However, glucagon-expressing tumours developed significantly more frequently in the 129S6/SvEv Men1+/- mice than in C57BL/6 Men1+/- mice (7/10 mice vs 1/15 mice, respectively; P < 0.002, Fig. 3B), such that glucagon-expressing tumours of the 129S6/SvEv Men1+/- mice accounted for 37% (13/35) of the total PNETs, whereas glucagon-expressing tumours of C57BL/6 Men1+/- mice accounted for only 2% (1/43) of all PNETs (P < 0.0001). This evidence concerns the gene GCG and neoplasm.