Cathepsin L-induced galectin-1 may act as a proangiogenic factor in the metastasis of high-grade serous carcinoma

Background:New treatment options for metastasised high-grade serous carcinoma (HGSC) are urgently needed. HGSC frequently metastasises to the omentum, inducing angiogenesis in the local omental microvasculature to facili-tate tumour growth. We previously showed that HGSC-secreted cathepsin L (CathL) induces pro-angiogenic changes in disease relevant human omental microvascular endothelial cells (HOMECs), suggesting a role in tumour angio-genesis. Here we investigate whether CathL acts by inducing local production of the carbohydrate-binding protein galectin-1 (Gal1), which has been reported to be involved in tumourigenesis in other tumours. Methods:HOMECs were used for all experiments. Gal1 mRNA and protein levels were measured by RT-PCR and ELISA respectively. Gal1-induced cell proliferation was assessed using WST-1 assay, migration using a transwell assay and in vivo Gal1 expression by immunohistochemistry. Results:CathL transcriptionally regulated HOMEC production and secretion of Gal1 via activation of NFκB (sig-nificantly inhibited by sulfasalazine). Gal1 significantly enhanced HOMEC migration (p < 0.001) and proliferation (p < 0.001), suggesting an autocrine action. The latter was significantly reduced by the MEK/ERK1/2 inhibitors U0126 and PD98059 suggesting downstream activation of this pathway. Immunohistochemical analysis of omenta from HGSC patients with or without metastatic disease demonstrated a positive correlation between Gal1 expression and number of microvessels (r =0.8702, p < 0.001), and area of vessels (r =0.7283, p < 0.001), supporting a proangiogenic role for Gal1 in omental metastases. Conclusion:HOMEC Gal1 transcription and release in response to CathL secreted from metastasising HGSC acts in an autocrine manner on the local microvasculature to induce pro-angiogenic changes, highlighting a potential new therapeutic target.