FN1 and small cell osteogenic sarcoma: A recent microproteomics study (126) confirmed this hypothesis, demonstrating that the SPARC protein is under-expressed in the Sertoli cells of patients with SCOS, leading to reduced expression of multiple genes related to cell adhesion (FN1, ITGA5, COL6A1, VWF, LAMB1 and THBS1) and some proteins essential for BTB formation and signal transmission through gap junctions, namely GJA1, CDH1, and ZO-1.