Samrat Roy*, Manoj Pandre*, Sundarajan Kannan, Rajesh Kumar RK, Chinmaya Amarkanth, Debabani Roy Chowdhury & Arnab Roy Chowdhury Survival and colonisation axis of metastasised cells in the secondary tissue: to target or not to target?, Mestastop Solutions Pvt. Ltd, Bangalore, India
Survival and colonisation axis of metastasised cells in the secondary tissue: to target or not to target?
We have previously shown that plasticity ratio (PR; mesenchymal to epithelial markers) plays a critical role in successful metastasis across multiple stages. Here we highlight the importance of PR during survival in the secondary tissue followed by subsequent colonisation and how one can manipulate it for drug discovery.
Wild type HT29 (PR 0.22) and engineered HT29#8C5 (PR 0.96) were initially used as a baseline to understand the functional differences between them during survival and colonisation. Cells with higher PR showed higher expression of PD-L1 and lesser susceptibility to apoptosis. Their ability to crosstalk with the secondary microenvironment was more evident from the higher exosome uptake capability. Metabolically, they had low dependence on lactate and glutamate but showed elevated autophagy and ROS generation. High PR cells had more cells in the G0 phase and lesser cells in the M phase than HT29.
By treating the 8C5 cells with retinoic acid (RA), a molecule that promotes MET, we could successfully decrease the PR and a concomitant increase in chemosensitivity and a significant transition of cells from G0 to M phase. RA treated 8C5 cells formed more colonies in the clonogenic assay and had lesser invasive prowess. Interestingly, when we treated Colo205, a wild type metastatic colon cancer cell line (PR 1) with RA, there was again a measurable change in PR, and we saw an increase in colony formation. Treatment of Colo205 with a chemotherapeutic agent also generated cells with lower PR and increased colony formation ability by promoting a G0 to S transition, suggesting the shift from M to E can be inadvertent and, therefore, a dual-edged sword.
We next tested the hypothesis of maintaining cells in the high PR axis by treating 8C5 cells with AGN193109. The compound abrogated RA mediated PR change and reduced colony formation in the clonogenic assay by preventing the shift of cells from the G to M phase. Currently, we are testing this hypothesis on primary patient tumors, comparing the two strategies of MET promotion and M-form maintenance.
Metastasis success depends on dissemination, survival and subsequent colonisation of the disseminated cells, and all efforts targeting the dissemination step have failed, suggesting there are more downstream rate-limiting steps. Our work identifies the colonisation axis as critical and suggests that targeting it in the right way might delay metastasis in clinical settings