Sperm-associated antigen 9 (SPAG9) promotes the survival and tumor growth of triple-negative breast cancer cells

Abstract

Recently, we demonstrated the association of sperm-associated antigen 9 (SPAG9) expression with breast cancer. Among breast cancer, 15 % of the cancers are diagnosed as triple-negative breast cancers (TNBC) based on hormone receptor status and represent an important clinical challenge because of lack of effective available targeted therapy. Therefore, in the present investigation, plasmid-based small hairpin (small hairpin RNA (shRNA)) approach was used to ablate SPAG9 in aggressive breast cancer cell line model (MDA-MB-231) in order to understand the role of SPAG9 at molecular level in apoptosis, cell cycle, and epithelial-to-mesenchymal transition (EMT) signaling. Our data in MDA-MB-231 cells showed that ablation of SPAG9 resulted in membrane blebbing, increased mitochondrial membrane potential, DNA fragmentation, phosphatidyl serine surface expression, and caspase activation. SPAG9 depletion also resulted in cell cycle arrest in G0-G1 phase and induced cellular senescence. In addition, in in vitro and in vivo xenograft studies, ablation of SPAG9 resulted in upregulation of p21 along with pro-apoptotic molecules such as BAK, BAX, BIM, BID, NOXA, AIF, Cyto-C, PARP1, APAF1, Caspase 3, and Caspase 9 and epithelial marker, E-cadherin. Also, SPAG9-depleted cells showed downregulation of cyclin B1, cyclin D1, cyclin E, CDK1, CDK4, CDK6, BCL2, Bcl-xL, XIAP, cIAP2, MCL1, GRP78, SLUG, SNAIL, TWIST, vimentin, N-cadherin, MMP2, MMP3, MMP9, SMA, and β-catenin. Collectively, our data suggests that SPAG9 promotes tumor growth by inhibiting apoptosis, altering cell cycle, and enhancing EMT signaling in in vitro cells and in vivo mouse model. Hence, SPAG9 may be a potential novel target for therapeutic use in TNBC treatment.

NFIB promotes cell survival by directly suppressing p21 transcription in TP53‐mutated triple‐negative breast cancer

“…p21 is an important regulator of cell proliferation and survival in TNBC cells under various stimulatory pathways . We therefore examined p21 protein levels upon NFIB depletion.…”

“…NFIB-depleted cells were larger and had a flattened shape compared with control cells. Flow cytometry analysis of MDA-MB-435 and HCC1806 showed increased proportions of cells in the S/G2 phases of the cell cycle upon NFIB depletion suggesting a role for NFIB in cell cycle progression p21 is an important regulator of cell proliferation and survival in TNBC cells under various stimulatory pathways [31][32][33]. We therefore examined p21 protein levels upon NFIB depletion.…”

Sperm associated antigen 9 (SPAG9) a promising therapeutic target of ovarian carcinoma

“…SPAG9 protein localization in different cell organelles of ovarian cancer cells was examined using IIF as described previously. 10 Images were captured using Carl Zeiss LSM 510 Meta confocal microscope (Zeiss, Oberkochen, Germany). For co-localization studies antibodies used were: endoplasmic reticulum (Calnexin; Sc70481), mitochondria (MTCO2; ab3298), Golgi bodies (GM130; Sc55591) and nuclear envelope (Lamin a/ c; Sc7292).…”

“…9 Recently, it has been reported that SPAG9 plays an important role in various molecular pathways including cell cycle, apoptosis and epithelial mesenchymal transition (EMT) in triple negative breast cancer. 10 However, till date the involvement of SPAG9 at molecular level in ovarian cancer is not yet explored.…”

Dendritic cells matured with recombinant human sperm associated antigen 9 (rhSPAG9) induce CD4+, CD8+ T cells and activate NK cells: A potential candidate molecule for immunotherapy in cervical cancer

“…Recently, sperm associated antigen 9 (SPAG9) has been shown to be expressed in various cancer types such as epithelial ovarian cancer (EOC-90%) [13], renal cell carcinoma (RCC-88%) [14], colorectal cancer (74%) [15], breast cancer (88%) [16] and cervical cancer (82%) [17]. Studies on SPAG9 also showed that it is associated with cellular proliferation, migration and invasion of cancer cells [18][19][20][21], and is capable of eliciting humoral immune responses in a majority of epithelial ovarian cancers (67%) [13], breast cancers (80%) [16], cervical cancers (80%) [17], renal cell carcinoma (77%) [14], colorectal cancer (74%) [15] and hepatocellular carcinoma [22]. However its antigenicity in invoking a cell mediated immune response has not been studied until now.…”