Expression, purification, and therapeutic implications of recombinant sFRP1

Expression and purification of recombinant human CCL5 and its biological characterization

C-C motif chemokine ligand 5 (CCL5) is crucial in the tumor microenvironment. It has been previously reported to act as a key role in tumor invasion and metastasis. However, the function of exogenous CCL5 in ovarian cancer has not been well-characterized. The present study attempted to express and purify recombinant CCL5 protein and investigate the exogenous CCL5 in ovarian cancer cell proliferation. The human CCL5 was amplified and inserted into the pET-30a vectors for prokaryotic expression in Escherichia coli BL21. Soluble His-CCL5 was successfully expressed with 0.1 mmol/L of isopropyl-β-D-1-tiogalactopiranoside at 25 ℃ and purified by affinity chromatography. Additionally, methyl thiazolyl tetrazolium (MTT) assay demonstrated that CCL5 promotes ovarian cancer cell proliferation; increases the phosphorylation levels of extracellular-signal-regulated kinase and mitogen-activated protein kinase/ERK kinase, and increases the mRNA levels of Jun, NF-κB2, Nras, Relb, and Traf2. Furthermore, treatment with the MEK inhibitor reduced the Jun, NF-κB2, and Traf2 mRNA levels, indicating that exogenous CCL5 increased ovarian cancer cell proliferation, through MEK/ERK pathway activation, and Jun, NF-κB2, and Traf2 expression. The present study provided primary data for further studies to discover more CCL5 functions in ovarian cancer.

Impact of Human Papillomavirus on Wnt/Beta-Catenin Signaling in Morphological Inconspicuous Cervicovaginal Cells

INTRODUCTION

The aim of this study was to identify early changes in the Wnt/beta-catenin signaling pathway in high-risk human papillomavirus (HPV) infected cervicovaginal cells and to correlate these changes with cell proliferation, apoptosis, and autophagic processes.

METHODS

We evaluated 91 cervicovaginal smears of women with (n = 41) and without (n = 50) HPV-DNA. Smears were stained against beta-catenin, c-myc, secreted frizzled-related protein 4 (sFRP4), cleaved caspase-3, and the autophagy markers Beclin-1 and light chain 3B. In addition, sFRP-1, -2, -3, -4, -5 mRNA levels were determined by quantitative reverse transcription-PCR in primary keratinocytes and FaDu cells expressing HPV16-E6, -E7, or -E6E7.

RESULTS

Our data indicated that the Wnt/beta-catenin signaling is activated in HPV (+) cervicovaginal cells that can already be detected in cells with no obvious changes in cellular morphology (HPV [+]/cyto [-]). These cells also had significantly higher sFRP4 levels when compared to HPV-negative samples. In primary keratinocytes, sFRP4 was found to be absent and sFRP1 and sFRP2 to be repressed in the presence of HPV16-E6 and E7. Interestingly, sFRP4 is expressed in FaDu cells and can be upregulated in the presence of E6E7. Curiously, SFRP4 expression correlated with an increase in the level of autophagic markers in HPV (+)/cyto (-) smears.

CONCLUSION

In conclusion, the activation of the Wnt/beta-catenin signaling pathway and upregulation of sFRP4, paralleled by an activation of the autophagic pathway may represent predisposing cellular factors early after HPV infection which need to be further determined in larger study.

Purification of recombinant human chemokine CCL2 in E. coli and its function in ovarian cancer

Chemokine (CC-motif) ligand 2 (CCL2) is an inflammatory cytokine that regulates the infiltration and migration of monocytes. It is highly expressed by both tumor and stromal cells and has been associated with tumorigenesis. However, the effect of the exogenous administration of CCL2 on ovarian cancer remains largely unknown. In this report, we attempted to establish an expression system in Escherichia coli to produce recombinant hCCL2. The recombinant plasmid containing the hCCL2 cDNA was prepared using the prokaryotic-expression plasmid pGEX-5X-3 and transformed into E. coli BL21. GST-hCCL2 was successfully induced by 0.1 mmol/L IPTG at 20 °C for 6 h, and the recombinant protein was purified using affinity chromatography. The purified protein was identified by SDS-PAGE and Western Blot. In vitro experiments revealed that rhCCL2 promoted the proliferation of ovarian cancer cells and increased the levels of phosphorylation of MEK and ERK1/2, and the levels of JUN, RELB and NF-κB2 mRNA. Furthermore, inhibition of ERK signaling by treatment with PD98059 decreased ovarian cancer cell proliferation and levels of JUN, RELB, and NF-κB2 mRNA, indicating that exogenous rhCCL2 increased the proliferation of ovarian cancer cells, partially by activating the MAPK/ERK pathway, and by targeting JUN, RELB, and NF-κB2. Our study uncovered a promoting role of exogenous CCL2 on ovarian cancer cell proliferation through the MAPK/ERK signaling pathway, which may facilitate the discovery of more potential roles of CCL2 in ovarian cancer.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-020-02571-0.

Loss of SFRP1 expression is a key progression event in gastrointestinal stromal tumor pathogenesis

The mechanism of high-grade transformation in gastrointestinal stromal tumors (GISTs) remains to be clarified. We aim to discover the key progression events by studying biphasic GISTs. The study group included 101 GISTs. Nineteen of these had been screened from 263 GISTs to represent the early stage of GIST high-grade transformation, characterized by juxtaposed low-grade and high-grade regions in the same tumor (so-called biphasic GISTs). Mutational analyses, fluorescence in situ hybridization (FISH), NanoString analyses, telomere analysis, and gene expression profiling were carried out, followed by in silico analyses, cell line study, and immunohistochemical validation. Using gene expression analysis, downregulation of SFRP1 was revealed to be the main event in GIST high-grade transformation (p = 0.013), accompanied by upregulation of EZH2. In silico analyses revealed that downregulation of SFRP1 was a common feature in GIST progression across several different series. Immunohistochemically, the expression of SFRP1 was validated to be significantly lower in high-grade GISTs (WHO risk group 3a or higher) than in low-grade GISTs (p < 0.001), and attenuation/loss of SFRP1 was associated with GIST tumor progression (p < 0.001). By NanoString and FISH analyses, chromosomal 9/9p loss was the only recurrent large-scale chromosome aberration in biphasic GISTs, with a correlation with SFRP1 downregulation. Subclones containing chromosome 9/9p loss could be appreciated in the low-grade parts of biphasic GISTs. TP53 mutation, RB1 loss, KIT/PDGFRA mutation, and alternative lengthening of telomeres did not play a significant role in GIST high-grade transformation. In conclusion, high-grade transformation of GISTs features SFRP1 downregulation and chromosome 9/9p loss.

SFRP1 increases TMPRSS2-ERG expression promoting neoplastic features in prostate cancer in vitro and in vivo

Background

Prostate cancer (PCa) is the second cause of cancer related death in North American men. Androgens play an important role in its progression by regulating the expression of several genes including fusion ones that results from structural chromosome rearrangements. TMPRSS2-ERG is a fusion gene commonly observed in over 50% of PCa tumors, and its expression can be transcriptionally regulated by the androgen receptor (AR) given its androgen responsive elements. TMPRSS2-ERG could be involved in epithelial–mesenchymal transition (EMT) during tumor development. ERG has been reported as a key transcriptional factor in the AR-ERG-WNT network where five SFRP proteins, structurally similar to WNT ligands and considered to be WNT pathway antagonists, can regulate signaling in the extracellular space  by binding to WNT proteins or Frizzled receptors. It has been shown that over-expression of SFRP1 protein can regulate the transcriptional activity of AR and inhibits the formation of colonies in LNCaP cells. However, the effect of SFRP1 has been controversial since differential effects have been observed depending on its concentration and tissue location. In this study, we explored the role of exogenous SFRP1 protein in cells expressing the TMPRSS2-ERG fusion.

Methods

To evaluate the effect of exogenous SFRP1 protein on PCa cells expressing TMPRSS2-ERG, we performed in silico analysis from TCGA cohort, expression assays by RT-qPCR and Western blot, cell viability and cell cycle measurements by cytometry, migration and invasion assays by xCELLigance system and murine xenografts.

Results

We demonstrated that SFRP1 protein increased ERG expression by promoting cellular migration in vitro and increasing tumor growth in vivo in PCa cells with the TMPRSS2-ERG fusion.

Conclusions

These results suggest the possible role of exogenous SFRP1 protein as a modulator of AR-ERG-WNT signaling network in cells positive to TMPRSS2-ERG. Further, investigation is needed to determine if SFRP1 protein could be a target in against this type of PCa.

sFRP1 has a biphasic effect on doxorubicin-induced cardiotoxicity in a cellular location-dependent manner in NRCMs and Rats

Doxorubicin (Dox) is an effective anticancer drug, however, its clinical application is restricted by the life-threatening cardiotoxic effects. Secreted Frizzled-related protein 1 (sFRP1) has been reported to participate in both the cancer and cardiovascular diseases and was one of the differential expression genes in normal hearts compared with Dox-treated hearts. Thus, it is important to reveal the potential role of sFRP1 in Dox-induced cardiotoxicity. Here, we show that sFRP1 has a biphasic effect on Dox-induced cardiotoxicity in a location-dependent manner. The secretion of sFRP1 was significantly increased in Dox-treated neonatal rat cardiomyocytes (NRCMs) (1 µM) and SD rats (5 mg/kg/injection at day 1, 5, and 9, i.p.). Adding the anti-sFRP1 antibody (0.5 µg/ml) and inhibiting sFRP1 secretion by caffeine (5 mM) both relieved Dox-induced cardiotoxicity through activating Wnt/β-catenin signaling, whereas increasing the secretion of sFRP1 by heparin (100 µg/ml) had the opposite effect. The intracellular level of sFRP1 was significantly decreased after Dox treatment both in vitro and in vivo. Knockdown of sFRP1 by sgRNA aggravated Dox-induced cardiotoxicity, while moderate overexpression of sFRP1 by Ad-sFRP1 exhibited protective effect. Besides, poly(ADP-ribosyl) polymerase-1 (PARP1) was screened as an interacting partner of sFRP1 in NRCMs by mass spectrometry. Our results suggested that the intracellular sFRP1 protected NRCMs from Dox-induced cardiotoxicity by interacting with PARP1. Thus, our results provide a novel evidence that sFRP1 has a biphasic effect on Dox-induced cardiotoxicity. In addition, the oversecretion of sFRP1 might be used as a biomarker to indicate the occurrence of cardiotoxicity induced by Dox treatment.

Antagonizing canonical Wnt signaling pathway by recombinant human sFRP4 purified from E. coli and its implications in cancer therapy

The Wnt signaling pathway plays a predominant role in aberrant proliferation in myriad of cancers. In non-cancerous cells, Wnts are blocked by the secreted frizzled-related proteins (sFRPs) that are generally downregulated in cancer cells. We have purified and characterized bacterially expressed glutathione S-transferase-tagged SFRP4 from a novel clone generated from human cell origin. Cervical cancer (HeLa) and lung cancer (A549) cells, in which Wnt and associated genes were found to be expressed, were treated with the purified recombinant sFRP4, which revealed a significant dose-dependent cell growth inhibition up to 40 %. The current investigation on functionality of this bacterially produced recombinant sFRP4 in arresting cancer cell proliferation is the first of its kind, where G2/M phase arrest and early apoptosis were evident. Increase in phosphorylated β-catenin in sFRP4 treatment indicated inhibition of Wnt pathway, which was further confirmed by downregulation of pro-proliferative genes, namely cyclin D1, c-myc, and survivin. Functional activity of recombinant sFRP4 was further exploited in co-therapy module with chemotherapeutic drugs to decipher molecular events. Collectively, our study on purified recombinant sFRP4 from bacterial host holds great promise in targeting Wnt signaling for exploring new strategies to combat cancer.