SOCS5 and SOCS6 have similar expression patterns in normal and cancer tissues

The Neglected Suppressor of Cytokine Signalling (SOCS): SOCS4-7

SOCS proteins are essential for the regulation of oncogenic, anti-pathogenic, and proinflammatory signalling cascades, including the JAK/STAT and NF-kB pathways, where they act as negative feedback regulators. Given their powerful role in a broad spectrum of biological processes, it is surprising that the functions of many SOCS proteins have not been widely explored. While the mechanisms of action of CIS, SOCS1-3 are well-documented, information regarding SOCS4-7 remains limited. However, recent studies have begun to elucidate the regulatory functions of these proteins during infection and disease, such as influenza infection, cancer and diabetes. Therefore, this review aims to describe and discuss studies detailing our current understanding of SOCS4-7, painting a clearer picture of the biological processes these regulatory proteins maintain. Indeed, our review highlights important evidence proving that all SOCS play a role in biological processes that are essential for normal immunological homeostasis, clearance of infection and avoidance of disease. Understanding how SOCS proteins interact with other proteins or how they are dysregulated in disease is likely to provide valuable insights for advancing therapeutic approaches.

Unraveling the complexity of STAT3 in cancer: molecular understanding and drug discovery

Signal transducer and activator of transcription 3 (STAT3) is a transcriptional factor involved in almost all cancer hallmark features including tumor proliferation, metastasis, angiogenesis, immunosuppression, tumor inflammation, metabolism reprogramming, drug resistance, cancer stemness. Therefore, STAT3 has become a promising therapeutic target in a wide range of cancers. This review focuses on the up-to-date knowledge of STAT3 signaling in cancer. We summarize both the positive and negative modulators of STAT3 together with the cancer hallmarks involving activities regulated by STAT3 and highlight its extremely sophisticated regulation on immunosuppression in tumor microenvironment and metabolic reprogramming. Direct and indirect inhibitors of STAT3 in preclinical and clinical studies also have been summarized and discussed. Additionally, we highlight and propose new strategies of targeting STAT3 and STAT3-based combinations with established chemotherapy, targeted therapy, immunotherapy and combination therapy. These efforts may provide new perspectives for STAT3-based target therapy in cancer.

Extracellular vesicle-encapsulated microRNA-296-3p from cancer-associated fibroblasts promotes ovarian cancer development through regulation of the PTEN/AKT and SOCS6/STAT3 pathways

Cancer-associated fibroblasts (CAFs), as important components of the tumor microenvironment, can regulate intercellular communication and tumor development by secreting extracellular vesicles (EVs). However, the role of CAF-derived EVs in ovarian cancer has not been fully elucidated. Here, using an EV-microRNA sequencing analysis, we reveal specific overexpression of microRNA (miR)-296-3p in activated CAF-derived EVs, which can be transferred to tumor cells to regulate the malignant phenotypes of ovarian cancer cells. Moreover, overexpression of miR-296-3p significantly promotes the proliferation, migration, invasion, and drug resistance of ovarian cancer cells in vitro, as well as tumor growth in vivo, while its inhibition has the opposite effects. Further mechanistic studies reveal that miR-296-3p promotes ovarian cancer progression by directly targeting PTEN and SOCS6 and activating AKT and STAT3 signaling pathways. Importantly, increased expression of miR-296-3p encapsulated in plasma EVs is closely correlated with tumorigenesis and chemoresistance in patients with ovarian cancer. Our results highlight the cancer-promoting role of CAF-derived EVs carrying miR-296-3p in ovarian cancer progression for the first time, and suggest that miR-296-3p encapsulated in CAF-derived EVs could be a diagnostic biomarker and therapeutic target for ovarian cancer.

Targeting and regulation of autophagy in hepatocellular carcinoma: revisiting the molecular interactions and mechanisms for new therapy approaches

Autophagy is an evolutionarily conserved process that plays a role in regulating homeostasis under physiological conditions. However, dysregulation of autophagy is observed in the development of human diseases, especially cancer. Autophagy has reciprocal functions in cancer and may be responsible for either survival or death. Hepatocellular carcinoma (HCC) is one of the most lethal and common malignancies of the liver, and smoking, infection, and alcohol consumption can lead to its development. Genetic mutations and alterations in molecular processes can exacerbate the progression of HCC. The function of autophagy in HCC is controversial and may be both tumor suppressive and tumor promoting. Activation of autophagy may affect apoptosis in HCC and is a regulator of proliferation and glucose metabolism. Induction of autophagy may promote tumor metastasis via induction of EMT. In addition, autophagy is a regulator of stem cell formation in HCC, and pro-survival autophagy leads to cancer cell resistance to chemotherapy and radiotherapy. Targeting autophagy impairs growth and metastasis in HCC and improves tumor cell response to therapy. Of note, a large number of signaling pathways such as STAT3, Wnt, miRNAs, lncRNAs, and circRNAs regulate autophagy in HCC. Moreover, regulation of autophagy (induction or inhibition) by antitumor agents could be suggested for effective treatment of HCC. In this paper, we comprehensively review the role and mechanisms of autophagy in HCC and discuss the potential benefit of targeting this process in the treatment of the cancer. Video Abstract.

SOCS5 knockdown suppresses metastasis of hepatocellular carcinoma by ameliorating HIF-1α-dependent mitochondrial damage

The Pringle maneuver (PM) is widely used during hepatocellular carcinoma (HCC) resection. However, it inevitably leads to ischemia and hypoxia, which promotes tumor metastasis. In this study, immunohistochemical staining of specimens from 130 HCC patients revealed that long-time PM significantly affected the prognosis of patients with high expression of suppressor of cytokine signaling 5 (SOCS5), but did not affect the prognosis of patients with low expression of SOCS5. The TCGA database showed that patients with high expression of SOCS5 had higher hypoxia scores, and it was proved that SOCS5 could promote the expression of hypoxia-inducible factor 1 subunit alpha (HIF-1α) protein by clinical tissue samples, cell experiments, lung metastases, and subcutaneous tumorigenesis experiments. Then, we used CoCl2 to construct a hypoxia model, and confirmed that SOCS5 knockdown resisted hypoxia-induced mitochondrial damage by inhibiting the expression of HIF-1α, thereby inhibiting the invasion and migration of HCC cells by immunofluorescence, electron microscopy, migration, invasion, and other experiments. We performed rescue experiments using LY294002 and rapamycin and confirmed that the knockdown of SOCS5-inhibited HCC cell invasion and migration by inhibiting the PI3K/Akt/mTOR/HIF-1α signaling axis. More importantly, we obtained consistent conclusions from clinical, cellular, and animal studies that the hypoxia-induced invasion and migration ability of SOCS5-inhibited HCC were weaker than that of normal HCC. In conclusion, we identified a novel role for SOCS5 in regulating HIF-1α-dependent mitochondrial damage and metastasis through the PI3K/Akt/mTOR pathway. The development of a SOCS5-specific inhibitor, an indirect inhibitor of HIF-1α, might be effective at controlling PM-induced tumor micrometastases during HCC resection.

Suppressors of Cytokine Signaling and Hepatocellular Carcinoma

Cytokines are secreted soluble glycoproteins that regulate cellular growth, proliferation, and differentiation. Suppressors of cytokine signaling (SOCS) proteins negatively regulate cytokine signaling and form a classical negative feedback loop in the signaling pathways. There are eight members of the SOCS family. The SOCS proteins are all comprised of a loosely conserved N-terminal domain, a central Src homology 2 (SH2) domain, and a highly conserved SOCS box at the C-terminus. The role of SOCS proteins has been implicated in the regulation of cytokines and growth factors in liver diseases. The SOCS1 and SOCS3 proteins are involved in immune response and inhibit protective interferon signaling in viral hepatitis. A decreased expression of SOCS3 is associated with advanced stage and poor prognosis of patients with hepatocellular carcinoma (HCC). DNA methylations of SOCS1 and SOCS3 are found in HCC. Precise regulation of liver regeneration is influenced by stimulatory and inhibitory factors after partial hepatectomy (PH), in particular, SOCS2 and SOCS3 are induced at an early time point after PH. Evidence supporting the important role of SOCS signaling during liver regeneration also supports a role of SOCS signaling in HCC. Immuno-oncology drugs are now the first-line therapy for advanced HCC. The SOCS can be potential targets for HCC in terms of cell proliferation, cell differentiation, and immune response. In this literature review, we summarize recent findings of the SOCS family proteins related to HCC and liver diseases.

LncRNA DHRS4-AS1 ameliorates hepatocellular carcinoma by suppressing proliferation and promoting apoptosis via miR-522-3p/SOCS5 axis

Recent years have seen much effect in revealing the pathological association between lncRNA and HCC. Herein, we identified lncRNA DHRS4-AS1 as a potential tumor suppressor in HCC. Firstly, it was discovered that DHRS4-AS1 was significantly down-regulated in HCC tissues compared to normal tissues based on the database TCGA. It was also detected in a lower-than-usual expression quantity in HCC tissues we collected and HCC cell lines. Kaplan-Meier survival analysis revealed that high expression of DHRS4-AS1 contributed to higher overall survival rate of HCC patients.DHRS4-AS1 expression was significantly correlated to tumor size (P = 0.02) and TNM stage (P = 0.045). CCK-8, BrdU and colony-forming assays collectively demonstrated that overexpression of DHRS4-AS1 significantly restrained HCC cell proliferation. In vivo xenograft animal experiment showed that DHRS4-AS1 could efficiently preclude the tumor growth of HCC. Further investigation performed using flow cytometry and western blot showed that DHRS4-AS1 exerted its effects by accelerating cell apoptosis and capturing cell cycle in G0/G1 phase. Our study subsequently lucubrated that miR-522-3p was a negative target of DHRS4-AS1. Increased expression level of miR-522-3p was examined in HCC tissues and cell lines. Similarly, miR-522-3p mimics could reverse the inhibitory effect on HCC brought by DHRS4-AS1. SOCS5 was then discovered as a down-stream target of miR-522-3p, which suggested that SOCS5 participated in DHRS4-AS1/miR-522-3p axis to collectively mediate the development of HCC. Our study provides lncRNA DHRS4-AS1/miR-522-3p/SOCS5 axis as a novel target for HCC therapeutic strategy with potentiality.

Inhibition of miR-1298-5p attenuates sepsis lung injury by targeting SOCS6

Sepsis is one of the leading causes of morbidity and mortality and a major cause of acute lung injury (ALI). carried by exosomes play a role in a variety of diseases. However,there are not many studies of exosomal miRNAs in sepsis and sepsis lung injury.miR-1298-5p and suppressor of cytokine signaling 6 (SOCS6) were silenced or overexpressed in human bronchial epithelial cells (BEAS-2B). PKH-67 Dye was used to trace exosome endocytosis. Cell permeability was evaluated by measuring trans-epithelial electrical resistance (TEER) and FITC dextran flux. ELISA kits were used for cytokine detection. Quantitative RT-PCR and western blots were used to evaluate gene expression. miR-1298-5p was elevated in exosomes from patients with sepsis lung injury (Sepsis_exo). Treatment of BEAS-2B cells using Sepsis_exo significantly inhibited cell proliferation, and induced cell permeability and inflammatory response. miR-1298-5p directly targeted SOCS6. Overexpressing SOCS6 reversed miR-1298-5p-induced cell permeability and inflammatory response. Inhibition of STAT3 blocked SOCS6-silencing caused significant increase of cell permeability and inflammation. Exosomes isolated from patients of sepsis lung injury increased cell permeability and inflammatory response in BEAS-2B cells through exosomal miR-1298-5p which targeted SOCS6 via STAT3 pathway. The findings highlight the importance of miR-1298-5p/SOCS6/STAT3 axis in sepsis lung injury and provide new insights into therapeutic strategies for sepsis lung injury.

Comprehensive analysis of suppressor of cytokine signaling proteins in human breast Cancer

Background

Abnormal expression of suppressor of cytokine signaling (SOCS) proteins regulates tumor angiogenesis and development in cancers. In this study, we aimed to perform a comprehensive bioinformatic analysis of SOCS proteins in breast invasive carcinoma (BRCA).

Methods

The gene expression, methylation level, copy number, protein expression and patient survival data related to SOCS family members in BRCA patients were obtained from the following databases: Oncomine, The Cancer Genome Atlas (TCGA), Genotype-Tissue Expression (GTEx), Human Protein Atlas (HPA), Gene Expression Profiling Interactive Analysis (GEPIA), PCViz, cBioPortal and Kaplan-Meier plotter. Correlation analyses, identification of interacting genes and construction of regulatory networks were performed by functional and pathway enrichment analyses, weighted gene coexpression network analysis (WGCNA) and gene set enrichment analysis (GSEA).

Results

Data related to 1109 BRCA tissues and 113 normal breast tissue samples were extracted from the TCGA database. SOCS2 and SOCS3 exhibited significantly lower mRNA expression levels in BRCA tissues than in normal tissues. BRCA patients with high mRNA levels of SOCS3 (p < 0.01) and SOCS4 (p < 0.05) were predicted to have significantly longer overall survival (OS) times. Multivariate analysis showed that SOCS3 was an independent prognostic factor for OS. High mRNA expression levels of SOCS2 (p < 0.001), SOCS3 (p < 0.001), and SOCS4 (p < 0.01), and a low expression level of SOCS5 (p < 0.001) were predicted to be significantly associated with better recurrence-free survival (RFS). Multivariate analysis showed that SOCS2 was an independent prognostic factor for RFS. Lower expression levels of SOCS2 and SOCS3 were observed in patients with tumors of more advanced clinical stage (p < 0.05). Functional and pathway enrichment analyses, together with WGCNA and GSEA, showed that SOCS3 and its interacting genes were significantly involved in the JAK-STAT signaling pathway, suggesting that JAK-STAT signaling might play a critical role in BRCA angiogenesis and development. Western blot results showed that overexpression of SOCS3 inhibited the activity of the JAK-STAT signaling pathway in vitro.

Conclusions

SOCS family proteins play a very important role in BRCA. SOCS3 may be a prognostic factor and SOCS2 may be a potential therapeutic target in breast cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08434-y.

MicroRNA-301a promotes pancreatic cancer invasion and metastasis through the JAK/STAT3 signaling pathway by targeting SOCS5

Pancreatic cancer is one of the most lethal digestive malignant tumors. We had previously found that microRNA-301a (miR-301a) is a oncogenic microRNA whose recognized conduce to nuclear factor-kappa B (NF-κB) activation in pancreatic cancer, yet the underlying mechanisms of miR-301a in promoting pancreatic cancer invasion and migration is obscure. In this work we found that high expression of miR-301a in human pancreatic cancer patients is related to poor survival. Overexpression of miR-301a enhances pancreatic cancer cell invasion, angiogenesis and migration, whereas inhibition of miR-301a suppresses pancreatic cancer cell invasion and reduces orthotopic pancreatic tumor growth and metastasis. Furthermore, suppressor of cytokine signaling 5 (SOCS5) is identified as a target gene of miR-301a. We found that miR-301a suppressed the expression of SOCS5 leads to janus kinase/signal transducer and activator of transcription 3 (JAK/STAT3) activation and is related to poor overall survival of pancreatic cancer patients. Taken together, our data show for the first time that the feedback loop between miR-301a and JAK/STAT3 pathway may play a significant role in pancreatic cancer invasion and metastasis. Targeting the loop may prove beneficial to prevent metastasis and provide a more effective therapeutic strategy for pancreatic cancer.

microRNA-454 promotes liver tumor-initiating cell expansion by regulating SOCS6

Tumor-initiating cells (T-ICs) are involved in the tumorigenesis, progression, drug resistance and recurrence of hepatocellular carcinoma (HCC). However, the underlying mechanism for the propagation of liver T-ICs remains unclear. Herein, we find that miR-454 is upregulated in liver T-ICs and has an important function in liver T-ICs. Functional studies have revealed that knockdown of miR-454 inhibits liver T-IC self-renewal and tumorigenesis. Conversely, forced miR-454 expression promotes liver T-IC self-renewal and tumorigenesis. Mechanistically, we found that miR-454 downregulates SOCS6 expression in liver T-ICs. The correlation between miR-454 and SOCS6 is validated in human HCC tissues. Furthermore, HCC cells that overexpress miR-454 are resistant to sorafenib treatment. Analysis of patient-derived xenografts (PDXs) further demonstrates that miR-454 may predict sorafenib benefits in HCC patients. In conclusion, our findings reveal the crucial role of miR-454 in liver T-IC expansion and sorafenib response.

SOCS5 inhibition induces autophagy to impair metastasis in hepatocellular carcinoma cells via the PI3K/Akt/mTOR pathway

SOCS5 is a member of the suppressor of cytokine signaling (SOCS) protein family with important yet incompletely understood biological functions in cancer. In hepatocellular carcinoma (HCC), controversial tumor-promoting and tumor-suppressive roles of SOCS5 have been reported. Our study aims to unravel novel functions of SOCS5 in HCC, especially that affecting metastasis. We examined the expression levels of SOCS5 in HCC using publicly available datasets, and in our patient cohort, using quantitative real-time PCR, western blotting, and immunohistochemistry. The association of SOCS5 expression with clinical pathological data of HCC patients was examined and that with the mTOR pathway was predicted. We further studied the effects of SOCS5 on PI3K/Akt/mTOR activity; HCC cell autophagy, migration, and invasion; and HCC cell metastasis in vitro and in vivo. We observed that SOCS5 was significantly overexpressed in HCC tissues, compared to adjacent non-tumor liver tissues, in both the public datasets and in our patient cohort. SOCS5 overexpression was significantly and inversely correlated with HCC patient prognosis. Moreover, SOCS5 overexpression promoted HCC cell migration and invasion in vitro by inactivating PI3K/Akt/mTOR-mediated autophagy. Conversely, SOCS5 inhibition suppressed HCC cell migration and invasion in vitro by activating PI3K/Akt/mTOR-mediated autophagy. Dual inhibition of SOCS5 and mTOR further enhanced autophagy and the subsequent anti-metastatic effects on HCC cells. In vivo, stable knockdown of SOCS5 reduced HCC cell metastasis. Overall, our study revealed a novel metastasis-promoting function of SOCS5 in HCC, acting via the PI3K/Akt/mTOR-mediated autophagy pathway. Combined inhibition of SOCS5 and mTOR may be a potential therapeutic approach to inhibit HCC metastasis and prolong patient survival.

Long noncoding RNA TUSC7 inhibits cell proliferation, migration and invasion by regulating SOCS4 (SOCS5) expression through targeting miR-616 in endometrial carcinoma

BACKGROUND

Long non-coding RNA (lncRNA) is emerging as an important regulator in various physiological and pathological processes. Recently, it was found that lncRNA long non-coding RNA tumor suppressor candidate 7 (TUSC7) could play tumor suppressive roles in several cancers. However, the function and underlying regulatory mechanism of lncRNA TUSC7 in endometrial carcinoma (EC) remains largely unclear.

METHODS

The expression levels of TUSC7 and microRNAs-616 (miR-616) were analyzed by real-time PCR and in situ hybridization. Cell cycle and cell metastasis associated protein expressions were determined by western blotting. Cell proliferation, cycle and metastasis were determined by CCK-8 cell viability, colony formation, flow cytometer, wound scratch and transwell assays respectively in vitro. RNA pull-down, luciferase and western blotting assays were used to examine the target relationship between TUSC7 and miR-616 or that between miR-616 and suppressors of cytokine signaling 4 (5) (SOCS4 (SOCS5)). The functional effects of TUSC7 through sponging miR-616 were further examined using a xenograft tumor mouse model in vivo.

RESULTS

TUSC7 was downexpressed in EC tissues and cell lines, and TUSC7 upregulation could remarkably inhibit cell proliferation, cycle progression and metastasis in EC cells. Mechanistic investigations demonstrated that TUSC7 can interact with miR-616 and decrease its expression, thereby upregulating the expression of miR-616's targets SOCS4 (SOCS5). Additionally, in vivo experiments using a xenograft tumor mouse model revealed that TUSC7 can serve as a tumor suppressor through sponging miR-616, and upregulating SOCS4 (SOCS5) in EC.

CONCLUSIONS

In this study, a newly identified regulatory mechanism of lncRNA TUSC7/miR-616/ SOCS4 (SOCS5) axis was systematically studied, which may hold promise as a promising target for EC treatment.

Negative regulators of STAT3 signaling pathway in cancers

STAT3 is the most ubiquitous member of the STAT family and involved in many biological processes, such as cell proliferation, differentiation, and apoptosis. Mounting evidence has revealed that STAT3 is aberrantly activated in many malignant tumors and plays a critical role in cancer progression. STAT3 is usually regarded as an effective molecular target for cancer treatment, and abolishing the STAT3 activity may diminish tumor growth and metastasis. Recent studies have shown that negative regulators of STAT3 signaling such as PIAS, SOCS, and PTP, can effectively retard tumor progression. However, PIAS, SOCS, and PTP have also been reported to correlate with tumor malignancy, and their biological function in tumorigenesis and antitumor therapy are somewhat controversial. In this review, we summarize actual knowledge on the negative regulators of STAT3 in tumors, and focus on the potential role of PIAS, SOCS, and PTP in cancer treatment. Furthermore, we also outline the STAT3 inhibitors that have entered clinical trials. Targeting STAT3 seems to be a promising strategy in cancer therapy.

miR-885-5p upregulation promotes colorectal cancer cell proliferation and migration by targeting suppressor of cytokine signaling

The aim of the present study was to investigate the role of microRNA (miR)-885-5p in colorectal cancer cell proliferation and migration, and to determine the possible underlying molecular mechanisms. The expression of miR-885-5p in colorectal cancer tissue and cells was detected by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The expression levels of three suppressor of cytokine signaling (SOCS) factors were detected by RT-qPCR and western blotting. The effects of miR-885-5p on tumor cell proliferation and migration were studied using MTT and Transwell assays, respectively. Additionally, the expression levels of epithelial-mesenchymal transition (EMT)-related proteins (N-cadherin, E-cadherin, vimentin and Snail) were detected by RT-qPCR and western blot analysis. Furthermore, the target of miR-885-5p was predicted and confirmed using a luciferase reporter assay. miR-885-5p was demonstrated to be upregulated and SOCS was downregulated in colorectal cancer tissue, and cells. miR-885-5p suppression significantly inhibited tumor cell proliferation and migration, promoted E-cadherin expression, and inhibited the expression levels of N-cadherin, vimentin and Snail. Further studies showed that SOCS5, SOCS6 and SOCS7 were direct targets of miR-885-5p. The results suggest that miR-885-5p suppression inhibited cell proliferation and migration, and the EMT process by targeting SOCS5, SOCS6 and SOCS7 genes in colorectal cancer. miR-885-5p and SOCS may be used for the diagnosis and treatment of colorectal cancer.

The role of small adaptor proteins in the control of oncogenic signalingr driven by tyrosine kinases in human cancer

Protein phosphorylation on tyrosine (Tyr) residues has evolved as an important mechanism to coordinate cell communication in multicellular organisms. The importance of this process has been revealed by the discovery of the prominent oncogenic properties of tyrosine kinases (TK) upon deregulation of their physiological activities, often due to protein overexpression and/or somatic mutation. Recent reports suggest that TK oncogenic signaling is also under the control of small adaptor proteins. These cytosolic proteins lack intrinsic catalytic activity and signal by linking two functional members of a catalytic pathway. While most adaptors display positive regulatory functions, a small group of this family exerts negative regulatory functions by targeting several components of the TK signaling cascade. Here, we review how these less studied adaptor proteins negatively control TK activities and how their loss of function induces abnormal TK signaling, promoting tumor formation. We also discuss the therapeutic consequences of this novel regulatory mechanism in human oncology.

Cell regulation by phosphotyrosine-targeted ubiquitin ligases

Three classes of E3 ubiquitin ligases, members of the Cbl, Hakai, and SOCS-Cul5-RING ligase families, stimulate the ubiquitination of phosphotyrosine-containing proteins, including receptor and nonreceptor tyrosine kinases and their phosphorylated substrates. Because ubiquitination frequently routes proteins for degradation by the lysosome or proteasome, these E3 ligases are able to potently inhibit tyrosine kinase signaling. Their loss or mutational inactivation can contribute to cancer, autoimmunity, or endocrine disorders, such as diabetes. However, these ligases also have biological functions that are independent of their ubiquitination activity. Here we review relevant literature and then focus on more-recent developments in understanding the structures, substrates, and pathways through which the phosphotyrosine-specific ubiquitin ligases regulate diverse aspects of cell biology.

SOCS6 is a selective suppressor of receptor tyrosine kinase signaling

The suppressors of cytokine signaling (SOCS) are well-known negative regulators of cytokine receptor signaling. SOCS6 is one of eight members of the SOCS family of proteins. Similar to other SOCS proteins, SOCS6 consists of an uncharacterized extended N-terminal region followed by an SH2 domain and a SOCS box. Unlike other SOCS proteins, SOCS6 is mainly involved in negative regulation of receptor tyrosine kinase signaling. SOCS6 is widely expressed in many tissues and is found to be downregulated in many cancers including colorectal cancer, gastric cancer, lung cancer, ovarian cancer, stomach cancer, thyroid cancer, hepatocellular carcinoma, and pancreatic cancer. SOCS6 is involved in negative regulation of receptor signaling by increasing degradation mediated by ubiquitination of receptors or substrate proteins and induces apoptosis by targeting mitochondrial proteins. Therefore, SOCS6 turns out as an important regulator of survival signaling and its activity is required for controlling receptor tyrosine kinase signaling.

Identification of SOCS2 and SOCS6 as biomarkers in human colorectal cancer

BACKGROUND

Over the past years, some members of the family of suppressor of cytokine signalling (SOCS) proteins have emerged as potential tumour suppressors. This study aimed at investigating the clinical significance of SOCS proteins in colorectal carcinoma (CRC).

METHODS

We integrated publicly available microarray expression data on CRC in humans, analysed the expression pattern of SOCSs and assessed the predictive power of SOCS2 and SOCS6 for diagnostic purposes by generating receiver operating characteristic curves. Using laser microdissected patient material we assessed SOCS expression on RNA and protein levels as well as their methylation status in an independent CRC patient cohort. Finally, we investigated the prognostic value of SOCS2 and SOCS6.

RESULTS

The meta-analysis as well as the independent patient cohort analysis reveal a stage-independent downregulation of SOCS2 and SOCS6 and identify both molecules as diagnostic biomarkers for CRC. We demonstrate a different methylation pattern within the SOCS2 promoter between tumour tissue and normal control tissue in 25% of CRC patients. Furthermore, early CRC stage patients with low expression of SOCS2 display significantly shorter disease-free survival.

CONCLUSIONS

Our data offers evidence that SOCS2 and SOCS6 levels are reduced in CRC and may serve as diagnostic biomarkers for CRC patients.

miR-17-5p promotes proliferation by targeting SOCS6 in gastric cancer cells

This study aimed to test the exact functions and potential mechanisms of miR-17-5p in gastric cancer. Using real-time PCR, miR-17-5p was found to be expressed more highly in gastric cancer compared with-normal tissues. Gain- and loss-of-function assays demonstrated that miR-17-5p increased the proliferation and growth of gastric cancer cells in vitro and in vivo. Through reporter gene and western blot assays, SOCS6 was shown to be a direct target of miR-17-5p, and proliferative assays confirmed that SOCS6 exerted opposing function to that of miR-17-5p in gastric cancer. In short, miR-17-5p might function as a pro-proliferative factor by repressing SOCS6 in gastric cancer.

The role of suppressors of cytokine signalling in human neoplasms

Suppressors of cytokine signalling 1-7 (SOCS1-7) and cytokine-inducible SH2-containing protein (CIS) are a group of intracellular proteins that are well known as JAK-STAT and several other signalling pathways negative feedback regulators. More recently several members have been identified as tumour suppressors and dysregulation of their biological roles in controlling cytokine and growth factor signalling may contribute to the development of many solid organ and haematological malignancies. This review explores their biological functions and their possible tumour suppressing role in human neoplasms.

Expression of SOCSs in human prostate cancer and their association in prognosis

Suppressors of cytokine signaling (SOCS) proteins have been identified as negative feedback regulators of cytokine-mediated signaling in various tissues, and demonstrated to play critical roles in tumorigenesis and tumor development of different cancers. The involvement of SOCSs in human prostate cancer (PCa) has not been fully elucidated. Thus, the aim of this study is to investigate the expression patterns and the clinical significance of SOCSs in PCa. The expression changes of SOCSs at mRNA and protein levels in human PCa tissues compared with adjacent benign prostate tissues were, respectively, detected by using real-time quantitative reverse transcriptase-polymerase chain reaction (QRT-PCR) and immunohistochemistry analyses. The associations of SOCSs expression with clinicopathological features and clinical outcome of PCa patients were further statistically analyzed. Among SOCSs, both QRT-PCR and immunohistochemistry analyses found that SOCS2 expression was upregulated (at mRNA level: change ratio = 1.98, P = 0.031; at protein level: 5.12 ± 0.60 vs. 2.68 ± 0.37, P = 0.016) and SOCS6 expression was downregulated (at mRNA level: change ratio = -1.65, P = 0.008; at protein level: 3.03 ± 0.32 vs. 4.0.72 ± 0.39, P = 0.004) in PCa tissues compared with those in non-cancerous prostate tissues. In addition, the upregulation of SOCS2 in PCa tissues was correlated with the lower Gleason score (P < 0.001), the absence of metastasis (P < 0.001) and the negative PSA failure (P = 0.009); the downregulation of SOCS6 tended to be found in PCa tissues with the higher Gleason score (P = 0.016), the advanced pathological stage (P = 0.007), the positive metastasis (P = 0.020), and the positive PSA failure (P = 0.032). Furthermore, both univariate and multivariate analyses showed that the downregulation of SOCS2 was an independent predictor of shorter biochemical recurrence-free survival. Our data offer the convincing evidence for the first time that the dysregulation of SOCS2 and SOCS6 may be associated with the aggressive progression of PCa. SOCS2 may be potential markers for prognosis in PCa patients.

Reduced expression of SOCS2 and SOCS6 in hepatocellular carcinoma correlates with aggressive tumor progression and poor prognosis

To investigate the clinical significance of suppressor of cytokine signaling (SOCS)-2 and SOCS6 in human hepatocellular carcinoma (HCC). The expression levels of SOCS2 and SOCS6 mRNA and protein in tumor, para-tumor and normal liver tissues were detected in 106 HCC patients by real-time quantitative RT-PCR (qRT-PCR) and Western blot. According to qRT-PCR and western blot analyses, we first found that both the expression levels of SOCS2 and SOCS6 mRNA and protein in HCC were significantly lower than those in para-tumor (both P < 0.001) and normal liver tissues (both P < 0.001). Then, the correlation analysis showed that both SOCS2 and SOCS6 protein downregulation were significantly correlated with advanced TNM stage (both P < 0.001) and high serum AFP (P = 0.008 and 0.01, respectively). Especially, the reduced expression of SOCS2 more frequently occurred in HCC patients with vascular invasion (P = 0.03), and that of SOCS6 was also associated with tumor recurrence (P = 0.01). Moreover, HCC patients with low expression of SOCS2 and SOCS6 had significantly shorter overall (P = 0.008 and 0.01, respectively) and disease-free survival (both P = 0.01). Furthermore, multivariate analysis showed that both SOCS2 and SOCS6 downregulation were independent prognostic factors of overall (P = 0.01 and 0.03, respectively) and disease-free survival (P = 0.01 and 0.03, respectively) in HCC. Our data demonstrate for the first time that SOCS2 and SOCS6 expression were remarkably reduced in HCC and may be served as potential prognostic markers for patients with this deadly disease.