In the gut, tumorigenesis arises from intestinal or colonic crypt stem cells. Currently, no definitive markers exist that reliably identify gut stem cells. Here, we used the putative stem cell marker doublecortin and CaM kinase-like-1 (DCAMKL-1) to examine radiation-induced stem cell apoptosis and adenomatous polyposis coli (APC)/multiple intestinal neoplasia (min) mice to determine the effects of APC mutation on DCAMKL-1 expression. Immunoreactive DCAMKL-1 staining was demonstrated in the intestinal stem cell zone. Furthermore, we observed apoptosis of the cells negative for DCAMKL-1 at 6 hours. We found DNA damage in all the cells in the crypt region, including the DCAMKL-1-positive cells. We also observed stem cell apoptosis and mitotic DCAMKL-1-expressing cells 24 hours after irradiation. Moreover, in APC/min mice, DCAMKL-1-expressing cells were negative for proliferating cell nuclear antigen and nuclear ␤-catenin in normal-appearing intestine. However, ␤-catenin was nuclear in DCAMKL-1-positive cells in adenomas. Thus, nuclear translocation of ␤-catenin distinguishes normal and adenoma stem cells. Targeting DCAMKL-1 may represent a strategy for developing novel chemotherapeutic agents. STEM CELLS 2008;26:630 -637 Disclosure of potential conflicts of interest is found at the end of this article.

Pancreatic cancer is an exceptionally aggressive disease in great need of more effective therapeutic options. Epithelial-mesenchymal transition (EMT) plays a key role in cancer invasion and metastasis and there is a gain of stem cell properties during EMT. Here we report increased expression of the putative pancreatic stem cell marker DCAMKL-1 in an established KRAS transgenic mouse model of pancreatic cancer and in human pancreatic adenocarcinoma. Co-localization of DCAMKL-1 with vimentin, a marker of mesenchymal lineage, along with 14-3-3 σ was observed within pre-malignant PanIN lesions that arise in the mouse model. siRNA-mediated knockdown of DCAMKL-1 in human pancreatic cancer cells induced microRNA miR-200a, an EMT inhibitor, along with down-regulation of EMT-associated transcription factors ZEB1, ZEB2, Snail, Slug and Twist. Furthermore, DCAMKL-1 knockdown resulted in downregulation of c-Myc and KRAS through a let-7a microRNA-dependent mechanism, and downregulation of Notch-1 through a miR-144 microRNA-dependent mechanism. These findings illustrate direct regulatory links between DCAMKL-1, microRNAs and EMT in pancreatic cancer. Moreover, they demonstrate a functional role for DCAMKL-1 in pancreatic cancer. Together, our results rationalize DCAMKL-1 as a therapeutic target for eradicating pancreatic cancers.

Diphenyl difluoroketone (EF24), a molecule having structural similarity to curcumin, was reported to inhibit proliferation of a variety of cancer cells in vitro. However, the efficacy and in vivo mechanism of action of EF24 in gastrointestinal cancer cells have not been investigated. Here, we assessed the in vivo therapeutic effects of EF24 on colon cancer cells. Using hexosaminidase assay, we determined that EF24 inhibits proliferation of HCT-116 and HT-29 colon and AGS gastric adenocarcinoma cells but not of mouse embryo fibroblasts. Furthermore, the cancer cells showed increased levels of activated caspase-3 and increased Bax to Bcl-2 and Bax to Bcl-xL ratios, suggesting that the cells were undergoing apoptosis. At the same time, cell cycle analysis showed that there was an increased number of cells in the G 2 -M phase. To determine the effects of EF24 in vivo, HCT-116 colon cancer xenografts were established in nude mice and EF24 was given i.p. EF24 significantly suppressed the growth of colon cancer tumor xenografts. Immunostaining for CD31 showed that there was a lower number of microvessels in the EF24-treated animals coupled with decreased cyclooxygenase-2, interleukin-8, and vascular endothelial growth factor mRNA and protein expression. Western blot analyses also showed decreased AKT and extracellular signal-regulated kinase activation in the tumors. Taken together, these data suggest that the novel curcumin-related compound EF24 is a potent antitumor agent that induces caspase-mediated apoptosis during mitosis and has significant therapeutic potential for gastrointestinal cancers. [Cancer Res 2008;68(6):1962-9]

RNA-binding proteins play a key role in post-transcriptional regulation of mRNA stability and translation. We have identified that RBM3, a translation regulatory protein, is significantly upregulated in human tumors, including a stage-dependent increase in colorectal tumors. Forced RBM3 overexpression in NIH3T3 mouse fibroblasts and SW480 human colon epithelial cells increases cell proliferation and development of compact multicellular spheroids in soft agar suggesting the ability to induce anchorage-independent growth. In contrast, downregulating RBM3 in HCT116 colon cancer cells with specific siRNA decreases cell growth in culture, which was partially overcome when treated with prostaglandin E 2 , a product of cyclooxygenase (COX)-2 enzyme activity. Knockdown also resulted in the growth arrest of tumor xenografts. We have also identified that RBM3 knockdown increases caspase-mediated apoptosis coupled with nuclear cyclin B1, and phosphorylated Cdc25c, Chk1 and Chk2 kinases, implying that under conditions of RBM3 downregulation, cells undergo mitotic catastrophe. RBM3 enhances COX-2, IL-8 and VEGF mRNA stability and translation. Conversely, RBM3 knockdown results in loss in the translation of these transcripts. These data demonstrate that the RNA stabilizing and translation regulatory protein RBM3 is a novel proto-oncogene that induces transformation when overexpressed and is essential for cells to progress through mitosis.

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It is thought that small intestinal epithelia (IE) undergo continuous self-renewal primarily due to their population of undifferentiated stem cells. These stem cells give rise to transit amplifying (daughter/progenitor) cells, which can differentiate into all mature cell types required for normal gut function. Identification of stem cells in IE is paramount to fully understanding this renewal process. One major obstacle in gastrointestinal stem cell biology has been the lack of definitive markers that identify small intestinal stem cells (ISCs). Here we demonstrate that the novel putative ISC marker doublecortin and CaM kinase-like-1 (DCAMKL-1) is predominantly expressed in quiescent cells in the lower two-thirds of intestinal crypt epithelium and in occasional crypt-based columnar cells (CBCs). In contrast, the novel putative stem cell marker leucine-rich-repeat-containing G-protein-coupled receptor (LGR5) is observed in rapidly cycling CBCs and in occasional crypt epithelial cells. Furthermore, functionally quiescent DCAMKL-1+ crypt epithelial cells retain bromo-deoxyuridine in a modified label retention assay. Moreover, we demonstrate that DCAMKL-1 is a cell surface expressing protein; DCAMKL-1+ cells, isolated from the adult mouse small intestine by fluorescence activated cell sorting, self-renew and ultimately form spheroids in suspension culture. These spheroids formed glandular epithelial structures in the flanks of athymic nude mice, which expressed multiple markers of gut epithelial lineage. Thus, DCAMKL-1 is a marker of quiescent ISCs and can be distinguished from the cycling stem/progenitors (LGR51). Moreover, DCAMKL-1 can be used to isolate normal small intestinal stem cells and represents a novel research tool for regenerative medicine and cancer therapy.

Background & Aims-MicroRNAs (miRNAs) are non-protein coding RNAs that regulate gene expression. The tumor suppressor miRNA let-7a has been reported to be inhibited posttranscriptionally in embryonic stem cells and in human cancers. The microtubule-associated kinase DCAMKL-1 is a putative intestinal stem cell marker that is expressed in ApcMin/+ adenomas. We investigated the role of DCAMKL-1 on expression of let-7a miRNA and the oncogene c-Myc and in tumorigenesis.

Stem cell pluripotency, angiogenesis and epithelial-mesenchymal transition (EMT) have been shown to be significantly upregulated in pancreatic ductal adenocarcinoma (PDAC) and many other aggressive cancers. The dysregulation of these processes is believed to play key roles in tumor initiation, progression, and metastasis, and is contributory to PDAC being the fourth leading cause of cancer-related deaths in the US. The tumor suppressor miRNA miR-145 downregulates critical pluripotency factors and oncogenes and results in repressed metastatic potential in PDAC. Additionally, the miR-200 family regulates several angiogenic factors which have been linked to metastasis in many solid tumors. We have previously demonstrated that downregulation of DCLK1 can upregulate critical miRNAs in both in vitro and in vivo cancer models and results in downregulation of c-MYC, KRAS, NOTCH1 and EMT-related transcription factors. A recent report has also shown that Dclk1 can distinguish between normal and tumor stem cells in Apc min/+ mice and that ablation of Dclk1+ cells resulted in regression of intestinal polyps without affecting homeostasis. Here we demonstrate that the knockdown of DCLK1 using poly(lactide-co-glycolide)-encapsulated-DCLK1-siRNA results in AsPC1 tumor growth arrest. Examination of xenograft tumors revealed, (a) increased miR-145 which results in decreased pluripotency maintenance factors OCT4, SOX2, NANOG, KLF4 as well as KRAS and RREB1; (b) increased let-7a which results in decreased pluripotency factor LIN28B; and (c) increased miR-200 which results in decreased VEGFR1, VEGFR2 and EMT-related transcription factors ZEB1, ZEB2, SNAIL and SLUG. Specificity of DCLK1 post-transcriptional regulation of the downstream targets of miR-145, miR-200 and let-7a was accomplished utilizing a luciferase-based reporter assay. We conclude that DCLK1 plays a significant master regulatory role in pancreatic tumorigenesis through the regulation of multiple tumor suppressor miRNAs and their downstream pro-tumorigenic pathways. This novel concept of targeting DCLK1 alone has several advantages over targeting single pathway or miRNA-based therapies for PDAC.