Progeny from irradiated colorectal cancer cells acquire an EMT-like phenotype and activate Wnt/β-catenin pathway

Evaluation of BMP-2 as a Differentiating and Radiosensitizing Agent for Colorectal Cancer Stem Cells

BACKGROUND

Despite effective clinical responses, a large proportion of patients undergo resistance to radiotherapy. The low response rate to current treatments in different stages of colorectal cancer depends on the prominent role of stem cells in cancer.

OBJECTIVE

In the present study, the role of BMP-2 as an ionizing radiation-sensitive factor in colorectal cancer cells was investigated.

METHODS

A sphere formation assay was used for the enrichment of HCT-116 cancer stem cells (CSCs). The effects of combination therapy (BMP-2+ radiation) on DNA damage response (DDR), proliferation, and apoptosis were evaluated in HCT-116 and CSCs. Gene expressions of CSCs and epithelialmesenchymal transition (EMT) markers were also evaluated.

RESULTS

We found that the sphere formation assay showed a significant increase in the percentage of CSCs. Moreover, expression of CSCs markers, EMT-related genes, and DNA repair proteins significantly decreased in HCT-116 cells compared to the CSCs group after radiation. In addition, BMP-2 promoted the radiosensitivity of HCT-116 cells by decreasing the survival rate of the treated cells at 2, 4, and 6 Gy compared to the control group in HCT-116 cells.

CONCLUSION

Our findings indicated that BMP-2 could affect numerous signaling pathways involved in radioresistance. Therefore, BMP-2 can be considered an appealing therapeutic target for the treatment of radioresistant human colorectal cancer.

Cancer stem cells (CSCs): key player of radiotherapy resistance and its clinical significance

Cancer stem cells (CSCs) are self-renewing and slow-multiplying micro subpopulations in tumour microenvironments. CSCs contribute to cancer's resistance to radiation (including radiation) and other treatments. CSCs control the heterogeneity of the tumour. It alters the tumour's microenvironment cellular singling and promotes epithelial-to-mesenchymal transition (EMT). Current research decodes the role of extracellular vesicles (EVs) and CSCs interlink in radiation resistance. Exosome is a subpopulation of EVs and originated from plasma membrane. It is secreted by several active cells. It involed in cellular communication and messenger of healthly and multiple pathological complications. Exosomal biological active cargos (DNA, RNA, protein, lipid and glycan), are capable to transform recipient cells' nature. The molecular signatures of CSCs and CSC-derived exosomes are potential source of cancer theranostics development. This review discusse cancer stem cells, radiation-mediated CSCs development, EMT associated with CSCs, the role of exosomes in radioresistance development, the current state of radiation therapy and the use of CSCs and CSCs-derived exosomes biomolecules as a clinical screening biomarker for cancer. This review gives new researchers a reason to keep an eye on the next phase of scientific research into cancer theranostics that will help mankind.

Single-copy Snail upregulation causes partial epithelial-mesenchymal transition in colon cancer cells

BACKGROUND

Epithelial-mesenchymal transition (EMT) is an embryonic programme implicated in cancer stem cells, metastasis and therapeutic resistance. Its role in cancer progression remains controversial because the transition can be partial or complete in different models and contexts.

METHODS

Using human colon cancer DLD-1 cells, we engineered a cell line with a single-copy of Snail that was doxycycline-inducible and compared it to existing EMT models in DLD-1. The effect of Snail upregulation was characterised functionally, morphologically, and by transcriptional profiling and protein expression.

RESULTS

Induction with doxycycline increased Snail expression to a level similar to that observed in cancer cell lines spontaneously expressing Snail and results in partial EMT. In comparison, higher levels of overexpression arising from introduction of episomal-Snail, results in complete EMT. DLD-1 cells with partial EMT show chemoresistance in vitro, increased tumour growth in vivo and decreased apoptosis.

CONCLUSIONS

These findings highlight that the amount of bioavailable Snail can dictate phenotypic outcome and that partial EMT may be a preferred outcome of models operating within a natural range of Snail overexpression.

Mechanisms of radioresistance and the underlying signaling pathways in colorectal cancer cells

Radiotherapy is one of the most common modalities for the treatment of a wide range of tumors, including colorectal cancer (CRC); however, radioresistance of cancer cells remains a major limitation for this treatment. Following radiotherapy, the activities of various cellular mechanisms and cell signaling pathways are altered, resulting in the development of radioresistance, which leads to therapeutic failure and poor prognosis in patients with cancer. Furthermore, even though several inhibitors have been developed to target tumor resistance, these molecules can induce side effects in nontumor cells due to low specificity and efficiency. However, the role of these mechanisms in CRC has not been extensively studied. This review discusses recent studies regarding the relationship between radioresistance and the alterations in a series of cellular mechanisms and cell signaling pathways that lead to therapeutic failure and tumor recurrence. Our review also presents recent advances in the in vitro/in vivo study models aimed at investigating the radioresistance mechanism in CRC. Furthermore, it provides a relevant biochemical basis in theory, which can be useful to improve radiotherapy sensitivity and prolong patient survival.

Targeting Epithelial-to-Mesenchymal Transition in Radioresistance: Crosslinked Mechanisms and Strategies

Radiotherapy exerts a crucial role in curing cancer, however, its treatment efficiency is mostly limited due to the presence of radioresistance. Epithelial-to-mesenchymal transition (EMT) is a biological process that endows the cancer cells with invasive and metastatic properties, as well as radioresistance. Many potential mechanisms of EMT-related radioresistance being reported have broaden our cognition, and hint us the importance of an overall understanding of the relationship between EMT and radioresistance. This review focuses on the recent progresses involved in EMT-related mechanisms in regulating radioresistance, irradiation-mediated EMT program, and the intervention strategies to increase tumor radiosensitivity, in order to improve radiotherapy efficiency and clinical outcomes of cancer patients.

Therapeutic strategies targeting Wnt/β‑catenin signaling for colorectal cancer (Review)

Colorectal cancer (CRC) is one of the most common carcinomas. Although great progress has been made in recent years, CRC survival remains unsatisfactory due to high metastasis and recurrence. Understanding the underlying molecular mechanisms of CRC tumorigenesis and metastasis has become increasingly important. Recently, aberrant Wnt/β‑catenin signaling has been reported to be strongly associated with CRC tumorigenesis, metastasis and recurrence. Therefore, the Wnt/β‑catenin signaling pathway has potential value as a therapeutic target for CRC. In the present review, the dysregulation of this pathway in CRC and the promoting or suppressing function of therapeutic targets on CRC were explored. In addition, the interaction between this pathway and epithelial‑mesenchymal transition (EMT), cell stemness, mutations, metastasis‑related genes and tumor angiogenesis in CRC cells were also investigated. Numerous studies on this pathway may help identify the potential diagnostic and prognostic markers and therapeutic targets for CRC.

Molecular mechanisms of chemo- and radiotherapy resistance and the potential implications for cancer treatment

Cancer is a leading cause of death worldwide. Surgery is the primary treatment approach for cancer, but the survival rate is very low due to the rapid progression of the disease and presence of local and distant metastasis at diagnosis. Adjuvant chemotherapy and radiotherapy are important components of the multidisciplinary approaches for cancer treatment. However, resistance to radiotherapy and chemotherapy may result in treatment failure or even cancer recurrence. Radioresistance in cancer is often caused by the repair response to radiation-induced DNA damage, cell cycle dysregulation, cancer stem cells (CSCs) resilience, and epithelial-mesenchymal transition (EMT). Understanding the molecular alterations that lead to radioresistance may provide new diagnostic markers and therapeutic targets to improve radiotherapy efficacy. Patients who develop resistance to chemotherapy drugs cannot benefit from the cytotoxicity induced by the prescribed drug and will likely have a poor outcome with these treatments. Chemotherapy often shows a low response rate due to various drug resistance mechanisms. This review focuses on the molecular mechanisms of radioresistance and chemoresistance in cancer and discusses recent developments in therapeutic strategies targeting chemoradiotherapy resistance to improve treatment outcomes.

Epithelial-to-Mesenchymal Transition in the Light of Plasticity and Hybrid E/M States

Epithelial-to-mesenchymal transition (EMT) is a cellular program which leads to cells losing epithelial features, including cell polarity, cell-cell adhesion and attachment to the basement membrane, while gaining mesenchymal characteristics, such as invasive properties and stemness. This program is involved in embryogenesis, wound healing and cancer progression. Over the years, the role of EMT in cancer progression has been heavily debated, and the requirement of this process in metastasis even has been disputed. In this review, we discuss previous discrepancies in the light of recent findings on EMT, plasticity and hybrid E/M states. Moreover, we highlight various tumor microenvironmental cues and cell intrinsic signaling pathways that induce and sustain EMT programs, plasticity and hybrid E/M states. Lastly, we discuss how recent findings on plasticity, especially on those that enable cells to switch between hybrid E/M states, have changed our understanding on the role of EMT in cancer metastasis, stemness and therapy resistance.

Kopsanone inhibits proliferation and migration of invasive colon cancer cells

Colorectal cancer (CRC) is the second leading cause of cancer-related death globally. In spite of the increasing knowledge on molecular characteristics of different cancer types including CRC, there is limitation in the development of an effective treatment. The present study aimed to verify the antitumor effect of kopsanone, an indole alkaloid. To achieve this, we treated human colon cancer cells (Caco-2 and HCT-116) with kopsanone and analyzed its effects on cell viability, cell-cell adhesion, and actin cytoskeleton organization. In addition, functional assays including micronuclei formation, colony formation, cell migration, and invasiveness were performed. We observed that kopsanone reduced viability and proliferation and induced micronuclei formation of HCT-116 cells. Also, kopsanone inhibited anchorage-dependent colony formation and modulated adherens junctions (AJs), thus increasing the localization of E-cadherin and β-catenin in the cytosol of the invasive cells. Finally, fluorescence assays showed that kopsanone decreased stress fibers formation and reduced migration but not invasion of HCT-116 cells. Taken together, these findings indicate that kopsanone reduces proliferation and migration of HCT-116 cells via modulation of AJs and can therefore be considered for future in vivo and clinical investigation as potential therapeutic agent for treatment of CRC.

Cofilin-1, LIMK1 and SSH1 are differentially expressed in locally advanced colorectal cancer and according to consensus molecular subtypes

Background

Colorectal cancer (CRC) is among the deadliest cancers, wherein early dissemination of tumor cells, and consequently, metastasis formation, are the main causes of mortality and poor prognosis. Cofilin-1 (CFL-1) and its modulators, LIMK1/SSH1, play key roles in mediating the invasiveness by driving actin cytoskeleton reorganization in various cancer types. However, their clinical significance and prognostic value in CRC has not been fully explored. Here, we evaluated the clinical contribution of these actin regulators according to TNM and consensus molecular subtypes (CMSs) classification.

Methods

CFL-1, LIMK1 and SSH1 mRNA/protein levels were assessed by real-time PCR and immunohistochemical analyses using normal adjacent and tumor tissues obtained from a clinical cohort of CRC patients. The expression levels of these proteins were associated with clinicopathological features by using the chi square test. In addition, using RNA-Seq data of CRC patients from The Cancer Genome Atlas (TCGA) database, we determine how these actin regulators are expressed and distributed according to TNM and CMSs classification. Based on gene expression profiling, Kaplan–Meier survival analysis was used to evaluated overall survival.

Results

Bioinformatic analysis revealed that LIMK1 expression was upregulated in all tumor stages. Patients with high levels of LIMK1 demonstrated significantly lower overall survival rates and exhibited greater lymph node metastatic potential in a clinical cohort. In contrast, CFL-1 and SSH1 have expression downregulated in all tumor stages. However, immunohistochemical analyses showed that patients with high protein levels of CFL-1 and SSH1 exhibited greater lymph node metastatic potential and greater depth of local invasion. In addition, using the CMSs classification to evaluate different biological phenotypes of CRC, we observed that LIMK1 and SSH1 genes are upregulated in immune (CMS1) and mesenchymal (CMS4) subtypes. However, patients with high levels of LIMK1 also demonstrated significantly lower overall survival rates in canonical (CMS2), and metabolic (CMS3) subtypes.

Conclusions

We demonstrated that CFL-1 and its modulators, LIMK1/SSH1, are differentially expressed and associated with lymph node metastasis in CRC. Finally, this expression profile may be useful to predict patients with aggressive signatures, particularly, the immune and mesenchymal subtypes of CRC.

TGF-β acts as a dual regulator of COX-2/PGE2 tumor promotion depending of its cross-interaction with H-Ras and Wnt/β-catenin pathways in colorectal cancer cells

Transforming growth factor-β (TGF-β) plays a dual role acting as tumor promoter or suppressor. Along with cyclooxygenase-2 (COX-2) and oncogenic Ras, this multifunctional cytokine is deregulated in colorectal cancer. Despite their individual abilities to promote tumor growth and invasion, the mechanisms of cross regulation between these pathways is still unclear. Here, we investigate the effects of TGF-β, Ras oncogene and COX-2 in the colorectal cancer context. We used colon adenocarcinoma cell line HT-29 and Ras-transformed IEC-6 cells, both treated with prostaglandin E₂ (PGE₂ ), TGF-β or a combined treatment with these agents. We demonstrated that PGE₂ alters the subcellular localization of E-cadherin and β-catenin and enhanced the tumorigenic potential in HT-29 cells. This effect was inhibited by TGF-β, indicating a tumor suppressor role. Conversely, in Ras-transformed IEC-6 cells, TGF-β induced COX-2 expression and increased invasiveness, acting as a tumor promoter. In IEC-6 Ras-transformed cells, TGF-β increased nuclear β-catenin and Wnt/β-catenin activation, opposite to what was seen in the PGE₂ and TGF-β joint treatment in HT-29 cells. Together, our findings show that TGF-β increases COX-2 levels and induces invasiveness cooperating with Ras in a Wnt/β-catenin activation-dependent manner. This shows TGF-β dual regulation over COX-2/PGE₂ tumor promotion depending on the H-Ras and Wnt/β-catenin pathways activation status in intestinal cancer cells.

Hypoxia, partial EMT and collective migration: Emerging culprits in metastasis

Epithelial-mesenchymal transition (EMT) is a cellular biological process involved in migration of primary cancer cells to secondary sites facilitating metastasis. Besides, EMT also confers properties such as stemness, drug resistance and immune evasion which can aid a successful colonization at the distant site. EMT is not a binary process; recent evidence suggests that cells in partial EMT or hybrid E/M phenotype(s) can have enhanced stemness and drug resistance as compared to those undergoing a complete EMT. Moreover, partial EMT enables collective migration of cells as clusters of circulating tumor cells or emboli, further endorsing that cells in hybrid E/M phenotypes may be the 'fittest' for metastasis. Here, we review mechanisms and implications of hybrid E/M phenotypes, including their reported association with hypoxia. Hypoxia-driven activation of HIF-1α can drive EMT. In addition, cyclic hypoxia, as compared to acute or chronic hypoxia, shows the highest levels of active HIF-1α and can augment cancer aggressiveness to a greater extent, including enriching for a partial EMT phenotype. We also discuss how metastasis is influenced by hypoxia, partial EMT and collective cell migration, and call for a better understanding of interconnections among these mechanisms. We discuss the known regulators of hypoxia, hybrid EMT and collective cell migration and highlight the gaps which needs to be filled for connecting these three axes which will increase our understanding of dynamics of metastasis and help control it more effectively.

Emerging role of tumor cell plasticity in modifying therapeutic response

Resistance to cancer therapy is a major barrier to cancer management. Conventional views have proposed that acquisition of resistance may result from genetic mutations. However, accumulating evidence implicates a key role of non-mutational resistance mechanisms underlying drug tolerance, the latter of which is the focus that will be discussed here. Such non-mutational processes are largely driven by tumor cell plasticity, which renders tumor cells insusceptible to the drug-targeted pathway, thereby facilitating the tumor cell survival and growth. The concept of tumor cell plasticity highlights the significance of re-activation of developmental programs that are closely correlated with epithelial-mesenchymal transition, acquisition properties of cancer stem cells, and trans-differentiation potential during drug exposure. From observations in various cancers, this concept provides an opportunity for investigating the nature of anticancer drug resistance. Over the years, our understanding of the emerging role of phenotype switching in modifying therapeutic response has considerably increased. This expanded knowledge of tumor cell plasticity contributes to developing novel therapeutic strategies or combination therapy regimens using available anticancer drugs, which are likely to improve patient outcomes in clinical practice.

Down-Regulation of miR-2053 Inhibits the Development and Progression of Esophageal Carcinoma by Targeting Fyn-Related Kinase (FRK)

BACKGROUND

MicroRNAs (miRNAs) play essential roles in the regulation and pathophysiology of various types of cancers including esophageal carcinoma (ESCA). Increasing numbers of miRNAs have been identified to be important regulators in the progression of ESCA by regulating gene expression. However, functional miRNAs and the underlying mechanisms involved in ESCA need sufficient elucidation.

AIMS

In the present study, the function of miR-2053 was investigated in ESCA cells.

METHODS

The expression of miR-2053 was detected in four different ESCA cell lines (Eca109, Ec9706, KYSE30, and TE-1 cells) and normal cell line (HEEC) by qRT-PCR. Cell proliferation, migration, and invasion abilities after knockdown of miR-2053 were assessed by CCK-8 assay, scratch assay, and transwell assay, respectively. Cell cycle of ESCA cells was detected by flow cytometric analysis. Expression of proteins in ESCA cells was detected by Western blot analysis.

RESULTS

The results showed that the expression of miR-2053 was remarkably up-regulated in ESCA tissues and cells lines. Down-regulation of miR-2053 markedly inhibited cell proliferation, migration, and invasion and markedly induced cell cycle arrest and cell apoptosis in ESCA cell lines. Fyn-related kinase (FRK) was a target gene of miR-2053. Moreover, down-regulation of miR-2053 mediated the protein kinase B (AKT)/mammalian target of rapamycin and Wnt3a/β-catenin signaling pathway in ESCA cell lines.

CONCLUSIONS

Our results together suggest the potential of regulating miR-2053 expression against development and progression of esophageal carcinoma by targeting FRK.

RBBP4 promotes colon cancer malignant progression via regulating Wnt/β-catenin pathway

BACKGROUND

Our previous study demonstrated that RBBP4 was upregulated in colon cancer and correlated with poor prognosis of colon cancer and hepatic metastasis. However, the potential biological function of RBBP4 in colon cancer is still unknown.

AIM

To investigate the biological role and the potential mechanisms of RBBP4 in colon cancer progression.

METHODS

Real-time polymerase chain reaction and western blot analysis were used to detect the expression of RBBP4 in colon cancer cell lines. The cell proliferation and viability of SW620 and HCT116 cells with RBBP4 knockdown was detected by Cell Counting Kit-8 and 5-ethynyl-2’-deoxyuridine staining. The transwell assay was used to detect the invasion and migration capabilities of colon cancer cells with RBBP4 knockdown. Flow cytometry apoptosis assay was used to detect the apoptosis of colon cancer cells. Western blotting analysis was used to detect the expression of epithelial-mesenchymal transition and apoptosis related markers in colon cancer. The nuclear translocation of β-catenin was examined by Western blotting analysis in colon cancer cells with RBBP4 knockdown. The TOPFlash luciferase assay was used to detect the effect of RBBP4 on Wnt/β-catenin activation. The rescue experiments were performed in colon cancer cells treated with Wnt/β-catenin activator LiCl and RBBP4 knockdown.

RESULTS

We found that RBBP4 was highly expressed in colon cancer cell lines. The 5-ethynyl-2’-deoxyuridine assay showed that knockdown of RBBP4 significantly inhibited cell proliferation. RBBP4 inhibition reduced cell invasion and migration via regulating proteins related to epithelial-mesenchymal transition. Knockdown of RBBP4 significantly inhibited survivin-mediated apoptosis. Mechanistically, the TOPFlash assay showed that RBBP4 knockdown increased activity of the Wnt/β-catenin pathway. Meanwhile, RBBP4 knockdown suppressed nuclear translocation of β-catenin. With Wnt/β-catenin activator, rescue experiments suggested that the role of RBBP4 in colon cancer progression was dependent on Wnt/β-catenin pathway.

CONCLUSION

RBBP4 promotes colon cancer development via increasing activity of the Wnt/β-catenin pathway. RBBP4 may serve as a novel therapeutic target in colon cancer.

The role of epithelial-mesenchymal transition in regulating radioresistance

Cancer patients with different stages can benefit from radiotherapy, but there are still limited due to inherent or acquired radioresistance. The epithelial-mesenchymal transition (EMT) is a complex biological process that is implicated in malignant characteristics of cancer, such as radioresistance. Although the possible mechanisms of EMT-dependent radioresistance are being extensively studied, there is a lack of a clear picture of the overall signaling of EMT-mediated radioresistance. In this review, we highlight the role and possible molecular mechanisms of EMT in cancer radioresistance, in particular to EMT-associated signaling pathway, EMT-inducing transcription factors (EMT-TFs), EMT-related non-coding RNAs. The knowledge of EMT-associated mechanisms of radioresistance will offer more potent therapy targets to improve the radiotherapy responses.

Docosahexaenoic acid promotes cell cycle arrest and decreases proliferation through WNT/β-catenin modulation in colorectal cancer cells exposed to γ-radiation

The effects of radiation are known to be potentiated by N-3 polyunsaturated fatty acids, which modulate several signaling pathways, but the molecular mechanisms through which these fatty acids enhance the anticancer effects of irradiation in colorectal cancer (CRC) treatment remain poorly elucidated. Here, we aimed to ascertain whether the fatty acid docosahexaenoic acid (DHA) exerts a modulating effect on the response elicited by radiation treatment (RT). Two CRC cell lines, Caco-2 and HT-29, were exposed to RT, DHA, or both (DHA + RT) for various times, and then cell viability, proliferation, and clonogenicity were assessed. Moreover, cell cycle, apoptosis, and necrosis were analyzed using flow cytometry, and the involvement of WNT/β-catenin signaling was investigated by immunofluorescence to determine nuclear β-catenin, GSK3β phosphorylation status, and TCF/LEF-activity reporter. DHA and RT applied separately diminished the viability of both HT-29 and Caco-2 cells, and DHA + RT caused a further reduction in proliferation mainly in HT-29 cells, particularly in terms of colony formation. Concomitantly, our results verified cell cycle arrest in G0/G1 phase, a reduction of cyclin D1 expression, and a decrease in GSK3β phosphorylation after the combined treatment. Furthermore, immunofluorescence quantification revealed that nuclear β-catenin was increased in RT-exposed cells, but this effect was abrogated in cells exposed to DHA + RT, and the results of TCF/LEF-activity assays confirmed that DHA attenuated the increase in nuclear β-catenin activity induced by irradiation. Our finding shows that DHA applied in combination with RT enhanced the antitumor effects of irradiation on CRC cells, and that the underlying mechanism involved the WNT/β-catenin pathway. © 2018 BioFactors, 45(1):24-34, 2019.

Myosin Heavy Chain 10 (MYH10) Gene Silencing Reduces Cell Migration and Invasion in the Glioma Cell Lines U251, T98G, and SHG44 by Inhibiting the Wnt/β-Catenin Pathway

Background

The myosin heavy chain 10 or MYH10 gene encodes non-muscle myosin II B (NM IIB), and is involved in tumor cell migration, invasion, extracellular matrix (ECM) production, and epithelial-mesenchymal transition (EMT). This study aimed to investigate the effects of the MYH10 gene on normal human glial cells and glioma cell lines in vitro, by gene silencing, and to determine the signaling pathways involved.

Material/Methods

The normal human glial cell line HEB, and the glioma cell lines, U251, T98G, and SHG44 were studied. Plasmid transfection silenced the MYH10 gene. The cell counting kit-8 (CCK-8) assay evaluated cell viability. Cell migration and invasion were evaluated using scratch and transwell assays. Western blot measured the protein expression levels, and quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect the mRNA expression levels, for MYH10, metastasis-associated protein 1 (MTA-1), matrix metalloproteinase (MMP)-1, MMP-9, tissue inhibitor of metalloproteinases 2 (TIMP2), collagen 1, E-cadherin, vimentin, Wnt3a, β-catenin, and cyclin D1.

Results

The MYH10 gene was overexpressed in U251, T98G, and SHG44 cells. MYH10 expression was down-regulated following siMYH10 plasmid interference, which also inhibited glioma cell migration and invasion. MYH10 gene silencing resulted in reduced expression of MTA-1, MPP-2, MMP-9 and vimentin, and increased expression of TIMP-2, E-cadherin and collagen 1 at the protein and mRNA level, and inhibited the Wnt/β-catenin pathway.

Conclusions

In human glioma cell lines, silencing the MYH10 gene reduced cell migration and invasion, by inhibiting the Wnt/β-catenin pathway, which may regulate the ECM and inhibit EMT in human glioma.

Modeling the effect of ascites-induced compression on ovarian cancer multicellular aggregates

Epithelial ovarian cancer (EOC) is the most lethal gynecological malignancy. EOC dissemination is predominantly via direct extension of cells and multicellular aggregates (MCAs) into the peritoneal cavity, which adhere to and induce retraction of peritoneal mesothelium and proliferate in the submesothelial matrix to generate metastatic lesions. Metastasis is facilitated by the accumulation of malignant ascites (500 ml to >2 l), resulting in physical discomfort and abdominal distension, and leading to poor prognosis. Although intraperitoneal fluid pressure is normally subatmospheric, an average intraperitoneal pressure of 30 cmH2O (22.1 mmHg) has been reported in women with EOC. In this study, to enable experimental evaluation of the impact of high intraperitoneal pressure on EOC progression, two new in vitro model systems were developed. Initial experiments evaluated EOC MCAs in pressure vessels connected to an Instron to apply short-term compressive force. A Flexcell Compression Plus system was then used to enable longer-term compression of MCAs in custom-designed hydrogel carriers. Results show changes in the expression of genes related to epithelial-mesenchymal transition as well as altered dispersal of compressed MCAs on collagen gels. These new model systems have utility for future analyses of compression-induced mechanotransduction and the resulting impact on cellular responses related to intraperitoneal metastatic dissemination.This article has an associated First Person interview with the first authors of the paper.

Cancer cell plasticity: Impact on tumor progression and therapy response

Most tumors exhibit intra-tumor heterogeneity, which is associated with disease progression and an impaired response to therapy. Cancer cell plasticity has been proposed as being an important mechanism that, along with genetic and epigenetic alterations, promotes cancer cell diversity and contributes to intra-tumor heterogeneity. Plasticity endows cancer cells with the capacity to shift dynamically between a differentiated state, with limited tumorigenic potential, and an undifferentiated or cancer stem-like cell (CSC) state, which is responsible for long-term tumor growth. In addition, it confers the ability to transit into distinct CSC states with different competence to invade, disseminate and seed metastasis. Cancer cell plasticity has been linked to the epithelial-to-mesenchymal transition program and relies not only on cell-autonomous mechanisms, but also on signals provided by the tumor microenvironment and/or induced in response to therapy. We provide an overview of the dynamic transition for cancer cell states, the mechanisms governing cell plasticity and their impact on tumor progression, metastasis and therapy response. Understanding the mechanisms involved in cancer cell plasticity will provide insights for establishing new therapeutic interventions.

Annexin A2 overexpression associates with colorectal cancer invasiveness and TGF-ß induced epithelial mesenchymal transition via Src/ANXA2/STAT3

Annexin A2 (ANXA2) is upregulated in several malignancies, including colorectal cancer (CRC). However, there is little knowledge on the molecular mechanisms involved to its upregulation. The aim of this study was to identify the mechanism through which ANXA2 overexpression leads to CRC progression and evaluate its potential prognostic value. We used human CRC samples to analyse the correlation between ANXA2 levels and tumour staging. ANXA2 expression was increased in CRC tissues compared to normal colon tissues. In addition, we observe increased ANXA2 levels in stage IV tumours and metastasis, when compared to stage I-III. Whereas E-cadherin, an epithelial marker, decreased in stage II-IV and increased in metastasis. We’ve also shown that TGF-β, a classic EMT inductor, caused upregulation of ANXA2, and internalization of both E-cadherin and ANXA2 in CRC cells. ANXA2 silencing hindered TGF-β-induced invasiveness, and inhibitors of the Src/ANXA2/STAT3 pathway reversed the EMT. In silico analysis confirmed overexpression of ANXA2 and association to the consensus moleculars subtypes (CMS) with the worst prognosis. Therefore, ANXA2 overexpression play a pivotal role in CRC invasiveness through Src/ANXA2/STAT3 pathway activation. The association of ANXA2 to distinct CMSs suggests the possible use of ANXA2 as a prognostic marker or directed target therapy.

Downregulation of lncRNA OGFRP1 inhibits hepatocellular carcinoma progression by AKT/mTOR and Wnt/β-catenin signaling pathways

Introduction

Increasing evidence demonstrates that long noncoding RNAs (lncRNAs) play important roles in the progression of hepatocellular carcinoma (HCC) by regulating gene expression. However, the identification of functional lncRNAs in HCC remains insufficient. Our study aimed to investigate the function of lncRNA OGFRP1, which has not been functionally researched before, in Hep3B and HepG2 cells.

Methods

lncRNA OGFRP1 in HCC cells was down-regulated by using RNAi technology. Quantitative real-time polymerase chain reaction was used to determine the mRNA expression of lncRNA OGFRP1. Cell proliferation was examined by CCK8 and clone formation assays. Cell cycle and apoptosis were analyzed by flow cytometry. Cell migration and invasion were assessed by using Scratch assay and transwell assay, respectively. Protein expression of signaling pathways was determined by using Western blot.

Results

Cell proliferation of Hep3B was significantly inhibited by down-regulation of lncRNA OGFRP1 (P<0.05). Moreover, siOGFRP1 transfection induced Hep3B cell cycle arrest and apoptosis by regulating the expression of related proteins. Cell migration and invasion of Hep3B were also significantly inhibited by down-regulation of lncRNA OGFRP1. Wnt/β-catenin signaling pathway, involved in epithelial–mesenchymal transition (EMT), was inactivated by lncRNA OGFRP1 downregulation, including decreased expression of Wnt3a, β-catenin, N-cadherin and vimentin and increased expression of E-cadherin. We also found that the inhibitory effect of lncRNA OGFRP1 knockdown on Hep3B was mediated by the AKT/mTOR signaling pathway and IGF-1, an AKT signaling activator, could rescue the cellular phenotype. However, knockdown of lncRNA OGFRP1 did not influence cell proliferation, migration and invasion in HepG2 cells.

Conclusion

We found that downregulation of lncRNA OGFRP1 suppressed the proliferation and EMT of HCC Hep3B cells through AKT and Wnt/β-catenin signaling pathways. However, lncRNA OGFRP1 exhibited a differentiated function in different HCC cell lines, which required further study in the future.

Effects of radiation on the metastatic process

Radiotherapy remains one of the corner stones in the treatment of various malignancies and often leads to an improvement in overall survival. Nonetheless, pre-clinical evidence indicates that radiation can entail pro-metastatic effects via multiple pathways. Via direct actions on cancer cells and indirect actions on the tumor microenvironment, radiation has the potential to enhance epithelial-to-mesenchymal transition, invasion, migration, angiogenesis and metastasis. However, the data remains ambiguous and clinical observations that unequivocally prove these findings are lacking. In this review we discuss the pre-clinical and clinical data on the local and systemic effect of irradiation on the metastatic process with an emphasis on the molecular pathways involved.

Clair DK, Kyprianou N. Profiles of Radioresistance Mechanisms in Prostate Cancer

Radiation therapy (RT) is commonly used for the treatment of localized prostate cancer (PCa). However, cancer cells often develop resistance to radiation through unknown mechanisms and pose an intractable challenge. Radiation resistance is highly unpredictable, rendering the treatment less effective in many patients and frequently causing metastasis and cancer recurrence. Understanding the molecular events that cause radioresistance in PCa will enable us to develop adjuvant treatments for enhancing the efficacy of RT. Radioresistant PCa depends on the elevated DNA repair system and the intracellular levels of reactive oxygen species (ROS) to proliferate, self-renew, and scavenge anti-cancer regimens, whereas the elevated heat shock protein 90 (HSP90) and the epithelial-mesenchymal transition (EMT) enable radioresistant PCa cells to metastasize after exposure to radiation. The up-regulation of the DNA repairing system, ROS, HSP90, and EMT effectors has been studied extensively, but not targeted by adjuvant therapy of radioresistant PCa. Here, we emphasize the effects of ionizing radiation and the mechanisms driving the emergence of radioresistant PCa. We also address the markers of radioresistance, the gene signatures for the predictive response to radiotherapy, and novel therapeutic platforms for targeting radioresistant PCa. This review provides significant insights into enhancing the current knowledge and the understanding toward optimization of these markers for the treatment of radioresistant PCa.

Cancer stem cells in progression of colorectal cancer

Colorectal cancer is one of the most common cancers worldwide with high mortality. Distant metastasis and relapse are major causes of patient death. Cancer stem cells (CSCs) play a critical role in the metastasis and relapse of colorectal cancer. CSCs are a subpopulation of cancer cells with unique properties of self-renewal, infinite division and multi-directional differentiation potential. Colorectal CSCs are defined with a group of cell surface markers, such as CD44, CD133, CD24, EpCAM, LGR5 and ALDH. They are highly tumorigenic, chemoresistant and radioresistant and thus are critical in the metastasis and recurrence of colorectal cancer and disease-free survival. This review article updates the colorectal CSCs with a focus on their role in tumor initiation, progression, drug resistance and tumor relapse.

Cancer stem cells and signaling pathways in radioresistance

Radiation therapy (RT) is one of the most important strategies in cancer treatment. Radioresistance (the failure to RT) results in locoregional recurrence and metastasis. Therefore, it is critically important to investigate the mechanisms leading to cancer radioresistance to overcome this problem and increase patients' survival. Currently, the majority of the radioresistance-associated researches have focused on preclinical studies. Although the exact mechanisms of cancer radioresistance have not been fully uncovered, accumulating evidence supports that cancer stem cells (CSCs) and different signaling pathways play important roles in regulating radiation response and radioresistance. Therefore, targeting CSCs or signaling pathway proteins may hold promise for developing novel combination modalities and overcoming radioresistance. The present review focuses on the key evidence of CSC markers and several important signaling pathways in cancer radioresistance and explores innovative approaches for future radiation treatment.

The role of N-glycans in colorectal cancer progression: potential biomarkers and therapeutic applications

Changes in glycosylation, which is one of the most common protein post-translational modifications, are considered to be a hallmark of cancer. N-glycans can modulate cell migration, cell-cell adhesion, cell signaling, growth and metastasis. The colorectal cancer (CRC) is a leading cause of cancer-related mortality and the correlation between CRC progression and changes in the pattern of expression of N-glycans is being considered in the search for new biomarkers. Here, we review the role of N-glycans in CRC cell biology. The perspectives on emerging N-glycan-related anticancer therapies, along with new insights and challenges, are also discussed.

Roles of Long Noncoding RNAs in Recurrence and Metastasis of Radiotherapy-Resistant Cancer Stem Cells

Radiotherapy is a well-established therapeutic regimen applied to treat at least half of all cancer patients worldwide. Radioresistance of cancers or failure to treat certain tumor types with radiation is associated with enhanced local invasion, metastasis and poor prognosis. Elucidation of the biological characteristics underlying radioresistance is therefore critical to ensure the development of effective strategies to resolve this issue, which remains an urgent medical problem. Cancer stem cells (CSCs) comprise a small population of tumor cells that constitute the origin of most cancer cell types. CSCs are virtually resistant to radiotherapy, and consequently contribute to recurrence and disease progression. Metastasis is an increasing problem in resistance to cancer radiotherapy and closely associated with the morbidity and mortality rates of several cancer types. Accumulating evidence has demonstrated that radiation induces epithelial–mesenchymal transition (EMT) accompanied by increased cancer recurrence, metastasis and CSC generation. CSCs are believed to serve as the basis of metastasis. Previous studies indicate that CSCs contribute to the generation of metastasis, either in a direct or indirect manner. Moreover, the heterogeneity of CSCs may be responsible for organ specificity and considerable complexity of metastases. Long noncoding RNAs (lncRNAs) are a class of noncoding molecules over 200 nucleotides in length involved in the initiation and progression of several cancer types. Recently, lncRNAs have attracted considerable attention as novel critical regulators of cancer progression and metastasis. In the current review, we have discussed lncRNA-mediated regulation of CSCs following radiotherapy, their association with tumor metastasis and significance in radioresistance of cancer.

Complex Determinants of Epithelial: Mesenchymal Phenotypic Plasticity in Ovarian Cancer

Unlike most epithelial malignancies which metastasize hematogenously, metastasis of epithelial ovarian cancer (EOC) occurs primarily via transcoelomic dissemination, characterized by exfoliation of cells from the primary tumor, avoidance of detachment-induced cell death (anoikis), movement throughout the peritoneal cavity as individual cells and multi-cellular aggregates (MCAs), adhesion to and disruption of the mesothelial lining of the peritoneum, and submesothelial matrix anchoring and proliferation to generate widely disseminated metastases. This exceptional microenvironment is highly permissive for phenotypic plasticity, enabling mesenchymal-to-epithelial (MET) and epithelial-to-mesenchymal (EMT) transitions. In this review, we summarize current knowledge on EOC heterogeneity in an EMT context, outline major regulators of EMT in ovarian cancer, address controversies in EMT and EOC chemoresistance, and highlight computational modeling approaches toward understanding EMT/MET in EOC.

Heterogeneous Cadherin Expression and Multicellular Aggregate Dynamics in Ovarian Cancer Dissemination

Epithelial ovarian carcinoma spreads via shedding of cells and multicellular aggregates (MCAs) from the primary tumor into peritoneal cavity, with subsequent intraperitoneal tumor cell:mesothelial cell adhesion as a key early event in metastatic seeding. Evaluation of human tumor extracts and tissues confirms that well-differentiated ovarian tumors express abundant E-cadherin (Ecad), whereas advanced lesions exhibit upregulated N-cadherin (Ncad). Two expression patterns are observed: “mixed cadherin,” in which distinct cells within the same tumor express either E- or Ncad, and “hybrid cadherin,” wherein single tumor cell(s) simultaneously expresses both cadherins. We demonstrate striking cadherin-dependent differences in cell-cell interactions, MCA formation, and aggregate ultrastructure. Mesenchymal-type Ncad+ cells formed stable, highly cohesive solid spheroids, whereas Ecad+ epithelial-type cells generated loosely adhesive cell clusters covered by uniform microvilli. Generation of “mixed cadherin” MCAs using fluorescently tagged cell populations revealed preferential sorting into cadherin-dependent clusters, whereas mixing of cell lines with common cadherin profiles generated homogeneous aggregates. Recapitulation of the “hybrid cadherin” Ecad+/Ncad+ phenotype, via insertion of the CDH2 gene into Ecad+ cells, resulted in the ability to form heterogeneous clusters with Ncad+ cells, significantly enhanced adhesion to organotypic mesomimetic cultures and peritoneal explants, and increased both migration and matrix invasion. Alternatively, insertion of CDH1 gene into Ncad+ cells greatly reduced cell-to-collagen, cell-to-mesothelium, and cell-to-peritoneum adhesion. Acquisition of the hybrid cadherin phenotype resulted in altered MCA surface morphology with increased surface projections and increased cell proliferation. Overall, these findings support the hypothesis that MCA cadherin composition impacts intraperitoneal cell and MCA dynamics and thereby affects ultimate metastatic success.

Induction of metastasis, cancer stem cell phenotype, and oncogenic metabolism in cancer cells by ionizing radiation

Radiation therapy is one of the major tools of cancer treatment, and is widely used for a variety of malignant tumours. Radiotherapy causes DNA damage directly by ionization or indirectly via the generation of reactive oxygen species (ROS), thereby destroying cancer cells. However, ionizing radiation (IR) paradoxically promotes metastasis and invasion of cancer cells by inducing the epithelial-mesenchymal transition (EMT). Metastasis is a major obstacle to successful cancer therapy, and is closely linked to the rates of morbidity and mortality of many cancers. ROS have been shown to play important roles in mediating the biological effects of IR. ROS have been implicated in IR-induced EMT, via activation of several EMT transcription factors—including Snail, HIF-1, ZEB1, and STAT3—that are activated by signalling pathways, including those of TGF-β, Wnt, Hedgehog, Notch, G-CSF, EGFR/PI3K/Akt, and MAPK. Cancer cells that undergo EMT have been shown to acquire stemness and undergo metabolic changes, although these points are debated. IR is known to induce cancer stem cell (CSC) properties, including dedifferentiation and self-renewal, and to promote oncogenic metabolism by activating these EMT-inducing pathways. Much accumulated evidence has shown that metabolic alterations in cancer cells are closely associated with the EMT and CSC phenotypes; specifically, the IR-induced oncogenic metabolism seems to be required for acquisition of the EMT and CSC phenotypes. IR can also elicit various changes in the tumour microenvironment (TME) that may affect invasion and metastasis. EMT, CSC, and oncogenic metabolism are involved in radioresistance; targeting them may improve the efficacy of radiotherapy, preventing tumour recurrence and metastasis. This study focuses on the molecular mechanisms of IR-induced EMT, CSCs, oncogenic metabolism, and alterations in the TME. We discuss how IR-induced EMT/CSC/oncogenic metabolism may promote resistance to radiotherapy; we also review efforts to develop therapeutic approaches to eliminate these IR-induced adverse effects.

Tumor Budding, Micropapillary Pattern, and Polyploidy Giant Cancer Cells in Colorectal Cancer: Current Status and Future Prospects

We previously reported that polyploid giant cancer cells (PGCGs) induced by CoCl₂ could form through endoreduplication or cell fusion. A single PGCC formed tumors in immunodeficient mice. PGCCs are also the key contributors to the cellular atypia and associate with the malignant grade of tumors. PGCCs have the properties of cancer stem cells and produce daughter cells via asymmetric cell division. Compared with diploid cancer cells, these daughter cells express less epithelial markers and acquire mesenchymal phenotype with importance in cancer development and progression. Tumor budding is generally recognized to correlate with a high recurrence rate, lymph node metastasis, chemoresistance, and poor prognosis of colorectal cancers (CRCs) and is a good indicator to predict the metastasis and aggressiveness in CRCs. Micropapillary pattern is a special morphologic pattern and also associates with tumor metastasis and poor prognosis. There are similar morphologic features and molecular phenotypes among tumor budding, micropapillary carcinoma pattern, and PGCCs with their budding daughter cells and all of them show strong ability of tumor invasion and migration. In this review, we discuss the cancer stem cell properties of PGCCs, the molecular mechanisms of their regulation, and the relationships with tumor budding and micropapillary pattern in CRCs.

Protein Markers Associated with an ALDH Sub-Population in Colorectal Cancer

ALDH has been shown to be a marker that denotes a sub-population of cancer stem cells in colorectal and other cancers. This sub-population of cells shows an increased risk for tumor initiation, metastasis, and resistance to chemotherapy and radiation resulting in recurrence and death. It is thus essential to identify the important signaling pathways related to ALDH1+ CSCs in colon cancer. The essential issue becomes to isolate pure sub-populations of cells from heterogeneous tissues for further analysis. To achieve this goal, tissues from colorectal cancer Stage III patients were immuno-stained with ALDH1 antibody. Target ALDH1+ and ALDH1- cells from the same tissue were micro-dissected using Laser Capture Microdissection (LCM). Captured cells were lysed and analyzed using LC-MS/MS where around 20,000 cells were available for analysis. This analysis resulted in 134 proteins which were differentially expressed between ALDH1+ and ALDH1- cells in three patient sample pairs. Based on these differentially expressed proteins an IPA pathway analysis was performed that showed two key pathways in cell to cell signaling and organismal injury and abnormalities. The IPA analysis revealed β-catenin, NFκB (p65) and TGFβ1 as important cancer-related proteins in these pathways. A TMA validation using immunofluorescence staining of tissue micro-arrays including 170 cases was used to verify that these key proteins were highly overexpressed in ALDH1+ cells in colon cancer tissues compared to ALDH1- cells.

The Role of EphA4 Signaling in Radiation-Induced EMT-Like Phenotype in Colorectal Cancer Cells

Radiotherapy is widely used for advanced rectal tumors. However, refractory metastasis has become the major cause of therapy failure in rectal cancer patients. Understanding the molecular mechanism that controls the aggressive cellular response to this treatment is essential for developing new therapeutic applications and improving radiotherapy response in colorectal cancer patients. Using the progeny of cells that were submitted to irradiation, we have demonstrated that the PI3K/AKT, Wnt/β-catenin signaling pathways as well as ERK1/2 downstream of EPHA4 receptor activation, play an important role in the regulation of events related with the EMT development, which may be associated with the therapeutic failure in rectal cancer after radiotherapy. Here, we further discuss about EphA4 receptor as a potential therapeutic target for the treatment of this cancer type. J. Cell. Biochem. 118: 442-445, 2017. © 2016 Wiley Periodicals, Inc.

The Role of E-Cadherin in Maintaining the Barrier Function of Corneal Epithelium after Treatment with Cultured Autologous Oral Mucosa Epithelial Cell Sheet Grafts for Limbal Stem Deficiency

The role of E-cadherin in epithelial barrier function of cultured autologous oral mucosa epithelial cell sheet (CAOMECS) grafts was examined. CAOMECS were cultured on a temperature-responsive surface and grafted onto rabbit corneas with Limbal Stem Cell Deficiency (LSCD). E-cadherin levels were significantly higher in CAOMECS compared to normal and LSCD epithelium. Beta-catenin colocalized with E-cadherin in CAOMECS cell membranes while phosphorylated beta-catenin was significantly increased. ZO-1, occludin, and Cnx43 were also strongly expressed in CAOMECS. E-cadherin and beta-catenin localization at the cell membrane was reduced in LSCD corneas, while CAOMECS-grafted corneas showed a restoration of E-cadherin and beta-catenin expression. LSCD corneas did not show continuous staining for ZO-1 or for Cnx43, while CAOMECS-grafted corneas showed a positive expression of ZO-1 and Cnx43. Cascade Blue® hydrazide did not pass through CAOMECS. Because E-cadherin interactions are calcium-dependent, EGTA was used to chelate calcium and disrupt cell adhesion. EGTA-treated CAOMECS completely detached from cell culture surface, and E-cadherin levels were significantly decreased. In conclusion, E cadherin high expression contributed to CAOMECS tight and gap junction protein recruitment at the cell membrane, thus promoting cellular adhesion and a functional barrier to protect the ocular surface.

Radiation induces the generation of cancer stem cells: A novel mechanism for cancer radioresistance

Radioresistance remains a major obstacle for the radiotherapy treatment of cancer. Previous studies have demonstrated that the radioresistance of cancer is due to the existence of intrinsic cancer stem cells (CSCs), which represent a small, but radioresistant cell subpopulation that exist in heterogeneous tumors. By contrast, non-stem cancer cells are considered to be radiosensitive and thus, easy to kill. However, recent studies have revealed that under conditions of radiation-induced stress, theoretically radiosensitive non-stem cancer cells may undergo dedifferentiation subsequently obtaining the phenotypes and functions of CSCs, including high resistance to radiotherapy, which indicates that radiation may directly result in the generation of novel CSCs from non-stem cancer cells. These findings suggest that in addition to intrinsic CSCs, non-stem cancer cells may also contribute to the relapse and metastasis of cancer following transformation into CSCs. This review aims to investigate the radiation-induced generation of CSCs, its association with epithelial-mesenchymal transition and its significance with regard to the radioresistance of cancer.

EphA4-mediated signaling regulates the aggressive phenotype of irradiation survivor colorectal cancer cells

Radiotherapy is widely used for advanced rectal tumors. However, tumor recurrence after this treatment tends to be more aggressive and is associated with a poor prognosis. Uncovering the molecular mechanism that controls this recurrence is essential for developing new therapeutic applications. In the present study, we demonstrated that radiation increases the EphA4 activation level of the survivor progeny of colorectal cancer cells submitted to this treatment and that such activation promoted the internalization of a complex E-cadherin-EphA4, inducing cell-cell adhesion disruption. Moreover, EphA4 knockdown in the progeny of irradiated cells reduced the migratory and invasive potentials and metalloprotease activity induced by irradiation. Finally, we demonstrated that the cell migration and invasion potential were regulated by AKT and ERK1/2 signaling, with the ERK1/2 activity being dependent on EphA4. In summary, our study demonstrates that these signaling pathways could be responsible for the therapeutic failure, thereby promoting local invasion and metastasis in rectal cancer after radiotherapy. We also postulate that EphA4 is a potential therapeutic target for colorectal cancer treatment.

Tumor Budding: The Name is EMT. Partial EMT

Tumor budding is a histological phenomenon encountered in various cancers, whereby individual malignant cells and/or small clusters of malignant cells are seen in the tumor stroma. Postulated to be mirror epithelial-mesenchymal transition, tumor budding has been associated with poor cancer outcomes. However, the vast heterogeneity in its exact definition, methodology of assessment, and patient stratification need to be resolved before it can be routinely used as a standardized prognostic feature. Here, we discuss the heterogeneity in defining and assessing tumor budding, its clinical significance across multiple cancer types, and its prospective implementation in clinical practice. Next, we review the emerging evidence about partial, rather than complete, epithelial-mesenchymal phenotype at the tumor bud level, and its connection with tumor proliferation, quiescence, and stemness. Finally, based on recent literature, indicating a co-expression of epithelial and mesenchymal markers in many tumor buds, we posit tumor budding to be a manifestation of this hybrid epithelial/mesenchymal phenotype displaying collective cell migration.

Implications of the Hybrid Epithelial/Mesenchymal Phenotype in Metastasis

Transitions between epithelial and mesenchymal phenotypes – the epithelial to ­mesenchymal transition (EMT) and its reverse the mesenchymal to epithelial transition (MET) – are hallmarks of cancer metastasis. While transitioning between the epithelial and mesenchymal phenotypes, cells can also attain a hybrid epithelial/mesenchymal (E/M) (i.e., partial or intermediate EMT) phenotype. Cells in this phenotype have mixed epithelial (e.g., adhesion) and mesenchymal (e.g., migration) properties, thereby allowing them to move collectively as clusters. If these clusters reach the bloodstream intact, they can give rise to clusters of circulating tumor cells (CTCs), as have often been seen experimentally. Here, we review the operating principles of the core regulatory network for EMT/MET that acts as a “three-way” switch giving rise to three distinct phenotypes – E, M and hybrid E/M – and present a theoretical framework that can elucidate the role of many other players in regulating epithelial plasticity. Furthermore, we highlight recent studies on partial EMT and its association with drug resistance and tumor-initiating potential; and discuss how cell–cell communication between cells in a partial EMT phenotype can enable the formation of clusters of CTCs. These clusters can be more apoptosis-resistant and have more tumor-initiating potential than singly moving CTCs with a wholly mesenchymal (complete EMT) phenotype. Also, more such clusters can be formed under inflammatory conditions that are often generated by various therapies. Finally, we discuss the multiple advantages that the partial EMT or hybrid E/M phenotype have as compared to a complete EMT phenotype and argue that these collectively migrating cells are the primary “bad actors” of metastasis.

The HSP90 Inhibitor Ganetespib Radiosensitizes Human Lung Adenocarcinoma Cells

The molecular chaperone HSP90 is involved in stabilization and function of multiple client proteins, many of which represent important oncogenic drivers in NSCLC. Utilization of HSP90 inhibitors as radiosensitizing agents is a promising approach. The antitumor activity of ganetespib, HSP90 inhibitor, was evaluated in human lung adenocarcinoma (AC) cells for its ability to potentiate the effects of IR treatment in both in vitro and in vivo. The cytotoxic effects of ganetespib included; G2/M cell cycle arrest, inhibition of DNA repair, apoptosis induction, and promotion of senescence. All of these antitumor effects were both concentration- and time-dependent. Both pretreatment and post-radiation treatment with ganetespib at low nanomolar concentrations induced radiosensitization in lung AC cells in vitro. Ganetespib may impart radiosensitization through multiple mechanisms: such as down regulation of the PI3K/Akt pathway; diminished DNA repair capacity and promotion of cellular senescence. In vivo, ganetespib reduced growth of T2821 tumor xenografts in mice and sensitized tumors to IR. Tumor irradiation led to dramatic upregulation of β-catenin expression in tumor tissues, an effect that was mitigated in T2821 xenografts when ganetespib was combined with IR treatments. These data highlight the promise of combining ganetespib with IR therapies in the treatment of AC lung tumors.

The role of cytoskeleton and adhesion proteins in the resistance to photodynamic therapy. Possible therapeutic interventions

It is known that Photodynamic Therapy (PDT) induces changes in the cytoskeleton, the cell shape, and the adhesion properties of tumour cells. In addition, these targets have also been demonstrated to be involved in the development of PDT resistance. The reversal of PDT resistance by manipulating the cell adhesion process to substrata has been out of reach. Even though the existence of cell adhesion-mediated PDT resistance has not been reported so far, it cannot be ruled out. In addition to its impact on the apoptotic response to photodamage, the cytoskeleton alterations are thought to be associated with the processes of metastasis and invasion after PDT. In this review, we will address the impact of photodamage on the microfilament and microtubule cytoskeleton components and its regulators on PDT-treated cells as well as on cell adhesion. We will also summarise the impact of PDT on the surviving and resistant cells and their metastatic potential. Possible strategies aimed at taking advantage of the changes induced by PDT on actin, tubulin and cell adhesion proteins by targeting these molecules will also be discussed.

Alterations of the apical junctional complex and actin cytoskeleton and their role in colorectal cancer progression

Colorectal cancer represents the fourth highest mortality rate among cancer types worldwide. An understanding of the molecular mechanisms that regulate their progression can prevents or reduces mortality due to this disease. Epithelial cells present an apical junctional complex connected to the actin cytoskeleton, which maintains the dynamic properties of this complex, tissue architecture and cell homeostasis. Several studies have indicated that apical junctional complex alterations and actin cytoskeleton disorganization play a critical role in epithelial cancer progression. However, few studies have examined the existence of an interrelation between these 2 components, particularly in colorectal cancer. This review discusses the recent progress toward elucidating the role of alterations of apical junctional complex constituents and of modifications of actin cytoskeleton organization and discusses how these events are interlinked to modulate cellular responses related to colorectal cancer progression toward successful metastasis.