Inhibition of SYK kinase does not confer a pro-proliferative or pro-invasive phenotype in breast epithelium or breast cancer cells.

SYK has been reported to possess both tumour promotor and repressor activities and deletion has been linked to a pro-proliferative / pro-invasive phenotype in breast tumours. It is unclear whether this is a consequence of protein deletion or loss of kinase activity. The SYK inhibitor, BI 1002494, caused no increase in proliferation in breast cancer cells or primary mammary epithelial cells in 2D or 3D cultures, nor changes in proliferation (CD1/2, CDK4, PCNA, Ki67) or invadopodia markers (MMP14, PARP, phospho-vimentin Ser56). BI 1002494 did not alter SYK protein expression. There was no change in phenotype observed in 3D cultures after addition of BI 1002494. Thirteen weeks of treatment with BI 1002494 resulted in no ductal branching or cellular proliferation in the mammary glands of mice. An in silico genetic analysis in breast tumour samples revealed no evidence that SYK has a typical tumour suppressor gene profile such as focal deletion, inactivating mutations or lower expression levels. Furthermore, SYK mutations were not associated with reduction in survival and disease-free period in breast cancer patients. In conclusion, small molecule inhibition of the kinase function of SYK does not contribute to a typical tumour suppressor profile.

Opposing effects of in vitro differentiated macrophages sub-type on epithelial wound healing.

Inappropriate repair responses to pulmonary epithelial injury have been linked to perturbation of epithelial barrier function and airway remodelling in a number of respiratory diseases, including chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis. We developed an in vitro mechanical scratch injury model in air-liquid interface differentiated primary human small airway epithelial cells that recapitulates many of the characteristics observed during epithelial wound injury in both human tissue and small animal models. Wound closure was initially associated with de-differentiation of the differentiated apical cells and rapid migration into the wound site, followed by proliferation of apical cells behind the wound edge, together with increases in FAK expression, fibronectin and reduction in PAI-1 which collectively facilitate cell motility and extracellular matrix deposition. Macrophages are intimately involved in wound repair so we sought to investigate the role of macrophage sub-types on this process in a novel primary human co-culture model. M1 macrophages promoted FAK expression and both M1 and M2 macrophages promoted epithelial de-differentiation. Interestingly, M2a macrophages inhibited both proliferation and fibronectin expression, possibly via the retinoic acid pathway, whereas M2b and M2c macrophages prevented fibronectin deposition, possibly via MMP expression. Collectively these data highlight the complex nature of epithelial wound closure, the differential impact of macrophage sub-types on this process, and the heterogenic and non-delineated function of these macrophages.