Vol. 4, 1013-1019, April 1998 Clinical Cancer Research 1013 Induction of Thymidine Phosphorylase Activity and Enhancement of Capecitabine Efficacy by Taxol/Taxotere in Human Cancer Xenografts Noriaki Sawada, Tohru Ishikawa, Yu Fukase, Miwa Nishida, Takashi Yoshikubo, and Hideo Ishitsuka’ Cytostatics Group, Nippon Roche Research Center, Kamakura-city, Kanagawa 247-0853, Japan ABSTRACT Thymidine phosphorylase (dThdPase) is an essential enzyme for the activation of the cytostatics capecitabine (N’-pentyloxycarbonyl-5’-deoxy-5-fluorocytidine) and its in- tennediate metabolite [5’-deoxy-5-fluorouridine (5’-dFUrd)] to 5-fluorouracil in tumors. We have tried to identify the best partners of capecitabine in combination therapy, such as dThdPase up-regulators, which may enhance the efficacy of this compound. Among various cytostatics studied with the WiDr human colon cancer xenograft model, Taxol, Taxo- tere, and mitomycin C greatly increased levels of human dThdPase in tumors, and cyclophosphamide slightly in- creased the enzyme level. These cytostatics simultaneously increased the levels of human tumor necrosis factor a (TNFa), which is an up-regulator of dThdPase. In cultures of the WiDr cells, however, Taxol did not up-regulate TNFa to a detectable level and only slightly enhanced levels of dThdPase. These results suggest that Taxol might indirectly elevate TNFa in tumor cells, which in turn up-regulated dThdPase in the tumor cells in the WiDr cancer xenograft. In the combination therapy, the efficacy of Taxol and Taxo- tere with either capecitabine or 5’-dFUrd was more than just additive. In contrast, Taxol and either 5-fluorouracil or UFT (a mixture of tegafur and uracil) in combination showed only additive activity. Taxol and Taxotere might enhance the efficacy ofcapecitabine and 5’-dFUrd, probably by modulating dThdPase activity in tumor tissues. INTRODUCTION Capecitabine generates 5-FUra2 selectively in tumors by three enzymes located in the liver and in tumors; the final step Received 9/5/97; revised 1/14/98;accepted 1/16/98. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. I To whom requests for reprints should be addressed, at Cytostatics Group, Nippon Roche Research Center, Kajiwara 200, Kamakura-city, Kanagawa 247-0853, Japan. Phone: 81-467-47-2220; Fax: 81-467-45- 6782. 2 The abbreviations used are: 5-FUra, 5-fluorouracil; dThdPase, thymi- dine phosphorylase; 5’-dFUrd, 5’-deoxy-5-fluorouridine; MMC, mito- mycin C; DXR, doxorubicin; CPA, cyclophosphamide; VCR, vincris- is the conversion of the intermediate metabolite 5’-dFUrd to 5-FUra by dThdPase in tumors (1, 2). The enzyme is now known to be an angiogenic factor (3, 4), and its activity is higher in various tumor tissues than in normal tissues adjacent to the tumors (5, 6). dThdPase is essential for the efficacy of capecit- abine and 5’-dFUrd. The susceptibility of tumor cells to 5’- dFUrd is reported to be enhanced by the transfection of the dThdPase gene (7, 20), whereas the activity of 5’-dFUrd was inhibited by dThdPase inhibitors (8). Therefore, it is expected that dThdPase up-regulators would enhance the efficacy of capecitabine and 5’-dFUrd. In fact, the efficacy of 5’-dFUrd has been reported to be enhanced through the up-regulation of this enzyme activity by various factors, such as IL-la, TNFa, IFN-y (9), basic fibroblast growth factor, platelet-derived growth fac- tor (10), and IFNot (11, 12). In addition, we preliminarily reported that IL-12 enhanced the efficacy of 5’-dFUrd and capecitabine in the in vivo tumor models indirectly through the up-regulation of IFNy, a dThdPase up-regulator (13, 14). Capecitabine is being assessed in clinical trials worldwide, and 5’-dFUrd is being marketed in Japan and in other Asian countries for the treatment of breast, colorectal, gastric, and other cancers. It is therefore of interest to know what factors and drugs used in cancer treatment other than cytokines could either directly or indirectly affect the levels of dThdPase. Among cytostatics, Taxol has been reported to elevate levels of TNFa, a potential dThdPase up-regulator, in macrophages (15-17). In the present study, we examined various cytostatics, including Taxol, to determine whether they affected dThdPase levels and enhanced the efficacy of capecitabine and 5’-dFUrd in combi- nation therapy. We found that several cytostatics, including Taxol and Taxotere, up-regulated the enzyme level in tumors, and these drugs in combination with either capecitabine or 5’-dFUrd showed additive to the synergistic activity. The mech- anism of the up-regulation is also discussed. MATERIALS AND METHODS Animals. Four- or 5-week-old male and female BALB/c nu/nu mice were obtained from SLC Japan, Ltd. (Shizuoka, Japan). Tumors. The human cancer lines used were obtained from the following institutions: colon cancer WiDr from the American Type Culture Collection (Rockville, MD) and MX-l from Dr. T. Tashiro (Cancer Chemotherapy Center, Japanese Foundation for Cancer Research, Tokyo, Japan). WiDr was maintained in vitro cultures with Eagle’s MEM containing 10% tine; VDS, vindesine; VLB, vinblastine; CDDP, cisplatin; MTX, methotrexate; TNFa, tumor necrosis factor a; IL, inter!eukin; MTh, maximum tolerated dose. Association for Cancer Research. by guest on September 1, 2020. Copyright 1998 American https://bloodcancerdiscov.aacrjournals.org Downloaded from
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Vol. 4, 1013-1019, April 1998 Clinical Cancer Research 1013
Induction of Thymidine Phosphorylase Activity and Enhancement
of Capecitabine Efficacy by Taxol/Taxotere in Human
Cancer Xenografts
Noriaki Sawada, Tohru Ishikawa, Yu Fukase,
Miwa Nishida, Takashi Yoshikubo, and
Hideo Ishitsuka’Cytostatics Group, Nippon Roche Research Center, Kamakura-city,Kanagawa 247-0853, Japan
ABSTRACT
Thymidine phosphorylase (dThdPase) is an essential
enzyme for the activation of the cytostatics capecitabine
(N�’-pentyloxycarbonyl-5’-deoxy-5-fluorocytidine) and its in-
tennediate metabolite [5’-deoxy-5-fluorouridine (5’-dFUrd)] to
5-fluorouracil in tumors. We have tried to identify the best
partners of capecitabine in combination therapy, such as
dThdPase up-regulators, which may enhance the efficacy of
this compound. Among various cytostatics studied with the
WiDr human colon cancer xenograft model, Taxol, Taxo-
tere, and mitomycin C greatly increased levels of human
dThdPase in tumors, and cyclophosphamide slightly in-
creased the enzyme level. These cytostatics simultaneously
increased the levels of human tumor necrosis factor a
(TNFa), which is an up-regulator of dThdPase. In cultures
of the WiDr cells, however, Taxol did not up-regulate TNFa
to a detectable level and only slightly enhanced levels of
dThdPase. These results suggest that Taxol might indirectly
elevate TNFa in tumor cells, which in turn up-regulated
dThdPase in the tumor cells in the WiDr cancer xenograft.
In the combination therapy, the efficacy of Taxol and Taxo-
tere with either capecitabine or 5’-dFUrd was more than
just additive. In contrast, Taxol and either 5-fluorouracil or
UFT (a mixture of tegafur and uracil) in combination
showed only additive activity. Taxol and Taxotere might
enhance the efficacy ofcapecitabine and 5’-dFUrd, probably
by modulating dThdPase activity in tumor tissues.
INTRODUCTION
Capecitabine generates 5-FUra2 selectively in tumors by
three enzymes located in the liver and in tumors; the final step
Received 9/5/97; revised 1/14/98;accepted 1/16/98.The costs of publication of this article were defrayed in part by thepayment of page charges. This article must therefore be hereby markedadvertisement in accordance with 18 U.S.C. Section 1734 solely to
indicate this fact.I To whom requests for reprints should be addressed, at CytostaticsGroup, Nippon Roche Research Center, Kajiwara 200, Kamakura-city,Kanagawa 247-0853, Japan. Phone: 81-467-47-2220; Fax: 81-467-45-
6782.2 The abbreviations used are:5-FUra, 5-fluorouracil; dThdPase, thymi-dine phosphorylase; 5’-dFUrd, 5’-deoxy-5-fluorouridine; MMC, mito-mycin C; DXR, doxorubicin; CPA, cyclophosphamide; VCR, vincris-
is the conversion of the intermediate metabolite 5’-dFUrd to
5-FUra by dThdPase in tumors (1, 2). The enzyme is now
known to be an angiogenic factor (3, 4), and its activity is higher
in various tumor tissues than in normal tissues adjacent to the
tumors (5, 6). dThdPase is essential for the efficacy of capecit-
abine and 5’-dFUrd. The susceptibility of tumor cells to 5’-
dFUrd is reported to be enhanced by the transfection of the
dThdPase gene (7, 20), whereas the activity of 5’-dFUrd was
inhibited by dThdPase inhibitors (8). Therefore, it is expected
that dThdPase up-regulators would enhance the efficacy of
capecitabine and 5’-dFUrd. In fact, the efficacy of 5’-dFUrd has
been reported to be enhanced through the up-regulation of this
enzyme activity by various factors, such as IL-la, TNFa, IFN-y
Fig. 1 Correlation between dThdPase levels in tumor tissues and tumorvolume change. Data points, data from individual mice tested in theexperiment shown in Table 1 (experiment 1). V. not treated; V. saline;� , Taxol; #{149}, Taxotere; 0, CDDP; #{149},DXR; EL MMC; U, VCR; i�,
VLB; A, VDS.
0 5 10 15 20
dlhdPase (unit /mg protein)
25 30
Fig. 2 Correlation between dThdPase and human INFa levels in tu-
mor tissues. Data points, data from individual mice tested in the exper-iment shown in Table 1 (experiment 1). Significance was calculated
assigning the human TNFa level below the detection limit as 80 pg/g of
tissue.
Clinical Cancer Research 1015
weight. Taxotere was dissolved in saline containing 2.5% eth-
anol and 2.5% polysorbate 80 and given iv. To evaluate the
antitumor effect of the cytostatics tested, the cytostatics were
given at doses ranging from #{189}to 1/is of the single LD50, except
for Taxol.
dThdPase Assays. Tumor tissues were homogenized in
10 mM Tris buffer (pH 7.4) containing 15 mtvi NaCl, 1.5 mrsi
MgCl2, and 50 p.M potassium phosphate with a glass homoge-
nizer, whereas tumor cells cultured were sonicated in 10 mrsi
PBS solution (pH 7.4). The homogenate was then centrifuged at
10,000 X g for 20 mmat 4#{176}C,and the supernatants were stored
at - 80#{176}Cuntil use. For the evaluation of Taxol and Taxotere on
WiDr in the time course experiments (see Fig. 3), the homoge-
nate was centrifuged at 105,000 X g for 90 mm. at 4#{176}C.The
supernatants were then dialyzed overnight against 20 nmt po-
tassium phosphate buffer containing I mt�i 3-mercaptoethanol
and stored at - 80#{176}Cuntil use. The protein concentration was
determined by the methods of Lowry et a! (21). The dThdPase
level was measured by ELISA with monoclonal antibodies
specific to human dThdPase as described previously by Nishida
et a!. (5). The monocional antibodies were not cross-reacted
with mouse dThdPase. One unit corresponds to the dThdPase
level of the standard enzyme solution (extracts of human colon
cancer xenograft HCT 116), which phosphorolyzes 5’-dFUrd to
5-FUra at a rate of 1 �i.g of 5-FUra/h (5).
TNFa Assays. The supernatants prepared from cul-
tured cells and tumor tissues were examined for their levels
of TNFes with ELISA method. Human TNFes produced in
tumor cells in human cancer xenografts was measured using
QUATIKINETM ELISA kit (R&D Systems), and mouse
TNFa produced by host cells was measured using a mouse
TNFa ELISA kit (Endogen). These ELISA assays are spe-
cific to only human TNFa and mouse TNFa, respectively.
Statistical Analysis. Tumor volume change and the dif-
ference of carcass body weight were analyzed using the
ANOVA test. The up-regulation of dThdPase was analyzed
using the Student’s t test. Differences were considered signifi-
cant when P was <0.05.
RESULTS
dThdPase Up-Regulation. Table 1 shows dThdPase
levels in tumor tissues, which were measured 8 days after the
test drugs were administered to mice bearing the WiDr human
colon cancer xenograft. Because the dThdPase levels were de-
tected by the ELISA with monoclonal antibodies specific to
human dThdPase, the levels of dThdPase measured corre-
sponded to those of the enzyme produced in the human cancer
cells. Taxol, Taxotere, and MMC greatly enhanced the levels of
dThdPase in the tumors, whereas CPA slightly enhanced the
enzyme level. In contrast, other cytostatics, such as CDDP,
DXR, VCR, VLB, VDS, and MTX, did not enhance dThdPase
levels.
Positive Correlation between dThdPase and Human
TNFa Up-Regulations. To obtain an insight to mechanisms
of the dThdPase elevation by the cytostatics, we compared the
degree of the dThdPase elevation with that of the antitumor
activity of the cytostatics and with that of the human TNFa
elevation in each mouse treated. There appears to be no corre-
lation between the dThdPase up-regulation and the efficacy
(Table 1 and Fig. 1). Only Taxol, Taxotere, and MMC elevated
dThdPase levels at doses showing the antitumor activity. There
was also no correlation between the up-regulation of dThdPase
and that of mouse TNFa, which is produced by host stromal
cells in the tumor tissue. In contrast, the dThdPase and human
TNFa elevation in tumors correlated with each other (Fig. 2).
This positive correlation was also observed in the time course
experiments, in which dThdPase and human TNFa levels were
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Days after Taxol administration Days after Taxotere administration
C�8
0
0.0)
E
C
Fig. 4 Effect of Taxol and Taxotere on human
TNFa of the WiDr human colon cancer tumor innude mice. The method is described in the legendto Fig. 3. Columns, mean human TNFa values;
bars, SD. Human TNFa levels below the detectionlimit were assigned as 80 pg/g of tissue. a: 0, notreatment; �, vehicle; 0, 15 mg/kg Taxol; U, 100mg/kg Taxol. b: D, no treatment; �, vehicle; 0,3.75 mg/kg Taxotere; U, 15 mg/kg laxotere.
1016 Enhancement of Capecitabine Efficacy by Taxanes
(U
II
Fig. 3 Effect of Taxol or Taxotere on dThdPase
up-regulation of the WiDr human colon cancertumor in nude mice. Mice bearing WiDr tumorsare randomized into groups of three mice each,and Taxol or Taxotere was administered iv. Micewere sacrificed and tumor tissues were excised atvarious days after administration. Columns, meandThdPase value; bars, SD. *, significantly differ-
ent from vehicle at each time point; P < 0.05. a:
0, no treatment; �, vehicle; 0, 15 mg/kg Taxol;U, 100 mg/kg Taxol. b: 0, no treatment; �, ye-
hide; 0, 3.75 mg/kg Taxotere; U, 15 mg/kg Taxo-
tere.
measured at several time points after Taxol and Taxotere were
given to mice bearing the WiDr human cancer xenograft (Figs.
3 and 4). Similar time course kinetics of dThdPase elevation was
observed in mice bearing other human cancer xenograft line,
MX-1 breast cancer (data were not shown).
dThdPase and TNFa Levels in Cell Cultures. To in-
vestigate whether Taxol directly up-regulates TNFa and
dThdPase, the WiDr human cancer cells were exposed to Taxol
in vitro for 4 h, and levels of TNFct and dThdPase were
measured after cultures of 3 days. The level of dThdPase in the
cultured WiDr cells was much lower than that observed in the
WiDr cancer xenograft (0.19 versus 2.2 units/mg of protein). In
addition, Taxol at concentrations of 150 nt�i (IC50 in 4 h drug-
exposure and the following 3-day culture) and 1000 nt�i en-
hanced the level of dThdPase by only 2.0- and 2. 1-fold and did
not induce TNFa up to a detectable level. Taxol might indirectly
induce TNFa and dThdPase in the human cancer xenograft
model.
Combination Therapy. The efficacy of fluoropyrimi-
dines in combination with Taxol or Taxotere was compared in
the WiDr human colon cancer xenograft, which is refractory to
fluoropyrimidines, and the MX-! human breast cancer xe-
nograft. Fluoropyrimidines were given at their MTh (WiDr) or
#{189}MTD (MX-1), whereas taxanes were given over a range of #{189}
MTD to MTD. Fig. 5, a and b, shows that the efficacy of Taxol
in combination with either capecitabine or 5’-dFUrd was more
than just additive, and the tumor regressed. In contrast, Taxol
and either 5-FUra or UFT in combination showed only additive
activity (Fig. 5, c and d). On the other hand, toxicity in terms of
weight loss does not appear to be synergistic (Fig. 5). The
additive to synergistic activity was also observed in combination
therapy with Taxotere and capecitabine in the same tumor
model (Fig. 6) and in the MX-1 human breast cancer xenograft
model (Fig. 7). No increase or additive effect in the toxicity was
observed in the combination with the taxanes and capecitabine,
and the degree of the increase was similar to that of the corn-
bination with the taxanes and 5-FUra (Figs. 6 and 7).
DISCUSSION
dThdPase, which converts 5’-dFUrd to 5-FUra, is essential
for the activation of capecitabine and 5 ‘-dFUrd in human cancer
cells (1, 2). The present study showed that several cytostatics,
such as Taxol, Taxotere, MMC, and CPA, elevated this enzyme
level in tumor cells in a human cancer xenograft. In addition,
both Taxol and Taxotere have thus far showed beuer efficacy in
combination therapy with 5’-dFUrd or capecitabine than with
5-FUra or UFF. The major difference between 5’-dFUrd/cape-
citabine and 5-FUra is that the efficacy of the former com-
pounds is greatly modulated by dThdPase. Elevating these en-
zyme levels by gene transfection or by dThdPase up-regulators
made tumor cells more susceptible to 5’-dFUrd (7, 20). Taxol
and Taxotere might enhance the efficacy of 5’-dFUrd and cape-
citabine by up-regulating the dThdPase levels in tumors.
Taxol and Taxotere up-regulated dThdPase levels at doses
inhibiting tumor growth; however, the enzyme up-regulation
does not always appear to correlate with tumor growth inhibi-
tion. CDDP, DXR, VCR, VLB, VDS, and MTX did not enhance
the enzyme level, although some of them inhibited tumor
growth. Levels of mouse TNFa produced in host stromal cells
in tumor tissues were not changed by the cytostatics. They were
elevated without Taxol or Taxotere probably by tumor environ-
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Fig. 5 Antitumor activity of thecombination of Taxol and fluoropy-rimidines on the growth of WiDrcolon cancer xenograft in nudemice. Taxol was administered iv.weekly at the optimal dose (15 mg/kg), and fluoropyrimidines were ad-ministered p.o. or i.p. five times aweek at the MID. Data points,
mean values of tumor volumechange and carcass body weight;
We thank Dr. Y. Tanaka, M. Endo, and N. Inagaki for helpful
discussion.
REFERENCES1. Kono, H., Hara, Y., Sugata, S. Karube, Y., Matsushima, Y., and
Ishitsuka, H. Activation of 5’-deoxy-5-fluorouridine by thymidine phos-
phorylase in human tumor tissues. Chem. Pharm. Bull. (Tokyo), 31:
175-178, 1983.
2. Miwa, M., Ura, M., Nishida, M., Sawada, N., Ishikawa, I., Mon. K.,Shimma, N., Umeda, I., and Ishitsuka, H. Design of a novel oral
fluoropyrimidine carbamate, capecitabine, which generates 5-fluoroura-cil selectively in tumors by enzymes concentrated in human liver and
cancer tissue. Eur. J. Cancer, in press, 1998.
3. Miyadera, K., Sumizawa, I., Haraguchi, M., Yoshida, H., Konstanty,
W., Yamada, Y., and Akiyama, S. Role of thymidine phosphorylaseactivity in the angiogenic effect of platelet-derived endothelial cell
growth factor/thymidine phosphorylase. Cancer Res., 55: 1687-1690,
1995.
4. Fox, S. B., Westwood, M., Moghaddam, A., Comley, M., lurley, H.,
Whitehouse, R. M., Bicknell, R., Gatter, K. C., and Harris, A. L. Theangiogenic factor platelet-derived endothelial cell growth factor/thymi-
dine phosphorylase is up-regulated in breast cancer epithelium and
endothelium. Br. J. Cancer, 73: 275-280, 1996.
5. Nishida, M., Hino, A., Mori, K., Matsumoto, I., Yoshikubo, I., and
Ishitsuka, H. Preparation of anti-human thymidine phosphorylase mono-
clonal antibody useful for detecting the enzyme levels in tumor tissues.
Biol. Pharm. Bull., 19: 1407-1411, 1996.
6. Takebayashi, Y., Akiyama, S., Akiba, S., Yamada, K., Miyadera, K.,Sumizawa, I., Yamada, Y., Murata, F., and Aikou, I. Clinicopathologicand prognostic significance of an angiogenic factor, thymidine phos-phorylase, in human colorectal carcinoma. J. Natl. Cancer Inst., 88:
1110-1117, 1996.
7. Haraguchi, M., Furukawa, I., Sumizawa, I., and Akiyama, S. Sen-sitivity of human KB cells expressing platelet-derived endothelial cell
growth factor to pyrimidine antimetabolites. Cancer Res., 53: 5680-
5682, 1993.
8. Miwa, M., Cook, A., and Ishitsuka, H. Enzymatic cleavage of various
fluorinated pyrimidine nucleosides to 5-fluorouracil and their antipro-liferative activities in human and murine tumor cells. Chem. Pharm.
Bull. (Tokyo), 34: 4225-4232, 1986.
9. Eda, H., Fujimoto, K., Watanabe, S., Ura, M., Hino, A., Tanaka, Y.,Wada, K., and Ishitsuka, H. Cytokines aiduce thymidine phosphorylaseexpression in tumor cells and make them more susceptible to 5 ‘-deoxy-
5-fluorouridine. Cancer Chemother. Pharmacol., 32: 333-338, 1993.
10. Eda, H., Fujimoto, K., Watanabe, S., Ishikawa, I., Ohiwa, I.,
latsuno, K., Tanaka, Y., and Ishitsuka, H. Cytokines induce uridinephosphorylase in mouse colon 26 carcinoma cells and make the cellsmore susceptible to 5’-deoxy-5-fluorouridine. Jpn. J. Cancer Res., 84:
341-347, 1993.
1 1. Tevaerai, H. I., Laurent, P. L., Suardet, L., Eliason, J. F., Give!,
J. C., and Odartchenko, N. Interactions of interferon-a2a with 5 ‘-deoxy-5-fluoroundine in colorectal cancer cells in vitro. Eur. J. Cancer, 28:
368-372, 1992.
12. Schwartz, E. L., Hoffman, M., O’Connor, C. J., and Walder, S.Stimulation of 5-fluorouracil metabolic activation by interferon-a2a in
human colon carcinoma cells. Biochem. Biophys. Res. Commun., 182:
1232-1239, 1992.
13. Tanaka, Y., Endo, M., Ouchi, K., Mori, K., and Ishitsuka, H.Augmentation of antitumor activity of 5 ‘-deoxy-5-fluorouridine byIL-l2 through the up-regulation of pyrimidine nucleoside phosphorylasein munne tumor models. Eur. J. Cancer, 33 (Suppl. 8): Sl76-S177,1997.
Ouchi, K., Yoshikubo, I., and Nishida, M. Capecitabine and the
dThdPase up-regulators IFN-y or laxol showed synergistic activity in
human cancer xenografts. Proc. Am. Assoc. Cancer Res., 37: 2766, 1996.
15. Ding, A. H., Porteu, F., Sanchez, E., and Nathan C. N. Shared
actions of endotoxin and Taxol on INF receptors and TNF release.
Science (Washington DC), 248: 370-372, 1990.
16. Bogdan, C., and Ding, A. Taxol, a microtubule-stabilizing antineo-
plastic agent, induces expression of tumor necrosis factor a and inter-
leukin-l in macrophages. J. Leukocyte Biol., 52: 1 19-121, 1992.
17. Burkhart, C. A., Berman, J. W., Swindell, C. S., and Horwitz, S. B.
Relationship between the structure of Taxol and other taxanes on in-
duction of tumor necrosis factor-a gene expression and cytotoxicity.
Cancer Res., 54: 5779-5782, 1994.
18. Tanaka, Y., Edit, H., Tanaka, I., Udagawa. I., Ishikawa. I., Horii, I.,and Ishitsuka, H. Experimental cancer cachexia induced by transplantablecolon 26 adenocarcinoma in mice. Cancer Res., 50: 2290-2295, 1990.
19. Arasaki, M., Ishitsuka, H., Kuruma, I., Miwa, M., Murasaki, C.,Shimma, N., and Umeda, I. N-Oxycarbonyl substituted 5’-deoxy-5-
fluorocytidines. European Patent Application No. 92121538.0, 1992.
20. Eda, H., Hasegawa, M., Tatsuno, K., Matsumoto, I., Watanabe, S.,Uchida, I., and Ishitsuka, H. Characteristics of human colon cancer
cells transfected with thymidine phosphorylase gene (in Japanese).
J. Jpn. Soc. Cancer Ther., 29: 164, 1994.
21. Lowry, 0. H., Rosebrough, N. J., Farr, A. L., and Randall, R. J.Protein measurement with the Folin phenol reagent. J. Biol. Chem., 193:
265-275, 1951.
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