An in vivo systematic genetic analysis of tumour progression in Drosophila identifies the cohesin complex as an invasion suppressor

Metastasis is the leading cause of death for cancer patients. Consequently it is imperative that we improve our understanding of the molecular mechanisms that underlie progression of tumour growth towards malignancy. Advances in genome characterisation technologies have been very successful in identifying commonly mutated or misregulated genes in a variety of human cancers. However the difficulty in evaluating whether these candidate genes drive tumour progression remains a major challenge. Using the genetic amenability of Drosophila melanogaster we generated tumours with specific genotypes in the living animal and carried out a detailed systematic loss-of-function analysis to identify conserved genes that enhance or suppress epithelial tumour progression. This enabled the discovery of functional cooperative regulators of invasion and the establishment of a network of conserved invasion suppressors. This includes constituents of the cohesin complex, which can either promote individual or collective invasion, depending on the severity of effect on cohesin function. We used Clariom™ S Assay arrays to detail the global programme of gene expression following STAG2 KD to detect DEG involved in regulation of cell motility and cell-cell junction assembly and maintenance. In order to assess the role of STAG2 in invasion, STAG2 was transiently knocked down by siRNA in MCF-7 cells 48h prior to RNA extraction and hybridization on Affymetrix microarrays. 3 independent experiments were performed, each including un-treated cells, cells treated with mock siRNA and cells treated with STAG2 siRNA. The microarray analysis was further conducted in triplicate for each sample.