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BackgroundLittle is known about colorectal cancer or colon and rectal cancer. Are they the same disease or different diseases?ObjectivesThe aim of this epidemiology study was to compare the features of colon and rectal cancer by using recent national cancer surveillance data.Design and settingData included colorectal cancer (1995–2008) from the Surveillance, Epidemiology, and End Results Program (SEER) database. Only adenocarcinoma was included for analysis.PatientsA total of 372,130 patients with a median follow-up of 32 months were analyzed.Main outcome measuresMean survival of patients with the same stage of colon and rectal cancer was evaluated.ResultsAround 35% of patients had stage information. Among them, colon cancer patients had better survival than those with rectal cancer, by a margin of 4 months in stage IIB. In stage IIIC and stage IV, rectal cancer patients had better survival than colon cancer patients, by about 3 months. Stage IIB colorectal cancer patients had a poorer prognosis than those with stage IIIA and IIIB colorectal cancer. After adjustment of age, sex and race, colon cancer patients had better survival than rectal cancer of stage IIB, but in stage IIIC and IV, rectal cancer patients had better survival than colon cancer.LimitationsThe study is limited by its retrospective nature.ConclusionThis was a population-based study. The prognosis of rectal cancer was not worse than that of colon cancer. Local advanced colorectal cancer had a poorer prognosis than local regional lymph node metastasis. Stage IIB might require more aggressive chemotherapy, and no less than that for stage III.

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 natural product justicidin A, an arylnaphthalide lignan isolated from Justicia procumbens, significantly inhibited the growth of human colorectal cancer cells HT-29 and HCT 116 at day 6 post-treatment. Further study revealed that justicidin A-treated HT-29 and HCT 116 colorectal cancer cells died of apoptosis. Justicidin A treatment caused DNA fragmentation and an increase in phosphatidylserine exposure of the cells. The number of cells in the sub-G1 phase was also increased upon justicidin A treatment. Caspase-9 but not caspase-8 was activated, suggesting that justicidin A treatment damaged mitochondria. The mitochondrial membrane potential was altered and cytochrome c and Smac were released from mitochondria to the cytoplasm upon justicidin A treatment. The level of Ku70 in the cytoplasm was decreased, but that of Bax in mitochondria was increased by justicidin A. Since Ku70 normally binds and sequesters Bax, these results suggest that justicidin A decreases the level of Ku70 leading to translocation of Bax from the cytosol to mitochondria to induce apoptosis. Oral administration of justicidin A was shown to suppress the growth of HT-29 cells transplanted into NOD-SCID mice, suggesting chemotherapeutic potential of justicidin A on colorectal cancer cells.

In an attempt to study the role of Eps8 in human carcinogenesis, we observe that ectopic overexpression of Eps8 in SW480 cells (low Eps8 expression) increases cell proliferation. By contrast, expressing eps8 small interference RNA in SW620 and WiDr cells (high Eps8 expression) reduces their proliferation rate. Interestingly, attenuation of Eps8 decreases Src Pi-Tyr-416, Shc Pi-Tyr-317, and serum-induced FAK Pi-Tyr-397 and Pi-Tyr-861. Remarkably, by virtue of mammalian target of rapamycin/STAT3 Pi-Ser-727, Eps8 modulates FAK expression required for cell proliferation. Within 62% of colorectal tumor specimens examined, >2-fold enhancement of Eps8 as compared with their normal counterparts is observed, especially for those from the advanced stage. In agreement with the modulation of FAK by Eps8, the concomitant expression of these two proteins in tumor specimens is observed. Notably, Eps8 attenuation also impedes the motility of SW620 and WiDr cells, which can be rescued by ectopically expressed FAK. This finding discloses the indispensability of Eps8 and FAK in cell locomotion. These results provide a novel mechanism for Eps8-mediated FAK expression and activation in colon cancer cells.The signal transduction of the epidermal growth factor receptor (EGFR) 2 is important for normal cell physiology (1, 2). During the search for novel EGFR substrates, Eps8 (EGFR pathway substrate number 8) as suggested by its designation was originally identified as a putative EGFR target devoid of phosphotyrosine-binding SH2 domain (3). Among its 97-and 68-kDa isoforms, only the former is well characterized and thus referred to as Eps8. Later, Eps8 also is the substrate for Src tyrosine kinase (4). In addition to tyrosyl phosphorylation, expression of Eps8 is also affected by Src activity (4, 5). Remarkably, its aberrant overexpression in murine fibroblasts can lead to cellular transformation (6), and of note, Eps8 overexpression contributes to Src-mediated transformation (7).As an adaptor protein, Eps8 contains several structural features such as a split pleckstrin homology, a putative nuclear targeting sequence, a central SH3 domain, and several prolinerich regions. Although the split pleckstrin homology confers the ability of Eps8 to associate with plasma membrane in response to serum stimulation and conveys signals to ERK activation (6), Eps8 can also complex with Abi-1/E3b1 and RN-tre separately through its SH3 domain (8, 9). By interacting with Abi-1 or RN-tre, Eps8 integrates signals leading to actin cytoskeleton via Rac and receptor endocytosis via Rab5, respectively (10, 11). Recently, IRSp53 has been demonstrated as an Eps8-binding protein whose complex with Eps8 reinforces Rac activation and cell migration in fibrosarcoma cells (12). Besides, Eps8 is also identified as an actin capper, which is capable of regulating actin-based motility (13).Focal adhesion kinase (FAK) is an intracellular tyrosine kinase localized prominently within focal adhesion (14, 15) and participates in a variety of integrin-elicited biological ac...

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.

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Over-expression of AURKC has been detected in human colorectal cancers, thyroid carcinoma and several cancer cell lines. However, the regulation and clinical implications of over-expressed AURKC in cancer cells are unclear. Here we show that elevated AURKC increases the proliferation, transformation and migration of cancer cells. Importantly, the kinase activity of AURKC is required for these tumour-associated properties. Analysis of human cancer specimens shows that the expression of AURKC is increased in cervical cancer, and is highly correlated with staging in colorectal cancer. Over-expressed AURKC-GFP localizes to the centromeric regions of mitotic chromosomes and results in a decreased level of AURKB, a key regulator of spindle checkpoint. Expression of AURKC is down-regulated by PLZF, a transcriptional repressor, through recruitment to its promoter region. The expression levels of PLZF and AURKC mRNA display opposite patterns in human cervical and colorectal cancers. Taken together, our results provide important insights into human cancers with AURKC expression, which may serve as a potential target for cancer therapy in the future.