C-Myc participates in β-catenin-mediated drug resistance in A549/DDP lung adenocarcinoma cells

Wnt signaling and tumors (Review)

Wnt signaling is a highly conserved evolutionary pathway that plays a key role in regulation of embryonic development, as well as tissue homeostasis and regeneration. Abnormalities in Wnt signaling are associated with tumorigenesis and development, leading to poor prognosis in patients with cancer. However, the pharmacological effects and mechanisms underlying Wnt signaling and its inhibition in cancer treatment remain unclear. In addition, potential side effects of inhibiting this process are not well understood. Therefore, the present review outlines the role of Wnt signaling in tumorigenesis, development, metastasis, cancer stem cells, radiotherapy resistance and tumor immunity. The present review further identifies inhibitors that target Wnt signaling to provide a potential novel direction for cancer treatment. This may facilitate early application of safe and effective drugs targeting Wnt signaling in clinical settings. An in-depth understanding of the mechanisms underlying inhibition of Wnt signaling may improve the prognosis of patients with cancer.

The role and mechanism of IFITM1 in developing acquired cisplatin resistance in small cell lung cancer

Platinum-based chemotherapies, historically the cornerstone of first-line treatment for small-cell lung cancer (SCLC), face a major hurdle: the frequent emergence of chemoresistance, notably to cisplatin (CDDP). Current understanding of the mechanisms driving CDDP resistance in SCLC is incomplete. Notably, Interferon inducible transmembrane protein1 (IFITM1) has been identified as a key player in the distant metastasis of SCLC. Analysis of The Cancer Genome Atlas (TCGA) database revealed that IFITM1 expression is markedly elevated in tumor tissues as compared to that from adjacent normal tissues, correlating with a worse prognosis for patients with SCLC. Our research focused on investigating the role of IFITM1 in the acquisition of cisplatin resistance in SCLC. Further clinical sample analysis highlighted a significant increase in IFITM1 levels in SCLC tissues from cisplatin-resistant patients versus those were responsive to CCDP treatment, with similar trends observed in cisplatin-resistant SCLC cells. Crucially, overexpression of IFITM1 reduced the sensitivity of SCLC cells to cisplatin, while silencing IFITM1 enhanced chemosensitivity in cisplatin-resistant strains. Our in vivo studies further confirmed that silencing IFITM1 significantly boosted the efficacy of cisplatin in inhibiting growth of subcutaneous tumors of NCI-H466/CDDP cells (cisplatin-resistant SCLC cells) in a mouse model. Mechanistically, IFITM1 appears to foster cisplatin resistance through activation of the Wnt/β-catenin pathway. In summary, our findings suggest that targeting IFITM1, alongside cisplatin treatment, could offer a promising therapeutic strategy to overcome resistance and improve outcomes for SCLC patients.

Exosomes Derived From Macrophages Enhance Aerobic Glycolysis and Chemoresistance in Lung Cancer by Stabilizing c-Myc via the Inhibition of NEDD4L

As one of the most common and lethal cancer, lung cancer severely threatens the health of human. It has been reported that tumor-associated macrophages promote initiation, progression, as well as chemoresistance in human cancers. However, the underneath molecular mechanism that drives chemoresistance in lung cancer is yet not fully characterized. In this article, we demonstrated that M2 macrophage-derived exosomes (MDE) is the key factor to promote cisplatin-resistance in lung cancer. MDE exhibited high expression level of several miRNA including miR-3679-5p. Mechanistically, miR-3679-5p was delivered to lung cancer cells by MDE, downregulating the expression of a known E3 ligase, NEDD4L, which has been identified as a key regulator controlling the stability of c-Myc. Such decreased NEDD4L expression level resulted in the stabilization of c-Myc and elevated glycolysis. The enhanced glycolysis drives the chemoresistance in lung cancer. Taken together, our findings not only show that M2 macrophage induce chemoresistance in lung cancer through MDE mediated miR-3679-5R/NEDD4L/c-Myc signaling cascade, but also shed the light on the mechanism of the cross-talk between M2 macrophage and lung cancers. By pinpointing a potential novel survival signaling pathway, our data could provide a new potential therapeutic target for lung cancer treatment and management.

miR‑576‑5p promotes epithelial‑to‑mesenchymal transition in colorectal cancer by targeting the Wnt5a‑mediated Wnt/β‑catenin signaling pathway

Colorectal cancer (CRC) is one of the most common types of malignancy and the third most commonly diagnosed form of cancer worldwide, ranking as the fourth leading cause of cancer‑associated mortality. MicroRNA (miR)‑576‑5p has been reported to be highly expressed in patients with CRC; however, its biological role remains unclear. The present study aimed therefore to investigate the biological role and underlying mechanism of miR‑576‑5p in CRC cell line SW480. The viability of SW480 cells following transfection with miR‑576‑5p mimic or inhibitor was analyzed using MTT assay. Wound healing and Transwell assays were performed to determine the cell migratory and invasive abilities, respectively. A dual luciferase reporter assay was used to verify the predicted binding site between miR‑576‑5p and Wnt5a. Reverse transcription‑quantitative PCR and western blotting were used to analyze the expression levels of miR‑576‑5p, E‑cadherin, N‑cadherin, vimentin, Snail1, Wnt5a, β‑catenin, c‑myc, cyclin D1 and p/t‑c‑Jun. Using bioinformatics analysis, high expression of miR‑576‑5p was found not only in tumor tissues, compared with the normal tissue, but also in CRC cells, compared with NCM460 cells. Furthermore, the inhibition of miR‑576‑5p expression significantly decreased the cell viability and the migratory and invasive abilities of SW480 cells, and suppressed the epithelial‑to‑mesenchymal transition (EMT). In addition, miR‑576‑5p could interact with Wnt5a and regulate the expression level of Wnt5a in order to influence the activity of Wnt/β‑catenin signaling. The results from rescue experiments further demonstrated that the effect of miR‑576‑5p overexpression on cell metastasis and EMT was reversed by Wnt5a overexpression or treatment with XAV‑939, which is an inhibitor of the Wnt/β‑catenin signaling pathway. In conclusion, the findings from the present study suggested that inhibition of miR‑576‑5p may suppress SW480 cell metastasis and EMT by targeting Wnt5a and regulating the Wnt5a‑mediated Wnt/β‑catenin signaling pathway, providing a potential therapeutic target for the treatment of CRC.

Wnt-β-catenin Signaling Pathway, the Achilles' Heels of Cancer Multidrug Resistance

BACKGROUND

Most of the anticancer chemotherapies are hampered via the development of multidrug resistance (MDR), which is the resistance of tumor cells against cytotoxic effects of multiple chemotherapeutic agents. Overexpression and/or over-activation of ATP-dependent drug efflux transporters is a key mechanism underlying MDR development. Moreover, enhancement of drug metabolism, changes in drug targets and aberrant activation of the main signaling pathways, including Wnt, Akt and NF-κB are also responsible for MDR.

METHODS

In this study, we have reviewed the roles of Wnt signaling in MDR as well as its potential therapeutic significance. Pubmed and Scopus have been searched using Wnt, β-catenin, cancer, MDR and multidrug resistance as keywords. The last search was done in March 2019. Manuscripts investigating the roles of Wnt signaling in MDR or studying the modulation of MDR through the inhibition of Wnt signaling have been involved in the study. The main focus of the manuscript is regulation of MDR related transporters by canonical Wnt signaling pathway.

RESULT AND CONCLUSION

Wnt signaling has been involved in several pathophysiological states, including carcinogenesis and embryonic development. Wnt signaling is linked to various aspects of MDR including P-glycoprotein and multidrug resistance protein 1 regulation through its canonical pathways. Aberrant activation of Wnt/β- catenin signaling leads to the induction of cancer MDR mainly through the overexpression and/or over-activation of MDR related transporters. Accordingly, Wnt/β-catenin signaling can be a potential target for modulating cancer MDR.

Exosomal Transfer Of Cisplatin-Induced miR-425-3p Confers Cisplatin Resistance In NSCLC Through Activating Autophagy

Introduction

Exosomes are important mediators of intercellular communication. Previously, we characterized circulating exosomal miR-425-3p as a non-invasive prognostic marker for predicting clinical response to platinum-based chemotherapy in patients with non-small cell lung cancer (NSCLC).

Methods

Circulating exosomal miR-425-3p was validated by qRT-PCR in paired serum samples from NSCLC patients during the course of platinum-based chemotherapy. Cell coculture was performed to examine the effects of exosomal miR-425-3p on the sensitivity of recipient A549 cells to cisplatin. Using bioinformatics, ChIP and luciferase reporter assays, the transcription factor essential for miR-425-3p expression was identified. Autophagic activity in the recipient cells was determined by Western blot and fluorescence microscopy.

Results

Higher levels of exosomal miR-425-3p were found in serum samples from the patients in tolerance versus those at baseline. An upward trend in the expression of circulating exosomal miR-425-3p was revealed during chemotherapy. Furthermore, the expression of exosomal miR-425-3p could be induced by cisplatin in NSCLC cells. Exosomes isolated from either cisplatin-treated or cisplatin-resistant NSCLC cells conferred chemoresistance to sensitive A549 cells in a miR-425-3p-dependent manner. Cisplatin-induced c-Myc was found to directly bind the miR-425-3p promoter and transactivated its expression. Exosomal miR-425-3p facilitated autophagic activation in the recipient cells by targeting AKT1, eventually leading to chemoresistance.

Discussion

Our results suggest that apart from a prognostic marker of treatment response, exosomal miR-425-3p might be a potential dynamic biomarker to tailor cisplatin resistance in NSCLC patients during the treatment and represent a promising therapeutic target for therapy-resistant NSCLC.

microRNA-1236-3p Regulates DDP Resistance in Lung Cancer Cells

Lung cancer is a malignant tumor leading to the most cancer-related deaths worldwide. The treatment efficiency of lung cancer remains poor mainly due to chemotherapy drug resistance, including cisplatin. MicroRNAs (miRNAs) are closely related to chemotherapy resistance of tumor cells. Here, we illustrated the underlying mechanism of miR-1236-3p on the DDP resistance in lung cancer cells. In this study, we found that the expression level of miR-1236-3p was significantly decreased in lung cancer tissues and A549 cell line. In addition, the half maximal inhibitory concentration (IC50) of DDP in A549 cells was significantly lower than that in A549/DDP cells, while the expression level of miR-1236-3p was prominently down-regulated in A549/DDP cells. Combining the online tool TargetScan and a dual-luciferase reporter assay, tumor protein, translationally-controlled 1 (TPT1) was proved to be the direct target gene of miR-1236-3p. The MTT and flow cytometry assays demonstrated that up-regulation of miR-1236-3p could markedly inhibit A549/DDP cell proliferation but promote apoptosis, which could be significantly reversed by pcDNA3.1-TPT1 plasmids. Finally, we further demonstrated that miR-1235-3p could restrain the expression levels of TPT1, Pim-3, phosphate-Bcl-2-associated death promoter (p-BAD) and B-cell lymphoma-extra large (Bcl-XL) in A549/DDP cells, while the inhibition could be reversed by pcDNA3.1-TPT1 as well. In a word, our study demonstrated that miR-1236-3p could reverse DDP resistance by modulation of TPT1 gene and inhibition of Pim-3 signaling pathway in lung cancer cells.

MicroRNA expression profiles and clinicopathological implications in lung adenocarcinoma according to EGFR, KRAS, and ALK status

Lung adenocarcinoma has distinctive clinicopathological features that are related to specific genetic alterations, including EGFR and KRAS mutations and ALK rearrangement. MicroRNAs are small non-coding RNAs that post-transcriptionally regulate many important biological processes and influence cancer phenotypes. This study retrospectively investigated microRNA expression profiles, and their clinicopathological implications, in lung adenocarcinoma according to genetic status (EGFR, KRAS, ALK, and triple negative). A total of 72 surgically resected lung adenocarcinoma specimens (19 EGFR-mutated, 17 KRAS-mutated, 16 ALK-rearranged, and 20 triple negative cancers) were screened for 23 microRNAs using quantitative real-time reverse transcriptase polymerase chain reaction. We then evaluated the associations between the microRNA expressions and the cancers’ genetic and clinicopathological features. Eight microRNAs were associated with clinicopathological features, such as male sex and ever-smoker status (high miR-373-3p, miR-1343-3p, miR-138-1-3p, and miR-764; low miR-27b-3p) and vascular invasion (high miR-27b-3p; low miR-1343-3p and miR-764). Clustering and discriminant analyses revealed that the microRNA expression patterns in the ALK group were different from those in the EGFR and KRAS groups. Five microRNAs (high miR-1343-3p; low miR-671-3p, miR-103a-3p, let-7e, and miR-342-3p) were especially distinctive in the ALK group, compared to the EGFR and KRAS groups. Moreover, a significant association was observed between ALK-rearrangement, decreased miR-342-3p expression, and immunohistochemical loss of E-cadherin. Therefore, microRNA expression profiles appear to have distinctive clinicopathological implications in ALK-rearranged lung adenocarcinoma. Furthermore, the association of ALK rearrangement, decreased miR-342-3p expression, and E-cadherin loss might indicate that miR-342-3p is involved in the ALK-associated phenotypes and epithelial-mesenchymal transition.

Atom Transfer Radical Polymerization of Multishelled Cationic Corona for the Systemic Delivery of siRNA

We propose an effective siRNA delivery system by preparing poly(DAMA-HEMA)-multilayered gold nanoparticles using multiple surface-initiated atom transfer radical polymerization processes. The polymeric multilayer structure is characterized by transmission electron microscopy, matrix-associated laser desorption/ionization time-of-flight mass spectrometry, UV-vis spectroscopy, Fourier transform infrared spectroscopy, dynamic light scattering, and ζ-potential. The amount of siRNA electrostatically incorporated into the nanoparticle can be tuned by the number of polymeric shells, which in turn influences the cellular uptake and gene silencing effect. In a bioreductive environment, the interlayer disulfide bond breaks to release the siRNA from the degraded polymeric shells. Intravenously injected c-Myc siRNA-incorporated particles accumulate in the tumor site of a murine lung carcinoma model and significantly suppress the tumor growth. Therefore, the combination of a size-tunable AuNP core and an ATRP-functionalized shell offers control and versatility in the effective delivery of siRNA.

Niclosamide enhances the cytotoxic effect of cisplatin in cisplatin-resistant human lung cancer cells via suppression of lung resistance-related protein and c-myc

Lung cancer is a leading cause of cancer-associated mortality worldwide. The cisplatin (DDP)-based chemotherapy remains the foundation of treatment for the majority of patients affected by advanced non-small cell lung cancer (NSCLC). However, DDP-resistance limits the clinical utility of this drug in patients with advanced NSCLC. The aim of the present study was to investigate the inhibitory effect of niclosamide on human lung cancer cell growth and to investigate the possible underlying mechanism. The effects of niclosamide on the proliferation of human lung adenocarcinoma (A549) and DDP-resistant (CR) human lung adenocarcinoma (A549/DDP) cells were examined by Cell Counting kit-8 assay. The impact of niclosamide on the apoptosis of A549/DDP cells was detected by Annexin V-fluorescein isothiocyanate/propidium iodide assay. The expression levels of cisplatin-resistant-associated molecules (lung resistance-related protein and c-myc) following niclosamide treatment in A549/DDP cells were evaluated by western blot analysis. The results indicated that niclosamide in combination with DDP demonstrated a synergistic effect in A549/DDP cells and directly induced apoptosis, which may be associated with caspase-3 activation. Furthermore, niclosamide decreased the expression level of c-myc protein, which may influence DDP sensitivity of A549/DDP cells. Thus, the present study indicates that niclosamide combined with DDP exerts a synergistic effect in cisplatin-resistant lung cancer cells and may present as a promising drug candidate in lung cancer therapy.

Vitamin D derivatives potentiate the anticancer and anti-angiogenic activity of tyrosine kinase inhibitors in combination with cytostatic drugs in an A549 non-small cell lung cancer model

Numerous in vitro and in vivo studies have demonstrated that calcitriol [1,25(OH)₂D₃] and different vitamin D analogs possess antineoplastic activity, regulating proliferation, differentiation and apoptosis, as well as angiogenesis. Vitamin D compounds have been shown to exert synergistic effects when used in combination with different agents used in anticancer therapies in different cancer models. The aim of this study was to evaluate the mechanisms of the cooperation of the vitamin D compounds [1,24(OH)₂D₃ (PRI-2191) and 1,25(OH)₂D₃] with tyrosine kinase inhibitors (imatinib and sunitinib) together with cytostatics (cisplatin and docetaxel) in an A549 non-small cell lung cancer model. The cytotoxic effects of the test compounds used in different combinations were evaluated on A549 lung cancer cells, as well as on human lung microvascular endothelial cells (HLMECs). The effects of such combinations on the cell cycle and cell death were also determined. In addition, changes in the expression of proteins involved in cell cycle regulation, angiogenesis and the action of vitamin D were analyzed. Moreover, the effects of 1,24(OH)₂D₃ on the anticancer activity of sunitinib and sunitinib in combination with docetaxel were examined in an A549 lung cancer model in vivo. Experiments aiming at evaluating the cytotoxicity of the combinations of the test agents revealed that imatinib and sunitinib together with cisplatin or docetaxel exerted potent anti-proliferative effects in vitro on A549 lung cancer cells and in HLMECs; however, 1,24(OH)₂D₃ and 1,25(OH)₂D₃ enhanced the cytotoxic effects only in the endothelial cells. Among the test agents, sunitinib and cisplatin decreased the secretion of vascular endothelial growth factor (VEGF)-A from the A549 lung cancer cells. The decrease in the VEGF-A level following incubation with cisplatin correlated with a higher p53 protein expression, while no such correlation was observed following treatment of the A549 cells with sunitinib. Sunitinib together with docetaxel and 1,24(OH)₂D₃ exhibited a more potent anticancer activity in the A549 lung cancer model compared to double combinations and to treatment with the compounds alone. The observed anticancer activity may be the result of the influence of the test agents on the process of tumor angiogenesis, for example, through the downregulation of VEGF-A expression in tumor and also on the induction of cell death inside the tumor.

Lariciresinol induces apoptosis in HepG2 cells via mitochondrial-mediated apoptosis pathway

Lariciresinol (LA) is one of the main active ingredients in many traditional medicinal plants such as Patrinia, and has the role of anti-liver cancer. However, the precise mechanisms are unclear. This study investigated the molecular mechanisms of LA against HepG2 cells. LA anti-tumor activity was assessed with the CCK-8, Ki-67, and immunofluorescence staining. Cells apoptotic ratio was evaluated by Annexin V/PI double-staining assay. A proteomic approach was used to identify differentially expressed proteins after LA treatment. JC-1 staining was carried out to detect the mitochondrial membrane potential (ΔΨm), and the Western blot analysis was used to analyse the apoptosis-associated proteins. Our results suggested that LA significantly suppressed the viability of HepG2 cells. The CCK-8 and Ki-67 expression indicated dose-dependent decreases in cell proliferation. Flow cytometry analysis showed that LA exhibited a apoptosis-inducing effect. The proteomic study observed the presence of apoptosis-associated proteins and mitochondrial dysfunction in HepG2 cells after LA-treatment. Further analysis showed that LA could trigger the mitochondrial-mediated apoptosis pathway, based on a decrease in ΔΨm; deliver of cytochrome c; activation of caspase-9/-3 and poly(ADP-ribose) polymerase; and decrease of the proportion of Bcl-2/Bax. Collectively, our studies found that LA exhibits significant cytotoxic effects by inhibiting cell proliferation, inducing apoptosis, possibly via activation of the mitochondrial-mediated apoptosis pathway.

The synthetic peptide CIGB-300 modulates CK2-dependent signaling pathways affecting the survival and chemoresistance of non-small cell lung cancer cell lines

BACKGROUND

Lung cancer is the most frequently diagnosed cancer and the leading cause of cancer-related deaths worldwide. Up to 80% of cancer patients are classified as non-small-cell lung cancer (NSCLC) and cisplatin remains as the gold standard chemotherapy treatment, despite its limited efficacy due to both intrinsic and acquired resistance. The CK2 is a Ser/Thr kinase overexpressed in various types of cancer, including lung cancer. CIGB-300 is an antitumor peptide with a novel mechanism of action, since it binds to CK2 substrates thus preventing the enzyme activity. The aim of this work was to analyze the effects of CIGB-300 treatment targeting CK2-dependent signaling pathways in NSCLC cell lines and whether it may help improve current chemotherapy treatment.

METHODS

The human NSCLC cell lines NCI-H125 and NIH-A549 were used. Tumor spheroids were obtained through the hanging-drop method. A cisplatin resistant A549 cell line was obtained by chronic administration of cisplatin. Cell viability, apoptosis, immunoblotting, immunofluorescence and luciferase reporter assays were used to assess CIGB-300 effects. A luminescent assay was used to monitor proteasome activity.

RESULTS

We demonstrated that CIGB-300 induces an anti-proliferative response both in monolayer- and three-dimensional NSCLC models, presenting rapid and complete peptide uptake. This effect was accompanied by the inhibition of the CK2-dependent canonical NF-κB pathway, evidenced by reduced RelA/p65 nuclear levels and NF-κB protein targets modulation in both lung cancer cell lines, as well as conditionally reduced NF-κB transcriptional activity. In addition, NF-κB modulation was associated with enhanced proteasome activity, possibly through its α7/C8 subunit. Neither the peptide nor a classical CK2 inhibitor affected cytoplasmic β-CATENIN basal levels. Given that NF-κB activation has been linked to cisplatin-induced resistance, we explored whether CIGB-300 could bring additional therapeutic benefits to the standard cisplatin treatment. We established a resistant cell line that showed higher p65 nuclear levels after cisplatin treatment as compared with the parental cell line. Remarkably, the cisplatin-resistant cell line became more sensitive to CIGB-300 treatment.

CONCLUSIONS

Our data provide new insights into CIGB-300 mechanism of action and suggest clinical potential on current NSCLC therapy.

β-Catenin signaling pathway regulates cisplatin resistance in lung adenocarcinoma cells by upregulating Bcl-xl

The Wnt/β-catenin signaling pathway has been reported to regulate cisplatin resistance in several types of cancer cell. The present study aimed to investigate the role and underlying mechanism of Wnt/β-catenin signaling in cisplatin resistance of lung adenocarcinoma cells. Wild-type and cisplatin-resistant A549 human lung adenocarcinoma cells (A549/WT and A549/CDDP, respectively) were cultured in vitro and exposed to different cisplatin concentrations. Cells were incubated with 10 mM lithium chloride (LiCl) to activate β-catenin signaling. Cell proliferation was determined using the MTS assay. Cell apoptosis was evaluated using Annexin V/propidium iodide double staining, followed by flow cytometry. β-catenin was knocked down using small interfering RNA (siRNA). The intracellular distribution of β-catenin was determined by immunocytochemistry, and the mRNA and protein expressions of target genes were examined by reverse transcription-quantitative polymerase chain reaction and western zblotting, respectively. β-catenin and B-cell lymphoma-extra large (Bcl-xl) were significantly upregulated in A549/CDDP cells compared with A549/WT cells (P<0.05). LiCl reduced the sensitivity of A549/WT cells to cisplatin (P<0.01); and upregulated, increased phosphorylation (P<0.05) and enhanced nuclear translocation of β-catenin. LiCl also significantly elevated the mRNA and protein expression levels of Bcl-xl (P<0.05). Notably, silencing of β-catenin with siRNA decreased the mRNA and protein expression of Bcl-xl, and sensitized A549/WT cells to cisplatin (P<0.01). The findings of the current study suggest that upregulation of β-catenin signaling may contribute to cisplatin resistance in lung adenocarcinoma cells by upregulating Bcl-xl. Therefore, molecular targeting of Wnt/β-catenin signaling may sensitize lung cancer cells to cisplatin.

c-Myc-miR-29c-REV3L signalling pathway drives the acquisition of temozolomide resistance in glioblastoma

Resistance to temozolomide poses a major clinical challenge in glioblastoma multiforme treatment, and the mechanisms underlying the development of temozolomide resistance remain poorly understood. Enhanced DNA repair and mutagenesis can allow tumour cells to survive, contributing to resistance and tumour recurrence. Here, using recurrent temozolomide-refractory glioblastoma specimens, temozolomide-resistant cells, and resistant-xenograft models, we report that loss of miR-29c via c-Myc drives the acquisition of temozolomide resistance through enhancement of REV3L-mediated DNA repair and mutagenesis in glioblastoma. Importantly, disruption of c-Myc/miR-29c/REV3L signalling may have dual anticancer effects, sensitizing the resistant tumours to therapy as well as preventing the emergence of acquired temozolomide resistance. Our findings suggest a rationale for targeting the c-Myc/miR-29c/REV3L signalling pathway as a promising therapeutic approach for glioblastoma, even in recurrent, treatment-refractory settings.

PCDH10 inhibits cell proliferation of multiple myeloma via the negative regulation of the Wnt/β-catenin/BCL-9 signaling pathway

The tumor suppressor protocadherin-10 (PCDH10) gene is important in cell proliferation, survival, apoptosis and migration. Inactivation of PCDH10 by promoter methylation is a frequent pathogenetic event in multiple myeloma (MM). The Wnt/β-catenin pathway is known to be involved in the cell growth of various types of cancer, including MM. However, the relationship between PCDH10 and Wnt signaling in MM remains unclear. In this study, we found that PCDH10 deficiency highly enhanced MM cell proliferation, Wnt signaling and the expression of BCL-9, an essential coactivator of Wnt transcriptional activity that is correlated with cell growth, survival and drug resistance. Restoration of PCDH10 suppressed nuclear localization of β-catenin, the activity of LEF/TCF, the expression of BCL-9 and AKT, whereas the expression of GSK3β was increased. The antagonistic effect of PCDH10 was associated with G1-phase blockage. Collectively, PCDH10 antagonized MM cell proliferation via the downregulation of Wnt/β-catenin/BCL-9 signaling, whereas PCDH10 repressed the expression of AKT to promote the expression of GSK3β and then to restrain the activation of β-catenin. Thus, the results offer a novel preclinical rationale in order to explore PCDH10 as an effective and selective therapeutic strategy to eradicate MM cells.

Targeting hypoxia-inducible factor-2α enhances sorafenib antitumor activity via β-catenin/C-Myc-dependent pathways in hepatocellular carcinoma

Sorafenib is a type of multikinase inhibitor that exhibits antiangiogenic and antiproliferative effects; in addition, sorafenib is a unique first-line drug recommended for the treatment of advanced hepatocellular carcinoma (HCC). However, the effectiveness of HCC treatment remains poor due to acquired drug resistance. It has been suggested that hypoxia, induced as a results of the antiangiogenic effects of sustained sorafenib treatment, may be an important factor in sorafenib resistance. The transcription factor hypoxia-inducible factor (HIF)-2α has been reported to be associated with cell proliferation under hypoxic conditions; therefore, it was hypothesized that hypoxia may enhance tumor cell proliferation via this mechanism. The present study aimed to evaluate whether the knock-down of HIF-2α was able to enhance the therapeutic efficacy of sorafenib in order to effectively treat HCC. The results demonstrated that hypoxia protected HCC cells against sorafenib; however, short hairpin RNA-HIF-2α transfection in combination with sorafenib treatment exhibited a significantly synergistic effect against HCC cell proliferation. In addition, HCC cells acquired increased β-catenin/C-Myc expression, which enhanced proliferation under hypoxic conditions; however, targeted knock-down of HIF-2α or C-Myc markedly decreased cell proliferation in HCC cells. In conclusion, the results of the present study indicated that the targeted knock-down of HIF-2α in combination with sorafenib may be a promising strategy for the treatment of HCC.