Cytogenetic Effects of CPT-11 and Its Active Metabolite, SN-38 on Human Lymphocytes

CPT-11, a new camptothecin analogue, has been demonstrated tobe a promising antineoplastic agent. Late side effects of carcinogenicityand teratogenicity have been unclear from clinical phase I andII trials. In order to elucidate the carcinogenicity and teratogenicityof CPT-11, we have examined the cytogenetic changes in humanperipheral blood lymphocytes induced by CPT-11 and its activemetabolite, SM-38. We have also analyzed the correlation betweenchromosomal damage and acute clinical side effects. When peripheralblood lymphocytes obtained from a healthy donor were exposedto CPT-11, SN-38, cisplatin and mitomycin C, a significant dose-dependentincrease of sister chromatid exchange (SCE) was obtained. TheSCE frequency per cell cultured with 0.244 nM SN-38 was similarto that cultured with 100 nM CPT-11, 300-500 times the concentrationof SN-38. A transient increase in SCE frequency was also observedin the peripheral blood lymphocytes of 11 cancer patients receiving100mg/m² of CPT-11 intravenously, compared with pretreatmentvalues (P= 0.0001). In addition, a significant correlation wasobserved between the frequency of SCE on day 3 and the degreeof decrease in platelet count (P= 0.012). In conclusion, SN-38might possibly have a high risk of mutagenicity and carcinogenicity;and measurement of SCE values in peripheral blood lymphocytesappears to have a potential application in the clinical predictionof chemotherapy-induced side effects.     

A Pharmacokinetic and Pharmacodynamic Analysis of CPT-11 and Its Active Metabolite SN-38

In the present study, an attempt was made to determine the precise pharmacokinetics of 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (CPT-11) and its active metabolite, 7-ethyl-10-hydroxycamptothecin (SN-38). The relationship between pharmacokinetic parameters and pharmacodynamic effects was also investigated to elucidate the cause of interpatient variation in side effects. Thirty-six patients entered the study. CPT-11, 100 mg/m², was administered by IV infusion over 90 min weekly for four consecutive weeks. The major dose-limiting toxicities were leukopenia and diarrhea. There was a positive correlation between the area under the concentration-time curve (AUC) of CPT-11 and percent decrease of WBC ( r =0.559). On the other hand, episodes of diarrhea had a better correlation with the AUC of SN-38 ( r =0.606) than that of CPT-11 ( r =0.408). Multivariate analysis revealed that the AUC of SN-38, AUC of CPT-11 and indocyanine green retention test were significant variables for the incidence of diarrhea and that both performance status and AUC of CPT-11 were significant variables for percent decrease of WBC. The large interpatient variability of the degree of leukopenia and diarrhea is due to a great plasma pharmacokinetic variation in CPT-11 or SN-38. The AUCs of CPT-11 and SN-38 obtained from the first administration of CPT-11 correlate with toxicities, but it is impossible to predict severe side effects before the administration of CPT-11 at the present time.     

Pharmacological Correlation between Total Drug Concentration and Lactones of CPT-11 and SN-38 in Patients Treated with CPT-11

The pharmacokinetics of 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (CPT-11) and its active metabolite, 7-ethyl-10-hydroxycamptothecin (SN-38), were examined to establish the pharmacokinetic variability of the active lactones of CPT-11 and SN-38 in comparison with that of the total (lactone and carboxylates) plasma CPT-11 and SN-38. Twelve patients with malignancies were entered in the study. All received 100 mg/m² of CPT-11 by intravenous drip infusion over 90 min. Blood was sampled at 10 time points in heparin-containing syringes. Analysis by high-performance liquid chromatography showed that the ratio of CPT-11 lactone to total CPT-11 concentration was highest (66%) just after the end of infusion and gradually decreased to 30% at 24 h. Almost 70% of SN-38 lactone was detected after the end of infusion and this decreased to 50% within 24 h. The standard errors of percent lactone of CPT-11 or SN-38 to total drug concentration at each sampling point were less than 12%. The area under the concentration-time curve (AUC) of total CPT-11 and that of total SN-38 were significantly correlated with the AUCs of the lactone CPT-11 and those of lactone SN-38, respectively. We conclude that, for practical purposes, monitoring of total CPT-11 and SN-38 has essentially the same clinical significance as monitoring of lactone CPT-11 and SN-38.     

Effective Irinotecan (CPT-11)-containing Liposomes: Intraliposomal Conversion to the Active Metabolite SN-38

Irinotecan hydrochloride (CPT-11) is a prodrug of SN-38, which is an active metabolite with anti-tumor activity and side toxicity. The activities of CPT-11 and SN-38 depend on the closed lactone ring form of SN-38. We have examined the tissue distributions of the closed and open forms of CPT-11 and SN-38 in Lewis lung carcinoma-bearing mice after the administration of liposomal CPT-11 (S-Lip) and polyethyleneglycol (PEG)-modified S-Lip (S-PEG). The plasma concentrations of closed CPT-11 and SN-38 were increased by liposomalization, and their blood circulation was prolonged by the PEG modification. The concentrations of closed CPT-11 and SN-38 in tumors were elevated by both the liposomalization and PEG modification. The closed/total ratio of SN-38 in the tumors of the S-PEG group was greater than that of the CPT-11 solution (Sol) group. Thus, SN-38 was thought to be generated in intact liposomes containing CPT-11. The bile concentration of closed SN-38, which is responsible for CPT-11-induced intestinal disorder, was decreased by liposomalization. In an in vitro experiment, the SN-38/CPT-11 ratio in the tumor cells of the S-Lip group was found to be higher than that of the Sol group, and the ratio of the closed form of SN-38 was increased by the liposomalization. Laser scanning confocal microscopy showed the generation of SN-38 in the liposomal membrane after the incubation of S-Lip with carboxylesterase. It is therefore considered that a part of CPT-11 is converted to SN-38 in the intact liposomes.     

A Limited Sampling Model for Estimating Pharmacokinetics of CPT-11 and Its Metabolite SN-38

The objective of this study was to develop a limited sampling model (LSM) to estimate the area under the curve (AUC) of 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (CPT-11) and that of 7-ethyl-10-hydroxycamptothecin (SN-38) as predictive pharmacokinetic variables for leukopenia and episodes of diarrhea induced by CPT-11 administration. The model was developed with a training set consisting of pharmacokinetic studies in 36 patients who received a 90-min i.v. infusion of CPT-11 at a dose of 100 mg/m². A multiple regression analysis of CPT-11 or SN-38 concentrations observed at each time point in the training set was used to predict the AUC of CPT-11 or SN-38. The final sampling models using only two time points were:
AUC_CPT-11=3.7891★C2.5+14.0479*C13.5+1.5463
AUC_SN-38=0.5319★C2.5+19.1468*C13.5+72.7349
where C2.5 and C13.5 are the plasma concentration of CPT-11 (μg/ml) or SN-38 (ng/ml) at 2.5 and 13.5 h after the initiation of CPT-11 infusion, respectively. The models were validated prospectively on a separate test data set of 12 patients receiving the same dose of CPT-11 investigated in a previous study. Validation of the final LSM on the test data set gave values of root mean square error (RMSE) of 12.72% and 5.97% for the AUC of CPT-11 and that of SN-38, respectively. The model can be used to monitor the AUCs of both CPT-11 and SN-38 for the early prediction of toxicities and to establish a pharmacokinetically based dose modification strategy for safe administration of CPT-11.     

Inhibition of intestinal microflora β-glucuronidase modifies the distribution of the active metabolite of the antitumor agent, irinotecan hydrochloride (CPT-11) in rats

Purpose: SN-38, a metabolite of irinotecan hydrochloride (CPT-11), is considered to play a key role in the development of diarrhea as well as in the antitumor activity of CPT-11. We have previously found that the inhibition of β-glucuronidase, which hydrolyzes detoxified SN-38 (SN-38 glucuronide) to reform SN-38, in the lumen by eliminating the intestinal microflora with antibiotics, markedly ameliorates the intestinal toxicity of CPT-11 in rats. In this study we compared the disposition of CPT-11 and its metabolites in rats treated with and without antibiotics. Methods: Rats were given drinking water containing 1 mg/ml penicillin and 2 mg/ml streptomycin from 5 days before the administration of CPT-11 (60 mg/kg i.v.) and throughout the experiment. CPT-11, SN-38 glucuronide and SN-38 concentrations in the blood, intestinal tissues and intestinal luminal contents were determined by HPLC. Results: Antibiotics had little or no effect on the pharmacokinetics of CPT-11, SN-38 glucuronide or SN-38 in the blood, or in the tissues or contents of the small intestine, which has less β-glucuronidase activity in its luminal contents. In contrast, antibiotics markedly reduced the AUC_1–24 h of SN-38 (by about 85%) in the large intestine tissue without changing that of CPT-11, and this was accompanied by a complete inhibition of the deconjugation of SN-38 glucuronide in the luminal contents. Conclusions: These results suggest that SN-38, which results from the hydrolysis of SN-38 glucuronide by β-glucuronidase in the intestinal microflora, contributes considerably to the distribution of SN-38 in the large intestine tissue, and that inhibition of the β-glucuronidase activity by antibiotics results in decreased accumulation of SN-38 in the large intestine. Received: 8 August 1997 / Accepted: 16 January 1998     

Synergistic Enhancement of Cisplatin Cytotoxicity by SN-38, an Active Metabolite of CPT-11, for Cisplatin-resistant HeLa Cells

A cisplatin ( cis -diamininedichloroplatinuin(II); CDDP)-resistant HeLa cell line (HeLa/CDDP cells), which showed more than 8-fold resistance to CDDF compared to the parent cells, was newly established for this study. HeLa/CDDP cells accumulated 50% less platinum than the parent cells. There was no difference in intracellular glutathione (GSH) content between the parent and HeLa/ CDDP cells. The dose modification factor by DL-buthionine-S, R-sulfoximine (BSO) pretreatment was similar in both cell lines. HeLa/CDDP cells had cross-resistance to diammine (l, l-cyclobutanedicarboxylato)platinum(II) (CBDCA), ( cis -diammine (glycolato)platinum (254-S), but not to (-)-(R)-2-aminomethylpyrrolidine(1,1-cyclobutanedicarboxylato)platinum(II) (DWA2114R), adriamycin, or VP-16. HeLa/CDDP cells showed a collateral sensitivity to 7-ethyl-10-hydroxycampto-thecin (SN-38), an active metabolite of 7-ethyl-10-[4-(l-piperidino)-l-piperidino]carbonyloxycamptothecin (CPT-11). Furthermore, isobologram analysis indicated synergistic interaction of CDDP and SN-38 only for HeLa/CDDP cells. The present study suggests that combination therapy with CDDP and CPT-11 may he potentially useful in the treatment of some patients with CDDP-resistant cancer.     

Induction of apoptosis in multi-drug resistant (MDR) human glioblastoma cells by SN-38, a metabolite of the camptothecin derivative CPT-11

 The overexpression of the multidrug resistance (mdr1) gene and its product, P-glycoprotein (P-gp), is thought to limit the successful chemotherapy of human tumors. Recent studies demonstrate that SN-38, a metabolite of the camptothecin (CPT) derivative CPT-11, has antitumor effects on several tumors, but the mechanisms responsible for its cytotoxicity remain unclear. We therefore determined whether SN-38 has cytotoxic effects on MDR human glioblastoma GB-1 cells and non-MDR human glioblastoma U87-MG cells. Furthermore, we determined what role SN-38 plays in the induction of cytotoxicity in these tumor cells. In this study, we demonstrated that SN-38 had significantly stronger antitumor effects on GB-1 and U-87MG cells than did CPT (P<0.01 and P<0.05, respectively). In addition, findings obtained using a DNA fragmentation assay, Hoechst 33258 staining, in situ end-labeling and cell cycle analysis demonstrated that SN-38 induced apoptosis in these tumors. Our results suggest that SN-38 has a stronger antitumor effect on malignant glioma cells regardless of MDR expression than does CPT, and therefore can be considered a new chemotherapeutic agent potentially effective in the treatment of human primary or recurrent malignant gliomas resistant to chemotherapy. Received: 6 October 1995/Accepted 29 June 1996     

Pharmacokinetic study of CPT-11, SN-38 and SN-38 glucuronide in the ascites,plasma and bile after intraperitoneal administration of CPT-11

We studied the pharmacokinetics of CPT-11 with intraperitoneal administration in a patient with a PTCD tube. The patient had advanced gastric cancer with peritoneal metastasis. CPT-11 was administrated in a dose of 40 mg and the intraperitoneal, plasma and bile levels of CPT-11, SN-38 and SN-38 glucuronide (SN-38 GLU) were measured periodically. The results showed that the periodical concentration pattern of CPT-11, SN-38 and SN-38 GLU in the bile was closely related to that of CPT-11 in the abdominal cavity.     

In vitro schedule-dependent interaction between paclitaxel and SN-38 (the active metabolite of irinotecan) in human carcinoma cell lines

Paclitaxel and irinotecan are important new anticancer agents. The combination of these two agents has been considered for use against a variety of advanced solid tumors. Since the schedule-dependent effects of this combination may be crucial to its use, we studied the interaction of paclitaxel and SN-38 (the active metabolite of irinotecan) in various schedules in four human cancer cell lines in culture. Cell growth inhibition after 5 days was determined using an MTT assay. The effects of drug combinations at the IC₈₀ level were analyzed by the isobologram method. Simultaneous exposure to paclitaxel and SN-38 for 24 h produced antagonistic (subadditive and protective) effects in the human lung cancer cell line A549, the breast cancer cell line MCF7, and the colon cancer cell line WiDr, and produced additive effects in the ovarian cancer cell line PA1. Sequential exposure to paclitaxel for 24 h followed by SN-38 for 24 h, and the reverse sequence, produced additive effects in all four cell lines. These findings suggest that sequential administration, not simultaneous administration, may be the appropriate schedule for the therapeutic combination of paclitaxel and irinotecan. Continued preclinical and clinical studies should provide further insights and assist in determining the optimal schedule for this combination in clinical use. Received: 25 February 1997 / Accepted: 6 November 1997     

Modulation of glucuronidation of SN-38, the active metabolite of irinotecan, by valproic acid and phenobarbital

 Purpose: Irinotecan (CPT-11) is hydrolyzed to its active metabolite SN-38 which is subsequently conjugated by uridine diphosphate glucuronosyl transferase (UDP-GT) to the glucuronide (SN-38G). Both preclinical and clinical data indicate that conjugation is a primary clearance mechanism for SN-38 with the plasma glucuronide levels being substantially higher than those of SN-38. This investigation was designed to determine the possibility of modulation of glucuronidation of SN-38 and its effect on the disposition of the parent drug and metabolites. Methods: Female Wistar rats were pretreated with 200 mg/kg valproic acid (VPA), an inhibitor of glucuronidation, 5 min prior to the administration of 20 mg/kg irinotecan. The control rats were given 20 mg/kg irinotecan only. To study the effect of inducers of UDP-GT activity, rats were pre- treated with phenobarbital (PB) before irinotecan administration. Results: Pretreatment with VPA caused a 99% inhibition in the formation of SN-38G leading to a 270% increase in the area under plasma concentration-time curve (AUC) of SN-38 compared with the control rats. The irinotecan estimations were unchanged in the two groups. PB pretreatment caused a 1.7-fold increase in the AUC of SN-38G and a concomitant 31% and 59% reduction in the AUCs of SN-38 and irinotecan, respectively. Conclusions: The most plausible explanation for the alterations in SN-38G disposition is inhibition of SN-38 conjugation by VPA and induction of the conjugation by PB. Received: 5 February 1996 / Accepted: 30 July 1996     

Combined effects of SN-38 and pentoxifylline on the induction of apoptosis through the activation of CPP-32 in pancreatic adenocarcinoma cell lines

Background. Pentoxifylline (PENT) is a theophylline derivative that enhances cytotoxic effects against tumor cells pretreated with antitumor agents. It has also been reported that chemotherapy can induce apoptosis in some carcinoma cells. We investigated the effects of PENT on human pancreatic adenocarcinoma cells pretreated with SN-38, an active form of CPT-11 (a camptothecin analogue) and we also examined the participation of CPP-32, a member of the interleukin 1β-converting enzyme (ICE) family proteases, in chemotherapeutic agent-induced apoptosis. Methods. Human pancreatic adenocarcinoma cells (PK-1, PK-8) were cultured in RPMI 1640. Lethal effects were examined by MTT assay; DNA fragmentation was analyzed by agarose gel electrophoresis; and Western blot analysis was performed with anti-CPP-32 monoclonal antibody. Results. Pretreatment with SN-38 followed by PENT increased the cytotoxic effect compared with that seen for treatment with SN-38 alone. Isobologram analysis of the IC₅₀ value revealed that PENT had supra-additive effects when administed after SN-38, but not when administered prior to or simultaneously with SN-38. Agarose gel electrophoresis showed typical DNA ladders in the DNA of cells treated with SN-38 and PENT. The acridine orange (AO) staining method was used to observe the morphological changes characteristic of apoptosis. Western blot analysis verified that activation of CPP-32 accompanied the development of apoptosis. In addition, SN-38-induced apoptosis was prevented by pretreatment with Ac-DEVD-CHO (DEVD), an inhibitor of CPP-32. Conclusions. These results indicate that the antitumor activity of SN-38 is attributable to apoptosis through the activation of CPP-32, and that combined treatment with PENT enhances the induction of apoptosis by SN-38. Accordingly, the use of PENT may provide a combined modality treatment for pancreatic cancer. Received: August 15, 1997 / Accepted: November 27, 1998     

Plasma and cerebrospinal fluid pharmacokinetics of 9-aminocamptothecin (9-AC), irinotecan (CPT-11), and SN-38 in nonhuman primates

Purpose: The plasma and cerebrospinal fluid (CSF) pharmacokinetics of the camptothecin analogs, 9-aminocamptothecin (9-AC) and irinotecan, were studied in a nonhuman primate model to determine their CSF penetration. Methods: 9-AC, 0.2 mg/kg (4 mg/m²) or 0.5 mg/kg (10 mg/m²), was infused intravenously over 15 min and irinotecan, 4.8 mg/kg (96 mg/m²) or 11.6 mg/kg (225 mg/m²), was infused over 30 min. Plasma and CSF samples were obtained at frequent intervals over 24 h. Lactone and total drug forms of 9-AC, irinotecan, and the active metabolite of irinotecan, SN-38, were quantified by reverse-phase HPLC. Results: 9-AC lactone had a clearance (CL) of 2.1 ± 0.9 l/kg per h, a volume of distribution at steady state (Vd_ss) of 1.6 ± 0.7 l/kg and a half-life (t_1/2) of 3.2 ± 0.8 h. The lactone form of 9-AC accounted for 26 ± 7% of the total drug in plasma. The CSF penetration of 9-AC lactone was limited. CSF 9-AC lactone concentration peaked 30 to 45 min after the dose at 11 to 21 nM (0.5 mg/kg dose), and the ratio of the areas under the CSF and plasma concentration-time curves (AUC^CSF: AUC^P) was only 3.5 ± 2.1%. For irinotecan, the CL was 3.4 ± 0.4 l/kg per h, the Vd_ss was 7.1 ± 1.3 l/kg, and the t_1/2 was 4.9 ± 2.2 h. Plasma AUCs of the lactone form of SN-38 were only 2.0% to 2.4% of the AUCs of irinotecan lactone. The lactone form of irinotecan accounted for 26 ± 5% of the total drug in plasma, and the lactone form of SN-38 accounted for 55 ± 6% of the total SN-38 in plasma. The AUC^CSF: AUC^P ratio for irinotecan lactone was 14 ± 3%. SN-38 lactone and carboxylate could not be measured (<1.0 nM ) in CSF. The AUC^CSF: AUC^P ratio for SN-38 lactone was estimated to be ≤ 8%. Conclusion: Despite their structural similarity, the CSF penetration of 9-AC and SN-38 is substantially less than that of topotecan which we previously found to have an AUC^CSF: AUC^P ratio of 32%. Received: 15 July 1997 / Accepted: 8 October 1997     

A pilot study on the safety of combining chrysin, a non-absorbable inducer of UGT1A1, and irinotecan (CPT-11) to treat metastatic colorectal cancer

Purpose: Recently, it was shown that chrysin causes upregulation of UGT1A1 in Caco-2 intestinal cells. Therefore, we proposed that oral chrysin may reduce irinotecan (CPT-11) induced diarrhoea by shifting the SN-38G/SN-38 equilibrium towards the inactive SN-38G in the gastrointestinal mucosa. The purpose of this study was to examine the safety of combining single agent CPT-11 with chrysin. Patients and methods: Twenty patients with previously treated advanced colorectal cancer were administered chrysin twice daily for 1 week preceding and succeeding treatment with single agent CPT-11 (350 mg/m² over 90 min every 3 weeks). Loperamide usage and bowel frequency/consistency were recorded by patients into a study diary and blood samples were collected for CPT-11 pharmacokinetic analysis. Results: There were no observable toxicities that could be attributed to chrysin use. The grades and frequency of delayed diarrhoea were mild, with only 10% of patients experiencing grade 3 toxicity. Loperamide usage was also modest with a median of 1–5 tablets per cycle (range: 0–22). Pharmacokinetic results revealed a mass ratio of plasma SN-38G/SN-38, which was very similar to historical controls (7.15±5.67, n=18). Conclusions: These findings, combined with the observation of clinical activity and grade 3/4 neutropenia in 25% of patients, suggest that combining chrysin with CPT-11 may be a safe and potentially useful means of preventing diarrhoea, although this needs to be further investigated in the setting of a randomised trial.     

hPF4 mRNA表达、血浆PF4水平与甲状腺乳头状癌颈部淋巴结转移的关系

 目的 探讨hPF4 mRNA表达、血浆PF4水平与甲状腺乳头状癌（PTC）颈部淋巴结转移的关系。 方法 应用逆转录多聚酶链反应（RT-PCR）技术检测40例PTC癌组织和10例癌旁正常组织hPF4mRNA的表达,并用酶标记免疫分析法（ELISA）测定40例PTC患者、20例健康体检者（对照组）的血浆PF4水平。 结果 （1）PTC癌组织hPF4mRNA阳性表达率分别为47.5%,明显低于正常组织（80％）（P<0.01）,而且hPF4mRNA阳性表达 PTC组的颈部淋巴结转移率均明显低于hPF4阴性表达PTC组（36.84％ vs. 90.48％,P<0.01）。（2）正常对照组、无淋巴结转移的PTC组和伴淋 巴结转移的PTC组间的PF4血浆浓度呈线性递减趋势,其中无淋巴结转移组的PF4血浆浓度［（2.96±0.21)ng/ml］高于转移组［（0.98±0.17)ng/ml］ （P<0.05）。（3）hPF4mRNA阳性表达PTC组的血浆PF4水平明显高于hPF4阴性表达组［（2.49±0.83）ng/ml vs. 0.94±0.13）ng/ml］ （P<0.01）。 结论 PTC患者血浆及局部癌灶PF4水平的下调可能是导致或助推PTC发生颈部淋巴结癌转移的成因之一。     

Preclinical Changes in Immunoreactivity and Cellular Architecture during the Progressive Development of Intracranial Neoplasms and an Immunotherapeutic Schedule with a Novel Biological Response Modifier,the T11TS / S-

Among neoplasms, brain tumors are particularly “ difficult to treat” because of the partial immune privileged ‍status of the brain and the presence of the blood brain barrier (Selmaj, 1996). Many details of progressive development ‍of brain tumors remain unexplored and elucidation of consequent changes of the immune system with correlated ‍cellular architecture and cell kinetics were the major objectives of the present course of investigations. Our studies ‍have indicated that the primary resistance by the immune system to a growing tumor declines after a certain point, ‍resulting in an immune suppressed state in a tumor bearing individual. The poor prognosis of malignant brain ‍tumors with classical treatments like surgery, radiotherapy and chemotherapy has led to interest in immunotherapeutic ‍protocols. In the present study, an attempt was made to determine the immunomodulatory and antitumor properties ‍of a transmembrane glycopeptide of sheep red blood cells (SRBCs), known as S-LFA3 or T11TS. Young Druckray ‍rat of both sexes aged 3-5 days were injected with N’-N’-ethyl nitrosourea (ENU) (i.p) to induce brain tumors and at ‍2,4,6,8 and 10 months of age were sacrificed for study of survival, tumor growth kinetics and immunological parameters ‍like lymphocyte rosette formation, denoting CD2 – CD58 interactions and phagocytosis by peripheral macrophages ‍and PMN hint at the changes during tumore development. In order to determine the immunomodulatory role of ‍T11TS, 7 month old ENU induced animals and controls were injected with the compound (1 ml., i.p). The data ‍obtained indicate that administration of T11TS results in increased survival of rats along with a decrease in growth ‍kinetics of tumor cells to the normal level when compared to ENU induced animals of the same age. Pointers to ‍mechanisms involving immunological investigations at the cellular level in these animals indicated improved ‍lymphocyte function in terms of E-rosetting, augmented cytotoxicity and enhanced PMN and macrophage function ‍in terms of phagocytosis. Finally histological examination showed complete reversal from the hyperplastic state to ‍normal cellular homeostasis, indicating antitumor efficacy of T11TS, correlating very well with the data from survival ‍and cell kinetic studies.