Showing papers by "Yung-Chi Cheng published in 2009"

Impairment of APE1 function enhances cellular sensitivity to clinically relevant alkylators and antimetabolites

Abstract: Base excision repair (BER) is the major pathway for removing mutagenic and cytotoxic oxidative and alkylation DNA modifications. Using a catalytically inactive, dominant negative protein form of human APE1, termed ED, which binds with high affinity to substrate DNA and blocks subsequent repair steps, we assessed the role of BER in mediating cellular resistance to clinically relevant alkylating drugs and antimetabolites. Colony formation assays revealed that ED expression enhanced cellular sensitivity to melphalan not at all; to decarbazine, thiotepa, busulfan and carmustine moderately (1.2- to 2.4-fold); and to streptozotocin and temozolomide significantly (2.0- to 5.3-fold). The effectiveness of ED to promote enhanced cytotoxicity generally correlated with the agent's (a) monofunctional nature, (b) capacity to induce N 7 -guanine and N 3 -adenine modifications, and (c) inability to generate O 6 -guanine adducts or DNA cross-links. ED also enhanced the cell killing potency of the antimetabolite troxacitabine, apparently by blocking the processing of DNA strand breaks, yet had no effect on the cytotoxicity of gemcitabine, results that agree well with the known efficiency of APE1 to excise these nucleoside analogues from DNA. Most impressively, ED expression produced an ∼5- and 25-fold augmentation of the cell killing effect of 5-fluorouracil and 5-fluorodeoxyuridine, respectively, implicating BER in the cellular response to such antimetabolites; the increased 5-fluorouracil sensitivity was associated with an accumulation of abasic sites and active caspase–positive staining. Our data suggest that APE1, and BER more broadly, is a potential target for inactivation in anticancer treatment paradigms that involve select alkylating agents or antimetabolites.

Phase I/II study of PHY906/capecitabine in advanced hepatocellular carcinoma.

Abstract: PHY906 is a Chinese medicine formula with claims for the treatment of severe gastrointestinal distress. PHY906 enhanced the therapeutic index of various chemotherapeutic agents in human hepatocellular carcinoma xenografts. Accordingly, here a phase I/II clinical study was conducted with the combination of capecitabine in patients with advanced, unresectable hepatocellular carcinoma. More than 60% of patients had either stable disease or better after two treatment cycles. Median overall survival was 9.2 months. Asian patients had a higher median overall survival (16.5 months) than non-Asian patients (6.2 months, p=0.03). Patients' quality of life did not deteriorate significantly during treatment. This finding supported further investigation of PHY906 as an adjuvant therapy of capecitabine in a larger hepatocellular cancer population.

Butyrate mediates nucleotide-binding and oligomerisation domain (NOD) 2-dependent mucosal immune responses against peptidoglycan

Abstract: The interaction between digestive tract microbiological flora and food has an important influence on human health. Butyrate is produced during the fermentation of dietary fibres by intestinal bacteria and plays an important role in the regulation of mucosal immunity. In this report, we studied the impact of butyrate on the defence mechanism against the bacterial membrane component peptidoglycan (PGN). Butyrate was found to enhance PGN-mediated IL-8 and GRO-α production. The expression of these chemokines required the activation of NF-κB and was dependent on the concentrations of butyrate and PGN. Butyrate was found to up-regulate nucleotide-binding and oligomerisation domain (NOD) 2, but not NOD1 or TLR2. NOD2 up-regulation was mediated by an increase in histone acetylation in the Nod2 promoter region, leading to enhanced PGN-induced IL-8 and GRO-α secretion. Knockdown of NOD2 and TLR2 by siRNA significantly reduced PGN-mediated chemokine production, suggesting that both NOD2 and TLR2 are required for maximal response. Our findings provide a better understanding of the mechanism by which butyrate regulates mucosal immunity for normal intestinal function. Based on the results of this study, we infer that dietary fibres can impact inflammatory bowel diseases.

Decreased levels of UMP kinase as a mechanism of fluoropyrimidine resistance

Abstract: 5-Fluorouracil (5-FU) continues to be widely used for treatment of gastrointestinal cancers. Because many tumors show primary or acquired resistance, it is important to understand the molecular basis underlying the mechanism of resistance to 5-FU. In addition to its effect on thymidylate synthase inhibition and DNA synthesis, 5-FU may also influence RNA metabolism. Our previous studies revealed that colorectal cancer cells resistant to bolus 5-FU (HCT-8/4hFU) showed significantly decreased incorporation of the drug into RNA. Resistance to bolus 5-FU was associated with lower expression of UMP kinase (UMPK), an enzyme that plays an important role in the activation of 5-FU to 5-FUTP and its incorporation into RNA. Activities of other 5-FU-metabolizing enzymes (e.g., thymidine kinase, uridine phosphorylase, thymidine phosphorylase, and orotate phosphoribosyltransferase) remained unchanged between sensitive and resistant cell lines. Herein, we show that UMPK down-regulation in 5-FU-sensitive cells (HCT-8/P) induces resistance to bolus 5-FU treatment. Moreover, HCT-8/4hFU cells are even more cross-resistant to treatment with 5-fluorouridine, consistent with the current understanding of 5-fluorouridine as a RNA-directed drug. Importantly, colorectal cancer hepatic metastases isolated from patients clinically resistant to weekly bolus 5-FU/leucovorin treatment exhibited decreased mRNA expression of UMPK but not thymidylate synthase or dihydropyrimidine dehydrogenase compared with tumor samples of patients not previously exposed to 5-FU. Our findings provide new insights into the mechanisms of acquired resistance to 5-FU in colorectal cancer and implicate UMPK as an important mechanism of clinical resistance to pulse 5-FU treatment in some patients.

Effect of hypoxia on the expression of phosphoglycerate kinase and antitumor activity of troxacitabine and gemcitabine in non-small cell lung carcinoma

Abstract: Beta-L-dioxolane-cytidine (L-OddC; BCH-4556; troxacitabine), a novel L-configuration deoxycytidine analogue, was under clinical trials for treating cancer. The cytotoxicity of L-OddC is dependent on its phosphorylation to L-OddCTP by phosphoglycerate kinase (PGK) and its subsequent addition into nuclear DNA. Because PGK is induced with hypoxia, the expression of hypoxia-inducible factor-1alpha and PGK of H460 cells (human non-small cell lung carcinoma) in vitro and in vivo was studied. In culture, hypoxic treatment induced the protein expression of PGK by 3-fold but had no effect on the protein expression of other L-OddC metabolism-associated enzymes such as apurinic/apyrimidinic endonuclease-1, deoxycytidine kinase, CMP kinase, and nM23 H1. Using a clonogenic assay, hypoxic treatment of H460 cells rendered cells 4-fold more susceptible to L-OddC but not to gemcitabine (dFdC) following exposure to drugs for one generation. Using hypoxia response element-luciferase reporter system, Western blotting, and immunohistochemistry, it was found that hypoxia-inducible factor-1alpha and PGK expression increased and could be correlated to tumor size. Despite dFdC being more toxic than L-OddC in cell culture, L-OddC (300 mg/kg i.p.) had a stronger antitumor activity than dFdC in H460 xenograft-bearing nude mice. Furthermore, L-OddC retained approximately 50% of its antitumor activity with oral gavage compared with i.p. delivery. Oral administration of L-OddC (600 mg/kg p.o.) had a similar area under the curve value compared with i.p. injection of dFdC (300 mg/kg i.p.). In conclusion, the hypoxia, which commonly exists in non-small cell lung carcinoma or other solid tumors resistant to radiotherapy or chemotherapy, is a favorable determinant to enhance the antitumor activity of L-OddC in vivo.

Impact of Novel Human Immunodeficiency Virus Type 1 Reverse Transcriptase Mutations P119S and T165A on 4′-Ethynylthymidine Analog Resistance Profile

Abstract: 2′,3′-Didehydro-3′-deoxy-4′-ethynylthymidine (4′-Ed4T), a derivative of stavudine (d4T), has potent activity against human immunodeficiency virus and is much less inhibitory to mitochondrial DNA synthesis and cell growth than its progenitor, d4T. 4′-Ed4T triphosphate was a better reverse transcriptase (RT) inhibitor than d4T triphosphate, due to the additional binding of the 4′-ethynyl group at a presumed hydrophobic pocket in the RT active site. Previous in vitro selection for 4′-Ed4T-resistant viral strains revealed M184V and P119S/T165A/M184V mutations on days 26 and 81, respectively; M184V and P119S/T165A/M184V conferred 3- and 130-fold resistance to 4′-Ed4T, respectively. We investigated the relative contributions of these mutations, engineered into the strain NL4-3 background, to drug resistance, RT activity, and viral growth. Viral variants with single RT mutations (P119S or T165A) did not show resistance to 4′-Ed4T; however, M184V and P119S/T165A/M184V conferred three- and fivefold resistance, respectively, compared with that of the wild-type virus. The P119S/M184V and T165A/M184V variants showed about fourfold resistance to 4′-Ed4T. The differences in the growth kinetics of the variants were not more than threefold. The purified RT of mutants with the P119S/M184V and T165A/M184V mutations were inhibited by 4′-Ed4TTP with 8- to 13-fold less efficiency than wild-type RT. M184V may be the primary resistance-associated mutation of 4′-Ed4T, and P119S and T165A are secondary mutations. On the basis of our findings and the results of structural modeling, a virus with a high degree of resistance to 4′-Ed4T (e.g., more than 50-fold resistance) will be difficult to develop. The previously observed 130-fold resistance of the virus with P119S/T165A/M184V to 4′-Ed4T may be partly due to mutations both in the RT sequence and outside the RT sequence.

A phase II study of capecitabine (CAP) plus PHY906 in patients (pts) with advanced pancreatic cancer (APC)

Abstract: e15508 Background: Gemcitabine (G) is regarded as the standard treatment for pts with APC. However, a standard second-line chemotherapy regimen has yet to be defined after G. PHY906, a 4-herb tradi...

Comparative study of the persistence of anti-HIV activity of deoxynucleoside HIV reverse transcriptase inhibitors after removal from culture

Abstract: Background Most in vitro assays of drug potency may not adequately predict the performance in vivo. Methods to assess the persistence of antiviral activity of deoxynucleoside analogs, which require intracellular activation to the active metabolites that can persist in cells, will be important for designing dosages, combination regimens, and assessing treatment compliance. Using an HIV-IIIB/TZM-bl indicator cell culture system, we assessed the ability of an inhibitor to protect cells from infection and to delay viral rebound after removal of inhibitor from culture.

Retention of Metabolites of 2′,3′-Didehydro-3′-Deoxy-4′-Ethynylthymidine, a Novel Anti-Human Immunodeficiency Virus Type 1 Thymidine Analog, in Cells

Abstract: 2′,3′-Didehydro-3′-deoxy-4′-ethynylthymidine (4′-Ed4T), a novel thymidine analog, has more potent anti-human immunodeficiency virus type 1 (HIV-1) activity than its progenitor, stavudine (d4T). The profile of the intracellular metabolites of 4′-Ed4T was qualitatively similar to that of zidovudine (AZT) but not to that of d4T, while after drug removal it showed more persistent anti-HIV activity than AZT or d4T in cell culture. When CEM cells were exposed to various concentrations of 4′-Ed4T, 4′-Ed4T was efficiently taken up by the cells and was readily phosphorylated to 4′-Ed4T monophosphate (4′-Ed4TMP), 4′-Ed4T diphosphate (4′-Ed4TDP), and 4′-Ed4T triphosphate (4′-Ed4TTP). Most importantly, 4′-Ed4TTP, the active metabolite of 4′-Ed4T, persisted significantly longer than 4′-Ed4TDP and 4′-Ed4TMP after drug removal. We further investigated the efflux profiles of 4′-Ed4T in the comparison with those of AZT in CEM cells. After drug removal, both 4′-Ed4T and AZT were effluxed from the cells in a time- and temperature-dependent manner. However, the efflux of 4′-Ed4T from cells was much less efficient than that of AZT. 4′-Ed4T was effluxed from cells only in its nucleoside form, while AZT was effluxed from cells in both its nucleoside and monophosphate forms. The mechanism-of-action study showed that the efflux of 4′-Ed4T or AZT nucleoside might be due to unknown nucleoside transporters which were not related to the equilibrative nucleoside transporters, while the efflux of AZT monophosphate might be due to multidrug resistance protein 4 (MRP4/ABCC4). The results demonstrated that no detectable 4′-Ed4TMP efflux and the less efficient efflux of 4′-Ed4T nucleoside from cells might be one of the biochemical determinants of its persistent antiviral activity in cell culture.

Use of the combination of phy906 and a tyrosine kinase inhibitor as a cancer treatment regimen

Abstract: This invention provides herbal compositions useful for increasing the therapeutic index of chemotherapeutic compounds This invention also provides methods useful for improving the quality of life of an individual undergoing chemotherapy Furthermore, this invention improves the treatment of cancer by administering the herbal composition PHY906 in combination with one or more chemotherapeutic compounds to a mammal undergoing such chemotherapy

Abstract #4584: Exploration of the mechanisms of PHY906 in reducing the intestinal toxicity caused by irinotecan

Abstract: PHY906 is a standardized four-herb traditional Chinese formulation that has been used for over 1700 years in the treatment of gastrointestinal ailments and is currently in anticancer clinical trials in the US as an adjuvant to chemotherapy. Preliminary clinical results indicated PHY906 could decrease G.I. toxicity triggered by irinotecan for treating colon cancer. In a murine colon-38 allograft model, PHY906 (500 mg bid days 0-3) alone, does not significantly inhibit tumor growth. However, the combination of PHY906 and irinotecan (360mg/kg, day 1) had higher anti-tumor activity in comparison to irinotecan alone. Additionally, PHY906 decreased weight loss caused by irinotecan. The impact of PHY906 on the intestinal toxicity caused by irinotecan at day 2 and day 4 were studied. Adding PHY906 to irinotecan treatment, a) reduced irinotecan induced degenerative changes throughout different regions of the intestine on day 4 but not on day 2, b) reduced irinotecan induced DNA damage and apoptosis of intestinal cells on day 4, c) promoted the re-growth of crypt cells which could be partially attributed to the wnt3a-potentiation activity of the aglycone component(s) of PHY906 on day 4, d) inhibited TNF-\#945; induced NF-kB activity, e) decreased the infiltration of neutrophils in intestinal crypt areas and decreased pro-inflammatory cytokine levels. In summary, our studies suggest that PHY906 reduces intestinal damage caused by irinotecan through the inhibition of inflammation and enhancement of intestinal repair by promoting intestinal progenitor cell proliferation. This work is supported by a supplement grant: CA-63477 from NCI, USA Citation Information: In: Proc Am Assoc Cancer Res; 2009 Apr 18-22; Denver, CO. Philadelphia (PA): AACR; 2009. Abstract nr 4584.

Effect of PHY906 on capecitabine (CAP)-induced diarrhea in patients with GI malignancies

Abstract: e20595 Background: 15.4% of pts with GI cancers treated with CAP alone at 1250mg/m2 BID D1–14 q 3 wks (14/7) develop G3/4 diarrhea (Hoff et al. JCO, 2001). PHY906 composed of 4 herbs, Scutellaria baicalensis Georgi, Glycyrrhiza uralensis Fisch., Ziziphus jujuba Mill., and Paeonia lactiflora Palla, has been used to treat diarrhea since approximately 300AD. Preliminary studies showed synergistic activity of PHY906 with chemotherapeutics and reduction of chemotherapy-induced GI toxicities, especially chemotherapy-induced diarrhea (CID). Methods: We prospectively evaluated 44 pts treated on a clinical study with CAP plus PHY906 for diarrhea (experimental arm) and compared to historical data by Hoff et al., CAP 14/7 alone arm (control arm). Experimental arm consisted of pts with refractory solid tumors in phase I and gemcitabine-refractory advanced pancreatic cancer (APC) in phase II. Ph I pts received PHY906 800mg BID D1–4 with escalating doses of CAP (1000mg/m2→1250mg/m2→1500 mg/m2→1750mg/m2 BID) D1 -7 q 2 w...