Loss of Sprouty2 in human high-grade serous ovarian carcinomas promotes EGF-induced E-cadherin down-regulation and cell invasion

microRNA 21 and long non-coding RNAs interplays underlie cancer pathophysiology: A narrative review

Non-coding RNAs (ncRNAs) are a diverse group of functional RNA molecules that lack the ability to code for proteins. Despite missing this traditional role, ncRNAs have emerged as crucial regulators of various biological processes and have been implicated in the development and progression of many diseases, including cancer. MicroRNAs (miRNAs) and long non-coding RNAs (lncRNAs) are two prominent classes of ncRNAs that have emerged as key players in cancer pathophysiology. In particular, miR-21 has been reported to exhibit oncogenic roles in various forms of human cancer, including prostate, breast, lung, and colorectal cancer. In this context, miR-21 overexpression is closely associated with tumor proliferation, growth, invasion, angiogenesis, and chemoresistance, whereas miR-21 inactivation is linked to the regression of most tumor-related processes. Accordingly, miR-21 is a crucial modulator of various canonical oncogenic pathways such as PTEN/PI3K/Akt, Wnt/β-catenin, STAT, p53, MMP2, and MMP9. Moreover, interplays between lncRNA and miRNA further complicate the regulatory mechanisms underlying tumor development and progression. In this regard, several lncRNAs have been found to interact with miR-21 and, by functioning as competitive endogenous RNAs (ceRNAs) or miRNA sponges, can modulate cancer tumorigenesis. This work presents and discusses recent findings highlighting the roles and pathophysiological implications of the miR-21-lncRNA regulatory axis in cancer occurrence, development, and progression. The data collected indicate that specific lncRNAs, such as MEG3, CASC2, and GAS5, are strongly associated with miR-21 in various types of cancer, including gastric, cervical, lung, and glioma. Indeed, these lncRNAs are well-known tumor suppressors and are commonly downregulated in different types of tumors. Conversely, by modulating various mechanisms and oncogenic signaling pathways, their overexpression has been linked with preventing tumor formation and development. This review highlights the significance of these regulatory pathways in cancer and their potential for use in cancer therapy as diagnostic and prognostic markers.

Role of SPRY4 in health and disease

SPRY4 is a protein encoding gene that belongs to the Spry family. It inhibits the mitogen-activated protein kinase (MAPK) signaling pathway and plays a role in various biological functions under normal and pathological conditions. The SPRY4 protein has a specific structure and interacts with other molecules to regulate cellular behavior. It serves as a negative feedback inhibitor of the receptor protein tyrosine kinases (RTK) signaling pathway and interferes with cell proliferation and migration. SPRY4 also influences inflammation, oxidative stress, and cell apoptosis. In different types of tumors, SPRY4 can act as a tumor suppressor or an oncogene. Its dysregulation is associated with the development and progression of various cancers, including colorectal cancer, glioblastoma, hepatocellular carcinoma, perihilar cholangiocarcinoma, gastric cancer, breast cancer, and lung cancer. SPRY4 is also involved in organ development and is associated with ischemic diseases. Further research is ongoing to understand the expression and function of SPRY4 in specific tumor microenvironments and its potential as a therapeutic target.

A novel Sprouty4-ERK1/2-Wnt/β-catenin regulatory loop in marrow stromal progenitor cells controls osteogenic and adipogenic differentiation

BACKGROUND

Sprouty (SPRY) proteins play critical roles in controlling cell proliferation, differentiation, and survival by inhibiting receptor tyrosine kinase (RTK)-mediated extracellular signal-regulated kinase (ERK) signaling. Recent studies have demonstrated that SPRY4 negatively regulates angiogenesis and tumor growth. However, whether SPRY4 regulates osteogenic and/or adipogenic differentiation of mesenchymal stem cells remains to be explored.

RESULTS

In this study, we investigated the expression pattern of Spry4 and found that its expression was regulated during the differentiation of mouse marrow stromal progenitor cells and increased in the metaphysis of ovariectomized mice. In vitro loss-of-function and gain-of-function studies demonstrated that SPRY4 inhibited osteogenic differentiation and stimulated adipogenic differentiation of progenitor cells. In vivo experiments showed that silencing of Spry4 in the marrow of C57BL/6 mice blocked fat accumulation and promoted osteoblast differentiation in ovariectomized mice. Mechanistic investigations revealed the inhibitory effect of SPRY4 on canonical wingless-type MMTV integration site (Wnt) signaling and ERK pathway. ERK1/2 was shown to interact with low-density lipoprotein receptor-related protein 6 (LRP6) and activate the canonical Wnt signaling pathway. Inactivation of Wnt signaling attenuated the inhibition of adipogenic differentiation and stimulation of osteogenic differentiation by Spry4 small interfering RNA (siRNA). Finally, promoter study revealed that β-catenin transcriptionally inhibited the expression of Spry4.

CONCLUSIONS

Our study for the first time suggests that a novel SPRY4-ERK1/2-Wnt/β-catenin regulatory loop exists in marrow stromal progenitor cells and plays a key role in cell fate determination. It also highlights the potential of SPRY4 as a novel therapeutic target for the treatment of metabolic bone disorders such as osteoporosis.

The Sprouty/Spred family as tumor suppressors: Coming of age

The Ras/Raf/ERK pathway is one of the most frequently dysregulated signaling pathways in various cancers. In some such cancers, Ras and Raf are hotspots for mutations, which cause continuous activation of this pathway. However, in some other cancers, it is known that negative regulators of the Ras/Raf/ERK pathway are responsible for uncontrolled activation. The Sprouty/Spred family is broadly recognized as important negative regulators of the Ras/Raf/ERK pathway, and its expression is downregulated in many malignancies, leading to hyperactivation of the Ras/Raf/ERK pathway. After the discovery of this family, intensive research investigated the mechanism by which it suppresses the Ras/Raf/ERK pathway and its roles in developmental and pathophysiological processes. In this review, we discuss the complicated roles of the Sprouty/Spred family in tumor initiation, promotion, and progression and its future therapeutic potential.

A potential clinical significance of DAB2IP and SPRY2 transcript variants in prostate cancer

Deregulation of key signaling pathways is one of the primary phenomena in carcinogenesis. DAB2IP and SPRY2 are regulatory elements, which act as feedback inhibitors of receptor tyrosine kinases signaling in mitogen-activated protein kinase pathway. These elements have also been implicated in the pathophysiology of cancer. Therefore, this study is aimed to investigate the expression of all known splice variants of DAB2IP and SPRY2 in prostate tissue. Fresh Prostate tissue samples (50 prostate cancer/ matched normal tissue and 30 BPH) were collected and total RNA was extracted followed by cDNA synthesis. The expression of DAB2IP and SPRY2 transcript variants were evaluated using RT-PCR and quantitative Real-time PCR. The results indicated significant down-regulation of DAB2IP transcript variant 1 in cancerous tissues compared to paired normal tissues (P = 0.001) as well as SPRY2 transcript variant 2 in cancerous tissues in comparison with the normal counterparts and BPH (P = 0.008 and P = 0.025, respectively). In addition, there was a significant negative correlation between DAB2IP.1 and SPRY2.2 expression with PSA levels in prostate cancer (P = 0.039 ρ =-0.24 and P = 0.045 ρ =-0.3, respectively). Interestingly, the down-regulation of DAB2IP.1 mRNA and SPRY2.2 mRNA was positively correlated in tumor samples (P = 0.002 ρ = 0.434). For the first time, this experiment highlights the deregulation of DAB2IP and SPRY2 transcript variants in human prostate cancer. The present study confirms and extends the previous reports through indicating transcript-specific down-regulation and significant association of DAB2IP and SPRY2 in prostate tumorigenesis.

Sprouty2 suppresses progression and correlates to favourable prognosis of intrahepatic cholangiocarcinoma via antagonizing FGFR2 signalling

Fibroblast growth factor receptor 2 (FGFR2) was demonstrated to correlate to the progression and prognosis of intrahepatic cholangiocarcinoma (ICC) by numerous evidences. However, as a well‐recognized suppressor of FGFR2 signalling, the clinical significance of Sprouty (SPRY) family of ICC has not been investigated. In our study, the expressions of SPRY1‐4 in 20 pairs of fresh tumour tissues were detected with qPCR, and in 108 cases of paraffin‐embedded tissues with immunohistochemistry. The prognostic value of SPRY family in ICC was estimated with univariate analysis and multivariate analysis. As a result, SPRY2 was identified as an independent prognostic biomarker predicting favourable prognosis of ICC. High SPRY2 expression was correlated with good differentiation of ICC. With silencing SPRY2 expression, we demonstrated that SPRY2 could suppress FGFR2‐induced ERK phosphorylation, migration, invasion and epithelial‐mesenchymal transition (EMT) under FGF1 stimulation. By overexpressing SPRY2‐wide type or SPRY2‐Y55F, the tyrosine‐55 of SPRY2 was demonstrated to be essential in suppressing ERK phosphorylation, tumour invasion and EMT of ICC cells. In conclusion, SPRY2 was correlated with favourable prognosis of ICC via suppressing FGFR2‐induced ERK phosphorylation, invasion and EMT. The phosphorylation of SPRY2‐Y55 was required in this tumour‐suppressing function of SPRY2.

Sprouty2 inhibits amphiregulin-induced down-regulation of E-cadherin and cell invasion in human ovarian cancer cells

Similar to Drosophila Sprouty (SPRY), mammalian SPRY proteins inhibit the receptor tyrosine kinase-mediated activation of cellular signaling pathways. SPRY2 expression levels have been shown to be down-regulated in human ovarian cancer, and patients with low SPRY2 expression have significantly poorer survival than those with high SPRY2 expression. In addition, epidermal growth factor receptor (EGFR) is overexpressed in human ovarian cancer and is associated with more aggressive clinical behavior and a poor prognosis. Amphiregulin (AREG), the most abundant EGFR ligand in ovarian cancer, binds exclusively to EGFR and stimulates ovarian cancer cell invasion by down-regulating E-cadherin expression. However, thus far, the roles of SPRY2 in AREG-regulated E-cadherin expression and cell invasion remain unclear. In the present study, we show that treatment with AREG up-regulated SPRY2 expression by activating the EGFR-mediated ERK1/2 signaling pathway in two human ovarian cancer cell lines, SKOV3 and OVCAR5. In addition, overexpression of SPRY2 attenuated the AREG-induced down-regulation of E-cadherin by inhibiting the induction of the E-cadherin transcriptional repressor, Snail. Moreover, SPRY2 overexpression attenuated AREG-stimulated cell invasion and proliferation. This study reveals that SPRY2 acts as a tumor suppressor in human ovarian cancer and illustrates the underlying mechanisms that can be used as possible targets for the development of novel therapeutics.

Epidermal growth factor promotes cyclin G2 degradation via calpain-mediated proteolysis in gynaecological cancer cells

Cyclin G2 (CCNG2) is an atypical cyclin that functions to inhibit cell cycle progression and is often dysregulated in human cancers. We have previously shown that cyclin G2 is highly unstable and can be degraded through the ubiquitin/proteasome pathway. Furthermore, cyclin G2 contains a PEST domain, which has been suggested to act as a signal for degradation by multiple proteases. In this study, we determined if calpains, a family of calcium-dependent proteases, are also involved in cyclin G2 degradation. The addition of calpain inhibitors or silencing of calpain expression by siRNAs strongly enhanced cyclin G2 levels. On the other hand, incubation of cell lysates with purified calpains or increasing the intracellular calcium concentration resulted in a decrease in cyclin G2 levels. Interestingly, the effect of calpain was found to be dependent on the phosphorylation of cyclin G2. Using a kinase inhibitor library, we found that Epidermal Growth Factor (EGF) Receptor is involved in cyclin G2 degradation and treatment with its ligand, EGF, induced cyclin G2 degradation. In addition, the presence of the PEST domain is necessary for calpain and EGF action. When the PEST domain was completely removed, calpain or EGF treatment failed to trigger degradation of cyclin G2. Taken together, these novel findings demonstrate that EGF-induced, calpain-mediated proteolysis contributes to the rapid destruction of cyclin G2 and that the PEST domain is critical for EGF/calpain actions.

Plakoglobin Reduces the in vitro Growth, Migration and Invasion of Ovarian Cancer Cells Expressing N-Cadherin and Mutant p53

Aberrant expression of cadherins and catenins plays pivotal roles in ovarian cancer development and progression. Plakoglobin (PG, γ-catenin) is a paralog of β-catenin with dual adhesive and signaling functions. While β-catenin has known oncogenic function, PG generally acts as a tumor/metastasis suppressor. We recently showed that PG interacted with p53 and that its growth/metastasis inhibitory function may be mediated by this interaction. Very little is known about the role of PG in ovarian cancer. Here, we investigated the in vitro tumor/metastasis suppressor effects of PG in ovarian cancer cell lines with mutant p53 expression and different cadherin profiles. We showed that the N-cadherin expressing and E-cadherin and PG deficient ES-2 cells were highly migratory and invasive, whereas OV-90 cells that express E-cadherin, PG and very little/no N-cadherin were not. Exogenous expression of PG or E-cadherin or N-cadherin knockdown in ES-2 cells (ES-2-E-cad, ES-2-PG and ES-2-shN-cad) significantly reduced their migration and invasion. Also, PG expression or N-cadherin knockdown significantly decreased ES-2 cells growth. Furthermore, PG interacted with both cadherins and with wild type and mutant p53 in normal ovarian and ES-2-PG cell lines, respectively.