Halofuginone inhibits radiotherapy-induced epithelial-mesenchymal transition in lung cancer

Overexpression of microRNA-611 inhibits TGF-β-induced epithelial-mesenchymal transition and migration in lung cancer cells through MAPKAP1

Metastasis is a major cause of death in patients with lung cancer (LC). microRNA-611 (miR-611), a miRNA, has been little studied in cancer. Here, we aimed to further elucidate the roles of miR-611 in epithelial-mesenchymal transition (EMT) and migration induced by transforming growth factor-β (TGF-β) in LC cells and the possible underlying mechanisms. miR-611 and MAPKAP1 expression was first identified in LC tissues from metastatic and nonmetastatic patients, and their expression was associated with overall survival. Gain- and loss-of-function experiments were performed to verify the impacts of miR-611 and MAPKAP1 on pAKT expression, EMT, and migration in LC cells treated with TGF-β. The interaction between miR-611 and MAPKAP1 was also determined with a luciferase reporter assay. In our study, miR-611 was expressed at low levels, and MAPKAP1 was highly expressed in LC tissues, which was associated with metastasis and short overall survival. Functionally, miR-611 inhibition or MAPKAP1 overexpression accelerated EMT and migration and upregulated pAKT in TGF-β-treated A549 and H1299 cells; miR-611 overexpression or MAPKAP1 silencing exerted the opposite effects as miR-611 inhibition or MAPKAP1 overexpression. Mechanistically, miR-611 could target and downregulate MAPKAP1. MAPKAP1 expression was also negatively correlated with miR-611 expression in LC tissues. In addition, miR-611 overexpression reduced the EMT and migration of TGF-β-treated A549 and H1299 cells by targeting MAPKAP1. In conclusion, miR-611 overexpression attenuated EMT and migration by targeting MAPKAP1 in TGF-β-induced LC cells, indicating that miR-611 is a biological target for LC treatment.

Radiation-induced H3K9 methylation on E-cadherin promoter mediated by ROS/Snail axis : Role of G9a signaling during lung epithelial-mesenchymal transition

Lung cancer patients who have undergone radiotherapy developed severe complications such as pneumonitis and fibrosis. Upon irradiation, epithelial cells acquire mesenchymal phenotype via a process called epithelial to mesenchymal transition (EMT), which plays a vital role in organ fibrosis. Several mechanisms have been studied on EMT, however, the correlation between radiation-induced EMT and epigenetic changes are not well known. In the present study, we investigated the role of histone methyltransferase G9a on radiation-induced EMT signaling. There was an increase in total global histone methylation level in irradiated epithelial cells. Western blot analysis on irradiated cells showed an increased expression of H3K9me2/3. The pre-treatment of G9a inhibitor enhanced E-cadherin expression and decreased the mesenchymal markers like N-cadherin, vimentin in the radiated group. Surprisingly, radiation-induced ROS generation and pERK1/2 levels were also inhibited by G9a inhibitor BIX01294, which is showing its antioxidant potential. The ChIP-qPCR analysis on the E-cadherin promoter suggested that G9a and Snail might have formed complex to enrich suppressive marker H3K9me2/3. On the whole, our present study suggested that 1] ROS could modify H3K9 methylation via G9a and promote radiation-induced lung EMT in Beas2B and A549 cells 2] E-cadherin promoter enrichment with heterochromatin mark H3K9me2 expression upon irradiation could be modified by regulating G9a methyltransferase.

Radiation-induced H3K9 tri-methylation in E-cadherin promoter during lung EMT: in vitro and in vivo approaches using vanillin

Radiotherapy is an important treatment regime for lung cancer, worldwide. However, radiation-induced pneumonitis and fibrosis are the treatment-limiting toxicities among patients who have undergone radiotherapy. The epithelial cells via epithelial to mesenchymal transition [EMT] acquires mesenchymal phenotype, which ultimately leads to fibrosis. Many investigations are focussed on understanding the signalling pathways mediating in EMT, however, the role of histone methylation is less understood in radiation-induced lung EMT. In the present study, we analysed the effect of vanillin, an antioxidant, on histone methylation during radiation-induced EMT. The thoracic region of Wistar rats was irradiated with a fractionated dose of X-ray (3 Gy/day) for two weeks (total of 30 Gy). The irradiated animals were sacrificed at the 8th and 16th weeks and tissues were used for analyses. Our data showed that radiation decreased the level of antioxidant enzymes such as SOD, catalase and reduced glutathione that would ultimately enhance oxidative stress in the tissues. Histopathological analysis revealed that radiation increased the infiltration of inflammatory cells to the tissue injury site. Total global histone methylation was increased upon irradiation, which was effectively prevented by vanillin administration. Vanillin enhanced E-cadherin expression and decreased the mesenchymal markers N-cadherin and vimentin in the irradiated lung tissue. The ChIP-qPCR analysis suggested that snail expression in the nucleus might involve in the enrichment of suppressive marker H3K9me3 on the E-cadherin promoter. Finally, we suggested that vanillin administration decreased radiation-induced oxidative stress and EMT expression. Additionally, irradiation increased the H3K9 methylation status with nuclear translocation of snail during lung EMT.

NRP1 regulates radiation-induced EMT via TGF-β/Smad signaling in lung adenocarcinoma cells

PURPOSE

Radiation has been shown to promote the epithelial-mesenchymal transition (EMT) in tumor cells, and TGF-β/Smad and PI3K-Akt signaling pathways play an important role in the EMT. In this study, we investigated the effects of neuropilin-1 (NRP1) on radiation-induced TGF-β/Smad and non-classical Smad signaling pathways in lung cancer cells, as well as the effects of NRP1 on invasion and migration.

MATERIALS AND METHODS

Changes in the expression levels of EMT markers (β-catenin, N-cadherin, and vimentin) and related transcription factors (Twist and ZEB1) in stably transfected cells were detected by Western blotting and qPCR, and changes were assessed by TGF-β/Smad and non-classical Smad signaling. Immunofluorescence was used to detect the expression of the cytoskeletal protein F-actin. Expression of TGF-β1 and CXCL-12 was detected by ELISA. Transwell and scratch assays were used to detect the invasive ability and migration of lung cancer cells, respectively.

RESULTS

Our results showed that ionizing radiation could induce the EMT as well as morphological changes in lung adenocarcinoma cells (A549); however, the effects were not significant in lung squamous carcinoma cells (SK-MES-1). Moreover, we showed that NRP1 promotes the EMT induced by ionizing radiation in A549 cells, which may be related to the increased expression of EMT-related transcription factors. NRP1 may promote the radiation-induced EMT of A549 cells mainly through TGF-β1/Smad2/3 signaling. NRP1 also enhanced radiation-induced invasion, migration, and CXCL-12 expression in A549 cells.

CONCLUSIONS

We conclude that NRP1 promotes radiation-induced EMT in lung adenocarcinoma cells via TGF-β1/Smad signaling and not non-classical Smad signaling, and enhances the invasion and migration of lung adenocarcinoma cells.

Proline Metabolism in Tumor Growth and Metastatic Progression

Cancer cells show a formidable capacity to survive under stringent conditions, to elude mechanisms of control, such as apoptosis, and to resist therapy. Cancer cells reprogram their metabolism to support uncontrolled proliferation and metastatic progression. Phenotypic and functional heterogeneity are hallmarks of cancer cells, which endow them with aggressiveness, metastatic capacity, and resistance to therapy. This heterogeneity is regulated by a variety of intrinsic and extrinsic stimuli including those from the tumor microenvironment. Increasing evidence points to a key role for the metabolism of non-essential amino acids in this complex scenario. Here we discuss the impact of proline metabolism in cancer development and progression, with particular emphasis on the enzymes involved in proline synthesis and catabolism, which are linked to pathways of energy, redox, and anaplerosis. In particular, we emphasize how proline availability influences collagen synthesis and maturation and the acquisition of cancer cell plasticity and heterogeneity. Specifically, we propose a model whereby proline availability generates a cycle based on collagen synthesis and degradation, which, in turn, influences the epigenetic landscape and tumor heterogeneity. Therapeutic strategies targeting this metabolic-epigenetic axis hold great promise for the treatment of metastatic cancers.

TGF-β in radiotherapy: Mechanisms of tumor resistance and normal tissues injury

Emerging evidences show that changes in tumor stroma can adapt cancer cells to radiotherapy, thereby leading to a reduction in tumor response to treatment. On the other hand, radiotherapy is associated with severe reactions in normal tissues which limit the amount radiation dose received by tumor. These challenges open a window in radiobiology and radiation oncology to explore mechanisms for improving tumor response and also alleviate side effects of radiotherapy. Transforming growth factor beta (TGF-β) is a well-known and multitasking cytokine that regulates a wide range of reactions and interactions within tumor and normal tissues. Within tumor microenvironment (TME), TGF-β is the most potent suppressor of immune system activity against cancer cells. This effect is mediated through stimulation of CD4+ which differentiates to T regulatory cells (Tregs), infiltration of fibroblasts and differentiation into cancer associated fibroblasts (CAFs), and also polarization of macrophages to M2 cells. These changes lead to suppression of cytotoxic CD8 + T lymphocytes (CTLs) and natural killer (NK) cells to kill cancer cells. TGF-β also plays a key role in the angiogenesis, invasion and DNA damage responses (DDR) in cancer cells. In normal tissues, TGF-β triggers the expression of a wide range of pro-oxidant and pro-fibrosis genes, leading to fibrosis, genomic instability and some other side effects. These properties of TGF-β make it a potential target to preserve normal tissues and sensitize tumor via its inhibition. In the current review, we aim to explain the mechanisms of upregulation of TGF-β and its consequences in both tumor and normal tissues.

SERPINB2 overexpression inhibited cell proliferation, invasion and migration, led to G2/M arrest, and increased radiosensitivity in nasopharyngeal carcinoma cells

The aim of this study was to evaluate the effect of SERPINB2 on cell proliferation, cell cycle, epithelial-mesenchymal transition (EMT), invasion, migration, and radiosensitivity in nasopharyngeal carcinoma cells. Both CNE2R and CNE2 cells were transfected with pEGFP-N1-SERPINB2. Cell proliferation was measured by MTT assay, cell cycle by flow cytometry, and SERpINB2 expression by quantitative real-time polymerase chain reaction (qRT-PCR). Western blot was carried out to detect the protein expression. In addition, SERPINB2 and β-catenin were located intracellularly using an immunofluorescent assay, and cell migration and invasion were measured by wound healing and Transwell assays, respectively. Radiosensitivity was assessed using colony formation and MTT assays. SERPINB2 expression was downregulated in CNE2R cells. After transfection with pEGFP-N1-SERPINB2, the OD values were decreased, and there was an increased fraction in the G2/M phase. Moreover, SERPINB2 overexpression could inhibit the invasion and migration capabilities of CNE2R and CNE2 cells, with downregulation of vimentin, N-cadherin, nuclear β-catenin, matrix metalloproteinase (MMP)-2 and MMP-9, and upregulation of E-cadherin. Moreover, transfection with the SERPINB2 plasmid reduced the growth rate of CNE2R cells at doses of 2, 4 and 6 Gy, and also decreased the surviving fractions. Overexpression of SERPINB2 could reduce the proliferation, invasion and migration capabilities of CNE2R and CNE2 cells, and led to G2/M arrest via EMT inhibition, and this may be a potential strategy for enhancing the radiation sensitivity of nasopharyngeal carcinoma cells.

miR-31 shuttled by halofuginone-induced exosomes suppresses MFC-7 cell proliferation by modulating the HDAC2/cell cycle signaling axis

Traditional Chinese medicine (TCM) are both historically important therapeutic agents and important source of new drugs. Halofuginone (HF), a small molecule alkaloid derived from febrifugine, has been shown to exert strong antiproliferative effects that differ markedly among various cell lines. However, whether HF inhibits MCF-7 cell growth in vitro and underlying mechanisms of this process are not yet clear. Here, we offer the strong evidence of the connection between HF treatment, exosome production and proliferation of MCF-7 cells. Our results showed that HF inhibits MCF-7 cell growth in both time- and dose-dependent manner. Further microRNA (miRNA) profiles analysis in HF treated and nontreated MCF-7 cell and exosomes observed that six miRNAs are particularly abundant and sorted in exosomes. miRNAs knockdown experiment in exosomes and the MCF-7 growth inhibition assay showed that exosomal microRNA-31 (miR-31) modulates MCF-7 cells growth by specially targeting the histone deacetylase 2 (HDAC2), which increases the levels of cyclin-dependent kinases 2 (CDK2) and cyclin D1 and suppresses the expression of p21. In conclusion, these data indicate that inhibition of exosome production reduces exosomal miR-31, which targets the HDAC2 and further regulates the level of cell cycle regulatory proteins, contributing to the anticancer functions of HF. Our data suggest a new role for HF and the exosome production in tumorigenesis and may provide novel insights into prevention and treatment of breast cancer.

Yifei Tongluo, a Chinese Herbal Formula, Suppresses Tumor Growth and Metastasis and Exerts Immunomodulatory Effect in Lewis Lung Carcinoma Mice

This study was aimed to investigate the anti-tumor, anti-metastasis and immunomodulatory effects of Yifei Tongluo (YFTL), a Chinese herbal formula, in Lewis lung carcinoma mice and to explore the underlying mechanisms. LLC cells were inoculated subcutaneously in C57BL/6 mice to establish the Lewis lung carcinoma model. We observed that YFTL effectively inhibited tumor growth and prolonged the overall survival of tumor-bearing mice. Additionally, YFTL treatment resulted in a significantly decreased number of surface lung metastatic lesions compared with the model control group. Meanwhile, TUNEL staining confirmed that the tumors from YFTL-treated mice exhibited a markedly higher apoptotic index. The results suggest that Akt and mitogen-activated protein kinase (MAPKs) pathways may be involved in YFTL-induced apoptosis. The results show that YFTL also inhibited the vascular endothelial growth factor (VEGF), matrix metalloproteinases (MMP)-2, MMP-9, N-cadherin, and Vimentin expression, but increased E-cadherin expression. Mechanistic studies indicated that YFTL could suppress the angiogenesis and the epithelial-mesenchymal transition (EMT) of the tumor through Akt/ERK1/2 and TGFβ1/Smad2 pathways. In addition, YFTL also showed immunomodulatory activities in improving the immunosuppressive state of tumor-bearing mice. Therefore, our findings could support the development of YFTL as a potential antineoplastic agent and a potentially useful anti-metastatic agent for lung carcinoma therapy.

Halofuginone-induced autophagy suppresses the migration and invasion of MCF-7 cells via regulation of STMN1 and p53

Traditional Chinese medicines have been recognized as especially promising anticancer agents in modern anticancer research. Halofuginone (HF), an analog of quinazolinone alkaloid extracted from Dichroa febrifuga, is widely used in traditional medicine. However, whether HF inhibits the growth of breast cancer cells and/or reduces the migration and invasion of MCF-7 human breast cancer cells, as well as the underlying mechanisms in vitro, remains unclear. In this study, we report that an HF extract inhibits the growth of MCF-7 cells and reduces their migration and invasion, an important feature of potential anticancer agents. In addition, HF significantly increases the activation of autophagy, which is closely associated with tumor metastasis. As STMN1 and p53 have been closely implicated in breast cancer progression, we analyzed their expression in the context of HF extract treatment. Western blot analysis showed that HF suppresses STMN1 and p53 expression and activity in an autophagy-dependent manner. Collectively, these data indicate that activation of autophagy reduces expression of STMN1 and p53, and the migration and invasion of cancer cells contributes to the anti-cancer effects of the HF. These findings may provide new insight into breast cancer prevention and therapy.

Effect of Trichostatin A on radiation induced epithelial-mesenchymal transition in A549 cells

Radiotherapy is used to treat tumors of different origins and nature, but often lead to development of radioresistance and metastasis of cells. Interestingly, radiation induces epithelial-mesenchymal transition (EMT), a process by which epithelial cells undergo mesenchymal phenotype and stimulates tumor progression capability. Our study investigated the effect of Trichostatin A (TSA), a natural derivate isolated from Streptomyces, upon radiation-induced lung EMT and we tried to understand the role of signaling molecules in irradiated lung cancer cells (A549). The cells were categorized into four groups: untreated control, radiation alone (R; 8Gy, X-ray), radiation combined with TSA (R + T) and TSA (100nM). Radiation-induced lung EMT were evidenced by decreased expression of epithelial marker like E-cadherin, Zona occluden1 (ZO-1) and increased expression of N-cadherin and Vimentin. The Snail protein, a master regulator of EMT, was observed to be elevated after radiation treatment. In addition, TGF-β1 signaling (smad2, 3, and 4) proteins were activated upon irradiation. Western blot data were supported by the altered m-RNA expression of E-cadherin, TGF-β and Snail genes and this effect were reversed by TSA treatment. In addition to this, as supportive evidence, we performed docking studies between snail protein and TSA using Auto docking software and results suggested that less binding energy was needed for the putative binding of TSA on C-terminal domain of Snail protein. Based on our report, we suggest that TSA can effectively inhibit radiation-induced EMT (i) by altering epithelial and mesenchymal markers (ii) by modulating signaling molecules of TGFβ1 pathway (iii) by inhibiting cancer cell migratory potential in A549 cells (iv)by effectively binding to Snail which is an enhancer of EMT.

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.

Reverse epithelial-mesenchymal transition contributes to the regain of drug sensitivity in tyrosine kinase inhibitor-resistant non-small cell lung cancer cells

Tyrosine kinase inhibitors (TKIs) are currently the first-line treatment for non-small cell lung cancer (NSCLC) patients with epidermal growth factor receptor (EGFR) mutations. These patients receive platinum-based chemotherapy as the second-line treatment after they develop resistance to TKIs. Many patients regain sensitivity to the TKIs used in the first-line treatment after the failure of chemotherapy. However, the molecular mechanism for the regain of TKI sensitivity is largely unknown. In this study, we established gefitinib-resistant PC9 and HCC827 cell lines, which did not harbor the EGFR T790M mutation and MET amplification but exhibited the epithelial-mesenchymal transition (EMT) phenotype. Overexpression of EMT inducers, Snail or Slug, in the parental lines promoted their resistance to gefitinib. The gefitinib-resistant cell lines regained their sensitivity to gefitinib and displayed reverse EMT phenotypes after long-term culture in gefitinib-free culture medium. Blockage of reverse EMT by stable expression of Snail or Slug prevented the regain of TKI sensitivity. In conclusion, reverse EMT is one of the major mechanisms for the regain of TKI sensitivity in TKI-resistant NSCLC cells, suggesting that the development of small molecules targeting the EMT process may prolong the efficacy of TKIs in NSCLC patients with EGFR mutations.

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.