The project has been very successfully completed and it has led to major publications (Krol et al., British Journal of Cancer, in press; Donato et al., Cell Rep, 2020; Gkountela et al., Cell, 2019; Szczerba et al., Nature, 2019) and patents filing. Specifically, we have found that intra-tumor hypoxia leads to cell-cell junction upregulation, including overexpression of NDRG1. In turn, NDRG1-positive CTC clusters lead to distant metastasis formation (Donato et al., Cell Rep, 2020). Previously, we also found that CTC clusters rely on specific cell-cell junction components such as CLDN3 and CLDN4 for maintaining their multicellular structure in circulation, and that their dissociation with FDA-approved compounds or knockout of CLDN3 and CLDN4 leads to DNA methylation remodelling at binding sites for stemness- and proliferation-associated transcription factors (Gkountela et al., Cell, 2019). This study has already led to the clinical testing of approved NaK-ATPase inhibitors for the treatment of patients with cancer. Further, we also found that CTCs can cluster with immune cells such as neutrophils, and that this association is mediated by the cell-cell junction component VCAM1. Interaction of CTCs with neutrophils leads to increased proliferation of CTCs within the bloodstream, and a higher ability to initiate metastasis (Szczerba et al., Nature, 2019). More recently, we could also determine that CTC clusters are not only present at late disease stage is patients, but they manifest early, i.e. before primary tumor surgery (Krol et al., British Journal of Cancer, in press). Altogether, the HOLDING-HANDS project has achieved very important results, some of which already translated into novel clinical trials and new approaches to suppress the metastatic spread of cancer. These results have been disseminated in a number of conferences, on social media and publications. Exploitation of the results in underway, as we plan to generate a spinoff company that will develop anti-cluster therapeutics for patients with cancer.
