Synthesis and antiproliferative activity of a tetrahydrofuran analog of FR901464.

FR901464 is a natural product that exhibits antiproliferative activity at single-digit nanomolar concentrations in cancer cells. Its tetrahydropyran-spiroepoxide covalently binds the spliceosome. Through our medicinal chemistry campaign, we serendipitously discovered that a bromoetherification formed a tetrahydrofuran. The tetrahydrofuran analog was three orders of magnitude less potent than the corresponding tetrahydropyran analogs. This study shows the significance of the tetrahydropyran ring that presents the epoxide toward the spliceosome.

Scutellaria baicalensis enhances 5-fluorouracil-based chemotherapy via inhibition of proliferative signaling pathways.

Fluoropyridine-based chemotherapy remains the most widely used treatment for colorectal cancer (CRC). In this study, we investigated the mechanism by which the natural product Scutellaria baicalensis (Huang Qin; HQ) and one of its main components baicalin enhanced 5-fluorouracil (5-FU) antitumor activity against CRC. Cell proliferation assays, cell cycle analysis, reverse-phase protein array (RPPA) analysis, immunoblot analysis, and qRT-PCR were performed to investigate the mechanism(s) of action of HQ and its active components on growth of CRC cells. HQ exhibited in vitro antiproliferative activity against drug resistant human CRC cells, against human and mouse CRC cells with different genetic backgrounds and normal human colon epithelial cells. In vivo animal models were used to document the antitumor activity of HQ and baicalin. The mechanism of growth inhibitory activity of HQ is due to inhibition of proliferative signaling pathways including the CDK-RB pathway. In addition, HQ enhanced the antitumor effects of 5-FU and capecitabine in vivo. Furthermore, we identified baicalin as an active component of HQ. The combination of baicalin and 5-FU demonstrated synergistic activity against 5-FU-resistant RKO-R10 cells. The combination significantly inhibited in vivo tumor growth greater than each treatment alone. RPPA results showed that the signaling pathway alterations in CRC cells were similar following HQ and baicalin treatment. Together, these results indicate that HQ and its component baicalin enhance the effect of 5-fluorouracil-based chemotherapy via inhibition of CDK-RB pathway. These findings may provide the rational basis for developing agents that can overcome the development of cellular drug resistance. Video Abstract.

Discovery of [1,2,4]triazolo[4,3-a]pyridines as potent Smoothened inhibitors targeting the Hedgehog pathway with improved antitumor activity in vivo.

Triple-negative breast cancer (TNBC), a subset of breast cancers, have poorer survival than other breast cancer types. Recent studies have demonstrated that the abnormal Hedgehog (Hh) pathway is activated in TNBC and that these treatment-resistant cancers are sensitive to inhibition of the Hh pathway. Smoothened (Smo) protein is a vital constituent in Hh signaling and an attractive drug target. Vismodegib (VIS) is one of the most widely studied Smo inhibitors. But the clinical application of Smo inhibitors is limited to adult patients with BCC and AML, with many side effects. Therefore, it's necessary to develop novel Smo inhibitor with better profiles. Twenty [1,2,4]triazolo[4,3-a]pyridines were designed, synthesized and screened as Smo inhibitors. Four of these novel compounds showed directly bound to Smo protein with stronger binding affinity than VIS. The new compounds showed broad anti-proliferative activity against cancer cell lines in vitro, especially triple-negative breast cancer cells. Mechanistic studies demonstrated that TPB15 markedly induced cell cycle arrest and apoptosis in MDA-MB-468 cells. TPB15 blocked Smo translocation into the cilia and reduced Smo protein and mRNA expression. Furthermore, the expression of the downstream regulatory factor glioma-associated oncogene 1 (Gli1) was significantly inhibited. Finally, TPB15 demonstrated greater anti-tumor activity in our animal models than VIS with lower toxicity. Hence, these results support further optimization of this novel scaffold to develop improved Smo antagonists.

Herbal formula Huang Qin Ge Gen Tang enhances 5-fluorouracil antitumor activity through modulation of the E2F1/TS pathway.

BACKGROUND: 5-Fluorouracil (5-FU) remains the most widely used agent to treat colorectal cancer (CRC). However, its clinical efficacy is currently limited by the development of drug resistance. Traditional Chinese Herbal Medicine (TCM) has been shown to enhance the efficacy of standard anticancer agents. However, there are only a limited number of well-controlled preclinical and clinical studies documenting the potential benefit of TCM. Herein, we screened a series of TCM formulas in in vitro and in vivo animal models to identify biologically active formulas that were effective against CRC. METHODS: Cell proliferation and clonogenic assays, cell cycle analysis, immunoblot analysis and qRT-PCR were performed to investigate the mechanism(s) of action of the most active formula Huang-Qin-Ge-Gen-Tang (HQGGT) on growth of human CRC cells. In vivo animal models were used to document the antitumor activity of HQGGT alone and HQGGT in combination with 5-FU. RESULTS: We identified HQGGT, which suppressed the in vivo growth of human colon cancer HT-29 xenografts without associated toxicities. HQGGT displayed anti-proliferative activity against a wide range of CRC cell lines. This growth suppression correlated with induction of apoptosis. HQGGT enhanced the cytotoxicity of 5-FU against human 5-FU-resistant cells (H630R1) and mouse colon cancer cells (MC38). Our studies showed that the mechanism of action of this synergism was the result of suppression of thymidylate synthase (TS) expression by HQGGT. We analyzed different batches of HQGGT and observed consistent chemical fingerprints and biological activity. Finally, we show that orally administered HQGGT significantly enhanced the antitumor effect of 5-FU in mice bearing MC38 xenografts. CONCLUSIONS: These findings provide support for the potential role of HQGGT as a novel modulator of fluoropyrimidine chemotherapy in the treatment of CRC.

Development of modified siRNA molecules incorporating 5-fluoro-2'-deoxyuridine residues to enhance cytotoxicity.

Therapeutic small interfering RNAs (siRNAs) are composed of chemically modified nucleotides, which enhance RNA stability and increase affinity in Watson-Crick base pairing. However, the precise fate of such modified nucleotides once the siRNA is degraded within the cell is unknown. Previously, we demonstrated that deoxythymidine release from degraded siRNAs reversed the cytotoxicity of thymidylate synthase (TS)-targeted siRNAs and other TS inhibitor compounds. We hypothesized that siRNAs could be designed with specific nucleoside analogues that, once released, would enhance siRNA cytotoxicity. TS-targeted siRNAs were designed that contained 5-fluoro-2'-deoxyuridine (FdU) moieties at various locations within the siRNA. After transfection, these siRNAs suppressed TS protein and messenger RNA expression with different efficiencies depending on the location of the FdU modification. FdU was rapidly released from the siRNA as evidenced by formation of the covalent inhibitory ternary complex formed between TS protein and the FdU metabolite, FdUMP. These modified siRNAs exhibited 10-100-fold greater cytotoxicity and induced multiple DNA damage repair and apoptotic pathways when compared with control siRNAs. The strategy of designing siRNA molecules that incorporate cytotoxic nucleosides represents a potentially novel drug development approach for the treatment of cancer and other human diseases.

Identification of Streptomyces sp. nov. WH26 producing cytotoxic compounds isolated from marine solar saltern in China.

A moderately halophilic actinomycetes strain, designated as WH26, was isolated from Weihai Solar Saltern in China. The identification of the strain WH26 was performed by its morphological characteristics, physiological and biochemical tests as well as phylogenetic analysis based on 16S rRNA sequence comparison. The results showed that the nucleotide sequence of the 16S rRNA gene (1,677 bp) of the strain WH26 exhibited close similarity (97-99 %) with other Streptomyces 16S rRNA genes and the strain WH26 was identified to belong to the genus Streptomyces. An ethyl acetate extraction of Streptomyces sp. nov. WH26 demonstrated significant cellular toxicity. Two compounds, 8-O-methyltetrangulol and naphthomycin A were isolated from the extract via silica gel column chromatography and HPLC. These two compounds showed potent cytotoxic activity against several human tumor cell lines including A549, HeLa, BEL-7402 and HT-29. The present studies suggest that moderately halophilic actinomycetes may be a novel biological source for the discovery of anticancer agents.

Synthesis and Conformational Analysis of FR901464-Based RNA Splicing Modulators and Their Synergism in Drug-Resistant Cancers.

FR901464 is a cytotoxic natural product that binds splicing factor 3B subunit 1 (SF3B1) and PHD finger protein 5A (PHF5A), the components of the human spliceosome. The amide-containing tetrahydropyran ring binds SF3B1, and it remains unclear how the substituents on the ring contribute to the binding. Here, we synthesized meayamycin D, an analogue of FR901464, and three additional analogues to probe the conformation through methyl scanning. We discovered that the amide-containing tetrahydropyran ring assumes only one of the two possible chair conformations and that methylation of the nitrogen distorts the chair form, dramatically reducing cytotoxicity. Meayamycin D induced alternative splicing of MCL-1, showed strong synergism with venetoclax in drug-resistant lung cancer cells, and was cancer-specific over normal cells. Meayamycin D incorporates an alkyl ether and shows a long half-life in mouse plasma. The characteristics of meayamycin D may provide an approach to designing other bioactive L-shaped molecules.

Quassinoid analogs exert potent antitumor activity via reversible protein biosynthesis inhibition in human colorectal cancer.

Cellular protein synthesis is accelerated in human colorectal cancer (CRC), and high expression of protein synthesis regulators in CRC patients is associated with poor prognosis. Thus, inhibition of protein synthesis may be an effective therapeutic strategy for CRC. We previously demonstrated that the quassinoid bruceantinol (BOL) had antitumor activity against CRC. Herein, potent tumor growth suppression (>80%) and STAT3 inhibition was observed in two different mouse models following BOL administration. Loss of body and spleen weight was observed but was eliminated upon nanoparticle encapsulation while maintaining strong antitumor activity. STAT3 siRNA knockdown exhibited modest suppression of cell proliferation. Surprisingly, STAT3 inhibition using a PROTAC degrader (SD-36) had little effect on cancer cell proliferation suggesting the possibility of additional mechanism(s) of action for quassinoids. BOL-resistant (BR) cell lines, HCT116BR and HCA7BR, were equally sensitive to standard CRC therapeutic agents and known STAT3 inhibitors but resistant to homoharringtonine (HHT), a known protein synthesis inhibitor. The ability of quassinoids to inhibit protein synthesis was dependent on the structure of the C15 sidechain. Of note, BOL did not inhibit protein synthesis in normal human colon epithelial cells whereas HHT and napabucasin remained effective in these normal cells. Novel quassinoids were designed, synthesized, and evaluated in pre-clinical CRC models. Treatment with the most potent analog, 5c, resulted in significant inhibition of cell proliferation and protein synthesis at nanomolar concentrations. These quassinoid analogs may represent a novel class of protein synthesis inhibitors for the treatment of human CRC.

Intermedin is overexpressed in hepatocellular carcinoma and regulates cell proliferation and survival.

Angiogenesis is one of the hallmarks of tumor growth and metastasis. Identification of tumor angiogenic factors has been a critical component in understanding cancer biology and treatment. Intermedin (IMD) has been reported to promote angiogenesis in a rat ischemic model and human umbilical vascular endothelial cells. Our study sought to determine the role of IMD in human hepatocellular carcinoma tumor progression. High IMD mRNA expression levels were observed in human hepatocellular carcinoma tumors, even in early stage disease, by real-time RT-PCR. Immunohistochemical analysis of hepatocellular carcinoma clinical samples demonstrated that the tumor regions were significantly more immunoreactive for IMD than adjacent benign liver. Inhibition of IMD expression using RNA interference reduced cell proliferation in SK-Hep-1 and SNU-398 cells. Blockage of IMD signaling using either an antagonist peptide or a neutralizing antibody inhibited growth in a dose-dependent manner with concomitant induction of apoptosis, causing cleavage of caspase-8 and downregulation of Gli1 and Bcl2. Conversely, addition of IMD active peptide increased the phosphorylation level of extracellular signal-regulated kinase. Thus, IMD might play an important role in cell proliferation and survival of hepatocellular carcinoma. Our data suggests that IMD is a potential biomarker and therapeutic target for hepatocellular carcinoma.

Pigment epithelium-derived factor regulates early pancreatic fibrotic responses and suppresses the profibrotic cytokine thrombospondin-1.

Pigment epithelium-derived factor (PEDF) is important for maintaining the normal extracellular matrix. We hypothesized that the initiation of pancreatic fibrosis is dependent on the loss of PEDF. Pancreatic PEDF expression was assessed in wild-type mice fed either a control or ethanol diet using an intragastric feeding model. Pancreatitis responses were elicited with either a single episode or a repetitive cerulein-induced (50 µg/kg, 6 hourly i.p. injections) protocol in wild-type and PEDF-null mice. Quantitative real-time PCR and immunoblotting were performed to assess fibrogenic responses. In wild-type animals, PEDF expression increased with pancreatitis and was more pronounced in mice fed ethanol. Compared with wild-type mice, α-smooth muscle actin staining and expression levels of fibrogenic markers (eg, transforming growth factor-ß1, platelet-derived growth factor, collagen I, and thrombospondin-1) were higher in PEDF-null mice at baseline. Sirius red staining revealed more fibrosis in PEDF-null versus wild-type pancreas 1 week after pancreatitis. Differences in tissue fibrosis resolved with longer recovery periods. PEDF overexpression suppressed thrombospondin-1 levels in vitro. Ethanol feeding and experimental pancreatitis increased PEDF expression in wild-type mice. PEDF-null mice, however, demonstrated enhanced early fibrotic responses compared with wild-type mice with pancreatitis. These findings indicate that PEDF acts as a compensatory antifibrotic cytokine in pancreatitis.

The vacuolar-ATPase modulates matrix metalloproteinase isoforms in human pancreatic cancer.

The vacuolar-ATPase (v-ATPase) is a proton transporter found on many intracellular organelles and the plasma membrane (PM). The v-ATPase on PMs of cancer cells may contribute to their invasive properties in vitro. Its relevance to human cancer tissues remains unclear. We investigated whether the expression and cellular localization of v-ATPase corresponded to the stage of human pancreatic cancer, and its effect on matrix metalloproteinase (MMP) activation in vitro. The intensity of v-ATPase staining increased significantly across the range of pancreatic histology from normal ducts to pancreatic intraepithelial neoplasms (PanIN), and finally pancreatic ductal adenocarcinoma (PDAC). Low-grade PanIN lesions displayed polarized staining confined to the basal aspect of the cell in the majority (86%) of fields examined. High-grade PanIN lesions and PDAC showed intense and diffuse v-ATPase localization. In pancreatic cancer cells, PM-associated v-ATPase colocalized with cortactin, a component of the leading edge that helps direct MMP release. Blockade of the v-ATPase with concanamycin or short-hairpin RNA targeting the V1E subunit reduced MMP-9 activity; this effect was greatest in cells with prominent PM-associated v-ATPase. In cells with detectable MMP-2 activities, however, treatment with concanamycin markedly increased MMP-2's most activated forms. V-ATPase blockade inhibited functional migration and invasion in those cells with predominantly MMP-9 activity. These results indicate that human PDAC specimens show loss of v-ATPase polarity and increased expression that correlates with increasing invasive potential. Thus, v-ATPase selectively modulates specific MMPs that may be linked to an invasive cancer phenotype.

Phase 1 study of safety, pharmacokinetics, and pharmacodynamics of tivantinib in combination with bevacizumab in adult patients with advanced solid tumors.

PURPOSE: We investigated the combination of tivantinib, a c-MET tyrosine kinase inhibitor (TKI), and bevacizumab, an anti-VEGF-A antibody. METHODS: Patients with advanced solid tumors received bevacizumab (10 mg/kg intravenously every 2 weeks) and escalating doses of tivantinib (120-360 mg orally twice daily). In addition to safety and preliminary efficacy, we evaluated pharmacokinetics of tivantinib and its metabolites, as well as pharmacodynamic biomarkers in peripheral blood and skin. RESULTS: Eleven patients received the combination treatment, which was generally well tolerated. The main dose-limiting toxicity was grade 3 hypertension, which was observed in four patients. Other toxicities included lymphopenia and electrolyte disturbances. No exposure-toxicity relationship was observed for tivantinib or metabolites. No clinical responses were observed. Mean levels of the serum cytokine bFGF increased (p = 0.008) after the bevacizumab-only lead-in and decreased back to baseline (p = 0.047) after addition of tivantinib. Tivantinib reduced levels of both phospho-MET (7/11 patients) and tubulin (4/11 patients) in skin. CONCLUSIONS: The combination of tivantinib and bevacizumab produced toxicities that were largely consistent with the safety profiles of the individual drugs. The study was terminated prior to establishment of the recommended phase II dose (RP2D) due to concerns regarding the mechanism of tivantinib, as well as lack of clinical efficacy seen in this and other studies. Tivantinib reversed the upregulation of bFGF caused by bevacizumab, which has been considered a potential mechanism of resistance to therapies targeting the VEGF pathway. The findings from this study suggest that the mechanism of action of tivantinib in humans may involve inhibition of both c-MET and tubulin expression. TRIAL REGISTRATION: NCT01749384 (First posted 12/13/2012).

Quantitative analysis of ATM phosphorylation in lymphocytes.

Since many anticancer therapies target DNA and DNA damage response pathways, biomarkers of DNA damage endpoints may prove valuable in basic and clinical cancer research. Ataxia telangiectasia-mutated (ATM) kinase is the principal regulator of cellular responses to DNA double-strand breaks (DSBs). In humans, ATM autophosphorylation at serine 1981 (p-S1981) is an immediate molecular response to nascent DSBs and ionizing radiation (IR). Here we describe the analytical characteristics and fit-for-purpose validation of a quantitative dual-labeled immunoblot that simultaneously measures p-S1981-ATM and pan-ATM in human peripheral blood mononuclear cells (PBMCs) following ex vivo exposure to 2 Gy IR, facilitating the calculation of %p-ATM. To validate our assay, we isolated PBMCs from 41 volunteers. We report that the median basal level of p-S1981-ATM and pan-ATM was 2.4 and 49.5 ng/107 PBMCs, respectively, resulting in %p-ATM of 4%. Following exposure of PBMCs to 2 Gy IR, p-S1981-ATM levels increased 12-fold to 29.8 ng/107 PBMCs resulting in %p-ATM of 63%. Interestingly, we show that PBMCs from women have a 2.6-fold greater median p-S1981-ATM level following IR exposure than men (44.4 versus 16.9 ng/107 cells; p < 0.01). This results in a significantly greater %p-ATM for women (68% versus 49%; p <  0.01). Our rigorous description of the analytical characteristics and reproducibility of phosphoprotein immunoblotting, along with our finding that the ATM DNA damage response is greater in women, has far reaching implications for biomedical researchers.

Targeting colon cancer with the novel STAT3 inhibitor bruceantinol.

STAT3, a transcriptional mediator of oncogenic signaling, is constitutively active in ~70% of human cancers. The development of STAT3 inhibitors remains an active area of research as no inhibitors have yet to be approved for the treatment of human cancer. Herein, we revealed that bruceantinol (BOL) is a novel STAT3 inhibitor demonstrating potent antitumor activity in in vitro and in vivo human colorectal cancer (CRC) models. BOL strongly inhibited STAT3 DNA-binding ability (IC50 = 2.4 pM), blocked the constitutive and IL-6-induced STAT3 activation in a dose- and time-dependent manner, and suppressed transcription of STAT3 target genes encoding anti-apoptosis factors (MCL-1, PTTG1, and survivin) and cell-cycle regulators (c-Myc). Structure-activity relationship studies demonstrated that the C15 side chain on BOL affected its ability to bind STAT3. Administration of 4 mg/kg BOL significantly inhibited CRC tumor xenografts [p < 0.001], but no effect was observed in a STAT3-/- tumor model. Additional studies showed that BOL effectively sensitized MEK inhibitors through repression of p-STAT3 and MCL-1 induction, known resistance mechanisms of MEK inhibition. Taken together, our findings suggest BOL is a novel therapeutic STAT3 inhibitor that can be used either alone or in combination with MEK inhibitors for the treatment of human CRC.

Identification of a cis-acting element of human dihydrofolate reductase mRNA.

Human dihydrofolate reductase (DHFR) is a critical target in cancer chemotherapy. Previous studies showed that an 82-nt RNA fragment within the DHFR mRNA protein-coding region functions as a DHFR cis-acting response element. In this study, we further investigated the key elements contained within this sequence that are required for the DHFR mRNA-DHFR protein interaction. Using enzymatic foot-printing assays and RNA-binding experiments, we isolated a 27-nt sequence (DHFR27, corresponding to nts 407-433), which bound with high affinity and specificity to human DHFR to form a ribonucleoprotein complex. In vivo transient transfection experiments using a luciferase reporter system revealed that DHFR27 RNA could repress the luciferase expression in a DHFR-dependent manner when placed upstream of luciferase mRNA. This work provides new insights into the essential molecular elements that mediate RNA-protein interactions.

Regulation of p53 expression in response to 5-fluorouracil in human cancer RKO cells.

PURPOSE: The purpose of the study is to investigate the regulation of p53 expression in response to 5-fluorouracil (5-FU) in human colon cancer cells. EXPERIMENTAL DESIGN: Human colon cancer RKO cells were used as our model system. The levels of p53 expression and p53 protein stability in response to 5-FU and doxorubicin were investigated. In addition, the acetylation and phosphorylation status of p53 after 5-FU and doxorubicin treatment was analyzed by Western immunoblot analysis. RESULTS: Treatment of human colon cancer RKO cells with 10 micromol/L 5-FU resulted in significantly increased levels of p53 protein with maximal induction observed at 24 h. The level of acetylated p53 after 5-FU exposure remained unchanged, whereas the phosphorylated form of p53 was expressed only after 24 h drug treatment. Northern blot analysis revealed no change in p53 mRNA levels after 5-FU treatment. No differences were observed in the half-life of p53 protein in control and 5-FU-treated cells, suggesting that the increase in p53 was the direct result of newly synthesized protein. In contrast, the maximal induction of p53, in response to doxorubicin, occurred at an earlier time point (4 h) when compared with cells treated with 5-FU (24 h). No corresponding change in p53 mRNA was observed. Levels of both the acetylated and phosphorylated forms of p53 were markedly increased upon doxorubicin exposure when compared with treatment with 5-FU, resulting in a significantly prolonged half-life of p53 (120 versus 20 min). CONCLUSION: These results, taken together, suggest that the regulatory mechanisms controlling p53 expression, in response to a cellular stress, are complex and are dependent upon the specific genotoxic agent. With regard to 5-FU, we show that translational regulation is an important process for controlling p53 expression. Studies are under way to define the specific mechanism(s) that control 5-FU-mediated translational regulation of p53.

Molecular subtypes of colorectal cancer in pre-clinical models show differential response to targeted therapies: Treatment implications beyond KRAS mutations.

Molecular subtypes of colorectal tumors are associated with prognosis and prediction for treatment benefit from chemotherapy. The purpose of this study was two-fold: 1) to determine the association of colorectal (CRC) molecular subtypes with response to targeted therapies in pre-clinical models and 2) to identify treatments for CRC stem-like subtype because these tumors are associated with a very poor patient prognosis. Eleven CRC cell lines were classified into molecular subtypes and tested for their response to pan-ERBB, MEK, and ERK inhibitors as single agents and in combination. All six inflammatory or TA cell lines were exquisitely sensitive to the combination of MEK and neratinib whereas all five stem-like cell lines were resistant. Growth inhibition in sensitive cell lines was greater with the combination than with either drug alone even in cell lines with KRAS mutations. The combination inhibited pERK in inflammatory cell lines but not in four out of five stem-like cell lines. MEK162 plus neratinib were synergistic in cell culture and xenograft models in inflammatory cell lines. The ERK inhibitor, SCH772984, down-regulated pERK, decreased cell viability, and was synergistic with neratinib in both inflammatory and stem-like subtypes. These results suggest that inhibition of pERK is a critical node in decreasing cell viability of stem-like CRC tumors. Our results also suggest that CRC molecular subtypes may yield predictive information and may help to identify patients who may respond to targeted inhibitors.

Phase I study of veliparib in combination with gemcitabine.

BACKGROUND: Veliparib (ABT-888) is an oral PARP inhibitor expected to increase gemcitabine activity. This phase I determined the maximal tolerable dose (MTD), dose-limiting toxicities (DLT), antitumor activity, pharmacokinetics (PK), and pharmacodynamics (PD) of veliparib combined with gemcitabine. METHODS: Patients with advanced solid tumors received veliparib (10-40-mg PO BID) on chemotherapy weeks with gemcitabine 500-750-mg/m2 IV on days 1, 8, and 15 (28-day cycle), or on days 1 and 8 (21-day cycle). The MTD, DLT, adverse events, PK, and PD were evaluated. RESULTS: Eleven patients were enrolled on the 28-day schedule. The 28-day schedule was considered intolerable and amended to a 21-day schedule, with 20 patients enrolled. Grade ≥ 3 adverse events were myelosuppression-related. The MTD was determined to be 750-mg/m2 gemcitabine IV on days 1 and 8- and 20-mg PO veliparib BID days 1-14 on a 21-day schedule. Of 27 patients evaluable for response, 3 had PR and 15 had SD. There was no evidence of any major drug-drug interaction, and PK parameter values for veliparib, gemcitabine, and dFdU were as expected. Analysis of PBMCs showed evidence of PARP inhibition and DNA damage associated with therapy. CONCLUSIONS: Gemcitabine at 750-mg/m2 IV on days 1 and 8 combined with veliparib at a dose of 20-mg PO BID days 1-14 on a 21-day schedule is relatively well-tolerated, with manageable, expected toxicities. Clinical responses were observed in a pretreated population of patients, suggesting that this combination should be further evaluated in the phase II setting.

Multi-level gene expression profiles affected by thymidylate synthase and 5-fluorouracil in colon cancer.

BACKGROUND: Thymidylate synthase (TS) is a critical target for cancer chemotherapy and is one of the most extensively studied biomarkers for fluoropyrimidine-based chemotherapy. In addition to its critical role in enzyme catalysis, TS functions as an RNA binding protein to regulate the expression of its own mRNA translation and other cellular mRNAs, such as p53, at the translational level. In this study, a comprehensive gene expression analysis at the levels of both transcriptional and post-transcriptional regulation was conducted to identify response markers using human genome array with TS-depleted human colon cancer HCT-C18 (TS-) cells and HCT-C18 (TS+) cells stably transfected with the human TS cDNA expression plasmid. RESULTS: A total of 38 genes were found to be significantly affected by TS based on the expression profiles of steady state mRNA transcripts. However, based on the expression profiles of polysome associated mRNA transcripts, over 149 genes were affected by TS overexpression. This indicates that additional post-transcriptionally controlled genes can be captured with profiling polysome associated mRNA population. This unique approach provides a comprehensive overview of genes affected by TS. Additional novel post-transcriptionally regulated genes affected by 5-fluorouracil (5-FU) treatment were also discovered via similar approach. CONCLUSION: To our knowledge, this is the first time that a comprehensive gene expression profile regulated by TS and 5-FU was analyzed at the multiple steps of gene regulation. This study will provide candidate markers that can be potentially used for predicting therapeutic outcomes for fluoropyrimidine-based cancer chemotherapy.

Short interfering RNA-mediated gene silencing of vascular endothelial growth factor: effects on cellular proliferation in colon cancer cells.

HYPOTHESIS: By using short interfering RNA (siRNA) to inhibit the in vitro expression of vascular endothelial growth factor (VEGF) A, we hope to further investigate the presence of an autocrine loop in colon cancer cells. We hypothesize that VEGF inhibition will result in decreased cellular proliferation. DESIGN: Human colon cancer cells were evaluated for the expression of VEGF and VEGF receptor 2 (VEGFR-2). In vitro assessments were then made of the ability of anti-VEGF siRNA to knock down expression of VEGF and the subsequent effect this decreased expression had on colon cancer cell proliferation. SETTING: Surgical oncology research laboratory. INTERVENTIONS: Human colon cancer cells from the RKO cell line were transfected with siRNA targeting the coding region of VEGF. MAIN OUTCOME MEASURES: Enzyme-linked immunosorbent assay, Northern blot analysis, and real-time quantitative polymerase chain reaction were performed to establish the ability of siRNA to decrease VEGF production. Proliferation assays were run on transfected and wild-type cells to establish concomitant decrease in VEGF expression and cellular proliferation. RESULTS: The RKO colon cancer cells expressed both VEGF and VEGFR-2. Those cells transfected with siRNA targeting VEGF showed a 94% knockdown in VEGF expression and a 67% decrease in cellular proliferation. CONCLUSION: Colon cancer cells expressing VEGF and VEGFR-2 may possess an autocrine growth pathway that can be effectively targeted using RNA interference as an antiangiogenic therapy.