Development and in-depth characterization of BRAFi-resistant melanoma cell lines in vitro and in vivo

Regardless of the clinical response and improved patient survival observed following treatment with BRAFi like Vemurafenib (Vem), rapid development of resistance still remains as a major obstacle in melanoma therapy. In this context, we developed and characterized two acquired Vem-resistant melanoma cell lines, A375V and SK-MEL-28V, and an intrinsically Vem-resistant cell line, RPMI-7951. Altered morphology and growth rate of the resistant cell lines displayed spindle-shaped cells with filopodia formation and enhanced proliferation rate as compared to parental cells. Further in vitro characterization in 2D models confirmed the emergence of a resistant phenotype in melanoma cells. To mimic the in vivo tumor microenvironment, spheroids were developed for both parental and resistant cell lines to recognize materialization of invadopodia structures demonstrating elevated invasiveness and proliferation of resistant cells-based spheroids, especially A375V. Importantly, we validated A375V cell line in vivo to prove its tumorigenicity and drug resistance in tumor xenograft model. Taken together, our established clinically relevant Vem-resistant tumor model could be beneficial to elucidate drug resistance mechanisms, screen and identify novel anticancer therapies to overcome BRAFi resistance in melanoma.

Dormancy of cutaneous melanoma

Many cancer-related deaths including melanoma result from metastases that develop months or years after the initial cancer therapy. Even the most effective drugs and immune therapies rarely eradicate all tumor cells. Instead, they strongly reduce cancer burden, permitting dormant cancer cells to persist in niches, where they establish a cellular homeostasis with their host without causing clinical symptoms. Dormant cancers respond poorly to most drugs and therapies since they do not proliferate and hide in niches. It therefore remains a major challenge to develop novel therapies for dormant cancers. In this review we focus on the mechanisms regulating the initiation of cutaneous melanoma dormancy as well as those which are involved in reawakening of dormant cutaneous melanoma cells. In recent years the role of neutrophils and niche components in reawakening of melanoma cells came into focus and indicate possible future therapeutic applications. Sophisticated in vitro and in vivo melanoma dormancy models are needed to make progress in this field and are discussed.

The Impact of JWH-133 on Articular Cartilage Regeneration in Osteoarthritis Via Metalloproteinase 13-Dependent Mechanism

Objective: Osteoarthritis (OA) is common degenerative joint disease, mostly characterized by gradual cartilage breakdown. Currently there are no disease-modifying drugs available, therefore, there is an increasing need for basic research to focus on cartilage function in OA. Changes in cannabinoid receptor 2 (CB2) expression were observed in the OA-affected joints, although its action on cartilage chondrocytes remain unclear. We studied the action of dimethylbutyl-deoxy-delta-8-THC (JWH-133), selective CB2 agonist, on chondrocytes metabolism using both in vitro and in vivo studies. Design: Intraarticular (i.a.) injection of monoiodoacetate (MIA) was used to induce OA in rats. OA-related pain symptoms were assessed by pressure application measurements (PAMs). Primary human chondrocytes treated with MIA were used to investigate action of JWH-133 on chondrocytes viability, proliferation, and motility. Cannabinoid system components, inflammatory cytokines and metalloproteinases (MMPs) expression was measured on messenger RNA and protein levels in chondrocytes and animal cartilage. Results: Repeated, i.a. administration of JWH-133 showed antinociceptive potential in PAM, as well as decreased levels of MMPs, which suggests that CB2 agonism may modify degradation of cartilage. JWH-133 administration partially reduced toxicity, increased proliferation, and chondrocytes' migration. Moreover, our data suggest that CB2 agonism leads to alleviation of MMPs expression both in vitro and in vivo. Conclusions: In this study, we demonstrate modifying effect of JWH-133 local administration on cartilage metabolism and MMP13 expression that was shown to be involved in cartilage degradation. CB2 receptors' activation may be of benefit for chondrocytes' proliferation, therefore delaying disease progression. Our results propose direction of studies on OA-modifying treatment that can benefit in management of human OA.

Circ_0084043-miR-134-5p axis regulates PCDH9 to suppress melanoma

The low survival rates, poor responses, and drug resistance of patients with melanoma make it urgent to find new therapeutic targets. This study investigated whether the circ_0084043-miR-134-5p axis regulates the antitumor effect of protocadherin 9 (PCDH9) in melanoma. Ectopic expression or knock down (KD) of PCDH9 with a lentivirus vector, we explored its effects on the proliferation, invasion, and apoptosis of melanoma and verified its regulatory effect on ras-related C3 botulinum toxin substrate 1 (RAC1), proline-rich tyrosine kinase 2 (Pyk2), Cyclin D1, matrix metalloproteinase 2 (MMP2), and MMP9. We further observed the effect of KD circ_0084043 on the malignant behavior of melanoma and studied whether circ_0084043 sponged miR-134-5p and regulated PCDH9. We found that circ_0084043 was overexpressed in melanoma and associated with the malignant phenotype. PCDH9 was poorly expressed in human melanoma tissues, and overexpression of PCDH9 inhibited melanoma progression. Quantitative real-time PCR and Western blotting results showed that overexpression of PCDH9 could downregulate RAC1, MMP2, and MMP9 and upregulate Pyk2 and Cyclin D1. Circ_0084043 KD inhibited invasion and promoted apoptosis in melanoma cells. Circ_0084043 could sponge miR-134-5p and thus indirectly regulate PCDH9. Furthermore, we discovered that inhibiting circ_0084043 had an anti–PD-Ll effect. In vivo, PCDH9 overexpression inhibited melanoma tumor growth, but PCDH9 KD promoted it. In conclusion, PCDH9, which is regulated by the circ 0084043-miR-134-5p axis, can suppress malignant biological behavior in melanoma and influence the expression levels of Pyk2, RAC1, Cyclin D1, MMP2, and MMP9.

Characterization of Vemurafenib-Resistant Melanoma Cell Lines Reveals Novel Hallmarks of Targeted Therapy Resistance

Regardless of the significant improvements in treatment of melanoma, the majority of patients develop resistance whose mechanisms are still not completely understood. Hence, we generated and characterized two melanoma-derived cell lines, primary WM793B and metastatic A375M, with acquired resistance to the RAF inhibitor vemurafenib. The morphology of the resistant primary WM793B melanoma cells showed EMT-like features and exhibited a hybrid phenotype with both epithelial and mesenchymal characteristics. Surprisingly, the vemurafenib-resistant melanoma cells showed a decreased migration ability but also displayed a tendency to collective migration. Signaling pathway analysis revealed the reactivation of MAPK and the activation of the PI3K/AKT pathway depending on the vemurafenib-resistant cell line. The acquired resistance to vemurafenib caused resistance to chemotherapy in primary WM793B melanoma cells. Furthermore, the cell-cycle analysis and altered levels of cell-cycle regulators revealed that resistant cells likely transiently enter into cell cycle arrest at the G0/G1 phase and gain slow-cycling cell features. A decreased level of NME1 and NME2 metastasis suppressor proteins were found in WM793B-resistant primary melanoma, which is possibly the result of vemurafenib-acquired resistance and is one of the causes of increased PI3K/AKT signaling. Further studies are needed to reveal the vemurafenib-dependent negative regulators of NME proteins, their role in PI3K/AKT signaling, and their influence on vemurafenib-resistant melanoma cell characteristics.

MMP9: A Tough Target for Targeted Therapy for Cancer

Having the capability to proteolyze diverse structural and signaling proteins, matrix metalloproteinase 9 (MMP9), one of the best-studied secretory endopeptidases, has been identified as a crucial mediator of processes closely associated with tumorigenesis, such as the extracellular matrix reorganization, epithelial to mesenchymal transition, cell migration, new blood vessel formation, and immune response. In this review, we present the current state of knowledge on MMP9 and its role in cancer growth in the context of cell adhesion/migration, cancer-related inflammation, and tumor microenvironment formation. We also summarize recent achievements in the development of selective MMP9 inhibitors and the limitations of using them as anticancer drugs.

Nuclear DLC1 exerts oncogenic function through association with FOXK1 for cooperative activation of MMP9 expression in melanoma

A Rho GTPase-activating protein (RhoGAP), deleted in liver cancer 1 (DLC1), is known to function as a tumor suppressor in various cancer types; however, whether DLC1 is a tumor-suppressor gene or an oncogene in melanoma remains to be clarified. Here we revealed that high DLC1 expression was detected in most of the melanoma tissues where it was localized in both the nuclei and the cytoplasm. Functional studies unveiled that DLC1 was both required and sufficient for melanoma growth and metastasis. These tumorigenic events were mediated by nuclear-localized DLC1 in a RhoGAP-independent manner. Mechanistically, mass spectrometry analysis identified a DLC1-associated protein, FOXK1 transcription factor, which mediated oncogenic events in melanoma by translocating and retaining DLC1 into the nucleus. RNA-sequencing profiling studies further revealed MMP9 as a direct target of FOXK1 through DLC1-regulated promoter occupancy for cooperative activation of MMP9 expression to promote melanoma invasion and metastasis. Concerted action of DLC1–FOXK1 in MMP9 gene regulation was further supported by their highly correlated expression in melanoma patients’ samples and cell lines. Together, our results not only unravel a mechanism by which nuclear DLC1 functions as an oncogene in melanoma but also suggest an unexpected role of RhoGAP protein in transcriptional regulation.

CRISPR-Cas9 Knockdown and Induced Expression of CD133 Reveal Essential Roles in Melanoma Invasion and Metastasis

CD133, known as prominin1, is a penta-span transmembrane glycoprotein presumably a cancer stem cell marker for carcinomas, glioblastomas, and melanomas. We showed that CD133(+) ‘melanoma-initiating cells’ are associated with chemoresistance, contributing to poor patient outcome. The current study investigates the role(s) of CD133 in invasion and metastasis. Magnetic-activated cell sorting of a melanoma cell line (BAKP) followed by transwell invasion assays revealed that CD133(+) cells are significantly more invasive than CD133(−) cells. Conditional reprogramming of BAKP CD133(+) cells maintained stable CD133 overexpression (BAK-R), and induced cancer stem cell markers, melanosphere formation, and chemoresistance to kinase inhibitors. BAK-R cells showed upregulated CD133 expression, and consequently were more invasive and metastatic than BAK-P cells in transwell and zebrafish assays. CD133 knockdown by siRNA or CRISPR-Cas9 (BAK-R-T3) in BAK-R cells reduced invasion and levels of matrix metalloproteinases MMP2/MMP9. BAK-R-SC cells, but not BAK-R-T3, were metastatic in zebrafish. While CD133 knockdown by siRNA or CRISPR-Cas9 in BAK-P cells attenuated invasion and diminished MMP2/MMP9 levels, doxycycline-induced CD133 expression in BAK-P cells enhanced invasion and MMP2/MMP9 concentrations. CD133 may therefore play an essential role in invasion and metastasis via upregulation of MMP2/MMP9, leading to tumor progression, and represents an attractive target for intervention in melanoma.

CD147 Is a Novel Chemotherapy or Prevention Target in Melanoma

CD147, also named as BSG, was first identified from F9 embryonal carcinoma cells (Miyauchi et al., 1990) and the human BSG locus on chromosome 19p13.3 containing 10 exons (Belton et al., 2008; Kaname et al., 1993; Liao et al., 2011), which encodes four alternatively spliced transcripts:CD147/Bsg-1,2,3,4 (Kaname et al., 1993; Liao et al., 2011). Bsg-1 has three Ig-like domains (CD147/Bsg-1) (Hanna et al., 2003; Ochrietor et al., 2003), while CD147/Bsg-3,4 contains a single Ig-like domain (Belton et al., 2008; Liao et al., 2011). Evidence shows that CD147/Bsg-2 is the most abundant and best characterized splice product, which contains two Ig-like domains (Weidle et al., 2010). Analysis of amino acids showed that CD147 contains a single-chain type I transmembrane domain composed of a 21-amino acid signal sequence, an extracellular domain consisting of 186 amino acids with two Ig-like domains and a cytoplasmic domain of 41 residues (Kanekura et al., 2010; Yurchenko et al., 2005). There are three glycosylation sites at three conserved asparagine (Asn 44, 152, and 186) in the CD147 N-terminal domain (Fadool et al., 1993; Tang et al., 2004; Yu et al., 2006), which could explain the molecular mass of CD147 shifts from a predicted molecular weight of about 27 kDa to 40-65 kDa with Western blotting. Inhibition of glycosylation by specific inhibitors showed that on carbohydrate side groups bearing β-1,6-branched, polylactosamine-type sugars, fucosylations are the major glycosylation type in N-glycosylation of CD147 (Ni et al., 2014; Riethdorf et al., 2006; Tang et al., 2004). In addition, N-glycosylation of CD147 has been identified as low glycosylated (approximately 32 kDa) or high glycosylated (approximately 45-65 kDa). The fully glycosylated mature CD147 (high-glycosylated CD147) is translocated to the plasma membrane, while low-glycosylated CD147 is the precursor of high-glycosylated CD147 in the endoplasmic reticulum, which requires additional modification in the Golgi prior to being expressed on the cell surface; high levels of glycosylation are a primary biochemical property of CD147 (Jia et al., 2006; Jiang et al., 2014; Ni et al., 2014; Tang et al., 2004).

MicroRNA-183 inhibits A375 human melanoma cell migration and invasion by targeting Ezrin and MMP-9

To assess the influence of microRNA-183 (miR-183) on the migration and invasion of A375 human melanoma cells, an A375 cell line with stable miR-183 overexpression or knockdown was constructed using lentiviral transfection. The change of miR-183 expression in these cells and in non-transfected controls was verified using reverse transcription-quantitative polymerase chain reaction. The impact of miR-183 on experimental A375 cell migration and invasion was assessed using a scratch and Transwell assay. The expression of Ezrin and matrix metalloprotease-9 (MMP-9), which are two mediator proteins that serve roles in tumor cell migration and invasion, were analyzed in each cell group via western blotting. The results of the present study indicated that miR-183 overexpression significantly inhibits A375 cell migration and invasion, which may be facilitated by miR-183 knockdown. Furthermore, Ezrin and MMP-9 protein levels were negatively associated with miR-183 expression, indicating that miR-183 may function as a tumor suppressor by inhibiting the expression of these two proteins. Additionally, miR-183 downregulation may be associated with the progression of melanoma.

MMP-9 as a Candidate Marker of Response to BRAF Inhibitors in Melanoma Patients With BRAFV600E Mutation Detected in Circulating-Free DNA

The BRAF^V600E mutation is associated with melanoma development and its detection in circulating-free DNA cannot be observed in all melanoma patients harboring this mutation in tumor specimens. Beside the circulating-free DNA BRAF^V600E mutation, other markers of therapeutic response should be identified. Matrix metalloproteinase-9 (MMP-9) could be one of them as its role as indicator of invasiveness in melanoma have been explored. In this study, MMP-9 was evaluated in melanoma cells after treatment with dabrafenib. In vitro data were validated in 26 melanoma patients, of which 14 treated with BRAF inhibitor alone and 12 treated with both BRAF and MEK inhibitors, by ELISA assay and droplet digital PCR for measuring MMP-9 serum levels and circulating-free DNA BRAF^V600E mutation, respectively. Statistical analyses were performed to evaluate the prognostic significance of MMP-9, progression-free survival (PFS) and overall survival (OS) according to the BRAF^V600E mutation and MMP-9 levels. The performed analyses showed that MMP-9 and pEKR1-2 were statistically down-regulated in melanoma cells after treatment with dabrafenib. Circulating-free DNA BRAF^V600E mutation was detected in 11 out of 26 melanoma patients showing higher levels of MMP-9 compared to those with undetectable BRAF^V600E mutation. Furthermore, higher levels of MMP-9 and circulating-free DNA BRAF^V600E mutation were associated with lower PFS and OS. Finally, the monitoring of therapy showed that MMP-9 significantly decreased at T1 and T2, but not at T-last, for the patients with detectable circulating-free DNA BRAF^V600E mutation. In conclusion, high levels of MMP-9 and circulating-free DNA BRAF^V600E mutation are associated with poor PFS and OS. MMP-9 may represent a promising indicator of response to BRAF inhibitors in combination with the detection of BRAF^V600E mutation.

Genetic variants in the metzincin metallopeptidase family genes predict melanoma survival

Metzincins are key molecules in the degradation of the extracellular matrix and play an important role in cellular processes such as cell migration, adhesion, and cell fusion of malignant tumors, including cutaneous melanoma (CM). We hypothesized that genetic variants of the metzincin metallopeptidase family genes would be associated with CM-specific survival (CMSS). To test this hypothesis, we first performed Cox proportional hazards regression analysis to evaluate the associations between genetic variants of 75 metzincin metallopeptidase family genes and CMSS using the dataset from the genome-wide association study (GWAS) from The University of Texas MD Anderson Cancer Center (MDACC) which included 858 non-Hispanic white patients with CM, and then validated using the dataset from the Harvard GWAS study which had 409 non-Hispanic white patients with invasive CM. Four independent SNPs (MMP16 rs10090371 C>A, ADAMTS3 rs788935 T>C, TLL2 rs10882807 T>C and MMP9 rs3918251 A>G) were identified as predictors of CMSS, with a variant-allele attributed hazards ratio (HR) of 1.73 (1.32-2.29, 9.68E-05), 1.46 (1.15-1.85, 0.002), 1.68 (1.31-2.14, 3.32E-05) and 0.67 (0.51-0.87, 0.003), respectively, in the meta-analysis of these two GWAS studies. Combined analysis of risk genotypes of these four SNPs revealed a decreased CMSS in a dose-response manner as the number of risk genotypes increased (P_trend < 0.001). An improvement was observed in the prediction model (area under the curve [AUC] = 81.4% vs. 78.6%), when these risk genotypes were added to the model containing non-genotyping variables. Our findings suggest that these genetic variants may be promising prognostic biomarkers for CMSS.

UVA-Irradiation Induces Melanoma Invasion via the Enhanced Warburg Effect

Melanoma is a malignant tumor in which UVA (320-400 nm) radiation is considered to be an important risk factor. But the role of UVA in melanoma progression toward an invasive phenotype is still not adequately investigated. For most proliferating tumor cells the preference of aerobic glycolysis has been described as the Warburg effect. Here we investigate the effect of UVA irradiation on changes in the Warburg effect and tumor progression toward invasive potential. On UVA irradiation, melanoma cell lines from initial tumors show an induction of the Warburg effect with increased glucose consumption and lactate production, which is at least partially mediated by reactive oxygen species. Associated with UVA treatment and enhanced lactic acid production, tumor-relevant proteases and in situ invasion is upregulated. Simultaneously, UVA increases intracellular concentrations of progression marker transketolase and activated protein kinase Akt, both involved in metabolic changes that increase with proliferation. Using invasion assays we show that lactic acid, resulting from the UVA enhanced and partially reactive oxygen species-mediated Warburg effect, increases the invasive potential of all melanoma cell lines investigated. Therefore, we demonstrate in melanoma cells that production of lactic acid, induced by UVA irradiation, increases invasiveness of melanoma cells via expression of tumor-relevant proteases.

Dual mechanisms of action of the RNA-binding protein human antigen R explains its regulatory effect on melanoma cell migration

Overexpression of wingless-type MMTV integration site family 5A (WNT5A) plays a significant role in melanoma cancer progression; however, the mechanism(s) involved remains unknown. In breast cancer, the human antigen R (HuR) has been implicated in the regulation of WNT5A expression. Here, we demonstrate that endogenous expression of WNT5A correlates with levels of active HuR in HTB63 and WM852 melanoma cells and that HuR binds to WNT5A messenger RNA in both cell lines. Although the HuR inhibitor MS-444 significantly impaired migration in both melanoma cell lines, it reduced WNT5A expression only in HTB63 cells, as did small interfering RNA knockdown of HuR. Consistent with this finding, MS-444-induced inhibition of HTB63 cell migration was restored by the addition of recombinant WNT5A, whereas MS-444-induced inhibition of WM852 cell migration was restored by the addition of recombinant matrix metalloproteinase-9, another HuR-regulated protein. Clearly, HuR positively regulates melanoma cell migration via at least 2 distinct mechanisms making HuR an attractive therapeutic target for halting melanoma dissemination.

Silencing Matrix Metalloproteinases 9 and 2 Inhibits Human Retinal Microvascular Endothelial Cell Invasion and Migration

PURPOSE

Proliferative retinal angiogenesis may severely impair the retina. Previous studies have indicated that matrix metalloproteinase (MMP)-2 and MMP-9 play important roles in the process of retinal angiogenesis. In this study, we suppressed MMP-2 and MMP-9 expression with RNA interference (RNAi) and then observed the inhibitory effects on the invasion and migration of human retinal microvascular endothelial cells (HRMECs).

METHODS

Small interfering RNAs against MMP-2 mRNA and MMP-9 mRNA were synthesized. After transfection, the MMP-2 and MMP-9 expression in HRMECs was examined by real-time polymerase chain reaction and Western blot analysis. Cell migration and invasion were measured with a migration assay and a scratch wound assay, respectively.

RESULTS

RNAi against MMP-2 and MMP-9 successfully inhibited the mRNA and protein expression of MMP-2 and MMP-9 in HRMECs. MMP-2 and MMP-9 knockdown could inhibit the invasion and migration of HRMECs.

CONCLUSIONS

These findings suggest that the RNAi approach towards MMP-2 and MMP-9 may be a potentially effective therapeutic method for the treatment of proliferative retinal angiogenesis.

The role of mechano-growth factor E peptide in the regulation of osteosarcoma

Osteosarcoma is one of the most common bone tumors, and exhibits a high degree of malignancy. Gene therapy is a novel approach to its treatment, however, specific target genes are required to enable effective use of this therapy. In order to investigate the effects of the mechano-growth factor E (MGF-E) peptide, which is derived from the IGF-I alternative splicing isoform, on the regulation of the development of osteosarcoma, the expression of MGF was detected in osteosarcoma cell lines with different degrees of malignancy. Concomitantly, exogenous MGF-E peptide was used to stimulate these osteosarcoma cell lines. The results demonstrated that MGF was overexpressed in malignant osteosarcoma cells, while it was not expressed in the least malignant osteosarcoma cells. Furthermore, MGF-E treatment altered the cell cycle distribution, and promoted the proliferation, migration and invasion of osteosarcoma cells. The possible mechanisms underlying these effects were detected by quantitative polymerase chain reaction and western blotting. Based on these results, it was hypothesized that MGF may be a suitable biomarker for malignant osteosarcoma phenotypes.

TPX2 siRNA regulates growth and invasion of esophageal cancer cells

PURPOSE

Observe how specific small RNA interference (siRNA) aimed at TPX2 gene suppresses TPX2 gene expression in esophageal cancer EC9706 cells and the effect on esophageal cancer cell growth and invasion ability.

METHODS

Transfect TPX2 siRNA into EC9706 cells via lipofectamin 2000. The experiments were divided into three groups, a negative control, a blank control and an siRNA interference group (24h, 48h, 72h, 96h). We examined RNA and protein level alteration of the TPX2 gene after TPX2 siRNA transfection by RT-PCR and Western blot analysis. Detection of how TPX2 siRNA influences EC9706 cell proliferation was done by MTT, cell apoptosis monitored through Tunel assay, in vitro invasion ability via Boyden chamber and cell cycle change by flow cytometry.

RESULTS

After effective siRNA transfection, TPX2 mRNA and protein expression level in siRNA interference group were (0.31±0.08, 0.39±0.12),72h after transfection, significantly lower than blank control group (1.00±0.01) and negative control group (0.98±0.11), (F=71.182, t1=8.17, t2=7.90, P<0.05); MTT results demonstrated that cell growth and proliferation were inhibited and the inhibition rate was up to 35.4% (P<0.05) compared with the control group. TUNEL results indicated that cell apoptosis index in siRNA interference group was 18.28±0.35, higher than that in blank control group (4.07±0.26)and negative control group (4.13±0.22), (F=244.5, t1=60.61, t2=53.32, P<0.01). Boyden chamber results showed that the transmembrane cell number was 45.30±8.08 in siRNA interference group, less than blank control group (121.90±7.83), (F=122.46, t1=11.81, t2=10.47, P<0.01); besides, in siRNA interference group cell invasion inhibition rate was 71.42±9.12, higher than negative control group (5.65±3.55), (t=14.256, P<0.01). Flow cytometry results illustrated that more EC9706 cells went into apoptosis and cell cycle arrested in S phase. Similar results were obtained by in vivo transplantation, as TPX2 siRNA transfection significantly reduced tumor growth of the xenograft in nude mice.

CONCLUSION

siRNA could effectively inhibit the invasion and metastasis of EC9706 cells, promote the apoptosis of tumor cells and may become a new approach for treatment of esophageal carcinoma.