CD151 promotes cancer cell metastasis via integrins α3β1 and α6β1 in vitro

Therapeutic Implications of the Drug Resistance Conferred by Extracellular Vesicles Derived from Triple-Negative Breast Cancer Cells

Anticancer drug resistance is a significant impediment in current cancer treatment. Extracellular vesicles (EVs) derived from cancer cells were recently acknowledged as a critical mechanism of drug resistance, tumor progression, and metastasis. EVs are enveloped vesicles comprising a lipid bilayer that transfers various cargo, including proteins, nucleic acids, lipids, and metabolites, from an originating cell to a recipient cell. Investigating the mechanisms whereby EVs confer drug resistance is still in the early stages. In this review, I analyze the roles of EVs derived from triple-negative breast cancer cells (TNBC-EVs) in anticancer drug resistance and discuss strategies to overcome TNBC-EV-mediated drug resistance.

Long noncoding RNA (lncRNA) HOTAIR: Pathogenic roles and therapeutic opportunities in gastric cancer

Gastric cancer is one of the first malignant cancers in the world and a large number of people die every year due to this disease. Many genetic and epigenetic risk factors have been identified that play a major role in gastric cancer. HOTAIR is an effective epigenetic agent known as long noncoding RNA (lncRNA). HOTAIR has been described to have biological functions in biochemical and cellular processes through interactions with many factors, leading to genomic stability, proliferation, survival, invasion, migration, metastasis, and drug resistance. In the present article, we reviewed the prognostic value of the molecular mechanisms underlying the HOTAIR regulation and its function in the development of Gastric Cancer, whereas elucidation of HOTAIR–protein and HOTAIR–DNA interactions can be helpful in the identification of cancer processes, leading to the development of potential therapeutic strategies.

Tetraspanins: Physiology, Colorectal Cancer Development, and Nanomediated Applications

Simple Summary

Considering the high incidence of colorectal cancer in adults, as well as the need for identifying novel therapies, we hereby explore the role of tetraspanins in the development of colorectal cancer. We have focused on variate aspects starting from the structure and general physiology and ending with the precise mechanisms involved in the dual reported role of tetraspanins (pro–tumoral and tumor suppressor key player element). Moreover, the present review focuses on the potential of tetraspanins as a target for nanotechnology-mediated therapies, also gathering the limited attempts towards this aim and their reported data.

Abstract

Tetraspanins are transmembrane proteins expressed in a multitude of cells throughout the organism. They contribute to many processes that surround cell–cell interactions and are associated with the progress of some diseases, including cancer. Their crucial role in cell physiology is often understated. Furthermore, recent studies have shown their great potential in being used as targeting molecules. Data have suggested the potential of tetraspanins as a targeting vector for nanomediated distribution and delivery for colorectal cancer applications. Our aim is to provide a review on the important part that tetraspanins play in the human organism and highlight their potential use for drug delivery systems using nanotechnology.

CD151 drives cancer progression depending on integrin α3β1 through EGFR signaling in non-small cell lung cancer

Background

Tetraspanins CD151, a transmembrane 4 superfamily protein, has been identified participating in the initiation of a variety of cancers. However, the precise function of CD151 in non-small cell lung cancer (NSCLC) remains unclear. Here, we addressed the pro-tumoral role of CD151 in NSCLC by targeting EGFR/ErbB2 which favors tumor proliferation, migration and invasion.

Methods

First, the mRNA expression levels of CD151 in NSCLC tissues and cell lines were measured by RT-PCR. Meanwhile, CD151 and its associated proteins were analyzed by western blotting. The expression levels of CD151 in NSCLC samples and its paired adjacent lung tissues were then verified by Immunohistochemistry. The protein interactions are evaluated by co-immunoprecipitation. Flow cytometry was applied to cell cycle analysis. CCK-8, EdU Incorporation, and clonogenic assays were used to analyze cell viability. Wound healing, transwell migration, and matrigel invasion assays were utilized to assess the motility of tumor cells. To investigate the role of CD151 in vivo, lung carcinoma xenograft mouse model was applied.

Results

High CD151 expression was identified in NSCLC tissues and cell lines, and its high expression was significantly associated with poor prognosis of NSCLC patients. Further, knockdown of CD151 in vitro inhibited tumor proliferation, migration, and invasion. Besides, inoculation of nude mice with CD151-overexpressing tumor cells exhibited substantial tumor proliferation compared to that in control mice which inoculated with vector-transfected tumor cells. Noteworthy, we found that overexpression of CD151 conferred cell migration and invasion by interacting with integrins. We next sought to demonstrate that CD151 regulated downstream signaling pathways via activation of EGFR/ErbB2 in NSCLC cells. Therefore, we infer that CD151 probably affects the sensitivity of NSCLC in response to anti-cancer drugs.

Conclusions

Based on these results, we demonstrated a new mechanism of CD151-mediated tumor progression by targeting EGFR/ErbB2 signaling pathway, by which CD151 promotes NSCLC proliferation, migration, and invasion, which may considered as a potential target of NSCLC treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-01998-4.

Inhibition of Ezrin suppresses cell migration and invasion in human nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is one of the most severe types of malignant cancer of the head and neck as it is difficult to treat. Ezrin is highly expressed in numerous types of cancer. However, the role of Ezrin in NPC has not been fully investigated and further studies are required in order to uncover its therapeutic potential in the treatment of NPC. The aim of the present study was to investigate the expression of Ezrin in human NPC and to evaluate the effect of knockdown of Ezrin using small interfering (si)-RNA on NPC cell migration and invasion. The expression levels of Ezrin were determined using reverse transcription-quantitative polymerase chain reaction, immunohistochemical staining and western blotting. Following transfection of Ezrin-siRNA into NPC cells, cell invasion and migration were analyzed and the mRNA expression levels of matrix metalloproteinase(MMP)-2 and MMP9 were determined. The results revealed that the expression of Ezrin was markedly increased in human NPC tissue samples compared with normal adjacent nasopharyngeal tissue samples. Ezrin was also highly expressed in the NPC cell lines 6-10B and C6661 when compared with the normal nasopharyngeal cell line NP69. Transfection of NPC cell lines with siRNA targeting Ezrin significantly inhibited NPC cell migration and invasion, and downregulated the mRNA expression level of MMP2; however, no effect was observed on MMP9 mRNA expression. At the same time, knockdown of Ezrin significantly decreased the expression levels of phosphatidylinositol 3-kinase (PI3K) and phosphorylated protein kinase B (Akt), which downregulated the mRNA expression of MMP2. In conclusion, the results revealed that knockdown of Ezrin suppressed NPC migration and invasion by reducing the mRNA expression of MMP2 via the PI3K/Akt signaling pathway. These results highlight the important role of Ezrin in NPC cell migration and invasion. In addition, they indicate that silencing of Ezrin may serve as a potential therapeutic strategy to treat human NPC.

C5aR1 regulates migration of suppressive myeloid cells required for costimulatory blockade-induced murine allograft survival

Costimulatory blockade-induced murine cardiac allograft survival requires intragraft accumulation of CD11b⁺ Ly6C^lo Ly6G^- regulatory myeloid cells (Mregs) that expand regulatory T cells (Tregs) and suppress effector T cells (Teffs). We previously showed that C5a receptor (C5aR1) signaling on T cells activates Teffs and inhibits Tregs, but whether and/or how C5aR1 affects Mregs required for transplant survival is unknown. Although BALB/c hearts survived >60 days in anti-CD154 (MR1)-treated or cytotoxic T-lymphocyte associated protein 4 (CTLA4)-Ig-treated wild-type (WT) recipients, they were rejected at ~30 days in MR1-treated or CTLA4-Ig-treated recipients selectively deficient in C5aR1 restricted to myeloid cells (C5ar1^fl/fl xLysM-Cre). This accelerated rejection was associated with ~2-fold more donor-reactive T cells and ~40% less expansion of donor-reactive Tregs. Analysis of graft-infiltrating mononuclear cells on posttransplant day 6 revealed fewer Ly6C^lo monocytes in C5ar1^fl/fl xLysM-Cre recipients. Expression profiling of intragraft Ly6C^lo monocytes showed that C5aR1 deficiency downregulated genes related to migration/locomotion without changes in genes associated with suppressive function. Cotransfer of C5ar1^fl/fl and C5ar1^fl/fl xLysM-Cre myeloid cells into MR1-treated allograft recipients resulted in less accumulation of C5ar1^-/- cells within the allografts, and in vitro assays confirmed that Ly6C^hi myeloid cells migrate to C5a/C5aR1-initiated signals. Together, our results newly link myeloid cell-expressed C5aR1 to intragraft accumulation of myeloid cells required for prolongation of heart transplant survival induced by costimulatory blockade.

TSPAN1 upregulates MMP2 to promote pancreatic cancer cell migration and invasion via PLCγ

Pancreatic cancer (PC), a malignancy of the digestive system, has one of the highest rates of metastasis and mortality. It is characterized by the detachment, migration, implantation and infiltration of tumor cells to form metastases or recurrent foci. Tetraspanin 1 (TSPAN1), a novel member of the TSPAN superfamily, is highly expressed in many types of cancer, including gastric, colon, liver and esophageal cancer. It has also been associated with lymph node metastasis, tumor recurrence and metastasis. However, the role of TSPAN1 in PC has not been fully elucidated. The aim of the present study was to determine the expression of TSPAN1 in human PC tissue samples and cell lines. Additionally, the functions of TSPAN1 in PC cell migration and invasion were assessed. The protein and gene expression of TSPAN1 was analyzed in clinical PC tissue samples and human PC cell lines (SW1990, BxPC3, Capan1 and PANC-1) via immunohistochemistry, reverse transcription-quantitative polymerase chain reaction and western blotting. The effect of TSPAN1 downregulation and overexpression in PC cells, via transfection with siRNA and pLNCX-TSPAN1-cDNA recombinant plasmid, respectively, on cell invasion and migration were assessed. Additionally, the mRNA expression of matrix metalloproteinase (MMP2) and MMP9 were determined. In clinical PC tissue samples, the expression of TSPAN1 was markedly increased when compared with normal pancreatic tissue samples. TSPAN1 was also highly expressed in PC cell lines compared with HPDE, a normal pancreatic cell line. Transfection with siRNA targeting TSPAN1 in PC cell lines significantly suppressed PC cell migration and invasion, and downregulated the expression of MMP2. However, there was no effect on MMP9. Consistently, PC cell migration and invasion together with MMP2 mRNA expression were markedly increased following TSPAN1 ectopic overexpression. The present study utilized small interfering RNAs (siRNA) targeted to phospholipase Cγ (PLCγ) to demonstrate that TSPAN1 siRNA suppressed PC cell migration and invasion, and MMP2 mRNA expression by blocking the translocation and phosphorylation of PLCγ. The results of the present study revealed that TSPAN1 has an important function in human PC cell migration and invasion by modulating MMP2 expression via PLCγ. Thus, the results indicate that the silencing of TSPAN1 may be a potential therapeutic target for the treatment of PC.

Silencing Tspan1 inhibits migration and invasion, and induces the apoptosis of human pancreatic cancer cells

Pancreatic cancer (PCC) is one of the most dangerous types of tumor as it is very difficult to treat and its 5-year survival rate is <6%. To date, there have been no effective therapeutic strategies to treat PCC, thus, novel effective therapeutic methods are required. Tetraspanin 1 (Tspan1) is a novel member of the tetraspanins superfamily and is highly expressed in a variety of types of cancer, including gastric, hepatocellular and colonic carcinomas. However, the detailed functional role of Tspan1 in pancreatic cancer cells is still unclear and further investigation is required to uncover its therapeutic potential for the treatment of different tumor types. The purpose of the present study was to investigate the expression of Tspan1 in human PCC tissues and cells, and explore the effect of Tspan1 silencing on invasion, migration, cell survival and apoptosis in human PCC to clarify its function. Expression levels of Tspan1 were analyzed in human pancreatic cancer tissues and the cell lines Capan-2 and SW1990 using immunohistochemistry staining, reverse transcription-quantitative polymerase chain reaction and western blotting. The effects of downregulation of Tspan1 expression on cell survival, apoptosis, invasion and migration were investigated viaTspan1-small interfering (si)RNA transfection into human PCC cell lines. The results indicated that Tspan1 expression was increased in human PCC tissues compared with the adjacent normal pancreatic tissues. Tspan1 was highly expressed in the human PCC cell lines Capan-2 and SW1990 when compared with the normal pancreatic cell line HPC-Y5. In addition, transfection with siRNA-targeting Tspan1 significantly reduced cell migration and invasion, and increased the cell apoptosis of Capan-2 and SW1990. The present findings highlighted the important role of Tspan1 in human PCC cell migration, invasion and apoptosis. Thus, Tspan1 RNA interference may serve as a potential therapeutic strategy to treat human PCC.

Expression of cluster of differentiation 151 prior to and following transcatheter arterial chemoembolization therapy in patients with hepatocellular carcinoma and its association with clinicopathological characteristics

Cluster of differentiation (CD)151, a member of tetraspanin family, is considered to be the first tetraspanin to be associated with tumor metastasis. Previous studies in vivo, in vitro and in the clinic have demonstrated that CD151 is involved in tumor progression at different levels through interaction with integrins, growth factor receptors and matrix metalloproteinases. Transcatheter arterial chemoembolization (TACE) is widely recommended for the treatment of patients with advanced hepatocellular carcinoma (HCC) worldwide. It has been hypothesized that TACE may create a hypoxic-ischemic environment that increases the expression of tumor progression-associated factors, promotes the angiogenesis of HCC, and initiates the recurrence and metastasis of HCC. Whether TACE promotes HCC progression remains controversial and numerous studies have focused on the influence of TACE on a number of tumor progression-associated factors. In the present study, the expression of serum CD151 in patients with HCC prior to and following TACE and its association with clinicopathological characteristics was investigated. It was revealed that the expression level of CD151 at 5-7 days post-TACE was significantly increased compared with pre-TACE levels. Risk factors and protective factors associated with tumor progression following a single TACE procedure and 18 months of follow-up were also identified. Furthermore, the present study revealed that a pre-TACE CD151 level of >0.3247 ng/ml and a 5-7 days post-TACE CD151 level of >0.3146 ng/ml revealed moderate sensitivity and specificity for predicting HCC progression following a single TACE procedure. The present study highlights CD151 as a useful marker in predicting the response to treatment and monitoring the disease course following TACE.

Regulation of Glioblastoma Tumor-Propagating Cells by the Integrin Partner Tetraspanin CD151

Glioblastoma (GBM) stem cells (GSCs) represent tumor-propagating cells with stem-like characteristics (stemness) that contribute disproportionately to GBM drug resistance and tumor recurrence. Understanding the mechanisms supporting GSC stemness is important for developing therapeutic strategies for targeting GSC-dependent oncogenic mechanisms. Using GBM-derived neurospheres, we identified the cell surface tetraspanin family member CD151 as a novel regulator of glioma cell stemness, GSC self-renewal capacity, migration, and tumor growth. CD151 was found to be overexpressed in GBM tumors and GBM neurospheres enriched in GSCs. Silencing CD151 inhibited neurosphere forming capacity, neurosphere cell proliferation, and migration and attenuated the expression of markers and transcriptional drivers of the GSC phenotype. Conversely, forced CD151 expression promoted neurosphere self-renewal, cell migration, and expression of stemness-associated transcription factors. CD151 was found to complex with integrins α3, α6, and β1 in neurosphere cells, and blocking CD151 interactions with integrins α3 and α6 inhibited AKT phosphorylation, a downstream effector of integrin signaling, and impaired sphere formation and neurosphere cell migration. Additionally, targeting CD151 in vivo inhibited the growth of GBM neurosphere-derived xenografts. These findings identify CD151 and its interactions with integrins α3 and α6 as potential therapeutic targets for inhibiting stemness-driving mechanisms and stem cell populations in GBM.

CD151 knockdown inhibits osteosarcoma metastasis through the GSK-3β/β-catenin/MMP9 pathway

Osteosarcoma (OS) is a primary bone malignancy with a high early metastatic propensity. It is crucial to find specific protein targets to develop therapeutic strategies against this lethal disease. Tetraspanin CD151 is involved in facilitating tumor metastasis. However, the role and molecular mechanism of CD151 in promoting OS metastasis remain enigmatic. In the present study, we used small interfering RNA (siRNA) to inhibit CD151 expression in highly metastatic OS cells and the results demonstrated that CD151 knockdown inhibited their migration, invasion and metastasis. We further investigated the molecular mechanism of CD151 by inhibiting genes known to be involved in metastasis in OS cells and found that CD151 modulated matrix metalloproteinase 9 (MMP9) expression through the glycogen synthase kinase 3 (GSK-3β)/β-catenin signaling pathway. We conclude that CD151 knockdown inhibits the expression of MMP9 through the GSK-3β/β‑catenin pathway and also inhibits OS migration and invasion in vitro and metastasis in vivo in highly metastatic OS. This suggests that CD151 may be a useful antimetastatic target for OS.

Tetraspanin CD37 Regulates β2 Integrin-Mediated Adhesion and Migration in Neutrophils

Deciphering the molecular basis of leukocyte recruitment is critical to the understanding of inflammation. In this study, we investigated the contribution of the tetraspanin CD37 to this key process. CD37-deficient mice showed impaired neutrophil recruitment in a peritonitis model. Intravital microscopic analysis indicated that the absence of CD37 impaired the capacity of leukocytes to follow a CXCL1 chemotactic gradient accurately in the interstitium. Moreover, analysis of CXCL1-induced leukocyte-endothelial cell interactions in postcapillary venules revealed that CXCL1-induced neutrophil adhesion and transmigration were reduced in the absence of CD37, consistent with a reduced capacity to undergo β2 integrin-dependent adhesion. This result was supported by in vitro flow chamber experiments that demonstrated an impairment in adhesion of CD37-deficient neutrophils to the β2 integrin ligand, ICAM-1, despite the normal display of high-affinity β2 integrins. Superresolution microscopic assessment of localization of CD37 and CD18 in ICAM-1-adherent neutrophils demonstrated that these molecules do not significantly cocluster in the cell membrane, arguing against the possibility that CD37 regulates β2 integrin function via a direct molecular interaction. Moreover, CD37 ablation did not affect β2 integrin clustering. In contrast, the absence of CD37 in neutrophils impaired actin polymerization, cell spreading and polarization, dysregulated Rac-1 activation, and accelerated β2 integrin internalization. Together, these data indicate that CD37 promotes neutrophil adhesion and recruitment via the promotion of cytoskeletal function downstream of integrin-mediated adhesion.

Tetraspanins as regulators of the tumour microenvironment: implications for metastasis and therapeutic strategies

One of the hallmarks of cancer is the ability to activate invasion and metastasis. Cancer morbidity and mortality are largely related to the spread of the primary, localized tumour to adjacent and distant sites. Appropriate management and treatment decisions based on predicting metastatic disease at the time of diagnosis is thus crucial, which supports better understanding of the metastatic process. There are components of metastasis that are common to all primary tumours: dissociation from the primary tumour mass, reorganization/remodelling of extracellular matrix, cell migration, recognition and movement through endothelial cells and the vascular circulation and lodgement and proliferation within ectopic stroma. One of the key and initial events is the increased ability of cancer cells to move, escaping the regulation of normal physiological control. The cellular cytoskeleton plays an important role in cancer cell motility and active cytoskeletal rearrangement can result in metastatic disease. This active change in cytoskeletal dynamics results in manipulation of plasma membrane and cellular balance between cellular adhesion and motility which in turn determines cancer cell movement. Members of the tetraspanin family of proteins play important roles in regulation of cancer cell migration and cancer-endothelial cell interactions, which are critical for cancer invasion and metastasis. Their involvements in active cytoskeletal dynamics, cancer metastasis and potential clinical application will be discussed in this review. In particular, the tetraspanin member, CD151, is highlighted for its major role in cancer invasion and metastasis.

LINKED ARTICLES

This article is part of a themed section on Cytoskeleton, Extracellular Matrix, Cell Migration, Wound Healing and Related Topics. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-24.

Tetraspanins in cell migration

Tetraspanins are a superfamily of small transmembrane proteins that are expressed in almost all eukaryotic cells. Through interacting with one another and with other membrane and intracellular proteins, tetraspanins regulate a wide range of proteins such as integrins, cell surface receptors, and signaling molecules, and thereby engage in diverse cellular processes ranging from cell adhesion and migration to proliferation and differentiation. In particular, tetraspanins modulate the function of proteins involved in all determining factors of cell migration including cell-cell adhesion, cell-ECM adhesion, cytoskeletal protrusion/contraction, and proteolytic ECM remodeling. We herein provide a brief overview of collective in vitro and in vivo studies of tetraspanins to illustrate their regulatory functions in the migration and trafficking of cancer cells, vascular endothelial cells, skin cells (keratinocytes and fibroblasts), and leukocytes. We also discuss the involvement of tetraspanins in various pathologic and remedial processes that rely on cell migration and their potential value as targets for therapeutic intervention.

CD151-A Striking Marker for Cancer Therapy

Cluster of differentiation 151 (CD151) is a member of the mammalian tetraspanin family, which is involved in diverse functions such as maintaining normal cellular integrity, cell-to-cell communication, wound healing, platelet aggregation, trafficking, cell motility and angiogenesis. CD151 also supports de novo carcinogenesis in human skin squamous cell carcinoma (SCC) and tumor metastasis. CD151 interacts with α3β1 and α6β4 integrins through palmitoylation where cysteine plays an important role in the association of CD151 with integrins and non-integrin proteins. Invasion and metastasis of cancer cells were diminished by decreasing CD151 association with integrins. CD151 functions at various stages of cancer, including metastatic cascade and primary tumor growth, thus reinforcing the importance of CD151 as a target in oncology. The present review highlights the role of CD151 in tumor metastasis and its importance in cancer therapy.

Relationship between expression of CD151 and Integrin α6 and epithelial-mesenchymal transition in colorectal cancer

AIM: To investigate the relationship between CD151 and Integrin α6 expression and clinicopathological parameters in colorectal cancer, and analyze the role of the two proteins in epithelial-mesenchymal transition (EMT).

METHODS: Immunohistochemistry was performed to detect the expression of CD151, Integrin α6, E-cadherin and Vimentin in 132 colorectal cancer specimens using tissue microarray.

RESULTS: The positive rates of CD151 and Integrin α6 in colorectal cancer tissues were 65.9% and 75.7%, respectively, significantly higher than those in tumor-adjacent normal tissues. CD151 and Integrin α6 expression was closely related with the depth of invasion and lymph lode metastasis, while the expression of CD151 was closely associated with low E-cadherin expression and high Vimentin expression.

CONCLUSION: CD151 may accelerate the invasion and metastasis of colorectal cancer by promoting EMT.

Cancer cells remodel themselves and vasculature to overcome the endothelial barrier

Metastasis refers to the spread of cancer cells from a primary tumor to distant organs mostly via the bloodstream. During the metastatic process, cancer cells invade blood vessels to enter circulation, and later exit the vasculature at a distant site. Endothelial cells that line blood vessels normally serve as a barrier to the movement of cells into or out of the blood. It is thus critical to understand how metastatic cancer cells overcome the endothelial barrier. Epithelial cancer cells acquire increased motility and invasiveness through epithelial-to-mesenchymal transition (EMT), which enables them to move toward vasculature. Cancer cells also express a variety of adhesion molecules that allow them to attach to vascular endothelium. Finally, cancer cells secrete or induce growth factors and cytokines to actively prompt vascular hyperpermeability that compromises endothelial barrier function and facilitates transmigration of cancer cells through the vascular wall. Elucidation of the mechanisms underlying metastatic dissemination may help develop new anti-metastasis therapeutics.

Tetraspanin proteins promote multiple cancer stages

An abundance of evidence shows supporting roles for tetraspanin proteins in human cancer. Many studies show that the expression of tetraspanins correlates with tumour stage, tumour type and patient outcome. In addition, perturbations of tetraspanins in tumour cell lines can considerably affect cell growth, morphology, invasion, tumour engraftment and metastasis. This Review emphasizes new studies that have used de novo mouse cancer models to show that select tetraspanin proteins have key roles in tumour initiation, promotion and metastasis. This Review also emphasizes how tetraspanin proteins can sometimes participate in tumour angiogenesis. These recent data build an increasingly strong case for tetraspanins as therapeutic targets.

RNA interference targeting human integrin α6 suppresses the metastasis potential of hepatocellular carcinoma cells

Background

Increased metastasis has been proved to be associated with a poor prognosis for hepatocellular carcinoma (HCC). There are higher-level expressions of integrin α6 in the tissues of HCC patients with a higher fatality rate. The aim of this study is to investigate the effect of short hairpin RNA (shRNA) silencing integrin α6 expression on the proliferation and metastasis in HCC cell lines.

Methods

Two human HCC cell lines, HepG2 and Bel-7402 were transfected with shRNA targeting human integrin α6. Protein and mRNA expression level were determined by western blot and real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR) to detect the transfected efficacy. The metastasis potential of HCC cells was evaluated by their proliferation, adhesion and invasion abilities. Cell proliferation was measured by MTT assay. Adhesion ability was measured by adhesion and spreading assays. The expression of matrix metalloproteinases (MMPs) was measured by qRT-PCR. The potential of invasion was measured by qRT-PCR and Transwell chamber assay. PI3K inhibitor LY294002 was used to explore the signal pathways of integrin α6 in HCC cells.

Results

Western blot and qRT-PCR detection showed that over 75% of integrin α6 expression in HCC cells was through knockdown by shRNA. Proliferation, adhesion, spreading and invasion of HepG2 and Bel-7402 cells were dramatically decreased in cells transfected with shRNA compared to the control cells. P-ERK and p-AKT were reduced by shRNA targeting integrin α6 and PI3K inhibitor LY294002.

Conclusion

Knockdown integrin α6 can inhibit the proliferation and metastasis of HCC cells through PI3K/ARK and MAPK/ERK signal pathways by shRNA in vitro. Integrin α6 can mediate the metastasis potential, and can be used as a candidate target for therapy in HCC resulting in improved patients’ survival.

Oncogenic H-ras reprograms Madin-Darby canine kidney (MDCK) cell-derived exosomal proteins following epithelial-mesenchymal transition

Epithelial-mesenchymal transition (EMT) is a highly conserved morphogenic process defined by the loss of epithelial characteristics and the acquisition of a mesenchymal phenotype. EMT is associated with increased aggressiveness, invasiveness, and metastatic potential in carcinoma cells. To assess the contribution of extracellular vesicles following EMT, we conducted a proteomic analysis of exosomes released from Madin-Darby canine kidney (MDCK) cells, and MDCK cells transformed with oncogenic H-Ras (21D1 cells). Exosomes are 40-100 nm membranous vesicles originating from the inward budding of late endosomes and multivesicular bodies and are released from cells on fusion of multivesicular bodies with the plasma membrane. Exosomes from MDCK cells (MDCK-Exos) and 21D1 cells (21D1-Exos) were purified from cell culture media using density gradient centrifugation (OptiPrep™), and protein content identified by GeLC-MS/MS proteomic profiling. Both MDCK- and 21D1-Exos populations were morphologically similar by cryo-electron microscopy and contained stereotypical exosome marker proteins such as TSG101, Alix, and CD63. In this study we show that the expression levels of typical EMT hallmark proteins seen in whole cells correlate with those observed in MDCK- and 21D1-Exos, i.e. reduction of characteristic inhibitor of angiogenesis, thrombospondin-1, and epithelial markers E-cadherin, and EpCAM, with a concomitant up-regulation of mesenchymal makers such as vimentin. Further, we reveal that 21D1-Exos are enriched with several proteases (e.g. MMP-1, -14, -19, ADAM-10, and ADAMTS1), and integrins (e.g. ITGB1, ITGA3, and ITGA6) that have been recently implicated in regulating the tumor microenvironment to promote metastatic progression. A salient finding of this study was the unique presence of key transcriptional regulators (e.g. the master transcriptional regulator YBX1) and core splicing complex components (e.g. SF3B1, SF3B3, and SFRS1) in mesenchymal 21D1-Exos. Taken together, our findings reveal that exosomes from Ras-transformed MDCK cells are reprogrammed with factors which may be capable of inducing EMT in recipient cells.