Sperm-Associated Antigen 5 Knockout Reduces Doxorubicin and Docetaxel Resistance in Triple-Negative Breast Cancer MDA-MB-231 and BT549 Cells

Sperm-associated antigen 5 (SPAG5), also known as Astrin, was previously demonstrated as a biomarker for cellular resistance to major breast cancer therapies, including chemo-, endocrine- and targeted therapy. However, the contribution of SPAG5 to anthracycline- and taxane-based chemotherapy in triple-negative breast cancer (TNBC) remains controversial. In the present study, the SPAG5 knockout cell model was established by using clustered regularly interspaced palindromic repeats (CRISPR)-CRISPR-associated protein 9 (Cas9) system in MDA-MB-231 and BT549 TNBC cell lines. The knockout of SPAG5 was confirmed on both gene and protein levels using genomic PCR, DNA sequencing and western blotting. The functional loss of SPAG5 was determined by colony-formation assay. SPAG5-regulated doxorubicin- and docetaxel-resistance was assessed by MTT and apoptosis assays. The results indicated that all the SPAG5 knockout MDA-MB-231 and BT549 clones were biallelic, where one allele was replaced by the donor template, and the other allele had the same "T" insertion (indel) adjacent to the cutting sites of gRNAs at the exon 1 boundary, irrespective of the gRNAs and cell lines. The locus of indel interrupted the SPAG5 transcription by damaging the GT-AG mRNA processing rule. Deletion of SPAG5 decreased clonogenicity in both MDA-MB-231 and BT549 cells. SPAG5 was able to regulate the resistance and the drug-induced apoptosis of both doxorubicin and docetaxel. In conclusion, recombinant plasmid-based CRISPR-Cas9 technology can be used to delete the SPAG5 gene in the TNBC cell lines. SPAG5 has an important role in regulating cell proliferation and doxorubicin- and docetaxel-resistance in MDA-MB-231 and BT549 cells.

Pan-cancer analysis: SPAG5 is an immunological and prognostic biomarker for multiple cancers

Sperm-associated antigen 5 (SPAG5) is a mitotic spindle protein that regulates the separation of sister chromatids into daughter cells. Recent studies have discovered its overexpression in various cancers, suggesting its oncogenic characteristics and functions. However, a comprehensive analysis of SPAG5 regarding its diagnostic, prognostic, and immune-related effects across different cancer types is lacking. In this study, we employed bioinformatics methods and integrated multiple public databases to explore the potential oncogenic role of SPAG5. We analyzed its expression, prognosis, related chemicals, enriched pathways, immune infiltration, and its impact on different tumor genetic alterations. The results revealed that SPAG5 is highly expressed in most cancers and significantly correlates with poor patient prognosis. Additionally, SPAG5 expression showed potential for early cancer diagnosis in 15 different cancer types. In terms of tumor immunity, high expression of SPAG5 was associated with an immunosuppressive tumor microenvironment and immune therapy efficacy indicators. SPAG5 expression exhibited a negative correlation with most immune cell infiltrates but demonstrated a significant positive correlation with Th2 cells and MDSC cells. Multicolor fluorescence immunohistochemistry demonstrated that SPAG5 activates immune cell populations within tumors, indicating its significant role in the tumor microenvironment. Enrichment analysis indicated that SPAG5-related genes are mainly involved in cell cycle, cellular senescence, P53 signaling pathway, and FoxO signaling pathway. Furthermore, we confirmed the high expression of SPAG5 in cancer cells and observed that its knockdown upregulated the expression of the p53 protein. In conclusion, SPAG5 holds value as a diagnostic, prognostic, and immune biomarker in various cancers and may provide a novel target for tumor immunotherapy.

SPAG5 Activates PI3K/AKT Pathway and Promotes the Tumor Progression and Chemo-Resistance in Gastric Cancer

The sperm-associated antigen 5 (SPAG5) is an important protein in mitosis and cell cycle checkpoint regulation, with more attention as a novel oncogene in various cancers. High level of SPAG5 expression has been detected in our clinical gastric cancer (GC) samples and The Cancer Genome Atlas GC data. However, the bio-function and potential mechanism of SPAG5 in GC remain unclear. In this study, we investigated the role of SPAG5 in GC development and the correlation between SPAG5 and 5-fluorouracil (5-FU) treatment. SPAG5 expression was increased in GC samples compared with that in normal tissues (80.8% vs. 22.0%), which was apparently associated with a worse outcome. Biological experiments showed that knockdown of SPAG5 induced apoptosis and suppressed proliferation in cells and animal models. Downregulation of SPAG5 enhanced the sensitivity of 5-FU in GC cells. Gene microarray chip identified 856 upregulated and 787 downregulated genes in SPAG5 silencing cells. Furthermore, 12 significant genes, including CDKN1A, CDKN1B, EIF4E, MAPK1, and HSP90B1, belonged to the PI3K/AKT signaling pathway using ingenuity pathway analysis. Meanwhile, real-time PCR and Western blotting results showed that knockdown of SPAG5 inhibited PI3K/AKT signaling pathway. Collectively, SPAG5 promotes the growth of GC cells by regulating PI3K/AKT signaling pathway, which could be the promising target gene in GC therapy.

SPAG5 as a novel biomarker and potential therapeutic target via regulating AKT pathway in multiple myeloma

SPAG5, as a spindle-associated protein in mitosis, has been observed to have oncogenic activities in solid tumors. Here, we identified that SPAG5 expression was correlated with the deterioration of plasma cell malignancy and SPAG5 overexpression (OE) predicted unfavorable outcomes in multiple myeloma (MM). SPAG5 knockdown led to anti-MM effects in MM cell lines and animal xenograft models by regulating cell growth and apoptosis. Furthermore, gene set enrichment analysis (GSEA) revealed that PI3K/AKT/mTOR pathway was enriched in MM samples with highly expressed SPAG5 from GSE datasets. There was a concurrent downregulation of phosphorylation levels in the AKT/mTOR pathway. Yet OE of SPAG5 could restore the cell growth and p-AKT levels in MM cells after treatment with the AKT inhibitor MK2206. Taken together, SPAG5 could serve as a novel biomarker, and targeting the SPAG5 might have therapeutic potential in MM.

The interactome of CLUH reveals its association to SPAG5 and its co-translational proximity to mitochondrial proteins

BACKGROUND

Mitochondria require thousands of proteins to fulfill their essential function in energy production and other fundamental biological processes. These proteins are mostly encoded by the nuclear genome, translated in the cytoplasm before being imported into the organelle. RNA binding proteins (RBPs) are central players in the regulation of this process by affecting mRNA translation, stability, or localization. CLUH is an RBP recognizing specifically mRNAs coding for mitochondrial proteins, but its precise molecular function and interacting partners remain undiscovered in mammals.

RESULTS

Here we reveal for the first time CLUH interactome in mammalian cells. Using both co-IP and BioID proximity-labeling approaches, we identify novel molecular partners interacting stably or transiently with CLUH in HCT116 cells and mouse embryonic stem cells. We reveal stable RNA-independent interactions of CLUH with itself and with SPAG5 in cytosolic granular structures. More importantly, we uncover an unexpected proximity of CLUH to mitochondrial proteins and their cognate mRNAs in the cytosol. We show that this interaction occurs during the process of active translation and is dependent on CLUH TPR domain.

CONCLUSIONS

Overall, through the analysis of CLUH interactome, our study sheds a new light on CLUH molecular function by revealing new partners and by highlighting its link to the translation and subcellular localization of some mRNAs coding for mitochondrial proteins.

SPAG5 Is Involved in Human Gliomagenesis Through the Regulation of Cell Proliferation and Apoptosis

Background

Glioma is the most frequent malignant primary brain tumor in adults.

Objective

To explore the role of sperm-associated antigen 5 (SPAG5) in glioma.

Methods

The association between SPAG5 expression and clinical features was investigated based on The Cancer Genome Atlas (TCGA) datasets. The function of SPAG5 in glioma was analyzed using U87 and U251 cells. Knockdown glioma cells were constructed by shRNA interference. qRT-PCR and Western blotting were used to measure the expression of SPAG5 and Cadherin 2 (CDH2). Cell proliferation and apoptosis were measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, caspase 3/7 assay, and high-content screening (HCS) proliferation analysis and colony formation assay. Transwell assays and wound-healing assays were used to investigate cell migration and invasion.

Results

The increased expression of SPAG5 was correlated with poor outcomes in glioma patients. Knocking down SPAG5 could inhibit the proliferation and colony formation and promoted the apoptosis of glioma cells. Knocking down SPAG5 could also inhibit cell migration and invasion and the expression of CDH2. Overexpression of CDH2 with SPAG5 depletion could restore the proliferation and inhibit the apoptosis of glioma cells, which also promoted cell migration and invasion.

Conclusions

SPAG5 is a promising prognostic factor and potential therapeutic target for clinical intervention in glioma.

MiR-133a-3p attenuates resistance of non-small cell lung cancer cells to gefitinib by targeting SPAG5

Background

Gefitinib is an epidermal growth factor receptor tyrosine kinase inhibitor (EGFR‐TKI), clinically used to treat patients with non‐small cell lung cancer driven by EGFR mutations. Unfortunately, EGFR‐TKI resistance has become a clinical problem for the effective treatment of NSCLC patients. The purpose of this study was to explore the effect and mechanism of miR‐133a‐3p on the gefitinib sensitivity of NSCLC cells.

Methods

The gefitinib‐resistant PC9 (PC9/GR) cells were established through repeated long‐term exposure to gefitinib for half a year. Then, PC9/GR cells were transfected with miR‐133a‐3p mimics and PC9 cells were transfected with miR‐133a‐3p inhibitors to increase or decrease the expression of miR‐133a‐3p. CCK‐8 assay, colony formation assay, and caspase‐3 activity assay were employed to detect cell resistance to gefitinib. Quantitative real‐time PCR and Western blotting were used to evaluate the levels of miR‐133a‐3p, SPAG5, and other related genes. Starbase database was used to predict the target gene of miR‐133a‐3p and the prognosis of NSCLC patients. Target gene of miR‐133a‐3p was verified through dual‐luciferase reporter gene assay.

Results

MiR‐133a‐3p was significantly downregulated in gefitinib‐resistant cell line PC9/GR vs. gefitinib‐sensitive cell line PC9. Overexpression of miR‐133a‐3p increased the sensitivity of NSCLC cells to gefitinib and vice versa. Furthermore, SPAG5 is an important target gene of miR‐133a‐3p, and SPAG5 can reverse miR‐133a‐3p‐mediated gefitinib sensitivity of NSCLC cells.

Conclusions

These findings indicated that miR‐133a‐3p/SPAG5 axis played a vital role in acquired resistance to gefitinib in NSCLC cells, and miR‐133a‐3p may represent a potential therapeutic strategy for the treatment of human NSCLC.

High expression of sperm-associated antigen 5 correlates with poor survival in ovarian cancer

OBJECTIVES

Sperm-associated antigen 5 (SPAG5), a spindle-binding protein, regulates the process of mitosis. The present study focused on the relationship between SPAG5 expression and the clinicopathological characteristics and prognosis of ovarian cancer.

METHODS

First, we used the Gene Expression Omnibus (GEO) database to analyze SPAG5 expression in ovarian cancer and its clinical relevance. Subsequently, qPCR test was used to detect SPAG5 mRNA expression in 20 cases of ovarian cancer. The expression of SPAG5 protein in a tissue microarray containing 102 cases of ovarian cancer was detected by immunohistochemistry. Cox regression and Kaplan-Meier survival analyses were performed to identify the prognostic factors for the 102 ovarian cancer patients.

RESULTS

In the GEO datasets, SPAG5 mRNA expression was significantly higher in ovarian cancer tissues than that in normal ovarian tissues (P < 0.001). qPCR and immunohistochemistry showed that SPAG5 expression in ovarian cancer tissues was significantly higher than that in paracancerous tissues (P = 0.002, P < 0.001). The high expression of SPAG5 in ovarian cancer was correlated with histological type (P = 0.009), lymph node metastasis (P = 0.001), distant metastasis (P = 0.001), TNM stage (P = 0.001), and prognosis (P = 0.001). The Kaplan-Meier curve indicated that rates of disease-free survival (DFS) and overall survival (OS) were even lower in patients with high SPAG5 expression. Multivariate analysis showed that SPAG5 expression (P = 0.001) and TNM staging (P = 0.002) were independent prognostic factors for the DFS of ovarian cancer.

CONCLUSIONS

These results suggest that high SPAG5 expression was correlated with multiple clinicopathological features of ovarian cancer and can be used as an evaluation indicator for a poor ovarian cancer prognosis.

Investigation of the SPAG5 gene expression and amplification related to the NuMA mRNA levels in breast ductal carcinoma

Background

The cell proliferative markers are very important in breast cancer. Since SPAG5 and NuMA proteins play a significant role in the mitosis regulatory network and cell division, we aimed to study their mRNA levels as well as SPAG5 gene amplification correlated to clinicopathological status in ductal carcinoma of the breast.

Methods

SPAG5 and NuMA gene expressions were investigated in 40 breast cancer tissues and normal adjacent tissues via real-time PCR. PUM1 was selected as the reference gene. QMF PCR method was applied to study SPAG5 gene amplification and AGBL2, BOD1L, and POR were designated as internal control genes. Gene amplification was determined by calculating a dosage quotient for each DNA fragment.

Results

Increased SPAG5 mRNA expression was detected in breast cancer tissues (p = 0.005) and related to tumor size. No significant difference was observed between NuMA gene expression level in tumor tissue and the normal adjacent tissue (p = 0.56). However, we observed that NuMA expression was significantly increased in ER-positive tumor tissues. There was no clear correlation pattern between SPAG5 and NuMA mRNA levels (r = 0.33). Seventeen percent of tissues showed complete amplification in SPAG5 gene fragments.

Conclusion

Our results were consistent with the previous publications regarding SPAG5 gene expression and amplification in breast cancer with an emphasis on the prominent role of this protein in tumor pathogenesis. Our results failed to yield any correlation between SPAG5 and NuMA mRNA levels which implies independence of these genes in breast cancer pathogenesis.

SPAG5 promotes osteosarcoma metastasis via activation of FOXM1/MMP2 axis

Osteosarcoma (OS) is a primary malignancy of bone with a tendency to metastasize early. An understanding of the pathways that regulate OS metastasis is required for the design of novel treatment approaches. Sperm-associated antigen 5 (SPAG5) is upregulated and functions as a potential tumor promoter in diverse human cancers, but has yet to be investigated in the OS. In the present study, results showed that SPAG5 expression is upregulated in OS tissues, and SPAG5 overexpression is obviously associated with the malignant phenotype and poor survival in patients with OS. Multivariate analyses also revealed that SPAG5 overexpression is an independent prognostic factor for poor outcome of patients with OS. The functional assay indicated that SPAG5 silencing significantly inhibits the invasion and migration of OS cells in vitro. Additionally, knockdown of SPAG5 in OS cells suppresses lung metastasis in vivo. Further, we also found that SPAG5 silencing inhibits the epithelial-mesenchymal transition (EMT) process of OS cells. Moreover, our results indicated that SPAG5 promotes OS metastasis by increasing matrix metalloproteinase-2 (MMP2) expression, and demonstrated that MMP2 is crucial for the pro-metastasis role of SPAG5 in OS cells. Mechanistically, we identified that SPAG5 regulates MMP2 expression by modulating FOXM1 (Forkhead box M1) degradation to enhance the protein stability of FOXM1. Collectively, these findings describe the effects of SPAG5-FOXM1-MMP2 axis in the regulation of OS cell migration and metastasis formation. We provide a novel evidence that SPAG5 may serve as a prognostic indicator and potential therapeutic target for patients with osteosarcoma.

SPAG5: An Emerging Oncogene

Sperm-associated Antigen 5 (SPAG5) is a mitotic spindle protein. Recent studies have found that it is overexpressed in many human cancers and functions as an oncogene. Here, we summarize the current underlying mechanisms for its oncogenic roles in regulating cellular behaviors of cancer cells and discuss the possibility of targeting SPAG5 for cancer treatment.

SPAG5-AS1 inhibited autophagy and aggravated apoptosis of podocytes via SPAG5/AKT/mTOR pathway

Objectives

Podocyte injury is a prediction marker of diabetic nephropathy (DN), and AKT/mTOR pathway–mediated inhibition of autophagy is widely reported to contribute to podocyte damage. Recent study stated that sperm‐associated antigen 5 (SPAG5) activated AKT/mTOR signalling in bladder urothelial carcinoma, indicating SPAG5 might regulate autophagy and play a role in podocyte damage.

Materials and methods

Apoptosis and autophagy of human podocytes (HPCs) were detected by flow cytometry and immunofluorescence (IF). Gene level was assessed by Western blot and RT‐qPCR. Molecular interactions were determined by pulldown, RNA immunoprecipitation (RIP), co‐immunoprecipitation (co‐IP), chromatin immunoprecipitation (ChIP) and luciferase reporter assays.

Results

SPAG5 mRNA and protein levels were upregulated under high glucose treatment in HPCs. Silencing SPAG5 reversed the increase of apoptosis and decrease of autophagy in high glucose–treated HPCs. Later, we found a long non‐coding RNA (lncRNA) SPAG5 antisense RNA1 (SPAG5‐AS1) as a neighbour gene to SPAG5. Mechanistically, YY1 transcriptionally upregulated SPAG5‐AS1 and SPAG5 in high glucose–treated podocytes. SPAG5‐AS1 acted as a competitive endogenous RNA (ceRNA) to regulate miR‐769‐5p/YY1 axis and induce SPAG5. SPAG5‐AS1 interacted with ubiquitin‐specific peptidase 14 (USP14) and leads to de‐ubiquitination and stabilization of SPAG5 protein.

Conclusions

This study revealed that SPAG5‐AS1 inhibited autophagy and aggravated apoptosis of podocytes via SPAG5/AKT/mTOR pathway, indicating SPAG5‐AS1/SPAG5 as a potential target for the alleviation of podocyte injury and offering new thoughts for the treatments of DN.

MicroRNA-367-3p overexpression represses the proliferation and invasion of cervical cancer cells through downregulation of SPAG5-mediated Wnt/β-catenin signalling

MicroRNA-367-3p (miR-367-3p) has been previously reported as a cancer-related miRNA that is dysregulated in various cancer types and functions either as an oncogenic or as tumour suppressive miRNA. However, whether miR-367-3p is dysregulated in cervical cancer and, further, whether it contributes to the development and progression of the disease remains unknown. Here, our results demonstrated that miR-367-3p expression was markedly decreased in both cervical cancer tissues and cell lines compared with corresponding controls. In vitro experiments revealed that miR-367-3p overexpression repressed the proliferation and invasion of cervical cancer cells. Notably, sperm-associated antigen 5 (SPAG5) was identified as a target gene of miR-367-3p. Moreover, decreased expression of miR-367-3p was correlated with high expression of SPAG5 in cervical cancer tissue specimens. SPAG5 inhibition or miR-367-3p overexpression significantly downregulated Wnt/β-catenin signalling in cervical cancer cells. However, the antitumour effect mediated by miR-367-3p overexpression was partially reversed by SPAG5 overexpression. Overall, these findings demonstrate that miR-367-3p overexpression restricts the proliferation and invasion of cervical cancer cells through targeting SPAG5 to downregulate Wnt/β-catenin signalling, suggesting a mechanism for the tumour suppressive function of miR-367-3p in cervical cancer. Our study highlights the involvement of miR-367-3p/SPAG5/Wnt/β-catenin signalling axis in regulating the malignant progression of cervical cancer.

The prognostic association of SPAG5 gene expression in breast cancer patients with systematic therapy

Background

Despite much effort on the treatment of breast cancer over the decades, a great uncertainty regarding the appropriate molecular biomarkers and optimal therapeutic strategy still exists. This research was performed to analyze the association of SPAG5 gene expression with clinicopathological factors and survival outcomes.

Methods

We used a breast cancer database including 5667 patients with a mean follow-up of 69 months. Kaplan-Meier survival analyses for relapse free survival (RFS), overall survival (OS), and distant metastasis-free survival (DMFS) were performed. In addition, ROC analysis was performed to validate SPAG5 as a prognostic candidate gene.

Results

Mean SPAG5 expression value was significantly higher with some clinicopathological factors that resulted in tumor promotion and progression, including poor differentiated type, HER2 positive or TP53 mutated breast cancer. Based on ROC-analysis SPAG 5 is a suitable prognostic marker of poor survival. In patients who received chemotherapy alone, SPAG5 had only a moderate and not significant predictive impact on survival outcomes. However, in hormonal therapy, high SPAG5 expression could strongly predict prognosis with detrimental RFS (HR = 1.57, 95% CI 1.2–2.06, p = 0.001), OS (HR = 2, 95% CI 1.05–3.8, p = 0.03) and DMFS (HR = 2.36, 95% CI 1.57–3.54, p <  0.001), respectively. In addition, SPAG5 could only serve as a survival predictor in ER+, but not ER- breast cancer patients. Patients might also be at an increased risk of relapse despite being diagnosed with a lower grade cancer (well differentiated type).

Conclusions

SPAG5 could be used as an independent prognostic and predictive biomarker that might have clinical utility, especially in ER+ breast cancer patients who received hormonal therapy.

p53 suppression is essential for oncogenic SPAG5 upregulation in lung adenocarcinoma

Aberrant expression of sperm-associated antigen 5 (SPAG5) is implicated to play oncogenic roles in several types of cancers. However, the functions of SPAG5 in lung adenocarcinoma remain unclear. In this study, we investigated the role of SPAG5 in lung adenocarcinoma. We found that SPAG5 was upregulated in most of the lung adenocarcinoma cell lines as compared to normal lung epithelial cells. SPAG5 knockdown suppressed proliferation, colony forming, and migration of lung adenocarcinoma A549 cells in vitro and inhibited tumor growth in vivo. These suggest that upregulated SPAG5 promotes lung tumor progression. Importantly, treatment with MDM2 inhibitor, Nutlin-3a, restored p53 and p21 expression and suppressed SPAG5 expression in wild-type p53 lung adenocarcinoma cells, A549 and H460, but not in p53-null lung cancer cells, H1299. This suggests that the p53 signal pathway is essential for SPAG5 suppression. In addition, knocking-down p53 or p21 in A549 and H460 cells attenuated Nutlin-3a-induced repression of SPAG5, which further supports that the p53-p21 axis is required for SPAG5 repression. Thus, SPAG5 can serve as a prognostic marker, and therapeutic strategy targeting the p53-p21-SPAG5 axis may have important clinical implications.

SPAG5 contributes to the progression of gastric cancer by upregulation of Survivin depend on activating the wnt/β-catenin pathway

The sperm-associated antigen 5 (SPAG5) plays a key role in controlling cellular processes, including cell cycle progression and proliferation. However, the role of SPAG5 in gastric cancer (GC) remains unclear. Herein, our study showed that upregulation of SPAG5 was detected frequently in GC tissues, and was associated with significantly worse survival in patients with GC. Multivariate analyses revealed that high SPAG5 expression was an independent predictive marker for the poor prognosis of GC patients. Further, SPAG5 knockdown notably inhibited the proliferation abilities of GC in vivo and in vitro. Moreover, our results indicate that SPAG5 promotes cell progression by increasing Survivin expression, which has been reported to control the progression of GC. Moreover, our data demonstrate that Survivin is crucial for SPAG5-mediated GC cell progression in vitro and in vivo. Mechanistically, we demonstrated that SPAG5 promotes the progression of GC via enhancing the Wnt/β-catenin/Survivin axis. Collectively, our data suggest that SPAG5 plays a crucial oncogenic role in GC tumorigenesis, and we provide a novel evidence that SPAG5 may be serve as a prognostic and therapeutic target for GC patients.

SPAG5 upregulation contributes to enhanced c-MYC transcriptional activity via interaction with c-MYC binding protein in triple-negative breast cancer

BACKGROUND

Triple-negative breast cancer (TNBC) is an aggressive breast cancer subtype that lacks effective therapeutic targets. Sperm-associated antigen 5 (SPAG5) is a mitotic spindle-associated protein that is involved in various biological processes in cervical cancer and bladder urothelial carcinoma. However, the role of SPAG5 in TNBC remains undefined.

METHODS

The expression of SPAG5 was examined in TNBC patients via quantitative real-time polymerase chain reaction (qRT-PCR), western blotting, and immunohistochemistry (IHC). The biological functions of SPAG5 in TNBC and the underlying mechanisms were investigated in vitro and in vivo.

RESULTS

SPAG5 expression was significantly upregulated in TNBC tissues compared with that in paired adjacent noncancerous tissues (ANTs). High SPAG5 expression was associated with increased lymph node metastasis and high risk of local recurrence. SPAG5 protein expression was significantly associated with poor disease-free survival in TNBC. Gene set enrichment analysis of TNBC data from The Cancer Genome Atlas (TCGA) indicated that high SPAG5 expression was significantly associated with cell cycle and the ATR-BRCA pathway. Functional assays demonstrated that SPAG5 expression promoted tumor growth in vitro and in vivo. In addition, SPAG5-silenced cells were more sensitive to the PARP inhibitor (PARPi) olaparib. Mechanistically, SPAG5 interacted with c-MYC binding protein (MYCBP), thereby increasing MYCBP protein levels and leading to increased c-MYC transcriptional activity, which promoted the expression of the c-MYC target genes: CDC20, CDC25C, BRCA1, BRCA2, and RAD51.Knockdown of MYCBP or c-MYC abolished the SPAG5-induced cell-cycle progression and cell proliferation of TNBC.

CONCLUSIONS

Collectively, our results indict that SPAG5 is an efficient prognostic factor in TNBC, and that SPAG5 knockdown increases the sensitivity of TNBC to the PARPi olaparib. SPAG5 promotes tumor growth and DNA repair by increasing c-MYC transcriptional activity via interaction with MYCBP. The SPAG5/MYCBP/c-MYC axis may represent a potential therapeutic target for TNBC treatment.

SPAG5 promotes hepatocellular carcinoma progression by downregulating SCARA5 through modifying β-catenin degradation

BACKGROUND

The sperm-associated antigen 5 (SPAG5) plays a key role in controlling various cellular phenomena, including cell cycle progression and proliferation. However, the role of SPAG5 in hepatocellular carcinoma (HCC) remains unknown.

METHODS

This study investigated the function and clinical significance of SPAG5 protein expression in hepatocellular carcinoma. We analyzed SPAG5 expression in surgical specimens from 136 HCC patients. The correlation between the clinical characteristics and prognosis was also determined. Furthermore, the SPAG5 was overexpressed in HCC cell and silenced with shRNA in HCC cells. Moreover, cell proliferation and apoptosis were measured using Edu assay and flow cytometry and a molecular mechanism of SPAG5 promotes HCC progression was explored.

RESULTS

Herein, our study showed that upregulation of SPAG5 was detected frequently in primary HCC tissues, and was associated with significantly worse survival among the HCC patients. Multivariate analyses revealed that high SPAG5 expression was an independent predictive marker for the poor prognosis of HCC. SPAG5 silence effectively abolished the proliferation abilities of SPAG5 in vivo and in vitro, while induced apoptosis in HCC cells. Furthermore, our results indicate that SPAG5 promoted cell progression by decreasing SCARA5 expression, which has been reported to control the progression of HCC, and our data demonstrated that SCARA5 is crucial for SPAG5-mediated HCC cell progression in vitro and in vivo. Moreover, we found that the expression of SPAG5 and SCARA5 are inversely correlated in HCC tissues. In addition, we demonstrated that SPAG5 promoted progression in HCC via downregulating SCARA5 depended on the β-catenin/TCF4 signaling pathway. Interestingly, the underlying mechanism is which SPAG5 regulates SCARA5 expression by modulating β-catenin degradation.

CONCLUSIONS

Taken together, our data provide a novel evidence for the biological and clinical significance of SPAG5 as a potential biomarker, and we demonstrate that SPAG5-β-catenin-SCARA5 might be a novel pathway involved in HCC progression.

MicroRNA-1179 suppresses cell growth and invasion by targeting sperm-associated antigen 5-mediated Akt signaling in human non-small cell lung cancer

Accumulating evidence has identified microRNA-1179 (miR-1179) as a novel cancer-related miRNA that is dysregulated in multiple cancers and plays an important role in regulating cancer development and progression. However, little is known about the role of miR-1179 in non-small cell lung cancer (NSCLC). Thus, in the present study, we aimed to investigate the potential biological function and regulatory mechanism of miR-1179 in NSCLC. The results showed that decreased expression of miR-1179 expression was frequently detected in primary NSCLC tissues and cell lines. Overexpression of miR-1179 suppressed the growth and invasion of NSCLC cells in vitro while its inhibition promoted the opposite effect. Sperm-associated antigen 5 (SPAG5) was an identified as a target gene of miR-1179. Moreover, SPAG5 expression was increased in NSCLC cells and showed an inverse correlation with miR-1179 in NSCLC specimens. SPAG5 knockdown inhibited the growth and invasion of NSCLC cells, results that simulated a similar effect to miR-1179 overexpression. Mechanistic investigations showed that miR-1179 overexpression or SPAG5 knockdown significantly downregulated the activation of Akt signaling. Additionally, SPAG5 overexpression partially reversed the antitumor effect of miR-1179. Overall, our results demonstrated that miR-1179 inhibited the growth and invasion of NSCLC cells by targeting SPAG5 and inhibiting Akt, findings that highlight the importance of the miR-1179/SPAG5/Akt axis in the progression of NSCCL.

SPAG5 interacts with CEP55 and exerts oncogenic activities via PI3K/AKT pathway in hepatocellular carcinoma

Background

Deregulation of microtubules and centrosome integrity is response for the initiation and progression of human cancers. Sperm-associated antigen 5 (SPAG5) is essential for the spindle apparatus organization and chromosome segregation, but its role in hepatocellular carcinoma (HCC) remains undefined.

Methods

The expression of SPAG5 in HCC were examined in a large cohort of patients by RT-PCR, western blot and IHC. The clinical significance of SPAG5 was next determined by statistical analyses. The biological function of SPAG5 in HCC and the underlying mechanisms were investigated, using in vitro and in vivo models.

Results

Here, we demonstrated that SPAG5 exhibited pro-HCC activities via the activation of PI3K/AKT signaling pathway. SPAG5 expression was increased in HCC and correlated with poor outcomes in two independent cohorts containing 670 patients. High SPAG5 expression was associated with poor tumor differentiation, larger tumor size, advanced TNM stage, tumor vascular invasion and lymph node metastasis. In vitro and in vivo data showed that SPAG5 overexpression promoted tumor growth and metastasis, whereas SPAG5 knockdown led to the opposite phenotypes. SPAG5 interacted with centrosomal protein CEP55 to trigger the phosphorylation of AKT at Ser473. Inhibition of PI3K/AKT signaling markedly attenuated SPAG5-mediated cell growth. Furthermore, SPAG5 expression was suppressed by miR-363-3p which inhibited the activity of SPAG5 mRNA 3’UTR. Ectopic expression of SPAG5 partly abolished the miR-363-3p-caused cell cycle arrest and suppression of cell proliferation and migration.

Conclusions

Collectively, these findings indicate that SPAG5 serves a promising prognostic factor in HCC and functions as an oncogene via CEP55-mediated PI3K/AKT pathway. The newly identified miR-363-3p/SPAG5/CEP55 axis may represent a potential therapeutic target for the clinical intervention of HCC.

Electronic supplementary material

The online version of this article (10.1186/s12943-018-0872-3) contains supplementary material, which is available to authorized users.

miR-539 inhibits prostate cancer progression by directly targeting SPAG5

Background

We conducted multiple microarray datasets analyses from clinical and xenograft tumor tissues to search for disease progression-driving oncogenes in prostate cancer (PCa). Sperm-associated antigen 5 (SPAG5) attracted our attention. SPAG5 was recently identified as an oncogene participating in lung cancer and cervical cancer progression. However, the roles of SPAG5 in PCa progression remain unknown.

Methods

SPAG5 expression level in clinical primary PCa, metastatic PCa, castration resistant PCa, neuroendocrine PCa, and normal prostate tissues was investigated. We established multiple in vivo xenografts models using patient-derived tissues and investigated SPAG5 expression trend in these models. We also investigated the functions of SPAG5 in vivo and in vitro studies. Luciferase reporter assays were performed to investigate potential miRNAs that can regulate SPAG5.

Results

We identified that SPAG5 expression was gradually increased in PCa progression and its level was significantly associated with lymph node metastasis, clinical stage, Gleason score, and biochemical recurrence. Our results indicated that SPAG5 knockdown can drastically inhibit PCa cell proliferation, migration, and invasion in vitro and supress tumor growth and metastasis in vivo. We identified that miR-539 can directly target SPAG5. Ectopic overexpression of miR-539 can drastically inhibit SPAG5 expression and the restoration of SPAG5 expression can reverse the inhibitory effects of miR-539 on PCa cell proliferation and metastasis.

Conclusion

Our results collectively showed a progression-driving role of SPAG5 in PCa which can be regulated by miR-539, suggesting that miR-539/SPAG5 can serve as a potential therapeutic target for PCa.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-016-0337-8) contains supplementary material, which is available to authorized users.

OSBP-related protein 8 (ORP8) interacts with Homo sapiens sperm associated antigen 5 (SPAG5) and mediates oxysterol interference of HepG2 cell cycle

We earlier identified OSBP-related protein 8 (ORP8) as an endoplasmic reticulum/nuclear envelope oxysterol-binding protein implicated in cellular lipid homeostasis, migration, and organization of the microtubule cytoskeleton. Here, a yeast two-hybrid screen identified Homo sapiens sperm associated antigen 5 (SPAG5)/Astrin as interaction partner of ORP8. The putative interaction was further confirmed by pull-down and co-immunoprecipitation assays. ORP8 did not colocalize with kinetochore-associated SPAG5 in mitotic HepG2 or HuH7 cells, but overexpressed ORP8 was capable of recruiting SPAG5 onto endoplasmic reticulum membranes in interphase cells. In our experiments, 25-hydroxycholesterol (25OHC) retarded the HepG2 cell cycle, causing accumulation in G2/M phase; ORP8 overexpression resulted in the same phenotype. Importantly, ORP8 knock-down dramatically inhibited the oxysterol effect on HepG2 cell cycle, suggesting a mediating role of ORP8. Furthermore, knock-down of SPAG5 significantly reduced the effects of both ORP8 overexpression and 25OHC on the cell cycle, placing SPAG5 downstream of the two cell-cycle interfering factors. Taken together, the present results suggest that ORP8 may via SPAG5 mediate oxysterol interference of the HepG2 cell cycle.