Pharmacokinetics of N-2-chloroethylaziridine, a volatile cytotoxic metabolite of cyclophosphamide, in the rat

Objectives: The objectives of this study were to characterize pharmacokinetics of N-2-chloroethylaziridine (CEA) in the rat model and assess the in vivo fraction of total clearance of phosphoramide mustard (PM) that furnished CEA to circulation. Methods: The disposition of CEA was investigated following separate intravenous (iv) administrations of PM, synthetic CEA, and their combination to the Sprague-Dawley rats. In addition, in rats receiving prodrug cyclophosphamide (CP), plasma concentrations of CP and its metabolites, 4-hydroxycyclophosphamide (HOCP), PM, and CEA, were simultaneously quantified using GC/MS and stable isotope dilution techniques. Results: Following iv administration of synthetic CEA, concentrations of CEA declined biexponentially with the mean terminal half-life and total body clearance of 47.5 min and 167 ml/min/kg, respectively. Urinary excretion of unchanged CEA was 0.164% of the administered dose. CEA was found to be the major circulating metabolite after iv administration of precursor PM to rats. The fraction of total clearance of PM that furnished CEA to circulation was estimated to be 100%, indicating virtually complete availability of the metabolite to circulation once formed. In rats administered with CP, PM exhibited the highest plasma and urinary concentrations compared to HOCP and CEA. Conclusions: For the first time, CEA was demonstrated to be an important in vivo metabolite of CP in the present study. In light of the poor permeability and in vivo stability of PM, the ultimate DNA alkylator, the findings obtained in this study suggested that CEA may contribute significantly to the overall antitumor activity of prodrug CP.     

Comparative preclinical toxicology and pharmacology of isophosphoramide mustard, the active metabolite of ifosfamide

Background Isophosphoramide mustard (IPM) is the cytotoxic alkylating metabolite of Ifosfamide (IFOS). IPM is being readied for a phase I clinical trial. In the present preclinical study, IPM was evaluated for usage in multidose intravenous (IV) infusion protocols.Methods Mice and dogs received IV IPM daily for 3 days. Single-day dosing—oral and IV—to mice, rats, and monkeys is also reviewed for comparison. Complete toxicology studies were completed in the mice and dogs. For mice, dogs and monkeys, IV pharmacokinetic studies were conducted and compared.Results For mice, the LD₁₀ for the 3-day IV schedule for IPM was calculated to be 119 mg/kg (with 95% confidence limits of 87–134 mg/kg) (combined sexes), and for adult male dogs the maximum tolerated dose (MTD) was 5 mg/kg. Pharmacokinetic studies in mice, dogs and monkeys were compared and projected to human dosing. For dogs that received 10 mg/kg of IPM, T_1/2 was 0.99 h, and clearance was constant (1.01 l/h/kg). IPM was detected from 0 h to 1.5 h after the 5 mg/kg dose and from 0 h to 2 h after the 10 mg/kg dose; none was detected after 2 h. The IV MTD in dogs was 5 mg/kg per day for 3 days. Renal tubular necrosis and bone marrow failure were the causes of death. Transient liver, renal and bone marrow toxicity and gastrointestinal dysfunction were seen at low doses (<5 mg/kg) in dogs. In mice (receiving 100 mg/kg IV) plasma concentrations disappeared in less than 1 h (T_1/2 2 min), with a clearance of 8.44 l/h/kg. For monkeys, the mean T_1/2 was 4.2 h. Median clearance was 1.65 l/h/kg and no IPM was detected 4 h after dosing. No potential IPM metabolites could be detected in any of the studies. In vitro, plasma protein bound 90% of IPM within 5 min of incubation.Conclusions Predictions for human pharmacokinetic parameters and dosing are made from allometric analysis using the above three species. Data predicted an acceptable starting dose of 30 mg/m² with a clearance of 39.5 l/h, and a T_1/2 of 1 h 45 min for a 70-kg patient.     

Urinary stability of carboxycyclophosphamide and carboxyifosfamide, two major metabolites of the anticancer drugs cyclophosphamide and ifosfamide

Phosphorus-31 nuclear magnetic resonance spectroscopy was used to evaluate the stability of carboxycyclophosphamide (CXCP) and carboxyifosfamide (CXIF) in human urine at pH 7.0 and 5.5 at 25°, 8°, −20°, and −80 °C. At 25 °C and pH 7.0, CXCP and CXIF are relatively stable (≈10% degradation in 24 h). In contrast, they are much less stable at pH 5.5 (≈80% degradation of CXIF and ≈50% degradation of CXCP in 24 h). The rate of degradation of CXCP and CXIF was a function of the storage temperature of the urine samples but, even at −80 °C, was not negligible: ≈30% degradation for CXCP irrespective of pH and ≈40% and 50% degradation for CXIF at pH 7.0 and 5.5, respectively, after storage for 6 months. CXCP was more stable than CXIF at either pH (7.0 or 5.5) and at all storage temperatures (8°, −20°, or −80 °C) of the urine samples. CXCP and CXIF were more stable at pH 7.0 than at pH 5.5, although this difference fell with decreasing temperatures to be almost negligible at −80 °C. To ensure a true estimate of CXCP and CXIF levels, urine samples must be frozen and stored at −80 °C within a few hours of micturition. CXCP and CXIF assays should also be carried out within 2 months and 1 month of storage, respectively. Received: 13 July 1996 / Accepted: 20 January 1997     

DNA guanine-guanine crosslinking sequence specificity of isophosphoramide mustard, the alkylating metabolite of the clinical antitumor agent ifosfamide

Purpose: The purpose of this investigation was to determine the base sequence specificity of isophosphoramide mustard (IPM), the alkylating metabolite of ifosfamide, by crosslinking of designed DNA oligomers in comparison with the clinical alkylating agents mechlorethamine (ME) (nitrogen mustard) and phosphoramide mustard (PM), the alkylating metabolite of cyclophosphamide. Methods: IPM, as well as PM and ME were each reacted with three dodecameric duplexes, which were designed to detect interstrand crosslinking between guanines in 5′-GC-3′ (I), 5′-GNC-3′ (II) or 5′-GNNC-3′ (III) sequences (N=A or T). Results: All three agents preferentially react with 5′-GNC-3′ target sequences. The 5′-GNNC-3′ target sequence is less reactive by a factor of approximately 2.5- to 10-fold, while 5′-GC-3′ is of even lower reactivity. Conclusion: These results indicate that all three agents show approximately equal preference for reaction with a 5′-GNC-3′ target sequence in spite of the fact that IPM yields a 7-atom crosslink, while the other two agents yield 5-atom crosslinks. Received: 9 February 1999 / Accepted: 21 June 1999     

In vitro studies of the hyperthermic enhancement of activated ifosfamide (4-hydroperoxy-ifosfamide) and glucose isophosphoramide mustard

Purpose: To study the effect of hyperthermia on the cytotoxicity of glucose isophosphoramide mustard (D-19575), a derivative of ifosfamide, which does not require activation and preclinically demonstrates less nephrotoxicity and myelosuppression than ifosfamide.Methods: In vitro studies (using a crystal violet cell survival assay) of the interaction of hyperthermia with D-19575, as well as the activated form of ifosfamide (4-hydroperoxy-ifosfamide, D-18851), were performed using L929 and OVCAR-3 cell lines held at various temperatures (i.e. 37 °C (control), 40.5 °C, 41.8 °C, 42.5 °C, and 43 °C) for 65 min.Results: The following thermal enhancement ratios (TER) were demonstrated: D-19575 in L929 1.2, 2.0 and 2.3 at 40.5, 41.8 and 42.5 °C, respectively; for D-18851 in L929 1.7 at 41.8 °C; for D-19575 in OVCAR-3 2.1, 3.2 and 3.3 at 40.5, 41.8 and 42.5 °C, respectively; for D-18851 in OVCAR-3 4.6 at 41.8 °C. Conclusion: The significant observed increase in cytotoxicity of D-19575 caused by hyperthermia taken together with its known preclinical toxicity profile, encourage its further preclinical and ultimately clinical testing, including its use with whole body and regional hyperthermia. Received: 9 May 1996 / Accepted: 2 October 1996     

Effect of dose intensity of methotrexate, doxorubicin, and ifosfamide on the prognosis of patients with osteosarcoma

Background. The prognosis of patients with osteosarcoma has improved due to the introduction of systemic chemotherapy. The current study tried to identify the effect of each anti-tumor drug on the prognosis of patients with osteosarcoma. Methods. The records of 29 patients with osteosarcoma who received systemic chemotherapy were retrospectively analyzed. All tumors were classified as stage IIB (Enneking's surgical stage) and were located around the knee joint or more distal areas. The histologic response to preoperative chemotherapy was determined in 20 patients: 9 patients had grade 1, 4 grade 2, 5 grade 3, and 2 grade 4. The mean follow-up period was 102 months. Results. The 5-year overall survival and relapse-free survival (RFS) in the 29 patients was 47.7% and 41.4%, respectively. The 5-year RFS for the 7 good responders (grade 3 and 4) was 85.7%, and that for the 13 poor responders (grade 1 and 2) was 23.1% (P = 0.008). The mean preoperative dose intensity (DI) of methotrexate (MTX) for good responders was significantly higher than that for poor responders (P = 0.028). In 23 patients who received MTX and doxorubicin (ADR) but not ifosfamide (IFOS), the DI of MTX significantly influenced the RFS (P = 0.0128). In the 13 poor responders, 6 of whom received IFOS, the DI of IFOS and ADR significantly influenced RFS (P = 0.0112, 0.0395). Conclusion. The preoperative DI of MTX was related to the histologic response rate. The DI of MTX was significartly associated with the patients' RFS. In poor responders, the DI of IFOS and ADR influenced the patients' RFS. Received: November 17, 1997 / Accepted: July 9, 1998     

Quantitation by gas chromatography-chemical ionization mass spectrometry of cyclophosphamide, phosphoramide mustard, and nornitrogen mustard in the plasma and urine of patients receiving cyclophosphamide therapy

Unambiguous and sensitive methods based on gas chromatography-chemical ionization mass spectrometry have been developed to quantitate cyclophosphamide and two alkylating and cytotoxic metabolites, phosphoramide mustard and nornitrogen mustard. The levels of these materials have been determined in the plasma and urine of five patients receiving cyclophosphamide, 60 or 75 mg/kg i.v. Peak plasma levels of phosphoramide mustard of 50 to 100 nmoles/ml were found at 3 hr after cyclophosphamide administration. Variable levels of nornitrogen mustard were found in the plasma. This product may be arising in part from the decomposition of other metabolites during sample storage and preparation.     

Plasma pharmacokinetics of cyclophosphamide and its cytotoxic metabolites after intravenous versus oral administration in a randomized, crossover trial

Since cyclophosphamide is used by both oral and i.v. routes in the treatment of hematological and solid malignancies, we designed a randomized, crossover clinical trial to evaluate the pharmacokinetics of this anticancer agent after either administration route. Plasma levels of cyclophosphamide and its two cytotoxic metabolites, 4-hydroxycyclophosphamide and phosphoramide mustard, were determined in seven cancer patients randomly assigned to treatment initially with either orally or i.v. administered cyclophosphamide with a 30-day interim between alternate therapy courses. Oral treatment was used initially in five patients and i.v. treatment in two patients, and the pharmacokinetic parameter, area under the plasma disappearance curve, was determined for each metabolite in each patient for both routes of drug administration. Statistical comparison of area under the plasma disappearance curve values for this set of patients indicated no significant differences for either metabolite for oral versus i.v. drug treatment, suggesting equal efficacy for these two routes of cyclophosphamide administration.     

Phase II study of mitomycin,ifosfamide and cisplatin in adenocarcinoma of the oesophagus

 We evaluated the effect of brief neoadjuvant chemotherapy in patients with apparently operable adenocarcinoma of the oesophagus. Two courses of mitomycin (6 mg/m²), ifosfamide (3 g/m²) and cisplatin (50 mg/m²; MIC) were given followed by evaluation of response by barium swallow and computed tomography scan. Of 20 patients, 17 completed both courses and 4 (20%) showed a partial response. Toxicity was generally mild and consisted principally of nausea and vomiting. Altogether, 15 patients were surgically explored; resection was completed in 12 patients, 3 of whom died in hospital (25%). Neoadjuvant therapy with MIC offers no advantage over surgery alone. Received: 14 June 1993/Accepted: 12 July 1995     

High-dose ifosfamide,carboplatin, and etoposide pharmacokinetics: correlation of plasma drug levels with renal toxicity

An autologous bone marrow transplant regimen of ifosfamide, carboplatin, and etoposide (ICE) has been developed as treatment for certain malignancies. At maximum tolerated doses renal insufficiency precludes dose escalation. The objective was to examine whether measurement of plasma drug levels early during treatment would provide warning of renal failure. Nine patients received a 96-h continuous infusion of ifosfamide 16000 mg/m², carboplatin 1600 mg/m², and etoposide 1200 mg/m². Pharmacokinetics, including drug levels and plasma concentration-time curves, of ifosfamide, ultrafiltrable platinum (uPt) and etoposide were analyzed and correlated with renal function. One of the nine patients developed anuric renal failure requiring hemodialysis. By 17 h from the start of infusion, this patient showed substantially higher drug levels of ifosfamide (200 vs mean 217 M) and uPt (19 vs mean 10M) than those patients with preserved renal function. The 95% confidence intervals suggested that a 16–22 h ifosfamide level >153 M and an uPt level >M predict the development of significant renal dysfunction. Although drug levels were substantially higher at 56 h, the serum creatinine did not yet reflect kidney injury. This study suggests that high plasma ifosfamide and uPt levels, analyzed early in the course of a 96-h infusion of high-dose ICE, provide warning of severe and potentially fatal renal injury. Since ICE has substantial activity in a number of malignancies, but significant renal morbidity, real-time pharmacokineticguided dosing may reduce treatment-related toxicity.Supported in part by US. Public Health Service Grants PO1-CA-38493 and CA-06516 and a grant from the Mathers Foundation. Drs. Ayash and Schwartz are recipients of a Career Development Award from the American Cancer Society     

Antitumor activity of the type 1 plasminogen activator inhibitor and cytotoxic conjugate in vitro.

Many cancer cell lines and cancers overexpress receptor bound urokinase plasminogen activator on the cell surface. The urokinase plasminogen activator bound to its receptor remains on the cell surface for a prolonged period of time. When urokinase plasminogen activator/urokinase plasminogen activator receptor complex binds plasminogen activator inhibitor (PAI-1), the inhibitor triggers a series of events leading to internalization of the entire complex. This mechanism makes a very attractive target for localization and internalization of PAI-1-based cytotoxic compounds in cancer treatment. We investigated the antitumor activity of PAI-1/A-chain cholera toxin in vitro. Fibrosarcoma-derived HT1080 cells treated with PAI-1 conjugate showed at least 4 times higher cell killing than the control KD normal fibroblast cell line.     

Toxicity and antitumor activity of the vitamin D analogs PRI-1906 and PRI-1907 in combined treatment with cyclophosphamide in a mouse mammary cancer model

PURPOSE: Active and less toxic vitamin D analogs could be useful for clinical applications. In the present study, we evaluated the toxicity and antitumor effect of two new synthetic analogs of vitamin D, namely PRI-1906 [(24E)-24a-Homo-(1S)-1,25-dihydroxyergocalciferol] and its side-chain unsaturated homo analog PRI-1907. METHODS: The toxicity and calcemic activity, as well as antitumor effect of calcitriol analogs was investigated in vivo. The studies were performed in a mouse mammary 16/C cancer model. Since calcitriol and its analogs inhibited 16/C tumor growth only slightly, we applied them in the combined therapy with cyclophosphamide (CY). Moreover, cell cycle analysis and VDR and p27 expression were investigated. RESULTS: The LD(50 )values after five daily subcutaneous (s.c.) injections were 7.8, 10.0 and 2.4 mug/kg per day for calcitriol, PRI-1906 and PRI-1907, respectively. The serum calcium level increased to 40, 23 and 63% over the control for these compounds. We also compare the antitumor activity of the PRI-1906 with the calcitriol and previously studied PRI-2191 (1,24-dihydroxyvitamin D(3), tacalcitol). Statistically significant inhibition of tumor growth by calcitriol up to the eighth day was observed in all schedules applied. PRI-1906 inhibited the tumor growth at doses 1 and 5 mug/kg per day, and PRI-2191 only at the dose 5 mug/kg per day. CONCLUSION: Addition of vitamin D analogs increased the antitumor effect of CY. PRI-1906 exhibited toxicity higher than PRI-2191 but lower than calcitriol and antitumor activity similar to both PRI-2191 and calcitriol. This new analog seems to be a good candidate for the combined treatment of mammary cancer.     

Intrapleural extravasation of epirubicin, 5-fluouracil, and cyclophosphamide, treated with dexrazoxane

The extravasation of DNA-binding vesicant drugs, such as epirubicin, is a feared complication of chemotherapy and can lead to extensive damage at injury sites. We describe a 56-year-old woman with breast cancer who received adjuvant chemotherapy after a breast-preserving surgical procedure. Due to catheter tip misplacement, epirubicin, 5-fluouracil, and cyclophosphamide were administered intrapleurally. To minimize long-term sequelae, flushing of the cavities and systemic administration of steroids were performed. Besides this treatment, empirically, 3-day therapy with dexrazoxane was added to prevent tissue damage and the risk of cardiac damage. Because of the potential benefits of dexrazoxane and its relatively mild side effects, its use should be considered in cases of the intrapleural extravasation of anthracyclines. We do emphasis the need for stringent surgical and oncological nursing procedures when using central venous access catheters in oncology.     

Effects of paclitaxel,cyclophosphamide, ifosfamide,tamoxifen and cyclosporine on the metabolism of methoxymorpholinodoxorubicin in human liver microsomes

The effects of paclitaxel, cyclosporine, cyclophosphamide, ifosfamide and tamoxifen on the metabolism of methoxymorpholinodoxorubicin (MMDx), a novel anticancer agent, were investigated using human liver microsomes. Paclitaxel, tamoxifen and cyclosporine dramatically inhibited MMDx metabolism, whereas ifosfamide had only a slight effect at high concentrations (200-300 microM) and cyclophosphamide had no effect. The inhibition was dependent on the concentrations of both MMDx and the coincubated drug. Thus, with 1 microM MMDx, paclitaxel (5 microM), tamoxifen (1 microM) and cyclosporine (1 microM) decreased the metabolic rate of MMDx by 36%, 53% and 62%, respectively. At higher concentrations (10, 5 and 5 microM, respectively, with paclitaxel, tamoxifen and cyclosporine) the inhibition was 52%, 91% and 91%, respectively. These three drugs preferentially inhibited the formation of three metabolites (M2, M3 and M6) among eight metabolites produced in liver microsomes. The inhibitory concentrations of paclitaxel, tamoxifen and cyclosporine on MMDx metabolism were in the range of those observed in patients upon administration of these drugs, which are known to be CYP3A4 substrates. These findings suggest that CYP3A4 drug substrates and MMDx in combination must be used with caution, particularly in view of the fact that MMDx is considered as a prodrug whose activation is entirely dependent upon metabolic transformation by CYP3A4.     

Prophylactic alkalization of the urine during cytostatic tumor treatment with the oxazaphosphorine derivatives, cyclophosphamide and ifosfamide]

The so-called cystitis due to cyclophosphamide (Cytoxan) is caused by direct contact of the mucosa with alkylating metabolites in acid urine. These alkylating metabolites can be inactivated by instillation of cysteine into the urinary bladder. The cytostatically active metabolites of ifosfamide (Holoxan), a derivative of oxazaphosphorine, are eliminated by the kidneys as well. Their special toxicity is much higher than the toxicity of Cytoxan. The alkylating metabolites of ifosfamide cause urological complications essentially in supravesical areas (tubulopyelo-ureteritis). Some clinical trials demonstrate that increase of diuresis and alkalinization of urine by orally administered Uralyt-U are able to decrease concentration and aggressiveness of those metabolites.     

DICE方案治疗难治和复发性非霍奇金淋巴瘤的疗效分析

背景与目的:目前对于难治性和复发性非霍奇金淋巴瘤(non-Hodgkin)slymphoma,NHL)尚无标准解救化疗方案,本文旨在探讨DICE方案(地塞米松,异环磷酰胺,顺铂及VP-16)治疗难治和复发性NHL的疗效和不良反应。方法:80例难治和复发性NHL患者,其中T细胞NHL25例,B细胞NHL55例,既往均接受过6个周期的CHOP化疗方案无缓解。现采用DICE方案对患者进行解救治疗,并对毒副反应加以评估、预防及治疗。结果:80例患者接受6个周期DICE方案化疗后,总体有效率为56.3%,完全缓解率为27.5%;T、B细胞NHL有效率分别为48.0%、60.0%,完全缓解率为16.0%、32.7%(P>0.05);经DICE方案治疗的患者出现骨髓抑制、消化系统反应、脱发以及电解质紊乱发生率增高,经过治疗均恢复,无治疗相关死亡。结论:DICE方案治疗难治和复发性NHL有效。     

Efficacy and tolerability of paclitaxel,ifosfamide, and cisplatin as a neoadjuvant chemotherapy in locally advanced cervical carcinoma

Objective

To evaluate the efficacy and tolerability of a neoadjuvant paclitaxel, ifosfamide, and cisplatin chemotherapy in patients with locally advanced cervical carcinoma.

Methods

Patients with histologically confirmed locally advanced cervical carcinoma, aged ≥18 years, were treated with intravenous ifosfamide 5,000 mg/m² and mesna 5,000 mg/m², on day 1; intravenous paclitaxel 175 mg/m² and cisplatin 75 mg/m², on day 2; every 3 weeks for three cycles. Following chemotherapy, operable patients underwent radical hysterectomy and pelvic lymphadenectomy, and, if necessary, adjuvant radiotherapy.

Results

One hundred fifty-two patients with median age 53 years (range, 24 to 79 years), FIGO stage IIB in 126 (89%), were treated with chemotherapy for median 3 cycles (range, 1 to 3). Treatment was delayed or withdrawn in 23 patients (15%). One hundred thirty-nine patients (91%) underwent surgery. Postchemotherapy pathological complete response rate was 18% (25 patients). Postoperative radiotherapy was administered in 100 patients (72%). The 5-year overall survival and progression-free survival were 87.3% (95% confidence interval [CI], 84.5 to 90.3) and 76.4% (95% CI, 73.5 to 79.5), respectively.

Conclusion

Neoadjuvant paclitaxel, ifosfamide, and cisplatin chemotherapy was feasible and effective in the treatment of locally advanced cervical carcinoma patients with older age and more advanced disease stage than reported in previous studies. Hematological and renal toxicity could be carefully prevented.     

Effectiveness of novel combination chemotherapy, consisting of 5-fluorouracil, vincristine, cyclophosphamide and etoposide, in the treatment of low-grade gliomas in children

Low-grade gliomas (LGG), which account for about 30% of brain tumors in children, are usually treated with surgical excision and/or radiotherapy. For patients who have significant residual tumor after resection or relapse after radiation, the proper chemotherapy regimen has not yet been identified. Thirteen children diagnosed with LGG outside the cerebellum between January 1999 and December 2004, all of whom had significant residual tumor after surgical resection, relapsed after radiation or showed visual deterioration, were treated for 18 months with a multi-drug regimen of vincristine, etoposide, cyclophosphamide and 5-fluorouracil. Of the 7 patients who completed chemotherapy, 1 showed complete response (CR), 5 showed partial response (PR), and 1 had stable disease (SD). In 5 patients, chemotherapy was prematurely discontinued; 4 of these patients showed tumor progression and 1 had SD. One patient is still undergoing treatment. The side effects of chemotherapy were manageable. The median time to tumor response was 34 months (range, 2–82 months). The progression free survival was 67.3%. Pediatric LGG patients with residual tumor after surgery or who undergo relapse(s) may be successfully treated using our combination chemotherapy regimen.     

Antitumor effects of the benzophenanthridine alkaloid sanguinarine: Evidence and perspectives

Historically, natural products have represented a significant source of anticancer agents, with plant-derived drugs becoming increasingly explored. In particular, sanguinarine is a benzophenanthridine alkaloid obtained from the root of Sanguinaria canadensis, and from other poppy Fumaria species, with recognized anti-microbial, anti-oxidant and anti-inflammatory properties. Recently, increasing evidence that sanguinarine exibits anticancer potential through its capability of inducing apoptosis and/or antiproliferative effects on tumor cells, has been proved. Moreover, its antitumor seems to be due not only to its pro-apoptotic and inhibitory effects on tumor growth, but also to its antiangiogenic and anti-invasive properties. Although the precise mechanisms underlying the antitumor activity of this compound remain not fully understood, in this review we will focus on the most recent findings about the cellular and molecular pathways affected by sanguinarine, together with the rationale of its potential application in clinic. The complex of data currently available suggest the potential application of sanguinarine as an adjuvant in the therapy of cancer, but further pre-clinical studies are needed before such an antitumor strategy can be effectively translated in the clinical practice.