High hRFI expression correlates with resistance to fluoropyrimidines in human colon cancer cell lines and in xenografts

We previously reported that the over-expression of hRFI, a protein preferentially expressed in the digestive tract regions of several cancers, exhibited a tendency to inhibit TNF-alpha induced apoptosis. In this study, we sought to determine the potential effect of hRFI expression on the sensitivity to 5-fluorouracil (5-FU) and/or other fluoropyrimidines. For the whole lysates of 8 colon cancer cell lines, we performed Western blotting with anti-hRFI antibody and analyzed the correlations between the expression level of hRFI and the cell lines' sensitivity to 5-FU induced apoptosis. Furthermore, for a tissue microarray consisting of 32 xenograft derived human cancer cell lines, we examined the expression levels of hRFI and survivin by immunohistochemical staining, and analyzed the correlations between the expression of each protein and the sensitivity to several chemotherapeutic agents in the xenografts examined. Both in colon cancer cell lines and in xenografts, the expression level of hRFI was correlated with resistance to 5-FU and its derivatives. This evidence suggests that hRFI may be a marker predicting the response to fluorouracil derived chemotherapeutic agents and that the reduction of the expression level of hRFI might improve the outcome of chemotherapy.

In vitro antitumor activity of TAS-103 against freshly-isolated human colorectal cancer

DNA topoisomerases (Topo) are enzymes that relieve the secondary twist on the DNA strand in the process of DNA synthesis and transcription; therefore they are unique targeting molecules for the chemotherapy of colorectal cancer. TAS-103 (6-[[2-(dimethylamino)ethyl]amino]-3-hydroxy-7H-in-deno [2,1-c]quinolin-7-one dihydrochloride, MW; 406.31), a novel quinoline derivative, has recently been established as a Topo I and Topo II inhibitor. The aim of the present study was to investigate the antitumor activity of TAS-103 by the MTT assay in human highly-purified and freshly-isolated colorectal cancer cells. To our knowledge, this is the first data concerning the antitumor activity of TAS-103 in highly-purified and isolated human colorectal cancer cells. TAS-103 showed the strongest antitumor activity among the conventional anticancer agents for colorectal cancer (p<0.05). The combination with CDDP augmented the antitumor activity of TAS-103 (p<0.05), indicating that CDDP is one of the most potent candidates to be used in combination with TAS-103. To predict the clinical effect of TAS-103, the expressions of Topo I and Topo II were measured by quantitative PCR. However, a correlation between the expression of Topo and the antitumor activity of TAS-103 was not established. In conclusion, according to this data, TAS-103 may be useful in the chemotherapy of colorectal cancer.

DNA topoisomerase II as the target for the anticancer drug TOP-53: mechanistic basis for drug action

TOP-53 is a promising anticancer agent that displays high activity against non-small cell lung cancer in animal tumor models [Utsugi, T., et al. (1996) Cancer Res. 56, 2809-2814]. Compared to its parent compound, etoposide, TOP-53 is considerably more toxic to non-small cell lung cancer cells, is more active at generating chromosomal breaks, and displays improved cellular uptake and pharmacokinetics in animal lung tissues. Despite the preclinical success of TOP-53, several questions remain regarding its cytotoxic mechanism. Therefore, this study characterized the basis for drug action. Results indicate that topoisomerase II is the primary cytotoxic target for TOP-53. Furthermore, the drug kills cells by acting as a topoisomerase II poison. TOP-53 exhibits a DNA cleavage site specificity that is identical to that of etoposide. Like its parent compound, the drug increases the number of enzyme-mediated DNA breaks by interfering with the DNA religation activity of the enzyme. TOP-53 is considerably more efficient than etoposide at enhancing topoisomerase II-mediated DNA cleavage and exhibits high activity against human topoisomerase IIalpha and IIbeta in vitro and in cultured cells. Therefore, at least in part, the enhanced cytotoxic activity of TOP-53 can be attributed to an enhanced activity against topoisomerase II. Finally, TOP-53 displays nearly wild-type activity against a mutant yeast type II enzyme that is highly resistant to etoposide. This finding suggests that TOP-53 can retain activity against systems that have developed resistance to etoposide, and indicates that substituents on the etoposide C-ring are important for topoisomerase II-drug interactions.

Specific distribution of TOP-53 to the lung and lung-localized tumor is determined by its interaction with phospholipids

We have investigated the mechanism of TOP-53 distribution to the lung and lung-localized tumor. In contrast to etoposide (VP-16), TOP-53 contains a basic aminoalkyl group that may predispose it to interact specifically with phospholipids, consequently leading to an increase of drug accumulation in the tissues. Therefore, we have studied its interaction with phospholipids in vitro using an organic solvent-water partition system. TOP-53 appeared to have the most potent binding affinity (Ka = 563 x 10(-2) microM) to phosphatidylserine (PhS), whereas VP-16 showed no interaction with any phospholipid tested. PhS content determined after HPLC separation varied among tested tissues; however, large quantities were found in normal lung and lung cancer tissues far exceeding those present in the liver and kidney. The predicted tissue-to-plasma partition coefficient values, estimated based on PhS content and its binding affinity, resembled those experimentally determined. We concluded that tissue distribution of TOP-53 is determined by PhS content in the tissues and by binding affinity. As a result of specific accumulation in the lung, TOP-53 appeared to show a strong antitumor activity (increase of life span = 171%) against cancer metastasizing to the lung, whereas VP-16 was less effective (increase of life span = 78%). These results suggest that TOP-53 may have an advantage over VP-16 in the treatment of lung cancers in patients.

Establishment and characterization of 6-[[2-(Dimethylamino)ethyl]amino]-3-hydroxy-7H-indeno[2,1-c]quinolin-7-one dihydrochloride (TAS-103)-resistant cell lines

6-2-(Dimethylamino)ethylămino-3-hydroxy-7H-indeno2, 1-cquinolin-7-one dihydrochloride (TAS-103) is a novel anticancer agent that was developed to target both topoisomerase (Topo) I and Topo II. To elucidate its mechanism of action, we have established and characterized TAS-103-resistant cells, derived from mouse leukemia (P388), human colon cancer (DLD-1), and human lung adenocarcinoma (A549) cell lines, by exposure to stepwisely increasing concentrations of TAS-103 in the culture medium. P388 / TAS cells showed only cross-resistance to VP-16 and adriamycin (ADR). The Topo II activity in these cells was decreased to below one-fourth of that in the parental cells, while the Topo I activity remained unchanged. DLD / TAS cells appeared to be cross-resistant to VP-16, ADR, camptothecin (CPT), SN-38 and vincristine (VCR). The enzymatic activities of both Topo I and Topo II in these cells were decreased to one-fourth of that observed in the parental cells. Furthermore, the decreased activities were accompanied by lower expression at the mRNA and protein levels. A549 / TAS cells acquired cross-resistance to VP-16, ADR and VCR, though the Topo activities were virtually unchanged. In this cell line, the intracellular accumulation of TAS-103 was significantly decreased and the expression of multidrug resistance associated protein (MRP) was elevated when compared with the parental cells. The results indicate that the affected activities of Topo I and / or Topo II, and in some instances decreased accumulation of TAS-103, are associated with the development of resistance to TAS-103, although the main mechanism of resistance to TAS-103 varied among cell lines.

Mechanism of action of the dual topoisomerase-I and -II inhibitor TAS-103 and activity against (multi)drug resistant cells

TAS-103 is a recently developed dual inhibitor of topoisomerase-I (topo-I) and topoisomerase-II (topoII). TAS-103 has documented cytotoxicity in vitro and antitumor activity against a variety of mouse, rat, and human xenografts in vivo.

PURPOSE

To determine TAS-103 activity against (multi)drug resistant cells in vitro and to delineate its mechanism of action.

METHODS

TAS-103 was evaluated for activity against three human multidrug-resistant cell lines representing resistance mediated by P-glycoprotein (Pgp)-, multidrug resistance protein (MRP), and lung resistance protein (LRP) as well as one camptothecin-resistant cell line associated with a mutated topo-I enzyme. Drug sensitivity following short (2 h), intermediate (6-8 h) and long term (24 h) exposures were compared. The mechanism of action was studied by evaluating inhibition of topoisomerase-I and -II specific DNA relaxation assays, drug-induced DNA/protein cross-link formation, and competitive DNA intercalation with ethidium bromide.

RESULTS

Increasing the exposure time only modestly potentiated TAS-103 cytotoxicity (3-5 fold) demonstrating a lack of strong exposure duration dependency. TAS-103 cytotoxicity was not affected by the presence of any of the drug resistance mechanisms studied. TAS-103 inhibits topo-I and -II activity in DNA relaxation assays, but in our assay system TAS-103 was found to have only a weak ability to induce DNA-protein crosslinks. DNA migration patterns in agarose gel electrophoresis indicate that TAS-103 can interact directly with DNA. Also its ability to displace ethidium bromide which has intercalated into the DNA provides an indication on the nature of drug-DNA interaction.

CONCLUSIONS

TAS-103 cytotoxicity is not affected by the presence of Pgp, MRP, LRP or mutations in the CAM binding region of the topo-I enzyme and its growth-inhibitory effect appears to be weakly dependent on exposure duration. The presented evidence suggest that the inhibitory effects of TAS-103 on topo-I and -II may in part be related to its DNA binding rather than primarily through stabilization of topo-I or -II intermediates with DNA through specific binding to the enzymes.

In vitro antitumor activity of TAS-103, a novel quinoline derivative that targets topoisomerases I and II

TAS-103 is a novel anticancer agent targeting both topoisomerase (Topo) I and Topo II, that stabilizes cleavable complexes of Topo-DNA at the cellular level. In this study, the in vitro antitumor effects of TAS-103 were compared with those of other known Topo I and Topo II inhibitors. TAS-103 inhibited DNA synthesis more strongly than RNA and protein synthesis, and induced an increase of cell population in the S-G2/M phase. The cytotoxicity of TAS-103 was strongest against S-phase cells, but its cell cycle phase specificity was not clear, and depended on drug concentration and exposure time. The cytotoxicity of TAS-103 (IC50: 0.0030-0.23 microM) against various tumor cell lines was much stronger than that of VP-16 and comparable to that of SN-38. The cytotoxicity of TAS-103 seemed to be more related to the amount of protein-DNA complexes than to the accumulation of TAS-103 in the cells. P-Glycoprotein (P-gp)-mediated MDR, CDDP-resistant and 5-FU-resistant cell lines did not show cross-resistance to TAS-103. Although PC-7/CPT cells bearing a Topo I gene mutation showed cross-resistance to TAS-103, the sensitivity of P388/CPT, HT-29/CPT and St-4/CPT cells, showing decreased Topo I expression, was not changed. KB/VM4 and HT-29/Etp cells, showing decreased Topo II expression, were slightly cross-resistant to TAS-103. These results suggest that TAS-103 may act as an inhibitor of both Topo I and Topo II at the cellular level. This property may be responsible for its strong antitumor effect and broad-spectrum, growth-inhibitory effect on drug-resistant cell lines.

Prediction of the optimum clinical dosing schedule for menogaril from results with tumor-bearing mice

Menogaril is an antitumor agent active after oral administration, and unlike other anthracyclines, extravasation cannot occur. When the IC90 values of menogaril were plotted versus exposure time on a double-logarithmic scale, the regression lines had slopes between -0.64 and -0.80. These results showed that the mode of action of menogaril was type lb, dependent on the area under the curve (AUC) of concentration versus time, like Adriamycin. In calculations that simulated pharmacokinetic findings if administration were for three consecutive days (the single dose given was 79 mg/kg) or on days 1 and 8 (the single dose was 238 mg/kg), the peak tumor concentration of menogaril was 1870 and 2985 ng/g and the AUC was 68,363 and 89,352 ng/g hour, respectively. Of the dosing schedules tried, these two dosing schedules were the optimum, with satisfactory antitumor activity against mouse solid tumor Colon 26 and with a wide range of effective dose concentrations. Since menogaril was AUC-dependent, it was possible to predict antitumor activity and to choose optimum dosing schedules on the basis of cell-kill kinetic and pharmacokinetic information.

Dystrophin, utrophin and beta-dystroglycan expression in skeletal muscle from patients with Becker muscular dystrophy

The precise localization and semiquantitative correlation of dystrophin, utrophin and beta-dystroglycan expression on the sarcolemma of skeletal muscle cells obtained from patients with Becker muscular dystrophy (BMD) was studied using three types of double immunofluorescence. Staining intensity was measured using a confocal laser microscope. Each of these proteins was identified at the same locus on the sarcolemma. The staining intensities of dystrophin and utrophin were approximately reciprocal at sarcolemmal sites where dystrophin expression was obviously observed. The staining intensity of beta-dystroglycan was strong in areas where dystrophin staining was also strong and utrophin expression was weak. Quantitative analysis revealed that the staining intensity of beta-dystroglycan minus that of dystrophin approximated the staining intensity of utrophin, indicating that the sum of dystrophin and utrophin expression corresponds to that of beta-dystroglycan. These results suggest that utrophin may compensate for dystrophin deficiency found in BMD by binding to beta-dystroglycan.

Antitumor activity of a novel podophyllotoxin derivative (TOP-53) against lung cancer and lung metastatic cancer

We synthesized a potent new antitumor podophyllotoxin derivative (4beta-aminoalkyl-4'-O-demethyl-4-desoxypodophyllotoxin; TOP-53) in our search for a drug that has strong activity against lung cancer and lung metastatic cancer. TOP-53 exhibited twice the inhibitory activity of etoposide (VP-16) against topoisomerase II and induced DNA strand breaks but showed no inhibitory activity against tubulin polymerization. The in vitro cytotoxic activity of TOP-53 assessed as IC50 was 0.016-0.37 microg/ml and 0.26-8.9 microg/ml against marine tumor and human non-small cell lung cancer (NSCLC) cell lines, respectively. TOP-53 exerted significant efficacy equivalent to that of VP-16 on s.c.-implanted murine solid tumors (Colon 26, B16-BL6, and Lewis lung carcinoma) at doses 3-5 times lower than that of VP-16. In human tumor xenografts using NSCLC, TOP-53 was active for four of five tumors, whereas VP-16 was active for two of five tumors. Potent inhibitory activity of TOP-53 was also found against a lung tumor (Lewis lung carcinoma) and four lung metastatic tumors (NL-22 and NL-17 colon cancer, UV2237M fibrosarcoma, and K1735M2 melanoma). TOP-53 appeared to be more active against four of them than VP-16. Thus, TOP-53 is not only active against s.c.-implanted lung cancers but also strongly active against lung localized tumor and metastatic tumors in the lungs. The high selectivity of TOP-53 was attributed to its high distribution into the lung and its persistence. TOP-53 is expected to be highly effective against lung cancer including NSCLC and various lung metastatic tumors in the clinical field.

Antitumor activity of menogaril alone, and in combination against human mammary cancer models in mice and rats

Menogaril is an antitumor agent different from other anthracyclines in being active after oral administration. To predict its clinical effectiveness by this route against human breast cancer, we compared its antitumor activity against breast cancer in experimental animals with that of injected Adriamycin. Menogaril had half the much antitumor activity of Adriamycin against human mammary cancer cell lines. Menogaril given orally also had a antitumor activity against mammary cancer caused by 7,12-dimethyl-benz[a]anthracene in rats comparable with that of Adriamycin. The high concentration of menogaril in tumor tissue seemed to contribute to its effectiveness. Of several combinations of cyclophosphamide, Adriamycin, menogaril, and 5-fluorouracil, the combination of cyclophosphamide, menogaril, and 5-fluorouracil was most effective against mouse leukemia L1210 and human breast cancer xenografts in mice. This combination might have antitumor activity against breast cancer superior to that of the therapy currently of first choice (cyclophosphamide, Adriamycin, and 5-fluorouracil) in the clinic.

Antitumor agents. 3. Synthesis and biological activity of 4 beta-alkyl derivatives containing hydroxy, amino, and amido groups of 4'-O-demethyl-4-desoxypodophyllotoxin as antitumor agents

A series of 4 beta-alkyl (7-10), 4 beta-aminoalkyl (12a-y), and 4 beta-amidoalkyl derivatives (14a-g) of 4'-O-demethyl-4-desoxypodophyllotoxin have been synthesized, and their cytotoxicity, inhibition of DNA topoisomerase II (Topo II), and tubulin polymerization were evaluated. All derivatives of 12a-y and 14a-g did not inhibit tubulin polymerization. Many compounds exhibited cytotoxicity and inhibition of Topo II. In particular, 12o, 12s, 12t, and 12u strongly inhibited Topo II (IC50 (microM) 32.5, 60.9, 58.8, and 33.6, respectively) and were strong cytotoxicity against P388 cells (IC50 (M) 1.0, 4.1, 3.3, and 3.0 x 10(-9), respectively), compared with VP-16 (IC50 (microM) 59.2, IC50 (M) 1 x 10(-8), respectively). These compounds were nearly equal to or superior to VP-16 in antitumor activity in vivo (L1210, P388, and Lewis lung) and were more cytotoxic against various human cell lines in vitro than VP-16.

Antitumor agents. II: Regio- and stereospecific syntheses of 1-beta-alkyl-1-desoxypodophyllotoxin derivatives and biological activity

1-beta-Alkyl derivatives of 1-desoxypodophyllotoxin were synthesized, and their cytotoxicity and inhibitory effects on DNA topoisomerase II (Topo-II) and tubulin polymerization were examined. The reaction of epipodophyllotoxin derivatives (1a-c) with trimethylallylsilane in the presence of boron trifluoride etherate gave 1-beta-allylated compounds (2a-c). The regiochemistry and the beta-stereochemistry of the 1-allyl group were confirmed by comparison of the 13C-NMR spectra and NOE's (%) of 2c, podophyllotoxin (POD) and epipodophyllotoxin (1b). 1-beta-Alkyl-1-desoxypodophyllotoxin derivatives (3-8) were prepared from 2b. None of the tested compounds (3-8) showed any inhibitory effect on Topo-II. 1-beta-Propyl compound (3) and its 4'-demethyl compound (4) inhibited tubulin polymerization and the cytotoxicities of these compounds were equal to that of VP-16. 1-beta-(2,3-Dihydroxypropyl) compounds (5 and 8) and 1-beta-(2,3-diacetoxypropyl) compounds (6 and 7) showed no inhibitory effect on tubulin polymerization. Although 5 did not inhibit either Topo-II activity or tubulin polymerization, it showed a high cytotoxicity against sarcoma 180.

Antitumor agents. I. DNA topoisomerase II inhibitory activity and the structural relationship of podophyllotoxin derivatives as antitumor agents

Various podophyllotoxin derivatives from desoxypodophyllotoxin (DPT) were synthesized to examine the structural relationships between the biological significance (cytotoxic effect, effects on DNA topoisomerase II and tubulin polymerization) in vitro and antitumor activity in vivo (L 1210). An intact 6,7-methylenedioxy group of DPT is necessary to inhibit tubulin polymerization and topoisomerase II. 4'-Phenolic hydroxyl group of DPT is essential to inhibit DNA topoisomerase II and the inhibitory effect on DNA topoisomerase II contributes to a high cytotoxicity. The introduction of an aminoalkoxy group at 1-position of DPT enhances the inhibitory activity against DNA topoisomerase II and cytotoxic effect, causing the inhibitory activity against tubulin polymerization to disappear. The results of antitumor test in mice bearing L 1210 on podophyllotoxin derivatives suggest the following: 1) the strong cytotoxic effect itself is not a good indication of antitumor activity in vivo as long as it is associated with inhibition of tubulin polymerization. DNA topoisomerase II inhibitory effect contributes to an antitumor activity in vivo; 2) detailed measurements of cytotoxicity and inhibition on DNA topoisomerase II and tubulin polymerization in vitro are necessary to evaluate podophyllotoxin derivatives.

Genetic control of signal transduction in mouse melanocytes

At the final step of melanocyte differentiation in mouse hair follicles, the cells produce melanin. The type of melanin they produce is, however, determined by the tissue environment of hair follicles. In wild-type mice, melanocytes located in hair bulbs synthesize eumelanin at the beginning of hair growth. They subsequently produce pheomelanin and finally produce eumelanin again. Therefore, the hair is characterized by a subterminal band of yellow, with the rest of it displaying black. This characteristic is called the agouti pattern and is known to be determined by the wild-type allele, A at the a (agouti) locus, which is considered to function in the follicular cells. Expression of the agouti pattern is altered by genetic substitutions at the a locus and the e (extension) locus. Animals heterozygous for the Ay (lethal yellow) allele exhibit yellow coat color; those homozygous for the e (recessive yellow) also produce yellow hair exclusively. By using an organ culture method, we demonstrated that alpha-MSH and cholera toxin, as well as forskolin, induced eumelanin synthesis in explants from lethal yellow mice (Ay/a). On the other hand, these reagents did not induce eumelanogenesis in the hair follicles of recessive yellow (e/e) mice. Therefore, we assume that the product of the a locus, which probably functions in follicle cells, interacts with alpha-MSH at the alpha-MSH receptor and that the e locus controls the functionality of adenylate cyclase in the membrane of mouse melanocytes.