissue histamine levels in mast cell-deficient mice (W/Wv) and in their littermates (Wv/+, W/+ and +/+) grafted with a methylcholanthrene-induced fibrosarcoma: correlation with tumour rejection.

There is evidence that mast cells and their degranulation products are involved in resistance against tumours. Previously, we have shown that tumour incidence and growth were inversely correlated with basal histamine levels, i.e. mast cell numbers, in tissues of W/Wv (mast cell-deficient), Wv/+ (partially mast cell-depleted), and +/+ (mast cell-sufficient) mice, and that histamine levels were increased in numerous tissues of tumour-bearing animals, including C57BL/6 and C3H mice, Sprague-Dawley and Commentry rats. The aim of this work was to analyse the incidence and growth of a grafted tumour (fibrosarcoma MC-B6-1) in W/+ mice, as compared with W/Wv, Wv/+ and +/+ mice, and to study the modifications in tissue histamine levels in W/+, W/Wv, Wv/+ and +/+ tumour-grafted mice, in order to determine whether or not these modifications were correlated with resistance to tumours. We report confirmation that tumour incidence and growth are inversely correlated with basal tissue histamine levels in W/Wv, Wv/+, and +/+ fibrosarcoma-bearing mice. However, in W/+ mice (normal tissue histamine levels), tumour incidence was the same as in Wv/+ mice. Histamine levels in tissues of W/Wv, Wv/+, W/+ and +/+ tumour bearing mice were not significantly different from those in controls. They were higher in some tissues of Wv/+ mice rejecting the tumour than in Wv/+ mice not rejecting the tumour. However, in W/+ and +/+ mice, histamine levels were not significantly different, and even tended to be lower in most tissues of mice rejecting the tumour than in mice accepting the tumour. Overall, these results suggest that resistance to tumours cannot be ascribed solely to mast cells, and that other mechanisms may also be involved. Thus, further experiments are needed to clarify the exact role of mast cells and mast cell-derived mediators and cytokines in the defence against tumours.