Muh-Hwa Yang

Connective Tissue Growth Factor Activates Pluripotency Genes and Mesenchymal–Epithelial Transition in Head and Neck Cancer Cells

The epithelial-mesenchymal transition (EMT) is a key mechanism in both embryonic development and cancer metastasis. The EMT introduces stem-like properties to cancer cells. However, during somatic cell reprogramming, mesenchymal-epithelial transition (MET), the reverse process of EMT, is a crucial step toward pluripotency. Connective tissue growth factor (CTGF) is a multifunctional secreted protein that acts as either an oncoprotein or a tumor suppressor among different cancers. Here, we show that in head and neck squamous cell carcinoma (HNSCC), CTGF promotes the MET and reduces invasiveness. Moreover, we found that CTGF enhances the stem-like properties of HNSCC cells and increases the expression of multiple pluripotency genes. Mechanistic studies showed that CTGF induces c-Jun expression through αvβ3 integrin and that c-Jun directly activates the transcription of the pluripotency genes NANOG, SOX2, and POU5F1. Knockdown of CTGF in TW2.6 cells was shown to reduce tumor formation and attenuate E-cadherin expression in xenotransplanted tumors. In HNSCC patient samples, CTGF expression was positively correlated with the levels of CDH1, NANOG, SOX2, and POU5F1. Coexpression of CTGF and the pluripotency genes was found to be associated with a worse prognosis. These findings are valuable in elucidating the interplay between epithelial plasticity and stem-like properties during cancer progression and provide useful information for developing a novel classification system and therapeutic strategies for HNSCC.

Direct regulation of TWIST by HIF-1alpha promotes metastasis.

Stabilization of the hypoxia-inducible factor-1α (HIF-1α) transcription complex, caused by intratumoural hypoxia, promotes tumour progression and metastasis, leading to treatment failure and mortality in different types of human cancers. The transcription factor TWIST is a master regulator of gastrulation and mesoderm-specification and was implicated recently as an essential mediator of cancer metastasis. Notably, HIF-1α- and TWIST-null mice show similarities in their phenotypes. Here, we have shown that hypoxia or overexpression of HIF-1α promotes epithelial–mesenchymal transition (EMT) and metastastic phenotypes. We also found that HIF-1 regulates the expression of TWIST by binding directly to the hypoxia-response element (HRE) in the TWIST proximal promoter. However, siRNA-mediated repression of TWIST in HIF-1α-overexpressing or hypoxic cells reversed EMT and metastastic phenotypes. Co-expression of HIF-1α, TWIST and Snail in primary tumours of patients with head and neck cancers correlated with metastasis and the worst prognosis. These results provide evidence of a key signalling pathway involving HIF-1α and TWIST that promotes metastasis in response to intratumoural hypoxia.

Bmi1 is essential in Twist1-induced epithelial-mesenchymal transition

The epithelial–mesenchymal transition (EMT), one of the main mechanisms underlying development of cancer metastasis, induces stem-like properties in epithelial cells. Bmi1 is a polycomb-group protein that maintains self-renewal, and is frequently overexpressed in human cancers. Here, we show the direct regulation of BMI1 by the EMT regulator, Twist1. Furthermore, Twist1 and Bmi1 were mutually essential to promote EMT and tumour-initiating capability. Twist1 and Bmi1 act cooperatively to repress expression of both E-cadherin and p16INK4a. In patients with head and neck cancers, increased levels of both Twist1 and Bmi1 correlated with downregulation of E-cadherin and p16INK4a, and was associated with the worst prognosis. These results suggest that Twist1-induced EMT and tumour-initiating capability in cancer cells occurs through chromatin remodelling, which leads to unfavourable clinical outcomes.

Comprehensive analysis of the independent effect of twist and snail in promoting metastasis of hepatocellular carcinoma

The epithelial‐mesenchymal transition (EMT) is critical for induction of invasiveness and metastasis of human cancers. In this study we investigated the expression profiles of the EMT markers, the relationship between EMT markers and patient/tumor/viral factors, and the interplay between major EMT regulators in human hepatocellular carcinoma (HCC). Reduced E‐cadherin and nonmembranous β‐catenin expression, the hallmarks of EMT, were shown in 60.2% and 51.5% of primary HCC samples, respectively. Overexpression of Snail, Twist, or Slug, the major regulators of EMT, was identified in 56.9%, 43.1%, and 51.4% of primary HCCs, respectively. Statistical analysis determined that Snail and Twist, but not Slug, are major EMT inducers in HCC: overexpression of Snail and/or Twist correlated with down‐regulation of E‐cadherin, nonmembranous expression of β‐catenin, and a worse prognosis. In contrast, there were no such significant differences in samples that overexpressed Slug. Coexpression of Snail and Twist correlated with the worst prognosis of HCC. Hepatitis C‐associated HCC was significantly correlated with Twist overexpression. HCC cell lines with increased Snail and Twist expression (e.g., Mahlavu) exhibited a greater capacity for invasiveness/metastasis than cells with low endogenous Twist/Snail expression (e.g., Huh‐7). Overexpression of Snail or/and Twist in Huh‐7 induced EMT and invasiveness/metastasis, whereas knockdown of Twist or Snail in Mahlavu reversed EMT and inhibited invasiveness/metastasis. Twist and Snail were independently regulated, but exerted an additive inhibitory effect to suppress E‐cadherin transcription. Conclusion: Our study provides a comprehensive profile of EMT markers in HCC, and the independent and collaborative effects of Snail and Twist on HCC metastasis were confirmed through different assays. (HEPATOLOGY 2009.)

Randomized Controlled Trial of Entecavir Prophylaxis for Rituximab-Associated Hepatitis B Virus Reactivation in Patients With Lymphoma and Resolved Hepatitis B

PURPOSE The role of antiviral prophylaxis in preventing hepatitis B virus (HBV) reactivation before rituximab-based chemotherapy in patients with lymphoma and resolved hepatitis B is unclear. PATIENTS AND METHODS Eighty patients with CD20(+) lymphoma and resolved hepatitis B were randomly assigned to receive either prophylactic entecavir (ETV) before chemotherapy to 3 months after completing chemotherapy (ETV prophylactic group, n = 41) or to receive therapeutic ETV at the time of HBV reactivation and hepatitis B surface antigen (HBsAg) reverse seroconversion since chemotherapy (control group, n = 39). RESULTS Fifty-eight patients (72.5%) were positive for hepatitis B surface antibody, and HBV DNA was undetectable in 50 patients (62.5%). During a mean 18-month follow-up period, one patient (2.4%) in the ETV prophylactic group and seven patients (17.9%) in the control group developed HBV reactivation (P = .027). The cumulative HBV reactivation rates at months 6, 12, and 18 after chemotherapy were 8%, 11.2%, and 25.9%, respectively, in the control group, and 0%, 0%, and 4.3% in the ETV prophylactic group (P = .019). Four patients (50%) in the control group had HBsAg reverse seroconversion after HBV reactivation. The cumulative HBsAg reverse seroconversion rates at months 6, 12, and 18 since chemotherapy were 0%, 6.4%, and 16.3% in the control group, respectively, which were significantly higher than those in the ETV prophylactic group (P = .032). Patients with detectable or undetectable viral load could develop HBV reactivation and HBsAg reverse seroconversion. CONCLUSION Undetectable HBV viral load before chemotherapy did not confer reactivation-free status. Antiviral prophylaxis can potentially prevent rituximab-associated HBV reactivation in patients with lymphoma and resolved hepatitis B.

SNAIL Regulates Interleukin-8 Expression, Stem Cell–Like Activity, and Tumorigenicity of Human Colorectal Carcinoma Cells

BACKGROUND & AIMS Some cancer cells have activities that are similar to those of stem cells from normal tissues, and cell dedifferentiation correlates with poor prognosis. Little is known about the mechanisms that regulate the stem cell-like features of cancer cells; we investigated genes associated with stem cell-like features of colorectal cancer (CRC) cells. METHODS We isolated colonospheres from primary CRC tissues and cell lines and characterized their gene expression patterns by microarray analysis. We also investigated the biological features of the colonosphere cells. RESULTS Expanded CRC colonospheres contained cells that expressed high levels of CD44 and CD166, which are markers of colon cancer stem cells, and had many features of cancer stem cells, including chemoresistance and radioresistance, the ability to initiate tumor formation, and activation of epithelial-mesenchymal transition (EMT). SNAIL, an activator of EMT, was expressed at high levels by CRC colonospheres. Overexpression of Snail in CRC cells induced most properties of colonospheres, including cell dedifferentiation. Two hundred twenty-seven SNAIL-activated genes were up-regulated in colonospheres; gene regulatory networks centered around interleukin (IL)-8 and JUN. Blocking IL-8 expression or activity disrupted SNAIL-induced stem cell-like features of colonospheres. We observed that SNAIL activated the expression of IL8 by direct binding to its E3/E4 E-boxes. In CRC tissues, SNAIL and IL-8 were coexpressed with the stem cell marker CD44 but not with CD133 or CD24. CONCLUSIONS In human CRC tissues, SNAIL regulates expression of IL-8 and other genes to induce cancer stem cell activities. Strategies that disrupt this pathway might be developed to block tumor formation by cancer stem cells.

Prognostic significance of hypoxia-inducible factor-1α, TWIST1 and Snail expression in resectable non-small cell lung cancer

Background: Metastasis is the most common cause of disease failure and mortality for non-small cell lung cancer (NSCLC) after surgical resection. Snail and TWIST1 are epithelial-mesenchymal transition (EMT) regulators which induce metastasis. Intratumoral hypoxia followed by stabilisation of hypoxia-inducible factor 1α (HIF-1α) promotes metastasis through regulation of certain EMT regulators. The aim of this study was to evaluate the prognostic value of HIF-1α, TWIST1 and Snail expression in patients with resectable NSCLC. Methods: A retrospective analysis of 87 patients with resectable NSCLC from Taipei Veterans General Hospital between 2003 and 2004 was performed using immunohistochemistry to analyse HIF-1α, TWIST1 and Snail expression. The association between HIF-1α, TWIST1 and Snail expression and patients’ overall and recurrence-free survivals was investigated. Results: Overexpression of HIF-1α, TWIST1 or Snail was shown in 32.2%, 36.8% and 55.2% of primary tumours, respectively. Overexpression of HIF-1α, TWIST1 or Snail in primary NSCLCs was associated with a shorter overall survival (p = 0.005, p = 0.026, p = 0.009, respectively), and overexpression of HIF-1α was associated with a shorter recurrence-free survival (p = 0.016). We categorised the patients into four groups according to the positivity of HIF-1α/TWIST1/Snail to investigate the accumulated effects of these markers on survival. Co-expression of more than two markers was an independent prognostic indicator for both recurrence-free survival and overall survival (p = 0.004 and p<0.001, respectively, by multivariate Cox proportional hazards model). Conclusions: Co-expression of more than two markers from HIF-1α, TWIST1 and Snail is a significant prognostic predictor in patients with NSCLC.

RAC1 activation mediates Twist1-induced cancer cell migration.

Epithelial–mesenchymal transition (EMT), which is characterized by the suppression of the adhesion protein E-cadherin, is a crucial process that promotes metastasis and stem-like properties of cancer cells. However, the dissociation of cellular aggregates is not sufficient to explain why cancer cells move, and the motile nature of cancer cells undergoing EMT remains elusive. Here, we identify a mechanism in which the EMT inducer Twist1 elicits cancer cell movement through activation of RAC1. Twist1 cooperates with BMI1 to suppress let-7i expression, which results in upregulation of NEDD9 and DOCK3, leading to RAC1 activation and enabling mesenchymal-mode movement in three-dimensional environments. Moreover, the suppression of let-7i contributes to Twist1-induced stem-like properties. Clinically, activation of the Twist1–let-7i–NEDD9 axis in head and neck cancer patients correlates with tumour invasiveness and worse outcome. Our results uncover an essential mechanism to explain how Twist1 induces the motile stem-like cancer cell phenotype beyond simply suppressing E-cadherin.

Overexpression of NBS1 induces epithelial-mesenchymal transition and co-expression of NBS1 and Snail predicts metastasis of head and neck cancer.

Major causes of head and neck squamous cell carcinoma (HNSCC)-related deaths are cervical node and distant metastasis. We previously demonstrated that overexpression of the DNA double-strand break repair protein Nijmegen breakage syndrome 1 (NBS1) is a prognostic marker of advanced HNSCCs. Epithelial-mesenchymal transition (EMT) was demonstrated to be the major mechanism responsible for mediating invasiveness and metastasis of late-stage cancers. We therefore investigated the role of NBS1 overexpression in mediating EMT and metastasis. NBS1 overexpression was associated with metastasis of HNSCC patients using tissue microarray–immunohistochemistry approach. Induction of EMT was observed in an NBS1-overexpressing HNSCC cell line (FADUNBS), whereas short-interference RNA (siRNA)-mediated repression of endogenous NBS1 reversed the shift of EMT markers. Increased migration/invasiveness of FADUNBS was shown by in vitro and in vivo assays. NBS1 overexpression upregulated the expression of an EMT regulator Snail and its downstream target matrix metalloproteinase-2. EMT phenotypes and increased migration/invasiveness of FADUNBS cells were reversed by siRNA-mediated repression of Snail expression or a phosphatidylinositol 3-kinase-specific inhibitor. In HNSCC samples, co-expression of NBS1/Snail in primary tumors correlated with metastasis and the worst prognosis. These results indicate that NBS1 overexpression induces EMT through the upregulation of Snail expression, and co-expression of NBS1/Snail predicts metastasis in HNSCCs.

MicroRNA-146a directs the symmetric division of Snail-dominant colorectal cancer stem cells

Asymmetrical cell division (ACD) maintains the proper number of stem cells to ensure self-renewal. In cancer cells, the deregulation of ACD disrupts the homeostasis of the stem cell pool and promotes tumour growth. However, this mechanism is unclear. Here, we show a reduction of ACD in spheroid-derived colorectal cancer stem cells (CRCSCs) compared with differentiated cancer cells. The epithelial–mesenchymal transition (EMT) inducer Snail is responsible for the ACD-to-symmetrical cell division (SCD) switch in CRCSCs. Mechanistically, Snail induces the expression of microRNA-146a (miR-146a) through the β-catenin–TCF4 complex. miR-146a targets Numb to stabilize β-catenin, which forms a feedback circuit to maintain Wnt activity and directs SCD. Interference with the Snail–miR-146a–β-catenin loop by inhibiting the MEK or Wnt activity reduces the symmetrical division of CRCSCs and attenuates tumorigenicity. In colorectal cancer patients, the SnailHighNumbLow profile is correlated with cetuximab resistance and a poorer prognosis. This study elucidates a unique mechanism of EMT-induced CRCSC expansion.