Natural resistance to apoptosis correlates with resistance to chemotherapy in colorectal cancer cells.
ABSTRACT Defects in apoptotic machinery vary among individual cancer cells, and the efficacy of chemotherapy in killing cancer cells depends on the successful induction of apoptosis. This study tested the hypothesis that the intrinsic ability of a cancer cell's natural resistance to apoptosis would indicate its ability in resistance to chemotherapy. Four widely studied human colorectal cancer cell lines, SW480, HT-29, LoVo and Caco-2, were examined for their apoptotic fates in spontaneous cultures for up to 6 days using flowcytometry. Chemoresponse of these cells was tested against anti-colorectal cancer drugs 5-fluorouracil (5-FU) and oxaliplatin (OXP) at different peak plasma concentrations (PPCs) using MTT assay. Apoptosis analyses demonstrated that, from Day 2 to Day 6 in spontaneous cultures, SW480 and HT-29 lines showed resistance to apoptosis by having much less average early and late apoptotic cells than LoVo and Caco-2 lines with differences of 3.2- to 5.2-fold. Interestingly, apoptosis-resistant SW480 and HT-29 exhibited higher chemoresistance to both 5-FU (P < 0.01 at 5×, 10×, and 50× PPC) and OXP (P < 0.01 at 5× and 10× PPC, and P < 0.05 at 50× PPC) than LoVo and Caco-2. Colorectal cancer cells' natural resistance to apoptosis is an intrinsic ability that correlates with resistance to chemotherapeutic drugs 5-FU and OXP. Cancer cells' natural apoptotic phenotypes may help predict the outcome of chemotherapy in colorectal cancers.
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ABSTRACT: This work aimed to develop a new therapeutic approach to increase the efficacy of 5-fluorouracil (5-FU) in the treatment of advanced or recurrent colon cancer. 5-FU-loaded biodegradable poly(ε-caprolactone) nanoparticles (PCL NPs) were combined with the cytotoxic suicide gene E (combined therapy). The SW480 human cancer cell line was used to assay the combined therapeutic strategy. This cell line was established from a primary adenocarcinoma of the colon and is characterized by an intrinsically high resistance to apoptosis that correlates with its resistance to 5-FU. 5-FU was absorbed into the matrix of the PCL NPs during synthesis using the interfacial polymer disposition method. The antitumor activity of gene E from the phage ϕX174 was tested by generating a stable clone (SW480/12/E). In addition, the localization of E protein and its activity in mitochondria were analyzed. We found that the incorporation of 5-FU into PCL NPs (which show no cytotoxicity alone), significantly improved the drug's anticancer activity, reducing the proliferation rate of colon cancer cells by up to 40-fold when compared with the nonincorporated drug alone. Furthermore, E gene expression sensitized colon cancer cells to the cytotoxic action of the 5-FU-based nanomedicine. Our findings demonstrate that despite the inherent resistance of SW480 to apoptosis, E gene activity is mediated by an apoptotic phenomenon that includes modulation of caspase-9 and caspase-3 expression and intense mitochondrial damage. Finally, a strongly synergistic antiproliferative effect was observed in colon cancer cells when E gene expression was combined with the activity of the 5-FU-loaded PCL NPs, thereby indicating the potential therapeutic value of the combined therapy.International Journal of Nanomedicine 01/2012; 7:95-107. DOI:10.2147/IJN.S26401 · 4.20 Impact Factor
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ABSTRACT: We have examined the influence of the nitric oxide (NO)-modified anti-inflammatory drug (S,R)-3-phenyl-4,5-dihydro-5-isoxasole acetic acid (VGX-1027) named GIT-27NO or the NO-modified antiviral drug saquinavir (Saq) named Saq-NO on two colon cancer cell lines, mouse CT26CL25 and human HCT116. The effects of the drugs on cell viability, apoptosis, proliferation, and metastatic potential were analyzed. The release of NO and oxygen and nitrogen species was also determined. The efficacy of the drugs was evaluated in vivo in BALB/c mice injected with CT26CL25 cells. Both agents suppressed the growth of colon cancer cells in vitro and reduced tumor volume in syngeneic BALB/c mice. However, their mechanisms of action were different because GIT-27NO released larger amounts of nitrite than Saq-NO in cell cultures and its antitumor action depended on the intracellular NO release inside the cells. On the contrary, Saq-NO released barely detectable amounts of NO and its antitumor action was NO-independent. In fact, cotreatment with an NO-peroxynitrite scavenger revealed that GIT-27NO but not Saq-NO acts through peroxynitrite-mediated cell destruction. At the cellular level, GIT-27NO prevalently induced proapoptotic signals followed by caspase-dependent apoptosis. In contrast, Saq-NO blocked cell proliferation, changed the adhesive, migratory, and invasive properties of the cells, and decreased metastatic potential in vivo. In conclusion, differences in NO release and oxidative stress generation between GIT-27NO and Saq-NO resulted in different mechanisms that caused cell death.Molecular pharmacology 07/2012; 82(4):700-10. DOI:10.1124/mol.112.077842 · 4.12 Impact Factor
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ABSTRACT: In recent years, several antioxidant substances have been found to have an antiproliferative effect on various types of carcinomas. α-lipoic acid (ALA) induces apoptosis in several types of cancer cell lines, but it is difficult to apply α-lipoic acid in clinical use as it is easily oxidized and unstable. Recently, we succeeded in synthesizing the α-lipoic acid derivative sodium N-[6,8-dimercaptooctanoyl]-2-aminoethanesulfonate zinc complex (DHL-TauZnNa), which has highly stable antioxidant effects. We investigated whether DHL-TauZnNa elicits its antiproliferative effects in vivo and in vitro by inducing apoptosis, autophagy or cell cycle arrest, and we analyzed the expression of proteins related to these phenomena and their phosphorylation in HT-29 human colon cancer cells. Subcutaneously administered DHL-TauZnNa treatment applied daily for 41 days significantly inhibited tumor growth by 43% in a xenograft mouse model (P=0.0271). DHL-TauZnNa significantly reduced cell viability over that of controls in the trypan-blue exclusion test in a time- and dose-dependent manner (P<0.05). DHL-TauZnNa increased the proportion of cells in S phase and decreased that of cells in G0/G1 phase in the cell cycle analysis of HT-29 cells. Although DHL-TauZnNa did not increase caspase-3/7 activity and DNA fragmentation in flow cytometry analysis, it increased the expression of microtubule-associated protein light chain 3-II. Autophagosomes and autolysosomes were observed by electron microscopy in the cytoplasm of HT-29 cells treated with DHL-TauZnNa. These results suggest that DHL-TauZnNa inhibited the proliferation of HT-29 cells through the mechanisms of G2/M cell cycle arrest and autophagy but not that of apoptosis. The newly synthesized ALA derivative DHL-TauZnNa may be expected to become a novel cancer therapeutic strategy through its induction of autophagy.Oncology Reports 04/2013; 29(6). DOI:10.3892/or.2013.2394 · 2.19 Impact Factor