Proteomic analysis of proton beam irradiated human melanoma cells

Melanoma, Melanin, and Melanogenesis: The Yin and Yang Relationship

Melanin pigment plays a critical role in the protection against the harmful effects of ultraviolet radiation and other environmental stressors. It is produced by the enzymatic transformation of L-tyrosine to dopaquinone and subsequent chemical and biochemical reactions resulting in the formation of various 5,6-dihydroxyindole-2-carboxylic acid (DHICA) and 5,6-dihydroxyindole (DHI) oligomers-main constituents of eumelanin, and benzothiazine and benzothiazole units of pheomelanin. The biosynthesis of melanin is regulated by sun exposure and by many hormonal factors at the tissue, cellular, and subcellular levels. While the presence of melanin protects against the development of skin cancers including cutaneous melanoma, its presence may be necessary for the malignant transformation of melanocytes. This shows a complex role of melanogenesis in melanoma development defined by chemical properties of melanin and the nature of generating pathways such as eu- and pheomelanogenesis. While eumelanin is believed to provide radioprotection and photoprotection by acting as an efficient antioxidant and sunscreen, pheomelanin, being less photostable, can generate mutagenic environment after exposure to the short-wavelength UVR. Melanogenesis by itself and its highly reactive intermediates show cytotoxic, genotoxic, and mutagenic activities, and it can stimulate glycolysis and hypoxia-inducible factor 1-alpha (HIF-1α) activation, which, combined with their immunosuppressive effects, can lead to melanoma progression and resistance to immunotherapy. On the other hand, melanogenesis-related proteins can be a target for immunotherapy. Interestingly, clinicopathological analyses on advanced melanomas have shown a negative correlation between tumor pigmentation and diseases outcome as defined by overall survival and disease-free time. This indicates a "Yin and Yang" role for melanin and active melanogenesis in melanoma development, progression, and therapy. Furthermore, based on the clinical, experimental data and diverse effects of melanogenesis, we propose that inhibition of melanogenesis in advanced melanotic melanoma represents a realistic adjuvant strategy to enhance immuno-, radio-, and chemotherapy.

Valosin-Containing Protein (VCP)/p97: A Prognostic Biomarker and Therapeutic Target in Cancer

Valosin-containing protein (VCP)/p97, a member of the AAA+ ATPase family, is a molecular chaperone recruited to the endoplasmic reticulum (ER) membrane by binding to membrane adapters (nuclear protein localization protein 4 (NPL4), p47 and ubiquitin regulatory X (UBX) domain-containing protein 1 (UBXD1)), where it is involved in ER-associated protein degradation (ERAD). However, VCP/p97 interacts with many cofactors to participate in different cellular processes that are critical for cancer cell survival and aggressiveness. Indeed, VCP/p97 is reported to be overexpressed in many cancer types and is considered a potential cancer biomarker and therapeutic target. This review summarizes the role of VCP/p97 in different cancers and the advances in the discovery of small-molecule inhibitors with therapeutic potential, focusing on the challenges associated with cancer-related VCP mutations in the mechanisms of resistance to inhibitors.

MCM7 silencing promotes cutaneous melanoma cell autophagy and apoptosis by inactivating the AKT1/mTOR signaling pathway

Cutaneous melanoma (CM) has become a major public health concern. Studies illustrate that minichromosome maintenance protein 7 (MCM7) participate in various diseases including skin disease. Our study aimed to study the effects of MCM7 silencing on CM cell autophagy and apoptosis by modulating the AKT threonine kinase 1 (AKT1)/mechanistic target of rapamycin kinase (mTOR) signaling pathway. Initially, microarray analysis was used to screen the CM-related gene expression data as well as differentially expressed genes. Subsequently, MCM7 expression vector and lentivirus RNA used for MCM7 silencing (LV-shRNA-MCM7) were constructed, and these vectors, dimethyl sulfoxide (DMSO) and AKT activator SC79 were then introduced into CM cell line SK-MEL-2 to validate the role of MCM7 in cell autophagy, viability, apoptosis, cell cycle, migration, and invasion. To further investigate the regulatory mechanisms of MCM7 in CM progress, the expression of MCM7, AKT1, mTOR, cyclin D1, as well as autophagy and apoptosis relative factors, such as LC3B, SOD2, DJ-1, p62, Bcl-2, Bax, and caspase-3 in melanoma cells was determined. MCM7 might mediate the AKT1/mTOR signaling pathway to influence the progress of melanoma. MCM7 silencing contributed to the increased expression of Bax, capase-3, and autophagy-related genes (LC3B, SOD2, and DJ-1), but decreased the expression of Bcl-2, which suggested that MCM7 silencing promoted autophagy and cell apoptosis. At the same time, MCM7 silencing also attenuated cell viability, invasion, and migration, and reduced the cyclin D1 expression and protein levels of p-AKT1 and p-mTOR. Taken together, MCM7 silencing inhibited CM via inactivation of the AKT1/mTOR signaling pathway.

The Highlighted Role of GAPDH and Nitric-Oxide Synthase Regulator Activity in Proton Beam Irradiated Melanoma BLM Cells

Introduction: The human melanoma is a type of invasive tumor the treatment of which is challenging. To better understand the proton irradiation mechanisms as one of the widely applied therapy for this type of cancer, bioinformatics analysis of proteomics outcome could be beneficial. Methods: Protein-protein interaction network analysis of the differentially expressed proteins (DEPs) of melanoma BLM (BRO lung metastasis) cells in the treatment of 3 Gy dosage proton therapy was performed in this study via Cytoscape V.3.7.2. and its integrated plug-ins. Results: Eighteen DEPs were searched for network constructions and limited numbers of query +neighbor proteins were found central. The hub-bottlenecks (i.e. central nodes) were GAPDH, ACTB, ALB, AKT1, TP53, and EGFR. The fist mentioned proteins were from DEPs. The enrichment analysis of these elements identified nitric-oxide synthase regulator activity and the positive regulation of the norepinephrine uptake that may be the key to the mechanisms of proton therapy. Conclusion: In conclusion, the identified central nodes (EGFR, TP53, ALB, AKT1, GAPDH, and ACTB) and the related biological terms are the critical affected genes and biological terms in the irradiated melanoma cells.

Medium-thickness-dependent proton dosimetry for radiobiological experiments

A calibration method was proposed in the present work to determine the medium-thickness-dependent proton doses absorbed in cellular components (i.e., cellular cytoplasm and nucleus) in radiobiological experiments. Consideration of the dependency on medium thickness was crucial as the linear energy transfer (LET) of protons could rise to a sharp peak (known as the Bragg peak) towards the end of their ranges. Relationships between the calibration coefficient R vs medium-layer thickness were obtained for incident proton energies of 10, 15, 20, 25, 30 and 35 MeV, and for various medium thicknesses up to 5000 μm, where R was defined as the ratio D_A/D_E, D_A was the absorbed proton dose in cellular components, and D_E was the absorbed proton dose in a separate radiation detector. In the present work, D_A and D_E were determined using the MCNPX (Monte Carlo N-Particle eXtended) code version 2.4.0. For lower incident proton energies (i.e., 10, 15 and 20 MeV), formation of Bragg-peak-like features were noticed in their R-vs-medium-layer-thickness relationships, and large R values of >7 and >6 were obtained for cytoplasm and nucleus of cells, respectively, which highlighted the importance of careful consideration of the medium thickness in radiobiological experiments.

Increased elasticity of melanoma cells after low-LET proton beam due to actin cytoskeleton rearrangements

Cellular response to non-lethal radiation stress include perturbations in DNA repair, angiogenesis, migration, and adhesion, among others. Low-LET proton beam radiation has been shown to induce somewhat different biological response than photon radiation. For example, we have shown that non-lethal doses of proton beam radiation inhibited migration of cells and that this effect persisted long-term. Here, we have examined cellular elasticity and actin cytoskeleton organization in BLM cutaneous melanoma and Mel270 uveal melanoma cells. Proton beam radiation increased cellular elasticity to a greater extent than X-rays and both types of radiation induced changes in actin cytoskeleton organization. Vimentin level increased in BLM cells after both types of radiation. Our data show that cell elasticity increased substantially after low-LET proton beam and persisted long after radiation. This may have significant consequences for the migratory properties of melanoma cells, as well as for the cell susceptibility to therapy.

Role of caprin-1 in carcinogenesis

RNA-binding proteins serve an essential role in post-transcriptional gene regulation. Cytoplasmic activation/proliferation-associated protein-1 (caprin-1) is an RNA-binding protein that participates in the regulation of cell cycle control-associated genes. Caprin-1 acts alone or in combination with other RNA-binding proteins, such as RasGAP SH3-domain-binding protein 1 and fragile X mental retardation protein. In the tumorigenesis process, caprin-1 primarily functions by activating cell proliferation and upregulating the expression of immune checkpoint proteins. Through the formation of stress granules, caprin-1 is also involved in the process by which tumor cells adapt to adverse conditions, which contributes to radiation and chemotherapy resistance. Given its role in various clinical malignancies, caprin-1 holds the potential to be used as a biomarker and a target for the development of novel therapeutics. The present review describes this newly identified putative oncogenic protein and its possible impact on tumorigenesis.

Transplantable Melanomas in Hamsters and Gerbils as Models for Human Melanoma. Sensitization in Melanoma Radiotherapy-From Animal Models to Clinical Trials

The focus of the present review is to investigate the role of melanin in the radioprotection of melanoma and attempts to sensitize tumors to radiation by inhibiting melanogenesis. Early studies showed radical scavenging, oxygen consumption and adsorption as mechanisms of melanin radioprotection. Experimental models of melanoma in hamsters and in gerbils are described as well as their use in biochemical and radiobiological studies, including a spontaneously metastasizing ocular model. Some results from in vitro studies on the inhibition of melanogenesis are presented as well as radio-chelation therapy in experimental and clinical settings. In contrast to cutaneous melanoma, uveal melanoma is very successfully treated with radiation, both using photon and proton beams. We point out that the presence or lack of melanin pigmentation should be considered, when choosing therapeutic options, and that both the experimental and clinical data suggest that melanin could be a target for radiosensitizing melanoma cells to increase efficacy of radiotherapy against melanoma.

Unraveling the human protein atlas of metastatic melanoma in the course of ultraviolet radiation-derived photo-therapy

To explore the photo-therapeutic capacity of UV radiation in solid tumors, we herein employed an nLC-MS/MS technology to profile the proteomic landscape of irradiated WM-266-4 human metastatic-melanoma cells. Obtained data resulted in proteomic catalogues of 5982 and 7280 proteins for UVB- and UVC-radiation conditions, respectively, and indicated the ability of UVB/C-radiation forms to eliminate metastatic-melanoma cells through induction of synergistically operating programs of apoptosis and necroptosis. However, it seems that one or more WM-266-4 cell sub-populations may escape from UV-radiation's photo-damaging activity, acquiring, besides apoptosis tolerance, an EMT phenotype that likely offers them the advantage of developing resistance to certain chemotherapeutic drugs. Low levels of autophagy may also critically contribute to the selective survival and growth of UV-irradiated melanoma-cell escapers. These are the cells that must be systemically targeted with novel therapeutic schemes, like the one of UV radiation and Irinotecan herein suggested to be holding strong promise for the effective treatment of metastatic-melanoma patients. Given the dual nature of UV radiation to serve as both anti-tumorigenic and tumorigenic agent, all individuals being subjected to risk factors for melanoma development have to be appropriately informed and educated, in order to integrate the innovative PPPM concept in their healthcare-sector management.

SIGNIFICANCE

This study reports the application of nLC-MS/MS technology to deeply map the proteomic landscape of UV-irradiated human metastatic-melanoma cells. Data bioinformatics processing led to molecular-network reconstructions that unearthed the dual nature of UV radiation to serve as both anti-tumorigenic and tumorigenic factor in metastatic-melanoma cellular environments. Our UV radiation-derived "photo-proteomic" atlas may prove valuable for the identification of new biomarkers and development of novel therapies for the disease. Given that UV radiation represents a major risk factor causing melanoma, a PPPM-based life style and clinical practice must be embraced by all individuals being prone to disease's appearance and expansion.

Upregulation of caprin1 expression is associated with poor prognosis in hepatocellular carcinoma

Caprin-1 has been found to promotes osteosarcoma tumor growth, lung metastasis in mice, regulating the proliferation and invasion of human breast cancer cells and up-regulated in proton beam irradiated human melanoma cells. However, its clinical role, biological function in the hepatocellular carcinoma (HCC) remains unknown. In the present study, we investigated the clinical significance of Caprin1 in the HCC. Caprin1 expression was detected by immunohistochemistry, and the expression level was analyzed in 65 HCC tissues and paired peritumoral tissue. Prognostic value of Caprin1 in HCC was evaluated in 174 cases using Kaplan-Meier analysis. Univariate survival analysis and multiple Cox proportional hazards regression were performed using the Cox regression analysis. Immunohistochemistry revealed that Caprin1 expression in 65 HCC tissues was upregulated compared to paired peritumoral tissue (p=0.0064). Survival analysis in 174 HCC patient tissues was showed that high Caprin1 expression was significantly associated with worse overall survival (HR=1.513, p=0.042). In conclusion, high Caprin1 expression independently predicts a poor outcome for patients with HCC, supporting that Caprin1 may be a promising novel HCC prognostic factor.

Differential Response and Priming Dose Effect on the Proteome of Human Fibroblast and Stem Cells Induced by Exposure to Low Doses of Ionizing Radiation

It has been suggested that a mechanistic understanding of the cellular responses to low dose and dose rate may be valuable in reducing some of the uncertainties involved in current risk estimates for cancer- and non-cancer-related radiation effects that are inherited in the linear no-threshold hypothesis. In this study, the effects of low-dose radiation on the proteome in both human fibroblasts and stem cells were investigated. Particular emphasis was placed on examining: 1. the dose-response relationships for the differential expression of proteins in the low-dose range (40-140 mGy) of low-linear energy transfer (LET) radiation; and 2. the effect on differential expression of proteins of a priming dose given prior to a challenge dose (adaptive response effects). These studies were performed on cultured human fibroblasts (VH10) and human adipose-derived stem cells (ADSC). The results from the VH10 cell experiments demonstrated that low-doses of low-LET radiation induced unique patterns of differentially expressed proteins for each dose investigated. In addition, a low priming radiation dose significantly changed the protein expression induced by the subsequent challenge exposure. In the ADSC the number of differentially expressed proteins was markedly less compared to VH10 cells, indicating that ADSC differ in their intrinsic response to low doses of radiation. The proteomic results are further discussed in terms of possible pathways influenced by low-dose irradiation.

Proton Beams Inhibit Proliferation of Breast Cancer Cells by Altering DNA Methylation Status

Proton beam therapy has been gaining popularity in the management of a wide spectrum of cancers. However, little is known about the effect of proton beams on epigenetic alterations. In this study, the effects of proton beams on DNA methylation were evaluated in the breast cell lines MCF-10A and MCF-7. Pyrosequencing analysis of the long interspersed element 1 (LINE1) gene indicated that a few specific CpG sites were induced to be hypermethylated by proton beam treatment from 64.5 to 76.5% and from 57.7 to 60.0% (p < 0.05) in MCF-10A and MCF-7, respectively. Genome-wide methylation analysis identified “Developmental Disorder, Hereditary Disorder, Metabolic Disease” as the top network in the MCF-7 cell line. The proliferation rate significantly decreased in proton beam-treated cells, as judged by colony formation and cell proliferation assay. Upon treatment with the proton beam, expression of selected genes (MDH2, STYXL1, CPE, FAM91A1, and GPR37) was significantly changed in accordance with the changes of methylation level. Taken together, the findings demonstrate that proton beam-induced physiological changes of cancer cells via methylation modification assists in establishing the epigenetic basis of proton beam therapy for cancer.

Biological effects of lentivirus-mediated silencing of minichromosome maintenance protein 7 with shRNA on the liver cancer MHCC-97H cells

OBJECTIVE

This study was to specifically silence the minichromosome maintenance protein 7 (MCM7) expressions with lentivirus-mediated RNA interference technique in liver cancer MHCC-97H cells and its biological consequences were investigated.

METHODS

Human MCM7 sequence was used for the design of shRNA targeting MCM7 which was then introduced to lentivirus, followed by transfection into MHCC-97H cells. Real time quantitative PCR and Western blot assay were performed to detect the mRNA and protein expression of MCM7 in these cells. MTT assay was performed to detect cell proliferation, flow cytometry to detect cell cycle and apoptosis, scratch-wound assay to detect cell migration ability, and transwell invasion assay to evaluate the invasion of these cells.

RESULTS

We successfully constructed LV-mcm7-RNAi expressing MCM7 shRNA. PCR and Western blot assay showed the mRNA and protein expression of MCM7 reduced significantly when compared with negative control group (LV-NC-RNAi) and blank control group (P<0.05). As compared to blank control group and negative control group, the cell proliferation reduced dramatically (P<0.01), cells were mainly arrested in G0/G1 phase and apoptotic cells increased markedly in LV-mcm7-RNAi group. Moreover, cells transfected with LV-mcm7-RNAi showed significant reductions in the invasion and migration as compared to other groups (P<0.05).

CONCLUSION

Lentivirus mediated silencing of MCM7 with shRNA in MHCC-97H cells may inhibit the malignant behaviors of MHCC-97H cells (suppressed proliferation and compromised invasiveness), which is related to the cell cycle arrest and increase in apoptosis.

α-Actinin-4 is required for amoeboid-type invasiveness of melanoma cells

α-Actinin-4 (ACTN4), a key regulator of the actin cytoskeleton, is up-regulated in melanoma, though its role in melanoma remains speculative. We have discovered that in WM1158, a highly aggressive melanoma cell line, down-regulation of ACTN4 by shRNA induces a collagen I-dependent amoeboidal-to-mesenchymal transition. Re-expression of low levels of WT ACTN4 but not similar expression levels of ACTN1 successfully restores the amoeboidal morphology and limits collagen I gel compaction. A truncated ACTN4 mutant 1-890, which lacks the C-terminal tail, fails to rescue the amoeboidal morphology and to compact collagen I gel. Interestingly, in three-dimensional collagen I gels, ACTN4 KD cells are more polarized compared with cells in which scrambled shRNA is expressed. Surprisingly, ACTN4 KD cells migrate faster than the ones expressing the scrambled shRNA on a collagen I gel (two-dimensional) although these two cell lines migrate similarly on tissue culture. Most importantly, down-regulation of ACTN4 significantly reduced invasion of WM1158 cells into the three-dimensional collagen I gel, a representative of the dermis. Taken together, these findings suggest that ACTN4 plays an important role in maintaining the amoeboidal morphology of invasive melanoma and thus promoting dissemination through collagen-rich matrices.