Overcoming EMT-driven therapeutic resistance by BH3 mimetics

SNCA inhibits epithelial-mesenchymal transition and correlates to favorable prognosis of breast cancer

Alpha-synuclein (SNCA) is a pathological hallmark of Parkinson's disease, known to be involved in cancer occurrence and development; however, its specific effects in breast cancer remain unknown. Data from 150 patients with breast cancer were retrieved from tissue microarray and analyzed for SNCA protein level using immunohistochemistry. Functional enrichment analysis was performed to investigate the potential role of SNCA in breast cancer. SNCA-mediated inhibition of epithelial-mesenchymal transition (EMT) was confirmed with western blotting. The effects of SNCA on invasion and migration were evaluated using transwell and wound-healing experiments. Furthermore, the potential influence of SNCA expression level on drug sensitivity and tumor infiltration by immune cells was analyzed using the public databases. SNCA is lowly expressed in breast cancer tissues. Besides, in vitro and in vivo experiments, SNCA overexpression blocked EMT and metastasis, and the knockdown of SNCA resulted in the opposite effect. A mouse model of metastasis verified the restriction of metastatic ability in vivo. Further analysis revealed that SNCA enhances sensitivity to commonly used anti-breast tumor drugs and immune cell infiltration. SNCA blocks EMT and metastasis in breast cancer and its expression levels could be useful in predicting the chemosensitivity and evaluating the immune microenvironment in breast cancer.

Nc886 promotes renal cancer cell drug-resistance by enhancing EMT through Rock2 phosphorylation-mediated β-catenin nuclear translocation

Drug resistance is a significant challenge in the present treatment regimens of renal cell carcinoma (RCC). Our previous study confirmed that nc886 functions as an oncogene in RCC. Nevertheless, the role and underlying mechanism of nc886 in RCC drug resistance are unclear. In the present study, Sunitinib and Everolimus treatment, respectively, downregulated nc886 expression in a dose-dependent manner in all four renal cancer cell lines. Nc886 overexpression in 786-O cells and ACHN cells significantly reduced the sensitivity of cancer cells to both Sunitinib and Everolimus treatment, respectively, by promoting cell viability and inhibiting cell apoptosis, whereas nc886 silencing increased cancer cell sensitivity. In renal cancer cell line with the highest drug-resistance, 786-O cells, Sunitinib, or Everolimus treatment enhanced the cellular EMT and was further enhanced by nc886 overexpression while attenuated by nc886 silencing. In 786-O cells, nc886 overexpression significantly promoted EMT, ROCK2 phosphorylation, and β-catenin nucleus translocation under Sunitinib or Everolimus treatment. Moreover, ROCK2 silencing significantly reversed the effects of nc886 overexpression on EMT, ROCK2 phosphorylation, and β-catenin nucleus translocation, as well as drug-resistant renal cancer cell viability and apoptosis. In conclusion, it was demonstrated that nc886 promotes renal cancer cell proliferation, migration, and invasion, as demonstrated previously. nc886 also promotes renal cancer cell drug-resistance to Sunitinib or Everolimus by promoting EMT through Rock2 phosphorylation-mediated nuclear translocation of β-catenin.

Detection of cancer stem cells by EMT-specific biomarker-based peptide ligands

The occurrence of epithelial-mesenchymal transition (EMT) within tumors, which enables invasion and metastasis, is linked to cancer stem cells (CSCs) with drug and radiation resistance. We used two specific peptides, F7 and SP peptides, to detect EMT derived cells or CSCs. Human tongue squamous carcinoma cell line-SAS transfected with reporter genes was generated and followed by spheroid culture. A small molecule inhibitor-Unc0642 and low-dose ionizing radiation (IR) were used for induction of EMT. Confocal microscopic imaging and fluorescence-activated cell sorting analysis were performed to evaluate the binding ability and specificity of peptides. A SAS xenograft mouse model with EMT induction was established for assessing the binding affinity of peptides. The results showed that F7 and SP peptides not only specifically penetrated into cytoplasm of SAS cells but also bound to EMT derived cells and CSCs with high nucleolin and vimentin expression. In addition, the expression of CSC marker and the binding of peptides were increased in tumors isolated from Unc0642/IR-treated groups. Our study demonstrates the potential of these peptides for detecting EMT derived cells or CSCs and might provide an alternative isolation method for these subpopulations within the tumor in the future.

Epithelial-Mesenchymal Transition in Docetaxel-Resistant Prostate Cancer

Castration-resistant prostate cancer (CRPCa) is an advanced stage of prostate cancer in which a tumour progresses even under androgen deprivation. Treatment alternatives for CRPCa remain very limited and mostly rely on docetaxel-based chemotherapy. Despite being shown to increase patients’ overall survival, docetaxel’s clinical efficacy is impaired by development of chemoresistance. Most patients do not respond to docetaxel treatment and even those initially responsive ultimately develop resistance. Recently, chemoresistance was found to be closely related to epithelial-mesenchymal transition (EMT), a process in which epithelial cells transition into a mesenchymal phenotype. In fact, EMT markers are overexpressed in prostate cancer and are correlated to a higher Gleason score. For this reason, new therapeutic strategies are being studied to inhibit this process in several cancers. However, the clinical usefulness of targeting EMT as a way to overcome docetaxel resistance in CRPCa is still questionable and suffers from some significant limitations. This review briefly summarises the most common mechanisms of EMT-induced chemoresistance and evaluates its use as a new approach to overcome docetaxel resistance in CRPCa.

TGF-β reduces DNA ds-break repair mechanisms to heighten genetic diversity and adaptability of CD44+/CD24- cancer cells

Many lines of evidence have indicated that both genetic and non-genetic determinants can contribute to intra-tumor heterogeneity and influence cancer outcomes. Among the best described sub-population of cancer cells generated by non-genetic mechanisms are cells characterized by a CD44+/CD24- cell surface marker profile. Here, we report that human CD44+/CD24- cancer cells are genetically highly unstable because of intrinsic defects in their DNA-repair capabilities. In fact, in CD44+/CD24- cells, constitutive activation of the TGF-beta axis was both necessary and sufficient to reduce the expression of genes that are crucial in coordinating DNA damage repair mechanisms. Consequently, we observed that cancer cells that reside in a CD44+/CD24- state are characterized by increased accumulation of DNA copy number alterations, greater genetic diversity and improved adaptability to drug treatment. Together, these data suggest that the transition into a CD44+/CD24- cell state can promote intra-tumor genetic heterogeneity, spur tumor evolution and increase tumor fitness.

IWR-1 inhibits epithelial-mesenchymal transition of colorectal cancer cells through suppressing Wnt/β-catenin signaling as well as survivin expression

Aberrant activation of Wnt/β-catenin signaling is frequently observed in patients with colorectal cancer (CRC) and is considered a major determinant of CRC pathogenesis. CRC pathogenesis is particularly accompanied by epithelial-mesenchymal transition (EMT) and survivin expression. Here, we investigated the potential and mechanism of a novel Wnt/β-catenin inhibitor IWR-1 to suppress tumor metastasis in relation with EMT and survivin expression. We first determined the EMT reversal effects of IWR-1 in in vitro (HCT116 and HT29 cells) and ex vivo (specimens of CRC patients) CRC models. It was shown that IWR-1 inhibited cell proliferation and EMT even in the presence of TNF-α-induced cancer cell stimulation. IWR-1 also significantly suppressed cell migration, invasion, and matrix metalloproteinase activities of CRC cell lines. Furthermore, we showed the evidence that IWR-1 provides EMT reversal effects by directly suppressing survivin expression by the followings: 1) IWR-1 could not completely inhibit EMT in survivin-overexpressing HCT116 cells, 2) EMT reversal effects of IWR-1 were more pronounced in survivin-suppressed cells, and 3) Survivin promoter assay directly identified the survivin promoter region responsible for inhibition of survivin transcription by IWR-1. Taken altogether, our results demonstrate that IWR-1 has the potential to suppress tumor metastasis by inhibiting Wnt/β-catenin pathway as well as survivin expression. Therefore, IWR-1 could be considered for future clinical use as a therapeutic agent to treat CRC.

By inhibiting snail signaling and miR-23a-3p, osthole suppresses the EMT-mediated metastatic ability in prostate cancer

Here we showed that Osthole, 7-methoxy-8-(3-methyl-2-butenyl) coumarin, a bioactive coumarin derivative extracted from medicinal plants, inhibited migration, invasion, epithelial to mesenchymal transition (EMT) in androgen-independent prostate cancer (AIPC) cells in vitro and metastasis of AIPC in vivo. In patients, high Snail levels were correlated with a higher histological Gleason sum and poor survival rates. Osthole inhibited the TGF-β/Akt/MAPK pathways, reduced Snail-DNA-binding activity and induced E-cadherin. We found that osthole decreased miR-23a-3p. Ectopic miR-23a-3p suppressed E-cadherin 3′ untranslated region reporter activity and E-cadherin expression, and relieved the motility suppression caused by osthole treatment.

Zipper-interacting protein kinase promotes epithelial-mesenchymal transition, invasion and metastasis through AKT and NF-kB signaling and is associated with metastasis and poor prognosis in gastric cancer patients

Zipper-interacting Protein Kinase (ZIPK) belongs to the death-associated protein kinase family. ZIPK has been characterized as a tumor suppressor in various tumors, including gastric cancer. On the other hand, ZIPK also promotes cell survival. In this study, both in vitro and in vivo assays indicated that ZIPK promoted cell growth, proliferation, migration, invasion, tumor formation and metastasis in nude mice. ZIPK induced epithelial-mesenchymal transition (EMT) with increasing expression of β-catenin, mesenchymal markers, Snail and Slug, and with decreasing expression of E-cadherin. Furthermore, ZIPK activated the AKT/IκB/NF-κB pathway, which can promote EMT and metastasis. Additionally, ZIPK expression was detected in human primary gastric cancer and their matched metastatic lymph node samples by immunohistochemistry. Increased expression of ZIPK in lymph node metastases was significantly associated with stage VI and abdominal organ invasion. Survival analysis revealed that patients with increased ZIPK expression in metastatic lymph nodes had poor disease-specific survival. Taken together, our study reveals that ZIPK is a pro-oncogenic factor, which promotes cancer metastasis.

Granzyme M expressed by tumor cells promotes chemoresistance and EMT in vitro and metastasis in vivo associated with STAT3 activation

Granzyme M is a serine protease known to be often expressed by natural killer cells and induce target cells apoptosis in combination with perforin. However, we detected granzyme M expression in murine and human cancer cell lines and human tumor samples in our study. Granzyme M increased chemoresistance, colony-formation, cytokine secretion and invasiveness in vitro. Most importantly, granzyme M facilitated tumor growth and metastasis in vivo. Granzyme M induced the epithelial-mesenchymal transition (EMT) in cancer cells associated with STAT3 activation. Our study revealed the role of granzyme M expressed by tumor in chemoresistance, invasion, metastasis and EMT.

EMT, CTCs and CSCs in tumor relapse and drug-resistance

Tumor relapse and metastasis are the primary causes of poor survival rates in patients with advanced cancer despite successful resection or chemotherapeutic treatment. A primary cause of relapse and metastasis is the persistence of cancer stem cells (CSCs), which are highly resistant to chemotherapy. Although highly efficacious drugs suppressing several subpopulations of CSCs in various tissue-specific cancers are available, recurrence is still common in patients. To find more suitable therapy for relapse, the mechanisms underlying metastasis and drug-resistance associated with relapse-initiating CSCs need to be identified. Recent studies in circulating tumor cells (CTCs) of some cancer patients manifest phenotypes of both CSCs and epithelial-mesenchymal transition (EMT). These patients are unresponsive to standard chemotherapies and have low progression free survival, suggesting that EMT-positive CTCs are related to co-occur with or transform into relapse-initiating CSCs. Furthermore, EMT programming in cancer cells enables in the remodeling of extracellular matrix to break the dormancy of relapse-initiating CSCs. In this review, we extensively discuss the association of the EMT program with CTCs and CSCs to characterize a subpopulation of patients prone to relapses. Identifying the mechanisms by which EMT-transformed CTCs and CSCs initiate relapse could facilitate the development of new or enhanced personalized therapeutic regimens.

Induction of epithelial-mesenchymal transition via activation of epidermal growth factor receptor contributes to sunitinib resistance in human renal cell carcinoma cell lines

Sunitinib is widely used for treating renal cell carcinoma (RCC). However, some patients do not respond to treatment with this drug. We aimed to study the association between sunitinib sensitivity and epithelial-mesenchymal transition (EMT) regulation via epidermal growth factor receptor (EGFR) signaling, which is a mechanism of resistance to anticancer drugs. Three RCC cell lines (786-O, ACHN, and Caki-1) were used, and then we evaluated cell viability, EMT regulatory proteins, and signal transduction with sunitinib treatment. Cell viability of 786-O cells was maintained after treatment with sunitinib. After treatment with sunitinib, EGFR phosphorylation increased in 786-O cells, resulting in an increase in the phosphorylation of extracellular signal-regulated kinase, nuclear translocation of β-catenin, and expression of mesenchymal markers. These results suggest that sunitinib induced EMT via activation of EGFR in 786-O cells, but not in ACHN and Caki-1 cells. Caki-1/SN cells, a resistant cell line generated by continuous exposure to sunitinib, displayed increased phosphorylation of EGFR. Cell viability in the presence of sunitinib was decreased by erlotinib, as the selective inhibitor of EGFR, treatment in 786-O and Caki-1/SN cells. Similarly, erlotinib suppressed sunitinib-induced EGFR activation and upregulated mesenchymal markers. Thus, we postulate that resistance to sunitinib in RCC may be associated with EMT caused by activation of EGFR.

Translational potential of cancer stem cells: A review of the detection of cancer stem cells and their roles in cancer recurrence and cancer treatment

Cancer stem cells (CSCs) are a subpopulation of cancer cells with many clinical implications in most cancer types. One important clinical implication of CSCs is their role in cancer metastases, as reflected by their ability to initiate and drive micro and macro-metastases. The other important contributing factor for CSCs in cancer management is their function in causing treatment resistance and recurrence in cancer via their activation of different signalling pathways such as Notch, Wnt/β-catenin, TGF-β, Hedgehog, PI3K/Akt/mTOR and JAK/STAT pathways. Thus, many different therapeutic approaches are being tested for prevention and treatment of cancer recurrence. These may include treatment strategies targeting altered genetic signalling pathways by blocking specific cell surface molecules, altering the cancer microenvironments that nurture cancer stem cells, inducing differentiation of CSCs, immunotherapy based on CSCs associated antigens, exploiting metabolites to kill CSCs, and designing small interfering RNA/DNA molecules that especially target CSCs. Because of the huge potential of these approaches to improve cancer management, it is important to identify and isolate cancer stem cells for precise study and application of prior the research on their role in cancer. Commonly used methodologies for detection and isolation of CSCs include functional, image-based, molecular, cytological sorting and filtration approaches, the use of different surface markers and xenotransplantation. Overall, given their significance in cancer biology, refining the isolation and targeting of CSCs will play an important role in future management of cancer.