Hypoxia inducible factor-1 (HIF-1) is the master transcriptional regulator of the cellular response to altered oxygen levels. HIF-1α protein is elevated in most solid tumors and contributes to poor disease outcome by promoting tumor progression, metastasis, and resistance to chemotherapy. To date, the relationship between HIF-1 and these processes, particularly chemoresistance, has remained largely unexplored. Here, we show that expression of the MAPK-specific phosphatase dual-specificity phosphatase-2 (DUSP2) is markedly reduced or completely absent in many human cancers and that its level of expression inversely correlates with that of HIF-1α and with cancer malignancy. Analysis of human cancer cell lines indicated that HIF-1α inhibited DUSP2 transcription, which resulted in prolonged phosphorylation of ERK and, hence, increased chemoresistance. Knockdown of DUSP2 increased drug resistance under normoxia, while forced expression of DUSP2 abolished hypoxia-induced chemoresistance. Further, reexpression of DUSP2 during cancer progression caused tumor regression and markedly increased drug sensitivity in mice xenografted with human tumor cell lines. Furthermore, a variety of genes involved in drug response, angiogenesis, cell survival, and apoptosis were found to be downregulated by DUSP2. Our results demonstrate that DUSP2 is a key downstream regulator of HIF-1-mediated tumor progression and chemoresistance. DUSP2 therefore may represent a novel drug target of particular relevance in tumors resistant to conventional chemotherapy.

The switch of cellular metabolism from mitochondrial respiration to glycolysis is the hallmark of cancer cells and is associated with tumor malignancy. Pyruvate dehydrogenase kinase-1 (PDK1) and PDK3 participate in the metabolic switch of cancer cells; however, the medical significance of PDK1 and PDK3 in cancer progression is not known. Here, we assessed the expression profiles of PDK1 and PDK3 in colorectal cancer. Western blot analysis (n = 74) demonstrated that PDK3 was markedly increased in colon cancer compared to that in adjacent normal tissues, whereas PDK1 was decreased in cancer cells. In addition, PDK3 expression was positively correlated with that of hypoxia inducible factor-1α (HIF-1α) in cancer cells. Further analysis using immunohistochemical staining revealed that PDK3 levels were positively associated with severity of cancer and negatively associated with disease-free survival. In vitro studies using several colon cancer cell lines showed that PDK3 expression was controlled by HIF-1α and contributed to hypoxia-induced increased drug resistance, perhaps explaining why patients with PDK3 overexpression have a greater incidence of treatment failure. Taken together, our findings suggest that PDK3 plays an important role in the metabolic switch and drug resistance of colon cancer and is potentially a novel target for cancer therapy.

Purpose: The first step of metastasis is the detachment of cancer cells from the surrounding matrix and neighboring cells; however, how cancer cells accomplish this process remains unclear. Thus, we aimed to investigate the underlying mechanism that controls the early event of metastasis. Experimental Design: One hundred and thirty-seven paired colorectal carcinoma and normal colon tissues were examined by immunohistochemical staining and Western blot for the expression of CD151, a member of the tetraspanin family that plays important roles in cell adhesion and motility. The effect of CD151 on cancer cell adhesion was investigated under normoxia and hypoxia conditions. Results: The level of CD151 was down-regulated in colon cancer compared with the paired normal counterparts. Expression of CD151was negatively regulated by hypoxia inducible factor1^dependent hypoxic stress. Suppression of CD151by hypoxia caused the detachment of cancer cells from the surrounding matrix and neighboring cells whereas restoration of CD151expression during reoxygenation facilitated the adhesion capacity. Clinical examination further showed that metastasized cancer cells expressed a greater level of CD151 compared with that of primary tumor. Conclusion: Regulation of CD151 by oxygen tension may play an important role in cancer metastasis by regulating the detachment from the primary site and homing in the secondary site.Cancer metastasis is a complex, multistep process with mechanisms largely unknown despite intensive investigation in the past. The first step of metastasis is the detachment of cancer cells from the surrounding matrix and neighboring cells. Adhesions between normal epithelial cells and cell-matrix are strong so local cell invasion is not able to occur. Therefore, the necessary early event in cancer invasion and metastasis is the conversion of the stationary phenotype to the migratory phenotype. This can be achieved by down-regulation of cell adhesion molecules such as cadherins and integrins. Indeed, studies have revealed that loss or down-regulation of E-cadherin and one or more of the integrins is a common feature of several epithelial malignancies (1, 2). Nonetheless, the underlying mechanisms of causing the down-regulation of these molecules are not yet clear. In addition, whether there are other molecules that also control cancer cell adhesion needs to be elucidated.Many factors have been identified as playing important roles in the regulation of cancer metastasis. Among these, hypoxia is the most common and critical one. Because oxygen can only diffuse for 150 to 200 Am, cells will face the hypoxic stress when distances of cells from a capillary exceed this range. Owing to the rapid growing nature, cancer cells of solid tumors frequently encounter reduced oxygen tension. The hypoxic stress will force cancer cells to develop necessary processes such as induction of angiogenesis, metabolic switch, and migration to avoid cell death. These responses to hypoxia are mainly mediated through genes regulated by t...

Background Hypoxia suppresses global protein production, yet certain essential proteins are translated through alternative pathways to survive under hypoxic stress. Translation via the internal ribosome entry site (IRES) is a means to produce proteins under stress conditions such as hypoxia; however, the underlying mechanism remains largely uncharacterized. Methods Proteomic and bioinformatic analyses were employed to identify hnRNPM as an IRES interacting factor. Clinical specimens and mouse model of tumorigenesis were used for determining the expression and correlation of hnRNPM and its target gene. Transcriptomic and translatomic analyses were performed to profile target genes regulated by hnRNPM. Findings Hypoxia increases cytosolic hnRNPM binding onto its target mRNAs and promotes translation initiation. Clinical colon cancer specimens and mouse carcinogenesis model showed that hnRNPM is elevated during the development of colorectal cancer, and is associated with poor prognosis. Genome-wide transcriptomics and translatomics analyses revealed a unique set of hnRNPM-targeted genes involved in metabolic processes and cancer neoplasia are selectively translated under hypoxia. Interpretation These data highlight the critical role of hnRNPM-IRES-mediated translation in transforming hypoxia-induced proteome toward malignancy. Fund This work was supported by the Ministry of Science and Technology, Taiwan (MOST 104–2320-B-006-042 to HSS and MOST 105–2628-B-001-MY3 to TMC).

Colon cancer is a multiple-step disease with less 10% survival rate at late stage. To achieve improvement of colon cancer therapy, we aim to find novel oncogenes that contribute to colon cancer progression. By our in-house bioinformatic tool prediction, we identified TYRO3 to be a potential oncogene. TYRO3, a receptor tyrosine kinase, was reported to be overexpressed in melanoma via genomic screening; however, its role in cancer initiation, progression, and malignancy remains largely unknown. Herein, we showed that compared to normal colon tissue, TYRO3 is overexpressed in polyps and colon cancer tissue. The expression level in colon cancer is significantly associated with cancer malignancy. Overexpression of TYRO3 increased cell proliferation, motility, and anchorage-independent colony formation in vitro. Furthermore, we confirmed TYRO3 tumorigenic potential by xenograft model and metastatic assay in vivo. To investigate novel mechanisms mediated by TYRO3, we performed next generation sequencing (RNS-seq) to identify genes that were upregulated under TYRO3 overexpression. Results showed that TYRO3 significantly enriched genes involved in epithelial-mesenchymal transition and tumorigenesis, which is consistent with our hypothesis and finding. Taken together, these data provide evidence to support that TYRO3 plays an important role in malignant process of colon cancer progression likely through its novel functions in the nucleus. Citation Format: Chun Wei Chien, Yen-Yu Lai, Bo-Wen Lin, Shao-Chieh Lin, Jenq-Chang Lee, Shaw-Jenq Tsai. Overexpressed TYRO3 in colorectal cancer regulates tumorigenesis and metastasis. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5258. doi:10.1158/1538-7445.AM2014-5258