CCN5/WISP-2 promotes growth arrest of triple-negative breast cancer cells through accumulation and trafficking of p27 super(Kip1) via Skp2 and FOXO3a regulation

• Published in: Oncogene 2015-06, Vol.34 (24), p.3152-3163
• Main Authors: Haque, I, Banerjee, S, De, A, Maity, G, Sarkar, S, Majumdar, M, Jha, S S, McGragor, D, Banerjee, S K
• Format: Article
• Language: English
• ISSN: 0950-9232
• DOI: 10.1038/onc.2014.250

The matricellular protein CCN5/WISP-2 represents a promising target in triple-negative breast cancer (TNBC) because treatment or induced activation of CCN5 in TNBC cells promotes cell growth arrest at the G0/G1 phase, reduces cell proliferation and delays tumor growth in the xenograft model. Our studies found that the p27 super(Kip1) tumor suppressor protein is upregulated and relocalized to the nucleus from cytoplasm by CCN5 in these cells and that these two events (upregulation and relocalization of p27 super(Kip1)) are critical for CCN5-induced growth inhibition of TNBC cells. In the absence of CCN5, p27 super(Kip1) resides mostly in the cytoplasm, which is associated with the aggressive nature of cancer cells. Mechanistically, CCN5 inhibits Skp2 expression, which seems to stabilize the p27 super(Kip1) protein in these cells. On the other hand, CCN5 also recruits FOXO3a to mediate the transcriptional regulation of p27 super(Kip1). The recruitment of FOXO3a is achieved by the induction of its expression and activity through shifting from cytoplasm to the nucleus. Our data indicate that CCN5 blocks PI3K/AKT signaling to dephosphorylate at S318, S253 and Thr32 in FOXO3a for nuclear relocalization and activation of FOXO3a. Moreover, inhibition of alpha 6 beta 1 receptors diminishes CCN5 action on p27 super(Kip1) in TNBC cells. Collectively, these data suggest that CCN5 effectively inhibits TNBC growth through the accumulation and trafficking of p27 super(Kip1) via Skp2 and FOXO3a regulation, and thus, activation of CCN5 may have the therapeutic potential to kill TNBC.