SUMMARY We report a paracrine effect whereby endothelial cells (ECs) promote the cancer stem cell (CSC) phenotype of human colorectal cancer (CRC) cells. We showed that, without direct cell-cell contact, ECs secrete factors that promoted the CSC phenotype in CRC cells via Notch activation. In human CRC specimens, CD133 and Notch intracellular domain-positive cells co-localized with CRC cells in perivascular regions. An EC-derived, soluble form of Jagged-1, via ADAM17 proteolytic activity, led to Notch activation in CRC cells in a paracrine manner; these effects were blocked by immunodepletion of Jagged-1 in EC conditioned medium or blockade of ADAM17 activity. ECs play an active role in promoting Notch signaling and the CSC phenotype by secreting soluble Jagged-1.

Chronic infection and associated inflammation have long been suspected to promote human carcinogenesis. Recently, certain gut bacteria, including some in the genus, have been implicated in playing a role in human colorectal cancer development. However, the species and subspecies involved and their oncogenic mechanisms remain to be determined. We sought to identify the specific spp. and ssp. in clinical colorectal cancer specimens by targeted sequencing of 16S ribosomal RNA gene. Five spp. were identified in clinical colorectal cancer specimens. Additional analyses confirmed that ssp. was the most prevalent subspecies in human colorectal cancers. We also assessed inflammatory cytokines in colorectal cancer specimens using immunoassays and found that expression of the cytokines IL17A and TNFα was markedly increased but IL21 decreased in the colorectal tumors. Furthermore, the chemokine (C-C motif) ligand 20 was differentially expressed in colorectal tumors at all stages. In co-culture assays, ssp. induced CCL20 protein expression in colorectal cancer cells and monocytes. It also stimulated the monocyte/macrophage activation and migration. Our observations suggested that infection with ssp. in colorectal tissue could induce inflammatory response and promote colorectal cancer development. Further studies are warranted to determine if ssp. could be a novel target for colorectal cancer prevention and treatment..

Vertebrate tubulin is encoded by a multigene family that produces distinct gene products, or isotypes, of both the ␣-and ␤-tubulin subunits. The isotype sequences are conserved across species supporting the hypothesis that different isotypes subserve different functions. To date, however, most studies have demonstrated that tubulin isotypes are freely interchangeable and coassemble into all classes of microtubules. We now report that, in contrast to other isotypes, overexpression of a mouse class V ␤-tubulin cDNA in mammalian cells produces a strong, dose-dependent disruption of microtubule organization, increased microtubule fragmentation, and a concomitant reduction in cellular microtubule polymer levels. These changes also disrupt mitotic spindle assembly and block cell proliferation. Consistent with diminished microtubule assembly, there is an increased tolerance for the microtubule stabilizing drug, paclitaxel, which is able to reverse many of the effects of class V ␤-tubulin overexpression. Moreover, transfected cells selected in paclitaxel exhibit increased expression of class V ␤-tubulin, indicating that this isotype is responsible for the drug resistance. The results show that class V ␤-tubulin is functionally distinct from other tubulin isotypes and imparts unique properties on the microtubules into which it incorporates. INTRODUCTIONMicrotubules are essential filamentous structures in eukaryotic cells where they are responsible for the directed movement of vesicles, the organization of the endoplasmic reticulum and Golgi apparatus in the cytoplasm, and the equipartitioning of chromosomes before cell division. The organelles are assembled from heterodimers of ␣-and ␤-tubulin, which polymerize in a head-to-tail manner to form linear protofilaments, and these associate laterally into tubular structures that normally consist of 13 protofilaments. Vertebrate ␣-and ␤-tubulins are each encoded by a 6-to 7-member multigene family that produces highly homologous and conserved gene products that differ most radically in their last 10 -15 amino acids (Sullivan, 1988;Luduena, 1998). These carboxyl-terminal sequences have been used to assign ␤-tubulin gene products to seven distinct classes (Lopata and Cleveland, 1987). Each of these classes (hereafter referred to as ␤1, ␤2, ␤3, ␤4a, ␤4b, ␤5, and ␤6) defines a ␤-tubulin isotype that differs significantly from other isotypes within the same organism, but differs very little from the same isotype in other vertebrate species.With the discovery that tubulin proteins in an organism are heterogeneous, a hypothesis was formulated suggesting that different tubulin proteins might perform different functions in the cell (Fulton and Simpson, 1976). In the intervening years, however, most of the experimental and genetic evidence has argued that different ␤-tubulins coassemble freely into all cellular microtubules (see Joshi and Cleveland, 1990; Luduena, 1998 for reviews). In gene replacement experiments using the fungal organism, Aspergillus nidulans, for example, May demonst...

The involvement of tubulin mutations as a cause of clinical drug resistance has been intensely debated in recent years. In the studies described here, we used transfection to test whether β1-tubulin mutations and polymorphisms found in cancer patients are able to confer resistance to drugs that target microtubules. Three of four mutations (A185T, A248V, R306C, but not G437S) that we tested caused paclitaxel resistance, as indicated by the following observations: (a) essentially 100% of cells selected in paclitaxel contained transfected mutant tubulin; (b) paclitaxel resistance could be turned off using tetracycline to turn off transgene expression; (c) paclitaxel resistance increased as mutant tubulin production increased. All the paclitaxel resistance mutations disrupted microtubule assembly, conferred increased sensitivity to microtubule-disruptive drugs, and produced defects in mitosis. The results are consistent with a mechanism in which tubulin mutations alter microtubule stability in a way that counteracts drug action. These studies show that human tumor cells can acquire spontaneous mutations in β1-tubulin that cause resistance to paclitaxel, and suggest that patients with some polymorphisms in β1-tubulin may require higher drug concentrations for effective therapy. Mol Cancer Ther; 9(2); 327-35. ©2010 AACR.

ObjectiveTo investigate the function of a novel primate-specific long non-coding RNA (lncRNA), named FLANC, based on its genomic location (co-localised with a pyknon motif), and to characterise its potential as a biomarker and therapeutic target.DesignFLANC expression was analysed in 349 tumours from four cohorts and correlated to clinical data. In a series of multiple in vitro and in vivo models and molecular analyses, we characterised the fundamental biological roles of this lncRNA. We further explored the therapeutic potential of targeting FLANC in a mouse model of colorectal cancer (CRC) metastases.ResultsFLANC, a primate-specific lncRNA feebly expressed in normal colon cells, was significantly upregulated in cancer cells compared with normal colon samples in two independent cohorts. High levels of FLANC were associated with poor survival in two additional independent CRC patient cohorts. Both in vitro and in vivo experiments demonstrated that the modulation of FLANC expression influenced cellular growth, apoptosis, migration, angiogenesis and metastases formation ability of CRC cells. In vivo pharmacological targeting of FLANC by administration of 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine nanoparticles loaded with a specific small interfering RNA, induced significant decrease in metastases, without evident tissue toxicity or pro-inflammatory effects. Mechanistically, FLANC upregulated and prolonged the half-life of phosphorylated STAT3, inducing the overexpression of VEGFA, a key regulator of angiogenesis.ConclusionsBased on our findings, we discovered, FLANC as a novel primate-specific lncRNA that is highly upregulated in CRC cells and regulates metastases formation. Targeting primate-specific transcripts such as FLANC may represent a novel and low toxic therapeutic strategy for the treatment of patients.

Despite being amongst the most common oncogenes in human cancer, to date there are no effective clinical options for inhibiting KRAS activity. We investigated whether systemically delivered KRAS siRNAs have therapeutic potential in KRAS mutated cancer models. We identified KRAS siRNA sequences with notable potency in knocking-down KRAS expression. Using lung and colon adenocarcinoma cell lines, we assessed anti-proliferative effects of KRAS silencing in vitro. For in vivo experiments, we used a nano-liposomal delivery platform, DOPC, for systemic delivery of siRNAs. Various lung and colon cancer models were utilized to determine efficacy of systemic KRAS siRNA based on tumor growth, development of metastasis and down-stream signaling. KRAS siRNA sequences induced >90% knock-down of KRAS expression, significantly reducing viability in mutant cell lines. In the lung cancer model, KRAS siRNA treatment demonstrated significant reductions in primary tumor growth and distant metastatic disease, while the addition of CDDP was not additive. Significant reductions in Ki-67 indices were seen in all treatment groups, while significant increases in caspase-3 activity was only seen in the CDDP treatment groups. In the colon cancer model, KRAS siRNA reduced tumor KRAS and pERK expression. KRAS siRNAs significantly reduced HCP1 subcutaneous tumor growth, as well as outgrowth of liver metastases. Our studies demonstrate a proof-of-concept approach to therapeutic KRAS targeting using nanoparticle delivery of siRNA. This study highlights the potential translational impact of therapeutic RNA interference, which may have broad applications in oncology, especially for traditional “undruggable” targets.

Background:Vascular endothelial growth factor (VEGF) and its receptors (VEGFRs) are key regulators of angiogenesis, affecting endothelial cell survival and function. However, the effect of VEGF-VEGFR signalling on tumour cell function is not well understood. Our previous studies in colorectal cancer (CRC) cells have demonstrated an intracrine VEGF/VEGFR1 signalling mechanism that mediates CRC cell survival and chemo-sensitivity. Since extracellular VEGF signalling regulates migration of endothelial cells and various tumour cells, we attempted to determine whether intracrine VEGF signalling affects CRC cell motility.Methods:Migration and invasion of CRC cells, with and without VEGF or VEGFR1 depletion, were assayed using transwell migration chambers. Changes in cell morphology, epithelial-mesenchymal transition (EMT) markers, and markers of cell motility were assessed by immunostaining and western blot.Results:Depletion of intracellular VEGF and VEGFR1 in multiple CRC cell lines led to strong inhibition of migration and invasion of CRC cells. Except for Twist, there were no significant differences in markers of EMT between control and VEGF/VEGFR1-depleted CRC cells. However, VEGF/VEGFR1-depleted CRC cells demonstrated a significant reduction in levels of phosphorylated focal adhesion kinase and its upstream regulators pcMET and pEGFR.Conclusions:Inhibition of intracrine VEGF signalling strongly inhibits CRC cell migration and invasion by regulating proteins involved in cell motility.

The effects of vascular endothelial growth factor-A (VEGF-A/VEGF) and its receptors on endothelial cells function has been studied extensively, but their effects on tumor cells are less well defined. Studies of human colorectal cancer (CRC) cells where the VEGF gene has been deleted suggest an intracellular role of VEGF as a cell survival factor. In this study, we investigated the role intracrine VEGF signaling in CRC cell survival. In human CRC cells, RNAi-mediated depletion of VEGF decreased cell survival and enhanced sensitivity to chemotherapy. Unbiased reverse phase protein array studies and subsequent validation experiments indicated that impaired cell survival was a consequence of disrupted AKT and ERK1/2 (MAPK3/1) signaling, as evidenced by reduced phosphorylation. Inhibition of paracrine or autocrine VEGF signaling had no effect on phospho-AKT or phospho-ERK1/2 levels, indicating that VEGF mediates cell survival via an intracellular mechanism. Notably, RNAi-mediated depletion of VEGF receptor VEGFR1/FLT1 replicated the effects of VEGF depletion on phospho-AKT and phospho-ERK1/2 levels. Together, these studies show how VEGF functions as an intracrine survival factor in CRC cells, demonstrating its distinct role in CRC cell survival.