HSP90B1 and breast cancer: (Fig. 2a; Additional file 10: Table S2) In view of BC-related function of these BLBC-specifically secreted proteins, several factors involved in tumor progression and metastasis showed increased secretion, including CD44, [37] heat shock protein family A member 5 (HSPA5), [38] and heat shock protein 90 beta family member 1 (HSP90B1).