T26

Background

Epithelial ovarian cancer frequently metastasizes to the omentum, a process that requires pro-angiogenic activation of HOMECs by tumour -secreted factors in their microenvironment. We have previously shown that ovarian cancer cells secrete a range of factors with possible roles in metastatic angiogenesis including the lysosomal proteases cathepsin D (CD) and cathepsin L (CL). However, the role of these proteases in ovarian cancer metastasis to the omentum is not fully understood.

Aim

To investigate whether proliferative effects of CD and CL are dependent on their catalytic activity in HOMECs.

To investigate the intracellular signalling kinases activated by CD and CL.

Method

HOMEC proliferation was assessed by using a colorimetric (WST1) assay. Potential signalling pathways were examined by phosphokinase array and ELISAs. pH experiments were carried out examine whether the observed effects were due to the catalytic activity of CD and CL.

Result

CD and CL (50 ng/ml) significantly increased HOMEC proliferation to 141 ± 27% (p = 0.001, n = 50) and 151% ± 34% (p = 0.001, n = 45) respectively vs. control (100%) 72 h post-treatment. Inhibitors of CD and CL enzyme activity had no effect on HOMEC proliferation and subsequent pH data suggest a nonproteolytic mitogenic activity of these cathepsins. Both proteins induced phosphorylation of ERK1/2, AKT and p38α to ∼2, ∼1.5 and ∼1.5 folds respectively relative to total levels (compared to control).

Conclusion

CD and CL induced proliferation in HOMECs. CD and CL may non- proteolytically contribute to pro-angiogenic responses of the omental microvasculature. Induction of phosphorylation of proliferative kinases ERK1/2, AKT and p38α suggest possible downstream signalling cascades of these proteins.