The family consists of thrombospondins 1-5 and can be divided into 2 subgroups: A, which contains TSP-1 and TSP-2, and B, which contains TSP-3, TSP-4 and TSP-5 (also designated cartilage oligomeric protein or COMP).

[2] Since its first recognition, functions for TSP-1 have been found in multiple biological processes including angiogenesis, apoptosis, activation of TGF-beta and Immune regulation.

Since tumors overexpressing TSP-1 typically grow slower, exhibit less angiogenesis, and have fewer metastases, TSP1 is an attractive target for cancer treatment.

Because TSP1 is extremely large (~ 120 kDa monomer), not very abundant and exerts multiple actions, its clinical usefulness is questionable.

One analog, ABT-510, exhibits potent proapoptotic activity in cultured cells, while clinically it is very well tolerated with therapeutic benefits reported against several malignancies.