Sprouty4 interferes with cell proliferation and migration of breast cancer-derived cell lines

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.

SPRY4 inhibits and sensitizes the primary KIT mutants in gastrointestinal stromal tumors (GISTs) to imatinib

BACKGROUND

KIT is frequently mutated in gastrointestinal stromal tumors (GISTs), and the treatment of GISTs largely relies on targeting KIT currently. In this study, we aimed to investigate the role of sprouty RTK signaling antagonist 4 (SPRY4) in GISTs and related mechanisms.

METHODS

Ba/F3 cells and GIST-T1 cell were used as cell models, and mice carrying germline KIT/V558A mutation were used as animal model. Gene expression was examined by qRT-PCR and western blot. Protein association was examined by immunoprecipitation.

RESULTS

Our study revealed that KIT increased the expression of SPRY4 in GISTs. SPRY4 was found to bind to both wild-type KIT and primary KIT mutants in GISTs, and inhibited KIT expression and activation, leading to decreased cell survival and proliferation mediated by KIT. We also observed that inhibition of SPRY4 expression in KITV558A/WT mice led to increased tumorigenesis of GISTs in vivo. Moreover, our results demonstrated that SPRY4 enhanced the inhibitory effect of imatinib on the activation of primary KIT mutants, as well as on cell proliferation and survival mediated by the primary KIT mutants. However, in contrast to this, SPRY4 did not affect the expression and activation of drug-resistant secondary KIT mutants, nor did it affect the sensitivity of secondary KIT mutants to imatinib. These findings suggested that secondary KIT mutants regulate a different downstream signaling cascade than primary KIT mutants.

CONCLUSIONS

Our results suggested that SPRY4 acts as negative feedback of primary KIT mutants in GISTs by inhibiting KIT expression and activation. It can increase the sensitivity of primary KIT mutants to imatinib. In contrast, secondary KIT mutants are resistant to the inhibition of SPRY4.

The risk model construction of the genes regulated by H3K36me3 and H3K79me2 in breast cancer

Abnormal histone modifications (HMs) can promote the occurrence of breast cancer. To elucidate the relationship between HMs and gene expression, we analyzed HM binding patterns and calculated their signal changes between breast tumor cells and normal cells. On this basis, the influences of HM signal changes on the expression changes of breast cancer-related genes were estimated by three different methods. The results showed that H3K79me2 and H3K36me3 may contribute more to gene expression changes. Subsequently, 2109 genes with differential H3K79me2 or H3K36me3 levels during cancerogenesis were identified by the Shannon entropy and submitted to perform functional enrichment analyses. Enrichment analyses displayed that these genes were involved in pathways in cancer, human papillomavirus infection, and viral carcinogenesis. Univariate Cox, LASSO, and multivariate Cox regression analyses were then adopted, and nine potential breast cancer-related driver genes were extracted from the genes with differential H3K79me2/H3K36me3 levels in the TCGA cohort. To facilitate the application, the expression levels of nine driver genes were transformed into a risk score model, and its robustness was tested via time-dependent receiver operating characteristic curves in the TCGA dataset and an independent GEO dataset. At last, the distribution levels of H3K79me2 and H3K36me3 in the nine driver genes were reanalyzed in the two cell lines and the regions with significant signal changes were located.

Sprouty3, but Not Sprouty1, Expression Is Beneficial for the Malignant Potential of Osteosarcoma Cells

Sprouty proteins are widely accepted modulators of receptor tyrosine kinase-associated pathways and fulfill diversified roles in cancerogenesis dependent on the originating cells. In this study we detected a high expression of Sprouty3 in osteosarcoma-derived cells and addressed the question of whether Sprouty3 and Sprouty1 influence the malignant phenotype of this bone tumor entity. By using adenoviruses, the Sprouty proteins were expressed in two different cell lines and their influence on cellular behavior was assessed. Growth curve analyses and Scratch assays revealed that Sprouty3 accelerates cell proliferation and migration. Additionally, more colonies were grown in Soft agar if the cells express Sprouty3. In parallel, Sprouty1 had no significant effect on the measured endpoints of the study in osteosarcoma-derived cells. The promotion of the tumorigenic capacities in the presence of Sprouty3 coincided with an increased activation of signaling as measured by evaluating the phosphorylation of extracellular signal-regulated kinases (ERKs). Ectopic expression of a mutated Sprouty3 protein, in which the tyrosine necessary for its activation was substituted, resulted in inhibited migration of the treated cells. Our findings identify Sprouty3 as a candidate for a tumor promoter in osteosarcoma.

SPRY4 suppresses proliferation and induces apoptosis of colorectal cancer cells by repressing oncogene EZH2

Colorectal cancer (CRC), a common malignant tumor in the digestive tract, is a leading cause of cancer-related death. SPRY4 has been reported to act as a tumor suppressor gene in various tumors. This study aims to assess the role of SPRY4 in colorectal cancer (CRC) and uncover its underlying mechanisms. Firstly, the expression levels of SPRY4 were measured in CRC cell lines. SPRY4-overexpressing or silencing plasmids were transfected into CRC cells to regulate its expression level. CCK-8, colony formation, EdU assay, wound-healing and Transwell assays were performed to determine cell proliferation, invasion and migration abilities. Then, apoptosis was measured by flow cytometry analysis, and the expression of apoptosis-related protein was analyzed by western-blotting. Next, the in vivo tumorigenesis assay was performed in nude mice. According to the results, there was a lower expression of SPRY4 in CRC cell lines compared with normal cell line, and the overexpression of SPRY4 significantly suppressed cell proliferation, migration and invasion, and promoted apoptosis in SW480 cells. Moreover, the enhanced proliferation, invasion and migration upon SPRY4 silencing was reversed by EZH2 inhibition. In addition, we found that the overexpression of SPRY4 inhibited tumorigenesis in vivo by diminishing the size and weight of the tumors. Our study indicates that SPRY4 might be a potential tumor suppressor gene and prognostic factor for patients with CRC.

A Sprouty4 Mutation Identified in Kallmann Syndrome Increases the Inhibitory Potency of the Protein towards FGF and Connected Processes

Kallmann syndrome is the result of innate genetic defects in the fibroblast growth factor (FGF) regulated signaling network causing diminished signal transduction. One of the rare mutations associated with the syndrome alters the Sprouty (Spry)4 protein by converting the serine at position 241 into a tyrosine. In this study, we characterize the tyrosine Spry4 mutant protein in the primary human embryonic lung fibroblasts WI-38 and osteosarcoma-derived cell line U2OS. As demonstrated in a cell signaling assay, Spry4 gains the capability of inhibiting FGF, but not epithelial growth factor (EGF)-induced signaling as a consequence of the tyrosine substitution. Additionally, migration of normal embryonic lung fibroblasts and osteosarcoma-derived cells is potently inhibited by the tyrosine Spry4 variant, while an effect of the wildtype Spry4 protein is hardly measureable. Concerning cell proliferation, the unaltered Spry4 protein is ineffective to influence the WI-38 cells, while the mutated Spry4 protein decelerates the cell doubling. In summary, these data emphasize that like the other mutations associated with Kallmann syndrome the described Spry4 mutation creates a hyperactive version of a selective inhibitory molecule and can thereby contribute to a weakened FGF signaling. Additionally, the study pinpoints a Spry4 variation expanding the applicability of Spry4 in a potential cancer therapy.

SPRY4 regulates trophoblast proliferation and apoptosis via regulating IFN-γ-induced STAT1 expression and activation in recurrent miscarriage

PROBLEM

The dysregulation of trophoblast functions is one of the leading causes of recurrent miscarriage (RM), which frustrates 1%-5% of couples of childbearing ages. Sprouty 4 (SPRY4) is considered as a tumour suppressor and exerts a negative role in cell viability. However, its role in regulating trophoblast behaviors at the maternal-fetal interface remains largely unknown.

METHOD OF STUDY

First-trimester villous samples were collected from RM patients and healthy controls (HCs) to determine the SPRY4 expression in human placenta during early pregnancy. The HTR8/SVneo cell line was introduced to clarify trophoblast cell functions via transfecting with specific short interfering RNA against SPRY4 or SPRY4-overexpressing lentivirus in vitro. In addition, gene expression microarray analysis was performed to explore the downstream molecules and pathways.

RESULTS

Our results revealed that SPRY4 expression was significantly increased in the first-trimester cytotrophoblasts of RM patients compared with HCs. Furthermore, SPRY4 overexpression inhibited trophoblast proliferation and accelerated apoptosis in vitro, while SPRY4 knockdown reversed these effects. Mechanistically, IFN-γ -induced STAT1 expression and activation were involved in the regulation of trophoblast proliferation and apoptosis by SPRY4, and IFN-γ promoted SPRY4 expression and STAT1 phosphorylation through PI3K/AKT pathway. Additionally, both STAT1 and phosphorylated STAT (p-STAT) levels were also upregulated in trophoblasts from RM patients and positively correlated with SPRY4 expression.

CONCLUSION

Our findings indicate that SPRY4 may act as a negative regulator of trophoblast functions through upregulating IFN-γ/PI3K/AKT-induced STAT1 activation. High levels of SPRY4 and STAT1 may contribute to RM development and progression, and blocking of either target could be a novel therapeutic strategy for RM patients.

Sprouty3 and Sprouty4, Two Members of a Family Known to Inhibit FGF-Mediated Signaling, Exert Opposing Roles on Proliferation and Migration of Glioblastoma-Derived Cells

Dysregulation of receptor tyrosine kinase-induced pathways is a critical step driving the oncogenic potential of brain cancer. In this study, we investigated the role of two members of the Sprouty (Spry) family in brain cancer-derived cell lines. Using immunoblot analyses we found essential differences in the pattern of endogenous Spry3 and Spry4 expression. While Spry4 expression was mitogen-dependent and repressed in a number of cells from higher malignant brain cancers, Spry3 levels neither fluctuated in response to serum withdrawal nor were repressed in glioblastoma (GBM)-derived cell lines. In accordance to the well-known inhibitory role of Spry proteins in fibroblast growth factor (FGF)-mediated signaling, both Spry proteins were able to interfere with FGF-induced activation of the MAPK pathway although to a different extent. In response to serum solely, Spry4 exerts its role as a negative regulator of MAPK activation. Ectopic expression of Spry4 inhibited proliferation and migration of GBM-originated cells, positioning it as a tumor suppressor in brain cancer. In contrast, elevated Spry3 levels accelerated both proliferation and migration of these cell lines, while repression of Spry3 levels using shRNA caused a significant diminished growth and migration velocity rate of a GBM-derived cell line. This argues for a tumor-promoting function of Spry3 in GBMs. Based on these data we conclude that Spry3 and Spry4 fulfill different if not opposing roles within the cancerogenesis of brain malignancies.

Expression Signatures of Cisplatin- and Trametinib-Treated Early-Stage Medaka Melanomas

Small aquarium fish models provide useful systems not only for a better understanding of the molecular basis of many human diseases, but also for first-line screening to identify new drug candidates. For testing new chemical substances, current strategies mostly rely on easy to perform and efficient embryonic screens. Cancer, however, is a disease that develops mainly during juvenile and adult stage. Long-term treatment and the challenge to monitor changes in tumor phenotype make testing of large chemical libraries in juvenile and adult animals cost prohibitive. We hypothesized that changes in the gene expression profile should occur early during anti-tumor treatment, and the disease-associated transcriptional change should provide a reliable readout that can be utilized to evaluate drug-induced effects. For the current study, we used a previously established medaka melanoma model. As proof of principle, we showed that exposure of melanoma developing fish to the drugs cisplatin or trametinib, known cancer therapies, for a period of seven days is sufficient to detect treatment-induced changes in gene expression. By examining whole body transcriptome responses we provide a novel route toward gene panels that recapitulate anti-tumor outcomes thus allowing a screening of thousands of drugs using a whole-body vertebrate model. Our results suggest that using disease-associated transcriptional change to screen therapeutic molecules in small fish model is viable and may be applied to pre-clinical research and development stages in new drug discovery.

Spatial signal repression as an additional role of Sprouty2 protein variants

Sprouty2 (Spry2) is a prominent member of a protein family with crucial functions in the modulation of signal transduction. One of its main actions is the repression of mitogen-activated protein kinase (MAPK) pathway in response to growth factor-induced signalling. A common single nucleotide polymorphism within the Spry2 gene creates two protein variants where a proline adjacent to the serine rich domain is converted to an additional serine. Both protein variants perform similar functions although their efficiency in fulfilling these tasks varies. In this report, we used biochemical fractionation methods as well as confocal microscopy to analyse quantitative and qualitative differences in the distribution of Spry2 variants. We found that Spry2 proteins localize not solely to the plasma membrane, but also to other membrane engulfed compartments like for example the Golgi apparatus. In these less dense organelles, predominantly slower migrating forms reside indicating that posttranslational modification contributes to the distribution profile of Spry2. However there is no significant difference in the distribution of the two variants. Additionally, we found that Spry2 could be found exclusively in membrane fractions irrespective of the mitogen availability and the phosphorylation status. Considering the interference of extracellular signal-regulated kinase (ERK) activation in the cytoplasm, both Spry2 variants inhibited the levels of phosphorylated ERK (pERK) significantly to a similar extent. In contrast, the induction profiles of pERK levels were completely different in the nuclei. Again, both Spry2 variants diminished the levels of pERK. While the proline variant lowered the activation throughout the observation period, the serine variant failed to interfere with immediate accumulation of nuclear pERK levels, but the signal duration was shortened. Since the extent of the pERK inhibition in the nuclei was drastically more pronounced than in the cytoplasm, we conclude that Spry2 - in addition to its known functions as a repressor of general ERK phosphorylation - functions as a spatial repressor of nucleic ERK activation. Accordingly, a dominant negative version of Spry2 was only able to enhance the pERK levels of serum-deprived cells in the cytosol, while in the nucleus the intensity of the pERK signal in response to serum addition was significantly increased.

Commonly integrated epigenetic modifications of differentially expressed genes lead to adaptive resistance in cancer

Aim:

To investigate the integrated epigenetic regulation of acquired drug resistance in cancer.

Materials & methods:

Our gene expression data of five induced drug-tolerant cell models, one resistant cell line and one publicly available drug-resistant dataset were integrated to identify common differentially expressed genes and pathways. ChIP-seq and DNA methylation by HM450K beadchip were used to study the epigenetic profile of differential expressed genes.

Results & conclusion:

Integrated transcriptomic analysis identified a common ‘viral mimicry’ related gene signature in induced drug-tolerant cells and the resistant state. Analysis of the epigenetic regulation revealed a common set of down-regulated genes, which are marked and regulated by a concomitant loss of H3K4me3, gain of H3K9me3 and increment of regional DNA methylation levels associated with tumor suppressor genes and apoptotic signaling.

MicroRNA‑181 serves an oncogenic role in breast cancer via the inhibition of SPRY4

Numerous microRNAs (miRs) have been implicated in breast cancer; however, the molecular mechanism is not fully understood. The present study examined the function and regulatory mechanism of miR‑181 in breast cancer. Reverse transcription‑quantitative polymerase chain reaction and western blot analysis were used to examine the RNA and protein expression. MTT assay, wound healing assay and transwell assay were conducted to study cell proliferation, migration and invasion. Luciferase reporter gene assay was used to confirm targeting relationship. The results suggested that the miR‑181 expression levels were significantly higher in breast cancer cell lines and clinical tissue samples. The increased expression of miR‑181 was markedly associated with higher clinical stage and lymph node metastasis. The patients with high miR‑181 expression demonstrated worse prognosis compared with those with a low expression of miR‑181. Small interfering RNA‑induced miR‑181 downregulation significantly inhibited breast cancer cell proliferation, migration and invasion in vitro, and tumor growth in vivo. Protein sprouty homolog 4 (SPRY4), downregulated in breast cancer tissues and cell lines, was observed to be a novel target gene of miR‑181. Downregulation of SPRY4 was significantly associated with breast cancer progression in addition to poor prognosis. Knockdown of SPRY4 rescued the inhibitory effects of miR‑181 downregulation on the malignant phenotypes of breast cancer cells. Thus, the present study demonstrated that miR‑181 serves a promoting role in breast cancer at least in part through the inhibition of SPRY4 expression. The present results expand the understanding of the miR‑181/SPRY4 axis' function during for the malignant progression of breast cancer.

Oncogenic microRNA-411 promotes lung carcinogenesis by directly targeting suppressor genes SPRY4 and TXNIP

Lung cancer is one of the most common malignant diseases globally, composed of non-small cell lung cancer (NSCLC, 85%) and small cell lung cancer (SCLC, 15%). MicroRNAs (miRNAs) are single-stranded noncoding RNAs having important roles in lung cancer development. miR-411-5p/3p were reported to be increased significantly in human NSCLC tissues and cell lines. Moreover, miR-411-5p/3p overexpression could accelerate cell proliferation and migration, and impede cell apoptosis in NSCLC cell lines. Mechanically, SPRY4 is confirmed a direct target of miR-411-5p/3p. Furthermore, our findings showed that miR-411-5p/3p promoted lung tumor growth in vivo, decreased SPRY4 expression dramatically, and induced EGFR, AKT signaling activation, as well as epithelial–mesenchymal transition (EMT) simultaneously in tumor tissues. In addition, we showed that miR-411-5p also targeted tumor suppressor TXNIP, involved in regulating positively cell cycle progress in SPC-A1 cells rather than in H1299. Whether cell specificity of low TXNIP mRNA level in H1299 is responsible for the different response to cell cycle between H1299 and SPC-A1 would need further explorations. Collectively, these results suggest that miR-411-5p/3p are required for NSCLC development by suppressing SPRY4 and TXNIP; thus, the miR-411-SPRY4-AKT axis might act as a promising target for lung cancer therapy clinically.

The role of SMAD3 in the genetic predisposition to papillary thyroid carcinoma

PURPOSE

To identify and characterize the functional variants, regulatory gene networks, and potential binding targets of SMAD3 in the 15q22 thyroid cancer risk locus.

METHODS

We performed linkage disequilibrium (LD) and haplotype analyses to fine map the 15q22 locus. Luciferase reporter assays were applied to evaluate the regulatory effects of the candidate variants. Knockdown by small interfering RNA, microarray analysis, chromatin immunoprecipitation (ChIP) and quantitative real-time polymerase chain reaction assays were performed to reveal the regulatory gene network and identify its binding targets.

RESULTS

We report a 25.6-kb haplotype within SMAD3 containing numerous single-nucleotide polymorphisms (SNPs) in high LD. SNPs rs17293632 and rs4562997 were identified as functional variants of SMAD3 by luciferase assays within the LD region. These variants regulate SMAD3 transcription in an allele-specific manner through enhancer elements in introns of SMAD3. Knockdown of SMAD3 in thyroid cancer cell lines revealed its regulatory gene network including two upregulated genes, SPRY4 and SPRY4-IT1. Sequence analysis and ChIP assays validated the actual binding of SMAD3 protein to multiple SMAD binding element sites in the region upstream of SPRY4.

CONCLUSION

Our data provide a functional annotation of the 15q22 thyroid cancer risk locus.

Clinical impact of KMT2C and SPRY4 expression levels in intensively treated younger adult acute myeloid leukemia patients

OBJECTIVE

To evaluate the prognostic impact of gene expression levels (ELs) of two tumor suppressor genes, sprouty 4 (SPRY4, located on 5q) and lysine methyltransferase 2C (KMT2C, located on 7q) in correlation with clinical characteristics and genetic abnormalities assessed at initial diagnosis in acute myeloid leukemia (AML).

METHOD

Gene expression levels were measured on cDNA by RT-qPCR from diagnostic bone marrow samples of 275 intensively treated adult AML patients (median age, 48 years).

RESULTS

KMT2C ELs were significantly lower in abn7q/-7 (P = .001), whereas SPRY4 ELs were not associated with abn5q/-5. Higher KMT2C and SPRY4 ELs were significantly associated with lower genetic risk groups as defined by the European LeukemiaNet classification. Additionally, KMT2C ELs were lower in cytogenetically normal patients with DNMT3A (P = .01) or FLT3-ITD mutations (P = .05). KMT2C ELs were not associated with prognosis, whereas higher SPRY4 ELs showed a favorable impact on event-free (EFS, P = .01), relapse-free (RFS, P = .01) and in-trend on overall survival (P = .06) for cytogenetically abnormal patients, which was confirmed in multivariable analysis for EFS (HR, 0.84; 95%-CI, 0.73-0.97; P = .02) and RFS (HR, 0.85; 95%-CI, 0.73-0.98; P = .02).

CONCLUSION

Our data indicate that KMT2C ELs are associated with specific genetic features and that SPRY4 ELs may add prognostic information.

H3K27 acetylation activated-long non-coding RNA CCAT1 affects cell proliferation and migration by regulating SPRY4 and HOXB13 expression in esophageal squamous cell carcinoma

Recently, long non-coding RNAs (lncRNAs) have been shown to have important regulatory roles in human cancer biology. In our study, we found that lncRNA CCAT1, whose expression is significantly increased and is correlated with outcomes in Esophageal Squamous Cell Carcinoma (ESCC). Consecutive experiments confirmed that H3K27-acetylation could activate expression of colon cancer associated transcript-1 (CCAT1). Further experiments revealed that CCAT1 knockdown significantly repressed the proliferation and migration both in vitro and in vivo. RNA-seq analysis revealed that CCAT1 knockdown preferentially affected genes that are linked to cell proliferation, cell migration and cell adhesion. Mechanistic investigations found that CCAT1 could serve as a scaffold for two distinct epigenetic modification complexes (5΄ domain of CCAT1 binding Polycomb Repressive Complex 2 (PRC2) while 3΄ domain of CCAT1 binding SUV39H1) and modulate the histone methylation of promoter of SPRY4 (sprouty RTK signaling antagonist 4) in nucleus. In cytoplasm, CCAT1 regulates HOXB13 as a molecular decoy for miR-7, a microRNA that targets both CCAT1 and HOXB13, thus facilitating cell growth and migration. Together, our data demonstrated the important roles of CCAT1 in ESCC oncogenesis and might serve as targets for ESCC diagnosis and therapy.

Sprouty4 mRNA variants and protein expressions in breast and lung-derived cells

Sprouty proteins are modulators of mitogen-induced signalling processes and are therefore hypothesized to affect malignant diseases. As a member of the Sprouty family, Sprouty4 has been previously shown to function as a tumour suppressor in lung and breast cancer. The present study analysed the expression of two known Sprouty4 splice variants in cells established from malignant and normal lung and breast tissues using semi-quantitative reverse transcription-polymerase chain reaction and immunoblotting. The results indicated that the expression of the two messenger RNA (mRNA) variants was reduced in the cells derived from malignant tissue in comparison to the normal counterparts. Although the expression of the two splice variants were associated in both tissue types, on average, the relative expression of the longer variant was slightly increased in malignant cells compared with normal tissues. Notably, the protein levels reflected the expression observed at the mRNA level only in breast-derived cells. Contrarily, with regards to the measured mRNA levels, Sprouty4 protein was disproportional augmented in lung cells known to harbour the mutated K-Ras gene.

MicroRNA-21 Increases Proliferation and Cisplatin Sensitivity of Osteosarcoma-Derived Cells

Osteosarcoma is the most common primary bone tumor and poor prognosis for osteosarcoma patients is mainly due to chemotherapy resistance. MicroRNAs are important to maintain pathophysiological mechanisms of cancer and influence cell sensitivity to chemotherapy. In this study, we tested the functions of microRNA-21 for malignant features as well as for drug resistance of osteosarcoma. We used Northern blot to measure microRNA-21 levels in osteosarcoma-derived cell lines. MicroRNA-21 activity was modulated by either expressing a sponge to decrease its activity in an osteosarcoma-derived cell line expressing high levels of microRNA-21 or by introducing pri-microRNA-21 in a cell line with low endogenous levels. Cell migration was determined in a scratch assay and cell proliferation was measured by performing growth curve analysis. Sensitivity of the cells towards chemotherapeutics was investigated by performing cell viability assays and calculating the IC50 values. While cell migration was unaffected by modulated microRNA-21 levels, microRNA-21 inhibition slowed proliferation and exogenously expressed microRNA-21 promoted this process. Modulated microRNA-21 activity failed to effect sensitivity of osteosarcoma-derived cell lines to doxorubicin or methotrexate. Contrarily, reduction of microRNA-21 activity resulted in enhanced resistance towards cisplatin while ectopic expression of microRNA-21 showed the opposite effect. Increased microRNA-21 levels repressed the expression of Sprouty2 and ectopic expression of Sprouty2 was able to largely rescue the observed effects of microRNA-21 in osteosarcoma. In summary, our data indicate that in osteosarcoma microRNA-21 expression is an important component for regulation of cell proliferation and for determining sensitivity to cisplatin.

Suppression of Spry4 enhances cancer stem cell properties of human MDA-MB-231 breast carcinoma cells

BACKGROUND

Cancer stem cells contribute to tumor initiation, heterogeneity, and recurrence, and are critical targets in cancer therapy. Sprouty4 (Spry4) is a potent inhibitor of signal transduction pathways elicited by receptor tyrosine kinases, and has roles in regulating cell proliferation, migration and differentiation. Spry4 has been implicated as a tumor suppressor and in modulating embryonic stem cells.

OBJECTIVES

The purpose of this research was to test the novel idea that Spry4 regulates cancer stem cell properties in breast cancer.

METHODS

Loss-of function of Spry4 in human MDA-MB-231 cell was used to test our hypothesis. Spry4 knockdown or control cell lines were generated using lentiviral delivery of human Spry4 or non-targeting control shRNAs, and then selected with 2 μg/ml puromycin. Cell growth and migratory abilities were determined using growth curve and cell cycle flow cytometry analyses and scratch assays, respectively. Xenograft tumor model was used to determine the tumorigenic activity and metastasis in vivo. Cancer stem cell related markers were evaluated using immunoblotting assays and fluorescence-activated cell sorting. Cancer stem cell phenotype was evaluated using in vitro mammosphere formation and drug sensitivity tests, and in vivo limiting dilution tumor formation assay.

RESULTS

Two out of three tested human Spry4 shRNAs significantly suppressed the expression of endogenous Spry4 in MDA-MB-231 cells. Suppressing Spry4 expression increased MDA-MB-231 cell proliferation and migration. Suppressing Spry4 increased β3-integrin expression, and CD133(+)CD44(+) subpopulation. Suppressing Spry4 increased mammosphere formation, while decreasing the sensitivity of MDA-MB-231 cells to Paclitaxel treatment. Finally, suppressing Spry4 increased the potency of MDA-MB-231 cell tumor initiation, a feature attributed to cancer stem cells.

CONCLUSIONS

Our findings provide novel evidence that endogenous Spry4 may have tumor suppressive activity in breast cancer by suppressing cancer stem cell properties in addition to negative effects on tumor cell proliferation and migration.

Differential Effects of Variations at Codon 106 on Sprouty2 Functions in Lung Cancer-Derived Cells

Sprouty2 is a modulator of receptor tyrosine kinase-mediated signalling with an important role during lung carcinogenesis. Here, we characterize a Sprouty2 variant harbouring a substitution of proline 106 with serine. Serine substitution fails to influence expression, but accumulation of slower migrating phosphatase-sensitive forms indicates that its presence facilitates phosphorylation. In normal lung cells the serine variant is slightly more potent in inhibiting proliferation and migration. Additionally non-malignant cells expressing the major Sprouty2 variant attach more effective to fibronectin, while the serine variant only weakly stimulates cell adhesion. Mechanistically, the serine variant interferes less effectively with mitogen-activated protein kinase induction in response to serum. Concerning the positive Sprouty2 effect on epidermal growth factor receptor activation the serine variant is more potent. In all lung cancer-derived cell lines proliferation is more effectively inhibited if the Sprouty2 protein harbours the serine. In contrast, an increased interference of the serine Sprouty2 variant is only observed in cells with unaltered K-Ras. In cells harbouring a K-Ras mutation the serine conversion weakens the reduction of migration velocity indicating that dependent on the status of K-Ras the serine influences Sprouty2 functions differently. Accordingly, cell adhesion in cells with unaffected K-Ras is only stimulated by a Sprouty2 protein harbouring proline, while a serine conversion improves the attachment of the cells with constitutive active Ras. In summary our studies demonstrate that substitution of proline by serine at position 106 has biological significance and that the observed effects of this conversion depend on the activation status of endogenous K-Ras. J. Cell. Biochem. 117: 1822-1832, 2016. © 2016 Wiley Periodicals, Inc.

The increased Sprouty4 expression in response to serum is transcriptionally controlled by Specific protein 1

Sprouty proteins control length and intensity of the intracellular signal transduction cascade activated by mitogens in the cellular environment. As part of a negative feedback loop, their expression is supposed to be elevated by the same factors. In this report, Sprouty4 expression in response to serum and the underlying regulatory mechanisms were investigated. We verified that Sprouty4 expression is activated by serum addition in all tested cells independent of their origin. Strict correlation between Sprouty4 protein levels and promoter activity indicates mainly transcriptional regulation of Sprouty4 serum-responsiveness. Induction of the mitogen-activated protein kinase pathway is required for Sprouty4 promoter activation in the presence of serum. Nonetheless, signal transduction via this pathway is not sufficient to fully induce the Sprouty4 promoter. Instead, deletion and mutation analysis identified two annotated Specific protein 1 binding sites as the critical cis-elements responsible for conferring the serum induction of the promoter. Corroborating, repressed Specific protein 1 activity or levels result in constitutive lowered transcriptional activity of the Sprouty4 promoter. These data demonstrate that Specific protein 1 plays a crucial role in the regulation of Sprouty4 in response to serum.

The developing story of Sprouty and cancer

Sprouty proteins are evolutionarily conserved modulators of MAPK/ERK pathway. Through interacting with an increasing number of effectors, mediators, and regulators with ultimate influence on multiple targets within or beyond ERK, Sprouty orchestrates a complex, multilayered regulatory system and mediates a crosstalk among different signaling pathways for a coordinated cellular response. As such, Sprouty has been implicated in various developmental and physiological processes. Evidence shows that ERK is aberrantly activated in malignant conditions. Accordingly, Sprouty deregulation has been reported in different cancer types and shown to impact cancer development, progression, and metastasis. In this article, we have tried to provide an overview of the current knowledge about the Sprouty physiology and its regulatory functions in health, as well as an updated review of the Sprouty status in cancer. Putative implications of Sprouty in cancer biology, their clinical relevance, and their proposed applications are also revisited. As a developing story, however, role of Sprouty in cancer remains to be further elucidated.

Sprouty 2 protein, but not Sprouty 4, is an independent prognostic biomarker for human epithelial ovarian cancer

Sprouty proteins are evolutionary-conserved modulators of receptor tyrosine kinase signaling, deregulation of which has been implicated in the pathophysiology of cancer. In the present study, the expression status of Spry2 and Spry4 proteins and its clinical relevance in human epithelial ovarian cancer (EOC) were investigated retrospectively. We examined the immunohistochemical expression of Spry2 and Spry4 in matched tumor and normal tissue samples from 99 patients. The expression of ERK, p-ERK, Ki67, fibroblast growth factor-2, vascular endothelial growth factor and interleukin-6 and their correlation with Sprouty homologs were also evaluated. Moreover, the correlation between Spry2 and Spry4 and the clinicopathological characteristics were analyzed along with their predictive value for overall survival (OS) and disease-free survival (DFS). Our data indicated significant downregulation of Spry2 and Spry4 in tumor tissues (p < 0.0001). A significant inverse correlation was evident between Spry2 and p-ERK/ERK (p = 0.048), Ki67 (p = 0.011), disease stage (p = 0.013), tumor grade (p = 0.003), recurrence (p < 0.001) and post-treatment ascites (p = 0.001), individually. It was found that Spry2 low-expressing patients had significantly poorer OS (p = 0.002) and DFS (p = 0.004) than those with high expression of Spry2. Multivariate analysis showed that high Spry2 (p = 0.018), low stage (p = 0.049) and no residual tumor (p =0.006) were independent prognostic factors for a better OS. With regard to DFS, high Spry2 (p = 0.044) and low stage (p = 0.046) remained as independent predictors. In conclusion, we report for the first time significant downregulation of Spry2 and Spry4 proteins in human EOC. Spry2 expression was revealed to significantly impact tumor behavior with predictive value as an independent prognostic factor for survival and recurrence.

The expression of the Sprouty 1 protein inversely correlates with growth, proliferation, migration and invasion of ovarian cancer cells

Background

Our recent study on a panel of human ovarian cancer cells revealed that SKOV-3 cells barely express the Sprouty isoform 1 (Spry1) while 1A9 cells maintain it at a level similar to normal ovarian cells. Here we investigated the functional outcomes of induced alterations in the expression of Spry1 in the two cell lines in vitro.

Methods

Using the Spry1 specific plasmid and siRNA, the expression of Spry1 was induced and conversely silenced in SKOV-3 and 1A9 cells, respectively. The functional outcome was investigated by means of proliferation, MTT, scratch-wound, migration and invasion assays and selection of the stable clones. Mechanism of the effect was explored by Western blot.

Results

In the Spry1-transfected SKOV-3 cells, a significant reduction in growth and proliferation was evident. Stable clones of the Spry1-transfected SKOV-3 were almost undetectable after day 14. The number of migrated and invaded cells and the percentage of the scratch closure were significantly lower in the Spry1-transfected group. Spry1 silencing in 1A9 cells, on the other hand, led to a significant increase in cell growth and proliferation. The number of migrated and invaded cells and the percentage of the scratch closure significantly increased in Spry1-silenced 1A9 group. Mechanistically, overexpression of Bax, activation of caspases 3, 7, 8 and 9, cleavage of PARP and attenuation of Bcl-2 and Bcl-xl were observed along with reduced activation of Erk and Akt and increased amount and activity of PTEN in the Spry1-transfected SKOV-3 cells.

Conclusions

Here, we report the inverse correlation between the expression of Spry1 and growth, proliferation, invasion and migration of ovarian cancer cells.