The expression of SPARC in human tumors is consistent with its role during cell competition.

In Drosophila, the elimination of viable but suboptimal cells is mediated by cell competition, ensuring that these cells do not accumulate during development. In addition, certain genes such as the Drosophila homologue of human c-myc (dmyc) are able to transform cells into supercompetitors, which eliminate neighboring wild-type cells by apoptosis and overproliferate leaving total cell numbers unchanged. We have recently identified Drosophila SPARC as an early marker transcriptionally upregulated in loser cells that provides a transient protection by inhibiting caspase activation in outcompeted cells. Here, we explore whether the expression of SPARC in human tumors is consistent with a role for cell competition during human cancer and find that, consistent with the existence of competitive interactions between cancer and normal cells, SPARC is upregulated at the tumor-host boundaries in several types of human cancer.