ΔNp63α attenuates tumor aggressiveness by suppressing miR-205/ZEB1-mediated epithelial-mesenchymal transition in cervical squamous cell carcinoma

∆Np63α inhibits Rac1 activation and cancer cell invasion through suppression of PREX1

ΔNp63α, a member of the p53 family of transcription factors, plays a critical role in maintaining the proliferative potential of stem cells in the stratified epithelium. Although ΔNp63α is considered an oncogene and is frequently overexpressed in squamous cell carcinoma, loss of ΔNp63α expression is associated with increased tumor cell invasion and metastasis. We recently identified a ΔNp63α/miR-320a/PKCγ signaling axis that regulates cancer cell invasion by inhibiting phosphorylation of the small GTPase Rac1, a master switch of cell motility that positively regulates cell invasion in multiple human cancers. In this study, we identified a novel mechanism by which ΔNp63α negatively regulates Rac1 activity, by inhibiting the expression of the Rac-specific Guanine Exchange Factor PREX1. ΔNp63α knockdown in multiple squamous cell carcinoma cell lines leads to increased Rac1 activation, which is abrogated by treatment with the Rac1 inhibitor NSC23766. Furthermore, ΔNp63α negatively regulates PREX1 transcript and protein levels. Using a Rac-GEF activation assay, we also showed that ΔNp63α reduces the levels of active PREX1. The inhibition of the PREX1-Rac1 signaling axis by ΔNp63α leads to impaired cell invasion, thus establishing the functional relevance of this link. Our results elucidated a novel molecular mechanism by which ΔNp63α negatively affects cancer cell invasion and identifies the ΔNp63α/Rac1 axis as a potential target for metastasis.

Dysregulation of delta Np63 alpha in squamous cell carcinoma and its therapeutic targeting

The gene p63 has two isoforms -a full length transactivated isoform (TA) p63 and an amino-terminally truncated isoform, ∆Np63. DeltaNp63 alpha (∆Np63α) is the predominant splice variant of the isoform, ∆Np63 and is expressed in the basal layer of stratified epithelia. ∆Np63α that is normally essential for the epithelial lineage maintenance may be dysregulated in squamous cell carcinomas (SCCs). The pro-tumorigenic or antitumorigenic role of ∆Np63 is a highly contentious arena. ∆Np63α may act as a double-edged sword. It may either promote tumor progression, epithelial-mesenchymal transition, migration, chemoresistance, and immune-inflammatory responses, or inhibit the aforementioned phenomena depending upon cell type and tumor microenvironment. Several signaling pathways, transforming growth factor-β, Wnt and Notch, as well as epigenetic alterations involving microRNAs, and long noncoding RNAs are regulated by ∆Np63α. This review has attempted to provide an in-depth insight into the role of ∆Np63α in the development of SCCs during different stages of tumor formation and how it may be targeted for therapeutic implications.

ΔNp63α in cancer: importance and therapeutic opportunities

Our understanding of cancer and the key pathways that drive cancer survival has expanded rapidly over the past several decades. However, there are still important challenges that continue to impair patient survival, including our inability to target cancer stem cells (CSCs), metastasis, and drug resistance. The transcription factor p63 is a p53 family member with multiple isoforms that carry out a wide array of functions. Here, we discuss the critical importance of the ΔNp63α isoform in cancer and potential therapeutic strategies to target ΔNp63α expression to impair the CSC population, as well as to prevent metastasis and drug resistance to improve patient survival.

Interleukin-17A mediates tobacco smoke-induced lung cancer epithelial-mesenchymal transition through transcriptional regulation of ΔNp63α on miR-19

Interleukin-17A (IL-17A) is an essential inflammatory cytokine in the progress of carcinogenesis. Tobacco smoke (TS) is a major risk factor of lung cancer that influences epithelial-mesenchymal transition (EMT) process. However, the potential mechanism by which IL-17A mediates the progression of lung cancer in TS-induced EMT remains elusive. In the present study, it was revealed that the IL-17A level was elevated in lung cancer tissues, especially in tumor tissues of cases with experience of smoking, and a higher IL-17A level was correlated with induction of EMT in those specimens. Moreover, the expression of ΔNp63α was increased in IL-17A-stimulated lung cancer cells. ΔNp63α functioned as a key oncogene that bound to the miR-17-92 cluster promoter and transcriptionally increased the expression of miR-19 in lung cancer cells. Overexpression of miR-19 promoted EMT in lung cancer with downregulation of E-cadherin and upregulation of N-cadherin, while its inhibition suppressed EMT. Finally, the upregulated levels of IL-17A, ΔNp63α, and miR-19 along with the alteration of EMT-associated biomarkers were found in lung tissues of TS-exposed mice. Taken together, the abovementioned results suggest that IL-17A increases ΔNp63α expression, transcriptionally elevates miR-19 expression, and promotes TS-induced EMT in lung cancer. These findings may provide a new insight for the identification of therapeutic targets for lung cancer.

MicroRNAs and Their Influence on the ZEB Family: Mechanistic Aspects and Therapeutic Applications in Cancer Therapy

Molecular signaling pathways involved in cancer have been intensively studied due to their crucial role in cancer cell growth and dissemination. Among them, zinc finger E-box binding homeobox-1 (ZEB1) and -2 (ZEB2) are molecules that play vital roles in signaling pathways to ensure the survival of tumor cells, particularly through enhancing cell proliferation, promoting cell migration and invasion, and triggering drug resistance. Importantly, ZEB proteins are regulated by microRNAs (miRs). In this review, we demonstrate the impact that miRs have on cancer therapy, through their targeting of ZEB proteins. MiRs are able to act as onco-suppressor factors and inhibit the malignancy of tumor cells through ZEB1/2 down-regulation. This can lead to an inhibition of epithelial-mesenchymal transition (EMT) mechanism, therefore reducing metastasis. Additionally, miRs are able to inhibit ZEB1/2-mediated drug resistance and immunosuppression. Additionally, we explore the upstream modulators of miRs such as long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs), as these regulators can influence the inhibitory effect of miRs on ZEB proteins and cancer progression.

miR-205 Promotes Apoptosis of Cervical Cancer Cells and Enhances Drug Sensitivity of Cisplatin by Inhibiting YAP1

Objective: Elevated expression of Yes-associated protein (YAP1) involves in the pathogenesis of cervical cancer. Bioinformatics analysis showed a targeting relationship between miR-205 and the 3'-UTR of YAP1. In this study, we aim to explore the role of miR-205 in the proliferation, apoptosis, or cisplatin (CDDP) resistance of cervical cancer cells. Patients and Methods: The dual luciferase reporter gene assay verified the relationship between miR-205 and YAP1. The CDDP-resistant cell line Hela/CDDP cells were cultured in vitro and divided into miR-NC group, miR-205 mimic group, and miR-205 inhibitor group followed by analysis of the expression of miR-205 and YAP1 mRNA by quantitative real-time polymerase chain reaction (qRT-PCR), and YAP1 protein level by western blot. Results: There was a targeted relationship between miR-205 and YAP1 mRNA. Compared with cervical cell line HCerEpiC cells, miR-205 expression was significantly decreased and YAP1 mRNA and protein expression was significantly increased in Hela cells (p < 0.01). Compared with miR-NC group, YAP1 protein expression in HeLa/CDDP cells was significantly decreased, cell apoptosis was increased, and proliferation was inhibited in miR-205 mimic-transfected Hela/CDDP cells (p < 0.01). Opposite results were obtained in miR-205 inhibitor-transfected Hela/CDDP cells. Conclusions: The expression of miR-205 is related to the CDDP resistance of cervical cancer cells. Increasing the expression of miR-205 can downregulate the expression of YAP1, inhibit the proliferation and promote apoptosis of cervical cancer cells, and enhance the sensitivity to CDDP.

The Role of Epithelial-to-Mesenchymal Transition in Cutaneous Squamous Cell Carcinoma : Epithelial-to-Mesenchymal Transition in Cutaneous SCC

OPINION STATEMENT

The capacity of cells to modify their phenotypes from epithelial to mesenchymal (epithelial-to-mesenchymal transition or EMT) and vice versa provides them with a dynamic plasticity essential for human life, from embryogenesis to wound healing. Current knowledge about carcinogenetic mechanisms leaves little doubts on the pivotal participation of these interchangeable processes in cancer development, and their influence has been quite clearly established in the progression of cutaneous squamous cell carcinoma. A complex and ordered interplay of signals induces the shift between both phenotypes, providing cells with the most suitable state at every moment to face the next step in tumor invasion and dissemination. Some stimulatory triggers have opposite effects according to the biological context and in many cases exert collateral functions. This scenario makes finding an ideal therapeutic target difficult but provides the opportunity to intervene simultaneously at many different levels with small actions such as targeting the tumor environment. In any case, advances in knowledge of the EMT mechanisms and their influence on carcinogenesis and drug resistance will greatly influence the therapeutic strategies for many human tumors, including cutaneous squamous cell carcinoma.

Spatiotemporal Regulation of ΔNp63 by TGFβ-Regulated miRNAs Is Essential for Cancer Metastasis

ΔNp63 is a transcription factor of the p53 family and has crucial functions in normal development and disease. The expression pattern of ΔNp63 in human cancer suggests dynamic regulation of this isoform during cancer progression and metastasis. Many primary and metastatic tumors express high levels of ΔNp63, while ΔNp63 loss is crucial for tumor dissemination, indicating an oscillatory expression of ΔNp63 during cancer progression. Here, we use genetically engineered orthotopic mouse models of breast cancer to show that while depletion of ΔNp63 inhibits primary mammary adenocarcinoma development, oscillatory expression of ΔNp63 in established tumors is crucial for metastatic dissemination in breast cancer. A TGFβ-regulated miRNA network acted as upstream regulators of this oscillatory expression of ΔNp63 during cancer progression. This work sheds light on the pleiotropic roles of ΔNp63 in cancer and unveils critical functions of TGFβ in the metastatic process. SIGNIFICANCE: This study unveils TGFβ signaling and a network of four miRNAs as upstream regulators of ΔNp63, providing key information for the development of therapeutic strategies to treat cancers that commonly overexpress ΔNp63.

ΔNp63α suppresses cells invasion by downregulating PKCγ/Rac1 signaling through miR-320a

ΔNp63α, a member of the p53 family of transcription factors, is overexpressed in a number of cancers and plays a role in proliferation, differentiation, migration, and invasion. ΔNp63α has been shown to regulate several microRNAs that are involved in development and cancer. We identified miRNA miR-320a as a positively regulated target of ΔNp63α. Previous studies have shown that miR-320a is downregulated in colorectal cancer and targets the small GTPase Rac1, leading to a reduction in noncanonical WNT signaling and EMT, thereby inhibiting tumor metastasis and invasion. We showed that miR-320a is a direct target of ΔNp63α. Knockdown of ΔNp63α in HaCaT and A431 cells downregulates miR-320a levels and leads to a corresponding elevation in PKCγ transcript and protein levels. Rac1 phosphorylation at Ser71 was increased in the absence of ΔNp63α, whereas overexpression of ΔNp63α reversed S71 phosphorylation of Rac1. Moreover, increased PKCγ levels, Rac1 phosphorylation and cell invasion observed upon knockdown of ΔNp63α was reversed by either overexpressing miR-320a mimic or Rac1 silencing. Finally, silencing PKCγ or treatment with the PKC inhibitor Gö6976 reversed increased Rac1 phosphorylation and cell invasion observed upon silencing ΔNp63α. Taken together, our data suggest that ΔNp63α positively regulates miR-320a, thereby inhibiting PKCγ expression, Rac1 phosphorylation, and cancer invasion.

Downregulation of microRNA-205 inhibits cell invasion and angiogenesis of cervical cancer through TSLC1-mediated Akt signaling pathway

Cervical cancer (CC) is a common gynecological cancer and a leading cause of cancer-related deaths in women globally. Therefore, this study explores the action of microRNA-205 (miR-205) in the invasion, migration, and angiogenesis of CC through binding to tumor suppressor lung cancer 1 (TSLC1). Initially, the microarray analysis was used to select the candidate gene and the regulatory microRNA. Then, the target relationship between miR-205 and TSLC1 as well as the expression of miR-205, TSLC1, and p-Akt/total Akt in CC cells were determined. Afterwards, CC cell invasion and migration were detected after the treatment of miR-205 mimics/inhibitors and short hairpin RNA against TSLC1. After coculture of cancer cells and vascular endothelial cells, cell proliferation, tube formation, and microvessel density (MVD) were detected to determine the roles of miR-205 in angiogenesis. Finally, tumor growth in nude mice was measured in vivo. TSLC1 was determined as the candidate gene, which was found to be targeted and negatively regulated by miR-205. Then, downregulated miR-205 or forced TSLC1 expression inhibited invasion, migration, and angiogenesis in CC, corresponding to suppressed cell proliferation, tube formation, and expression of IL-8, VEGF, and bFGF, as well as the inhibited activation of the Akt signaling pathway. Furthermore, downregulation of miR-205 was found to exert an inhibitory role in tumor formation and MVD by elevating TSLC1 in CC in vivo. This study demonstrated that downregulated miR-205 inhibited cell invasion, migration, and angiogenesis in CC by inactivating the Akt signaling pathway via TSLC1 upregulation.

Functional Role of Non-Coding RNAs during Epithelial-To-Mesenchymal Transition

Epithelial-to-mesenchymal transition (EMT) is a key biological process involved in a multitude of developmental and pathological events. It is characterized by the progressive loss of cell-to-cell contacts and actin cytoskeletal rearrangements, leading to filopodia formation and the progressive up-regulation of a mesenchymal gene expression pattern enabling cell migration. Epithelial-to-mesenchymal transition is already observed in early embryonic stages such as gastrulation, when the epiblast undergoes an EMT process and therefore leads to the formation of the third embryonic layer, the mesoderm. Epithelial-to-mesenchymal transition is pivotal in multiple embryonic processes, such as for example during cardiovascular system development, as valve primordia are formed and the cardiac jelly is progressively invaded by endocardium-derived mesenchyme or as the external cardiac cell layer is established, i.e., the epicardium and cells detached migrate into the embryonic myocardial to form the cardiac fibrous skeleton and the coronary vasculature. Strikingly, the most important biological event in which EMT is pivotal is cancer development and metastasis. Over the last years, understanding of the transcriptional regulatory networks involved in EMT has greatly advanced. Several transcriptional factors such as Snail, Slug, Twist, Zeb1 and Zeb2 have been reported to play fundamental roles in EMT, leading in most cases to transcriptional repression of cell⁻cell interacting proteins such as ZO-1 and cadherins and activation of cytoskeletal markers such as vimentin. In recent years, a fundamental role for non-coding RNAs, particularly microRNAs and more recently long non-coding RNAs, has been identified in normal tissue development and homeostasis as well as in several oncogenic processes. In this study, we will provide a state-of-the-art review of the functional roles of non-coding RNAs, particularly microRNAs, in epithelial-to-mesenchymal transition in both developmental and pathological EMT.

Chemosensitization and inhibition of pancreatic cancer stem cell proliferation by overexpression of microRNA-205

Treatment of pancreatic cancer with gemcitabine (GEM) is limited due to its rapid plasma metabolism and development of chemoresistance. MicroRNA (miRNA) regulates cancer stem cell (CSC) maintenance and induces chemoresistance in cancer cells. In this study, we observed differential downregulation of miR-205 (miR-205-5p) in human pancreatic cancer tissues and cells. Compared to GEM-sensitive MIA PaCa-2 cells, miR-205 was highly downregulated in GEM-resistant MIA PaCa-2R cells. Lentivirus-mediated overexpression of miR-205 inhibits MIA PaCa-2R cell proliferation after GEM-treatment. Further investigation confirmed that miR-205 alone significantly reduces the proliferation of CSCs and tumor growth in mouse models. However, miR-205 in combination with GEM was more efficient in reducing the proliferation of CSCs and 3D spheroids. Moreover, miR-205 overexpressing MIA PaCa-2R cells induced orthotopic tumor growth was significantly inhibited after intravenous administration of GEM-conjugated methoxy poly(ethylene glycol)-block-poly(2-methyl-2-carboxyl-propylene carbonate)-graft-gemcitabine-graft-dodecanol (mPEG-b-PCC-g-GEM-g-DC) (mPEG-b-PCC-g-GEM-g-DC) polymeric micelles. Also, a reduction in CSCs, EMT and chemoresistance markers was observed in miR-205 overexpressing MIA PaCa-2R cells. Immunohistochemical analysis of orthotopic tumors showed a decrease in drug resistance protein caveolin-1 and cell proliferation marker Ki-67 in combination treatment. Overall, our findings suggest that miR-205 resensitizes GEM-resistant pancreatic cancer cells to GEM and acts as a tumor suppressor miRNA.

Long non-coding RNA SNHG1 regulates zinc finger E-box binding homeobox 1 expression by interacting with TAp63 and promotes cell metastasis and invasion in Lung squamous cell carcinoma

The long non-coding RNAs (lncRNAs) have been recently shown to participate in the progression of a variety of cancers. However, the biological role of lncRNAs and the underlying mechanisms in Lung squamous cell carcinoma (SCC) or lung adenocarcinoma (AD) remain unclear. Herein, we investigated expression of 5 lncRNAS (SNHG1, NCBP2-AS2, LINC01206, SOX2-OT and LINC01419) in SCC and AD tissues. SNHG1 was one of over-expressed lncRNAs in SCC tissues. Knockdown of SNHG1 significantly inhibited the proliferation, metastasis, invasive ability and induced apoptosis of SCC cells. Moreover, SNHG1 affected the expression of zinc finger E-box binding homeobox 1(ZEB1), which has also been observed to be up-regulated in SCC and to promote cell metastasis and invasion. Rather than direct interaction, SNHG1 regulated ZEB1expression by suppressing the activity of p63 TA isoform (TAp63), which is a repressor of ZEB1 and physically associates with SNHG1. Furthermore, SNHG1 promoted ZEB1 expression and promoted cell proliferation, metastasis, invasive but inhibited apoptosis of SCC cells via the TAp63/ZEB1 pathway. Taken together, our findings suggested that SNHG1 might play an oncogenic role in SCC through ZEB1 signaling pathway by inhibiting TAp63 and might serve as a valuable prognostic biomarker and therapeutic target for SCC patients.

MiR-21 and miR-205 are induced in invasive cutaneous squamous cell carcinomas

Cutaneous squamous cell carcinoma (cSCC) is a malignant proliferation of keratinocytes with an uncertain molecular basis causing significant morbidity. MicroRNAs (miRs) are small RNA molecules that regulate gene expression on post- transcriptional level. MiRs are critical to various biological processes. To determine if miRs play a role in pathogenesis of invasive cSCC, we collected patients' specimens from in situ and invasive cSCC (n = 19) and examined miRs expression levels using qPCR. Specifically, we evaluated miR-21, miR-103a, miR-186, miR-200b, miR-203, and miR-205 expression levels due to their role in skin biology and epithelial to mesenchymal transition. MiR levels were compared between in situ and invasive cSCCs. We found statistically significant (p ≤ 0.05) upregulation of miR-21 and miR-205 in invasive cSCC compared to cSCC in situ. We concluded that miR-21 and miR-205 may have diagnostic value in determining the invasive properties of cSCCs and that each cSCC displays unique miR profile, underscoring the possibility of personalized medicine approach in developing potential novel, less invasive treatments.

Cell-Type-Specific Chromatin States Differentially Prime Squamous Cell Carcinoma Tumor-Initiating Cells for Epithelial to Mesenchymal Transition

Epithelial to mesenchymal transition (EMT) in cancer cells has been associated with metastasis, stemness, and resistance to therapy. Some tumors undergo EMT while others do not, which may reflect intrinsic properties of their cell of origin. However, this possibility is largely unexplored. By targeting the same oncogenic mutations to discrete skin compartments, we show that cell-type-specific chromatin and transcriptional states differentially prime tumors to EMT. Squamous cell carcinomas (SCCs) derived from interfollicular epidermis (IFE) are generally well differentiated, while hair follicle (HF) stem cell-derived SCCs frequently exhibit EMT, efficiently form secondary tumors, and possess increased metastatic potential. Transcriptional and epigenomic profiling revealed that IFE and HF tumor-initiating cells possess distinct chromatin landscapes and gene regulatory networks associated with tumorigenesis and EMT that correlate with accessibility of key epithelial and EMT transcription factor binding sites. These findings highlight the importance of chromatin states and transcriptional priming in dictating tumor phenotypes and EMT.

The E6-TAp63β-Dicer feedback loop involves in miR-375 downregulation and epithelial-to-mesenchymal transition in HR-HPV+ cervical cancer cells

MiR-375 has been recognized as an important tumor suppressor and is usually downregulated in cervical cancer. However, how it is downregulated in cervical cancer is not clear. By using cancerous and normal cervical tissues, we observed that miR-375 and Dicer are both downregulated and were positively correlated. Overexpression of miR-375 resulted in decreased viral E6 and increased Dicer expression in both Hela and SiHa cells. Previous studies suggest that E6 can induce an accelerated degradation of TAp63β, while TAp63 can bind to and transactivate the Dicer promoter, exerting a direct regulation on transcription of Dicer. In this study, we found that miR-375 overexpression restored TAp63β expression. TAp63β overexpression significantly enhanced transcription and translation of Dicer, which further led to increased mature miR-375 levels. Therefore, we infer that there is an E6-TAp63β-Dicer feedback loop involved in miR-375 dysregulation in cervical cancer. Besides, we observed that enforced TAp63β expression significantly reduced the mesenchymal markers including N-cadherin, Vimentin, Snail, and Slug but increased the epithelial marker E-cadherin in both Hela and SiHa cells. The wound healing assay also confirmed that TAp63β overexpression significantly suppressed cervical cancer cell migration potential. These results suggest that TAp63β can inhibit epithelial-to-mesenchymal transition (EMT) of cervical cancer cells.