Up-Regulation of Follistatin-Like 1 By the Androgen Receptor and Melanoma Antigen-A11 in Prostate Cancer

FSTL1: A double-edged sword in cancer development

Flolistatin-related protein 1 (FSTL1), a secreted glycoprotein that is involved in many physiological functions, has attracted much interest and has been implicated in a wide range of diseases, including heart diseases and inflammatory diseases. In recent years, the involvement of FSTL1 in cancer progression has been implicated and researched. FSTL1 plays a contradictory role in cancer, depending on the cancer type as well as the contents of the tumor microenvironment. As reviewed here, the structure and distribution of FSTL1 are first introduced. Subsequently, the expression and clinical significance of FSTL1 in various types of cancer as a tumor enhancer or inhibitor are addressed. Furthermore, we discuss the functional role of FSTL1 in various processes that involve tumor cell proliferation, metastasis, immune responses, stemness, cell apoptosis, and resistance to chemotherapy. FSTL1 expression is tightly controlled in cancer, and a multitude of cancer-related signaling cascades like TGF-β/BMP/Smad signaling, AKT, NF-κB, and Wnt-β-catenin signaling pathways are modulated by FSTL1. Finally, FSTL1 as a therapeutic target using monoclonal antibodies is stated. Herein, we review recent findings showing the double-edged characteristics and mechanisms of FSTL1 in cancer and elaborate on the current understanding of therapeutic approaches targeting FSTL1.

Circ_TLK1 knockdown alleviates oxygen-glucose deprivation/reoxygenation-induced PC12 cell injury by regulating microRNA-136-5p/follistatin like-1 axis

BACKGROUND

Circular RNAs (circRNAs) are aberrantly expressed in the central nervous system (CNS) and are involved in diverse CNS diseases. However, the functions of circRNAs in ischemic stroke (IS) are largely unknown. In this study, we aimed to explore the effect of circ_TLK1 in oxygen-glucose deprivation/reoxygenation (OGD/R)-induced PC12 cell injury.

METHODS

Quantitative real-time polymerase chain reaction (qRT-PCR) was performed for the levels of circ_TLK1, TLK1, microRNA-136-5p (miR-136-5p), and follistatin like-1 (FSTL1). RNase R and Actinomycin D assays were conducted to analyze the features of circ_TLK1. 3-(4, 5-ethynyl-2'-deoxyuridine [EdU] assay and 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide (MTT) assay were adopted to analyze cell proliferation capacity. Flow cytometry analysis was applied to determine cell death. Western blot assay was employed to measure protein levels. The release of lactate dehydrogenase (LDH) was measured with specific kits. The interaction between circ_TLK1 and miR-136-5p, as well as miR-136-5p and FSTL1, was verified by Dual-luciferase reporter assay.

RESULTS

Circ_TLK1 was upregulated in OGD/R-injured PC12 cells. OGD/R treatment inhibited cell proliferation, promoted cell death, and increased LDH release in PC12 cells, while circ_TLK1 knockdown partially alleviated OGD/R-induced PC12 cell injury. Circ_TLK1 directly bound to miR-136-5p and miR-136-5p inhibition reversed the effect of circ_TLK1 knockdown on OGD/R-induced PC12 cell damage. Moreover, FSTL1 was targeted by miR-136-5p. MiR-136-5p upregulation inhibited PC12 cell injury induced by OGD/R, while FSTL1 overexpression partially reversed the effect.

CONCLUSION

Circ_TLK1 knockdown ameliorated OGD/R-induced PC12 cell injury by modulating miR-136-5p and FSTL1, which might provide a new understanding of IS treatment.

FSTL1 increases cisplatin sensitivity in epithelial ovarian cancer cells by inhibition of NF-κB pathway

OBJECTIVE

To investigate the effects of FSTL1-mediated NF-κB signaling pathway on cisplatin (DDP) sensitivity of EOC cells.

METHODS

FSTL1 expression was determined in epithelial ovarian cancer (EOC) tissues and corresponding adjacent tissues using immunohistochemistry. SKOV3 and SKOV3/DDP cells were transfected and grouped into Blank, Vector, and FSTL1 groups. The sensitivity and 50% inhibitory concentration (IC50) of cells treated with different concentrations of DDP were detected by MTT assay. SKOV3/DDP cells were treated with 20 μM DDP, followed by evaluation of cell proliferation, cell apoptosis and determination of NF-κB pathway-related proteins while SKOV3 cells without.

RESULTS

FSTL1 expression in EOC tissues and cells was significantly down-regulated, especially decreased in DDP-resistant EOC cells SKOV3/DDP. In SKOV3 cells and SKOV3/DDP cells, the cell viability was reduced and the DDP sensitivity was improved with the decreased IC50 after over-expressing FSTL1. Compared with Blank group, FSTL1 group had declined number of SKOV3 cell colonies and increased cell apoptosis, with obvious up-regulations of FSTL1, Bax/Bcl-2 and cleaved caspase-3 expression and the down-regulations of p-IκBα, p-p65 and survivin expression. Combination of up-regulation of FSTL1 and DDP treatment can also effectively reduce cell colony forming, increase cell apoptosis, and inhibit NF-κB pathway activity of SKOV3/DDP cells. Moreover, this combination can also significantly suppress the growth of subcutaneous xenograft tumors in nude mice.

CONCLUSION

FSTL1 may inhibit NF-κB signaling pathway to suppress the growth and promote the apoptosis of epithelial ovarian cancer cells, and thereby enhancing its DDP sensitivity.

Reduced cytoplasmic expression of MAGE-A2 predicts tumor aggressiveness and survival: an immunohistochemical analysis

BACKGROUND

Melanoma antigen gene A2 (MAGE-A2) is one of the most cancer-testis antigens overexpressed in various types of cancers. Silencing the MAGE-A2 expression inhibited the proliferation of prostate cancer (PCa) cells and increased the chemosensitivity. However, the expression pattern of MAGE-A2 in PCa tissue samples and its prognostic and therapeutic values for PCa patients is still unclear.

METHODS

In this study, for the first time, the staining pattern and clinical significance of MAGE-A2 were evaluated in 166 paraffin-embedded prostate tissues, including 148 cases of PCa and 18 cases of high-grade prostatic intraepithelial neoplasia (HPIN), by immunohistochemical analysis.

RESULTS

The simultaneous expression of both nuclear and cytoplasmic patterns of MAGE-A2 with different staining intensities was observed among studied cases. Increased expression of MAGE-A2 was significantly found in PCa tissues compared to HPIN cases (P < 0.0001). Among PCa samples, the strong staining intensity of nuclear expression was predominantly observed in comparison with cytoplasmic expression in PCa tissues (P < 0.0001). A significant and inverse correlation was found between the cytoplasmic expression of MAGE-A2 and increased Gleason score (P = 0.002). Increased cytoplasmic expression of MAGE-A2 was associated with longer biochemical recurrence-free survival (BCR-FS) and disease-free survival (DFS) of patients (P = 0.002, P = 0.001, respectively). In multivariate analysis, Gleason score and cytoplasmic expression of MAGE-A2 were independent predictors of the BCR-FS (P = 0.014; P = 0.028, respectively).

CONCLUSIONS

Taken together, cytoplasmic expression of MAGE-A2 was inversely proportional to the malignant grade and duration of recurrence of the disease in patients with PCa.

MAGE-A11 Expression Predicts Patient Prognosis in Head and Neck Squamous Cell Carcinoma

Background

Head and neck squamous cell carcinomas (HNSCCs) are the sixth most common cancer worldwide. Growing evidence showed that Melanoma-associated antigen-A11 (MAGE-A11) was abnormally expressed in various malignancies, but MAGE-A11 expression and its biological roles in HNSCC had not been reported in detail. The aim of the study was to investigate the association between MAGE-A11 signatures and clinicopathological features of HNSCC patients and uncover its potential mechanisms in HNSCC patients.

Methods

In the present study, we analyzed the expression of MAGE-A11 gene and evaluated the impact of MAGE-A11 genes expression on clinical outcome from the Cancer Genome Atlas (TCGA) database. MAGE-A11 expression was assessed in a well-characterized series of HNSCC (N = 75) with long-term follow-up and 10 cases of adjacent non-cancerous tissues, which were diagnosed between 2013 and 2014, by using immunohistochemistry. The correlation between MAGE-A11 expression and clinicopathological factors was analyzed. Kaplan-Meier and Cox regression analyses were used to assess the prognostic significance of MAGE-A11 expression among HNSCC patients.

Results

The results showed that MAGE-A11 mRNA expression was increased in HNSCC tissues compared to "normal" tissues (P < 10^-12). MAGE-A11 protein expression was not correlated with lymph node status, relapse, age, gender, histological grade, differentiation, clinical stage, tumor size, radiotherapy or chemotherapy. The patients with high MAGE-A11 expression had lower 5-year overall survival (OS) rates than those with low MAGE-A11 expression as determined using the Kaplan-Meier method. The univariate and multivariate analyses confirmed that elevated MAGE-A11 was an independent prognostic factor for the OS of HNSCC patients.

Conclusion

These findings indicate that MAGE-A11 may be a valuable diagnostic or prognostic marker as well as a potential molecular therapy target for HNSCC patients.

Determination of follistatin-like protein 1 expression in colorectal cancer and its association with clinical outcomes

Background

Follistatin-like protein 1 (FSTL1) has been demonstrated to play a controversial role in cancer. In this study, we aimed to investigate the expression of FSTL1 and its characteristics in patients with colorectal cancer (CRC).

Methods

Gene expression microarray assays in 30 CRC patients and a real-time quantitative polymerase chain reaction (RT-qPCR) of 22 patients were performed to compare the mRNA level of FSTL1 in tumor lesions and paired normal tissues. Also, 332 consecutive patients with pathologically confirmed CRC were selected to detect FSTL1 expression by using immunohistochemistry (IHC). Enzyme-linked immunosorbent assay (ELISA) was also applied to determine the serum level of FSTL1 in 60 CRC patients, as well as 34 healthy donors.

Results

Gene expression microarray assays and RT-qPCR in CRC tissues, as well as ELISA in the serum all, revealed that the expression level of FSTL1 was higher in cancer tissue of CRC patients compared with paired normal tissue or healthy donors. The IHC results suggested that FSTL1 was also higher in tumor tissues than in its normal counterparts, however interestingly, a narrow scan focusing on the stromal region indicated that FSTL1 was significantly higher in normal tissues than in cancerous tissues. Besides, higher FSTL1 expression in cancer tissue, as well as lower FSTL1 expression in cancer stroma, both correlated with a worse prognosis, and the latter was an independent prognostic factor.

Conclusions

Our results provide novel insight into the role of FSTL1 in CRC, and it might be an essential factor in CRC development.

Application of Prostate Cancer Models for Preclinical Study: Advantages and Limitations of Cell Lines, Patient-Derived Xenografts, and Three-Dimensional Culture of Patient-Derived Cells

Various preclinical models have been developed to clarify the pathophysiology of prostate cancer (PCa). Traditional PCa cell lines from clinical metastatic lesions, as exemplified by DU-145, PC-3, and LNCaP cells, are useful tools to define mechanisms underlying tumorigenesis and drug resistance. Cell line-based experiments, however, have limitations for preclinical studies because those cells are basically adapted to 2-dimensional monolayer culture conditions, in which the majority of primary PCa cells cannot survive. Recent tissue engineering enables generation of PCa patient-derived xenografts (PDXs) from both primary and metastatic lesions. Compared with fresh PCa tissue transplantation in athymic mice, co-injection of PCa tissues with extracellular matrix in highly immunodeficient mice has remarkably improved the success rate of PDX generation. PDX models have advantages to appropriately recapitulate the molecular diversity, cellular heterogeneity, and histology of original patient tumors. In contrast to PDX models, patient-derived organoid and spheroid PCa models in 3-dimensional culture are more feasible tools for in vitro studies for retaining the characteristics of patient tumors. In this article, we review PCa preclinical model cell lines and their sublines, PDXs, and patient-derived organoid and spheroid models. These PCa models will be applied to the development of new strategies for cancer precision medicine.

Deficiency of Follistatin-Like Protein 1 Accelerates the Growth of Breast Cancer Cells at Lung Metastatic Sites

Purpose

Follistatin-like protein 1 (FSTL1) is a secreted glycoprotein that has been shown to play a role in various types of cancer. However, the clinical significance and function of FSTL1 in breast cancer have not been reported. We investigated the role of FSTL1 in breast cancer in this study.

Methods

Enzyme-linked immunosorbent assays, western blot analysis, and reverse transcription polymerase chain reaction were used to monitor the expression of FSTL1 in breast cancer tissue and in serum samples from breast cancer patients. We employed a 4T1 breast cancer model and Fstl1 ^+/- mice for in vivo studies. Hematoxylin and eosin staining, western blot analysis, and RNA sequencing were used to analyze the effect of FSTL1 on primary tumor growth and lung metastasis.

Results

We demonstrated that the expression of FSTL1 is reduced in both the breast cancer tissue and the serum of breast cancer patients. We showed that reduced levels of FSTL1 in serum correlate with elevated expression of Ki-67 and epidermal growth factor receptor (EGFR) in cancer tissues. Moreover, lowered expression of FSTL1 was associated with decreased survival in breast cancer patients. Experiments on the Fstl1 ^+/- mouse model established that FSTL1 deficiency had no effect on primary tumor growth, but increased the lung metastases of breast cancer cells, resulting in reduced survival of tumor-bearing mice. RNA sequencing found significantly reduced expression of Egln3 and increased expression of EGFR in Fstl1 ^+/- mice. Thus, our results suggest that FSTL1 may affect the expression of EGFR through Egln3, inhibiting the proliferation of breast cancer cells at lung metastatic sites.

Conclusion

In conclusion, we suggest a suppressor role of FSTL1 in breast cancer lung metastasis. Furthermore, FSTL1 may represent a potential prognostic biomarker and a candidate therapeutic target in breast cancer patients.

Follistatin-like 1 in development and human diseases

Follistatin-like 1 (FSTL1) is a secreted glycoprotein displaying expression changes during development and disease, among which cardiovascular disease, cancer, and arthritis. The cardioprotective role of FSTL1 has been intensively studied over the last years, though its mechanism of action remains elusive. FSTL1 is involved in multiple signaling pathways and biological processes, including vascularization and regulation of the immune response, a feature that complicates its study. Binding to the DIP2A, TLR4 and BMP receptors have been shown, but other molecular partners probably exist. During cancer progression and rheumatoid arthritis, controversial data have been reported with respect to the proliferative, apoptotic, migratory, and inflammatory effects of FSTL1. This controversy might reside in the extensive post-transcriptional regulation of FSTL1. The FSTL1 primary transcript also encodes for a microRNA (miR-198) in primates and multiple microRNA-binding sites are present in the 3'UTR. The switch between expression of the FSTL1 protein and miR-198 is an important regulator of tumour metastasis and wound healing. The glycosylation state of FSTL1 is a determinant of biological activity, in cardiomyocytes the glycosylated form promoting proliferation and the non-glycosylated working anti-apoptotic. Moreover, the glycosylation state shows differences between species and tissues which might underlie the differences observed in in vitro studies. Finally, regulation at the level of protein secretion has been described.

FSTL1 contributes to tumor progression via attenuating apoptosis in a AKT/GSK-3β - dependent manner in hepatocellular carcinoma

BACKGROUND

Several investigations have demonstrated that follistatin-like 1 (FSTL1) is implicated in the initiation and progression of diverse cancers. It remains unclear whether FSTL1 acted as a cancer-promoting gene through its overexpression in HCC.

PATIENTS AND METHODS

We detected FSTL1 protein expression in 210 consecutive HCC cases curatively resected in our hospital between 2004 and 2007. The correlation between FSTL1 expression in HCC tissues and post-surgical prognosis of HCCs was analyzed. The in vitro experiments including apoptosis assessment, MTT, BrdU incorporation ELISA assay, Western immunoblotting, and qRT-PCR were performed to determine the impact of FSTL1 on apoptosis and proliferation abilities of HCC cells and the relevant mechanisms.

RESULTS

FSTL1 protein was found aberrantly increased in 172 of 210 HCC tissues (81.9%) compared to adjacent liver tissues. FSTL1 overexpression was apparently associated with larger tumor size, advanced TNM staging, portal vein invasion, intra-hepatic metastases. Patients with higher FSTL1 expression in tumors suffered from the worse overall survival rate as assessed by comparison of Kaplan-Meier survival curves. Higher FSTL1 expression in HCC tissues was identified as a independent poor post-surgical prognostic predictor for HCC. Silencing FSTL1 by siRNA promoted cell apoptosis and leaded to suppression of cell viability and proliferation in MHCC97h cells. Furthermore, enforced expression of FSTL1 obtained the opposite results in Huh7 cells. Mechanistic investigation showed that FSTL1 repressed HCC cell apoptosis through AKT/GSK-3β/Bcl2/BAX/Bim signaling.

CONCLUSION

These data proved that FSTL1 contributed to unfavorable post-surgical outcome of HCC patients via inhibiting cell apoptosis.

Follistatin-like protein 1 plays a tumor suppressor role in clear-cell renal cell carcinoma

BACKGROUND

We previously showed that the expression of follistatin-like protein 1 (FSTL1) was significantly down-regulated in metastatic clear-cell renal cell carcinoma (ccRCC). In this study, we aimed to characterize the role of FSTL1 in the development of ccRCC.

METHODS

The effects of FSTL1 on cell activity and cell cycle were investigated in ccRCC cell lines with altered FSTL1 expression. Gene expression microarray assays were performed to identify the major signaling pathways affected by FSTL1 knockdown. The expression of FSTL1 in ccRCC and its effect on postoperative prognosis were estimated in a cohort with 89 patients.

RESULTS

FSTL1 knockdown promoted anchorage-independent growth, migration, invasion, and cell cycle of ccRCC cell lines, whereas FSTL1 overexpression attenuated cell migration. FSTL1 knockdown up-regulated nuclear factor-κB (NF-κB) and hypoxia-inducible factor (HIF) signaling pathways, increased epithelial-to-mesenchymal transition, up-regulated interleukin-6 expression, and promoted tumor necrosis factor-α-induced degradation of NF-κB inhibitor (IκBα) in ccRCC cell lines. FSTL1 immunostaining was selectively positive in epithelial cytoplasm in the loop of Henle, and positive rate of FSTL1 was significantly lower in ccRCC tissues than in adjacent renal tissues (P < 0.001). The multivariate Cox regression analysis showed that the intratumoral FSTL1 expression conferred a favorable independent prognosis with a hazard ratio of 0.325 (95% confidence interval 0.118-0.894). HIF-2α expression was negatively correlated with FSTL1 expression in ccRCC specimens (r = - 0.229, P = 0.044). Intratumoral expression of HIF-2α, rather than HIF-1α, significantly predicted an unfavorable prognosis in ccRCC (log-rank, P = 0.038).

CONCLUSIONS

FSTL1 plays a tumor suppression role possibly via repressing the NF-κB and HIF-2α signaling pathways. To increase FSTL1 expression might be a candidate therapeutic strategy for metastatic ccRCC.

FSTL1 Promotes Metastasis and Chemoresistance in Esophageal Squamous Cell Carcinoma through NFκB-BMP Signaling Cross-talk

Esophageal squamous cell carcinoma (ESCC) has a generally poor prognosis, and molecular markers to improve early detection and predict outcomes are greatly needed. Here, we report that the BMP-binding follistatin-like protein FSTL1 is overexpressed in ESCCs, where it correlates with poor overall survival. Genetic amplification of FSTL1 or chromosome 3q, where it is located, occurred frequently in ESCC, where FSTL1 copy number correlated positively with higher FSTL1 protein expression. Elevating FSTL1 levels by various means was sufficient to drive ESCC cell proliferation, clonogenicity, migration, invasion, self-renewal, and cisplatin resistance in vitro and tumorigenicity and distant metastasis in vivo Conversely, FSTL1 attenuation by shRNA or neutralizing antibody elicited the opposite effects in ESCC cells. mRNA profiling analyses suggested that FSTL1 drives ESCC oncogenesis and metastasis through various pathways, with deregulation of NFκB and BMP signaling figuring prominently. Cross-talk between the NFκB and BMP pathways was evidenced by functional rescue experiments using inhibitors of NFκB and TLR4. Our results establish the significance of FSTL1 in driving oncogenesis and metastasis in ESCC by coordinating NFκB and BMP pathway control, with implications for its potential use as a diagnostic or prognostic biomarker and as a candidate therapeutic target in this disease setting. Cancer Res; 77(21); 5886-99. ©2017 AACR.

Effects of FSTL1 on the proliferation and motility of breast cancer cells and vascular endothelial cells

Background

Treatments that prevent the motility of breast cancer cells and inhibit formation of new capillary vessels are urgently needed. FSTL1 is a secreted protein that has been implicated in maintaining the normal physiological function of the cardiovascular system, in addition to a variety of other biological functions. We investigated the role of FSTL1 in the proliferation and migration of breast cancer and vascular endothelial cells.

Methods

Human umbilical vein endothelial cells and human breast cancer BT‐549 cells were used to test the effects of FSTL1 and the N‐terminal domain of FSTL1. Immunofluorescence microscopy and 3‐(4, 5‐dimethylthiazolyl‐2)‐2,5‐diphenyltetrazolium bromide, transwell invasion, and wound healing assays were conducted.

Results

Different doses of the N‐terminal fragment of FSTL1 (FSTL‐N) have variable effects on the migration of these cells. However, FSTL1 does not significantly affect tube formation in vitro from vascular endothelial cells. FSTL1‐FL and FSTL1‐N have modest effects on the invasion of breast cancer and vascular endothelial cells. Interestingly, FSTL1‐FL, but not FSTL‐N, modulates vascular endothelial cell polarization.

Conclusion

FSTL1 modestly affects the proliferation of breast cancer cells and vascular endothelial cells. Our findings improve our understanding of the functions of FSTL1 in breast cancer development and angiogenesis.