Current Molecular Medicine (v.16, #6)

Meet Our Associate Editor by Guo-Tong Xu (525-525).

Prostate cancer is highly prevalent among men in developed countries, but a significant proportion of detected cancers remain indolent, never progressing into aggressive carcinomas. This highlights the need to develop refined biomarkers that can distinguish between indolent and potentially dangerous cases. The prostate-specific G-protein coupled receptor (PSGR, or OR51E2) is an olfactory receptor family member with highly specific expression in human prostate epithelium that is highly overexpressed in PIN and prostate cancer. PSGR has been functionally implicated in prostate cancer cell invasiveness, suggesting a potential role in the transition to metastatic PCa. Recently, transgenic mice overexpressing PSGR in the prostate were reported to develop an acute inflammatory response followed by emergence of low grade PIN, whereas mice with compound PSGR overexpression and loss of PTEN exhibited accelerated formation of invasive prostate adenocarcinoma. This article will review recent PSGR findings with a focus on its role as a potential prostate cancer biomarker and regulator of prostate cancer invasion and inflammation.

The Role of the PERK/eIF2α/ATF4/CHOP Signaling Pathway in Tumor Progression During Endoplasmic Reticulum Stress by W. Rozpedek, D. Pytel, B. Mucha, H. Leszczynska, J.A. Diehl, I. Majsterek (533-544).
Hypoxia is a major hallmark of the tumor microenvironment that is strictly associated with rapid cancer progression and induction of metastasis. Hypoxia inhibits disulfide bond formation and impairs protein folding in the Endoplasmic Reticulum (ER). The stress in the ER induces the activation of Unfolded Protein Response (UPR) pathways via the induction of protein kinase RNA-like endoplasmic reticulum kinase (PERK). As a result, the level of phosphorylated Eukaryotic Initiation Factor 2 alpha (eIF2α) is markedly elevated, resulting in the promotion of a pro-adaptive signaling pathway by the inhibition of global protein synthesis and selective translation of Activating Transcription Factor 4 (ATF4). On the contrary, during conditions of prolonged ER stress, pro-adaptive responses fail and apoptotic cell death ensues. Interestingly, similar to the activity of the mitochondria, the ER may also directly activate the apoptotic pathway through ER stress-mediated leakage of calcium into the cytoplasm that leads to the activation of death effectors. Apoptotic cell death also ensues by ATF4-CHOP- mediated induction of several pro-apoptotic genes and suppression of the synthesis of anti-apoptotic Bcl-2 proteins. Advancing molecular insight into the transition of tumor cells from adaptation to apoptosis under hypoxia-induced ER stress may provide answers on how to overcome the limitations of current anti-tumor therapies. Targeting components of the UPR pathways may provide more effective elimination of tumor cells and as a result, contribute to the development of more promising anti-tumor therapeutic agents.

Small RNAs Play Big Roles: MicroRNAs in Diabetic Wound Healing by F. Fahs, X.-L. Bi, F.-S. Yu, L. Zhou, Q.-S. Mi (545-552).
Skin and corneal wounds in diabetics are a major healthcare burden. MicroRNAs are small, non-coding RNAs that post-transcriptionally regulate the expression of proteincoding genes. Studies have identified microRNAs involved in all phases of wound healing. The dysregulation of microRNAs can contribute to impaired or delayed skin and corneal wound healing in diabetics. Here, we present a comprehensive review of the literature involving microRNAs in diabetic skin and corneal wound healing as well as those serving as potential biomarkers for diabetic wound healing.

Human Adipose-Derived Stem Cells Delay Retinal Degeneration in Royal College of Surgeons Rats Through Anti-Apoptotic and VEGF-Mediated Neuroprotective Effects by Z. Li, J. Wang, F. Gao, J. Zhang, H. Tian, X. Shi, C. Lian, Y. Sun, W. Li, J.-Y. Xu, P. Li, J. Zhang, Z. Gao, J. Xu, F. Wang, L. Lu, G.-T. Xu (553-566).
Stem cell therapy is a promising therapeutic approach for retinal degeneration (RD). Our study investigated the effects of human adipose derived stem cell (hADSCs) on Royal College of Surgeons (RCS) rats.
Methods: Green fluorescent protein (GFP)-labeled hADSCs were transplanted subretinally into RCS rats at postnatal (PN) 21 days to explore potential therapeutic effects, while adeno-associated viral vector (AAV2)-vascular endothelial growth factor (VEGF) and siVEGF-hADSCs were used to aid the mechanistic dissections. Visual function was evaluated by Electroretinogram (ERG) recording. Potential transdifferentiations were examined by Immunofluorescence (IF) and gene expressions were analyzed by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Apoptotic retinal cells were detected by Terminal Deoxynucleotidyl Transferase dUTP Nick End Labeling (TUNEL) assay and the cytokines secreted by hADSCs were measured by Enzyme-linked Immunosorbent Assay (ELISA).
Results: The visual function of RCS rats began to decrease one week after their eyes opened at PN week 3 and almost lost in PN 5 weeks, accompanied by the loss of retinal outer nuclear layer (ONL). Subretinal transplantation of hADSCs significantly improved the visual function 2 weeks after the transplantation and such therapeutic effect persisted up to 8 weeks after the treatment (PN 11 weeks), with 3-4 rows of photoreceptors remained in the ONL and reduced apoptosis. Consistent with these phenotypic changes, the gene expression of rod photoreceptor markers Rhodopsin (Rho), Crx and Opsin (Opn1) in RCS rats showed obvious decreasing trends over time after PN 3 weeks, but were elevated with hADSC treatment. hADSC transplantation also repressed the expressions of Bax, Bak and Caspase 3, but not the expression of anti-apoptotic genes, including Bcl-2 and Bcl-XL. Finally, substantial VEGF, hepatocyte growth factor (HGF) and pigment epithelium-derived factor (PEDF) secretions from hADSCs were detected, while endogenous Vegf expression level decreased over time in RCS rats. The treatment of AAV2-VEGF showed comparable therapeutic effects as hADSCs but siRNA knockdown of VEGF in hADSCs essentially abolished the therapeutic effects.
Conclusions: Subretinal transplantation of hADSCs in RCS rats effectively delayed the retinal degeneration, enhanced the retinal cell survival and improved the visual function. Mechanistically this was mainly due to hADSC dependent anti-apoptotic and neuroprotective effects through its secretion of growth and neurotrophic factors including VEGF. Clinical application of hADSCs merits further investigation.

Subpopulations of Bone Marrow Mesenchymal Stem Cells Exhibit Differential Effects in Delaying Retinal Degeneration by P. Li, H. Tian, Z. Li, L. Wang, F. Gao, Q. Ou, C. Lian, W. Li, C. Jin, J. Zhang, J.-Y. Xu, J. Wang, J. Zhang, F. Wang, L. Lu, G.-T. Xu (567-581).
Bone marrow mesenchymal stem cells (BMSCs) have a therapeutic role in retinal degeneration (RD). However, heterogeneity of BMSCs may be associated with differential therapeutic effects in RD. In order to confirm this hypothesis, two subsets of rat BMSCs, termed rBMSC1 and rBMSC2, were obtained, characterized and functionally evaluated in the treatment of RD of Royal College of Surgeons (RCS) rats. Both subpopulations expressed mesenchymal stem cells (MSC) markers CD29 and CD90, but were negative for hemacyte antigen CD11b and CD45 expression. In comparison with rBMSC2, rBMSC1 showed higher rate of proliferation, stronger colony formation, and increased adipogenic potential, whereas rBMSC2 exhibited higher osteogenic potential. Microarray analysis showed differential gene expression patterns between rBMSC1 and rBMSC2, including functions related to proliferation, differentiation, immunoregulation, stem cell maintenance and division, survival and antiapoptosis. After subretinal transplantation in RCS rats, rBMSC1 showed stronger rescue effect than rBMSC2, including increased b-wave amplitude, restored retinal nuclear layer thickness, and decreased number of apoptotic photoreceptors, whereas the rescue function of rBMSC2 was essentially not better than the control. Histological analysis also demonstrated that rBMSC1 possessed a higher survival rate than rBMSC2 in subretinal space. In addition, treatment of basic fibroblast growth factor, an accompanying event in subretinal injection, triggered more robust increase in secretion of growth factors by rBMSC1 as compared to rBMSC2. Taken together, these results have suggested that the different therapeutic functions of BMSC subpopulations are attributed to their distinct survival capabilities and paracrine functions. The underlying mechanisms responsible for the different functions of BMSC subpopulation may lead to a new strategy for the treatment of RD.

LASS5 Interacts with SDHB and Synergistically Represses p53 and p21 Activity by Z. Jiang, F. Li, Y. Wan, Z. Han, W. Yuan, L. Cao, Y. Deng, X. Peng, F. Chen, X. Fan, X. Liu, G. Dai, Y. Wang, Q. Zeng, Y. Shi, Z. Zhou, Y. Chen, W. Xu, S. Luo, S. Chen, X. Ye, X. Mo, X. Wu, Y. Li (582-590).
Longevity Assurance 5 (LASS5), a member of the LASS/Ceramide Synthases family, synthesizes C16-ceramide and is implicated in tumor biology. However, its precise role is not yet well understood. A yeast two-hybrid screen was performed using a human cDNA library to identify potential LASS5- interaction partners. One identified clone encodes succinate dehydrogenase subunit B (SDHB). Mammalian two-hybrid assays showed that LASS5 interacts with SDHB, and the result was also confirmed by GST pull-down and coimmunoprecipitation assays. The C-terminal fragment of SDHB was required for the interaction. LASS5 and SDHB were co-localized in COS-7 cells. LASS5 and SDHB expressions were found to be up-regulated in neuroglioma tissue. Transfection assays showed that LASS5 or SDHB expression repressed p53 or p21 reporter activity, respectively. Simultaneous LASS5 and SDHB expression resulted in stronger repression of p53 and p21 reporter activity, suggesting that LASS5 and SDHB interaction may synergistically affect transcriptional regulation of p53 and p21. Our data provide new molecular insights into potential roles of LASS5 and SDHB in tumor biology.

The normal function of pancreatic beta cells is vital to the control of blood glucose. Earlier research suggests that the traditional Chinese medicine Cortex Lycii Radicis may help protect pancreatic beta cells and improve insulin sensitivity. However, the specific effects and molecular mechanism of this herb have not been described. Thus, we investigated the role of Cortex Lycii Radicis in regulating the proliferation, apoptosis, and autophagy of INS-1 pancreatic beta cells. Our study revealed that Cortex Lycii Radicis extracts could promote INS-1 cell proliferation and inhibit cell apoptosis under high glucose conditions. We also evaluated the formation of autophagosomes and found that GFP-LC3 fusion protein was translocated to the autophagosome membrane. Autophagosomes increased in the group treated with Cortex Lycii Radicis compared with the no treatment control group, indicating that these extracts could promote the activation of autophagy in INS-1 cells. Our findings suggest a significant association of the Cortex Lycii Radicis extracts treatment with apoptosis and autophagy, which protects the function of pancreatic beta cells, providing evidence for the development of a new drug for diabetes treatment.

Follistatin-related protein (FSRP), which belongs to a member of the follistatin family, has been postulated to be a new negative regulator of myostatin (MSTN) and is involved in muscle development. In this study, we cloned the complete cDNA sequence of FSRP-1 from Chinese perch muscle. FSRP-1 mRNA was highly expressed in the fast muscle and brain tissue of adult fish. The expression of FSRP-1 rapidly increased at 90 days post hatching (dph) in the fast muscle of Chinese perch. Furthermore, to investigate the roles of FSRP-1 in muscle growth, we constructed a FSRP- 1 expression vector and isolated FSRP-1 fusion protein. The purified FSRP-1 fusion protein was injected into the muscle tissues of the Chinese perch (90 dph). The results showed that the number of muscle fibers and the satellite cell activation frequency were increased in the FSRP-1 treatment group. In addition, the myostatin (MSTN) expression was significantly decreased upon the FSRP-1 treatment. Collectively, the results suggest a possible mechanism of the FSRP-1 for inhibiting MSTN activity and enhancing muscle growth and renewal in vivo, and it may provide an applicable implication for the defected muscle repairing and regeneration.