Gastric cancer has a high mortality rate associated with its late stage diagnosis. Although Gp130 knock-in mutant mice (gp130F/F) develop benign gastric tumours dependent upon IL-11-induced Stat3/mTORC activation with hallmarks of early stage intestinal-type gastric cancer in humans, there is an urgent need to develop mouse models that mimic the progression from adenoma to carcinoma and metastasis. Macrophages are a major component of the tumour micro-environment, and their increased numbers and alternative activation is commonly associated with tumour progression and metastasis.
Haematopoietic Cell Kinase (Hck) is a myeloid-specific Src family kinase that is involved in polarization of alternatively activated macrophages, which correlate with a poor prognosis for human gastric cancer. To establish whether aberrant Hck activation would induce tumourigenesis, Hck mutant mice that exhibit constitutive kinase activation (HckUp/Up) were crossed with gp130F/+ mice that are predisposed to gastric tumour development. Surprisingly, the resulting gp130F/+;HckUp/Up compound mutants developed tumours similar to gp130F/F animals, while gp130F/+ mice remained tumour-free. Furthermore, tumours in 9 month old gp130F/+;HckUp/Up mutants showed sub-mucosal invasion, which was not observed in gp130F/F mice.
Western blotting and immunohistochemical analysis revealed a significant increase in tumour cell proliferation in gp130F/+;HckUp/Up mutants compared to gp130F/F animals, consistent with an increased abundance of phosphorylated cytoplasmic signalling proteins commonly dysregulated during gastric tumourigenesis. While the total number of macrophages remained unaffected, qPCR analysis of purified tumour-associated macrophages from gp130F/+;HckUp/Up mice showed a significant increase in markers of alternative macrophage activation when compared to cells from gp130F/F animals. Furthermore, reciprocal adoptive transfer of HckUp/Up bone-marrow into gp130 mutant recipients was sufficient to increase tumour burden and promote alternative macrophage polarisation.
Collectively, our results demonstrate that aberrant Hck activation promotes polarisation towards alternative macrophage activation and confers an invasive gastric cancer phenotype.