Pharmacokinetic/pharmacodynamic interactions of intensive cyclophosphamide, cisplatin, and BCNU in patients with breast cancer

Alkylating Agent-Induced NRF2 Blocks Endoplasmic Reticulum Stress-Mediated Apoptosis via Control of Glutathione Pools and Protein Thiol Homeostasis

Alkylating agents are a commonly used cytotoxic class of anticancer drugs. Understanding the mechanisms whereby cells respond to these drugs is key to identify means to improve therapy while reducing toxicity. By integrating genome-wide gene expression profiling, protein analysis, and functional cell validation, we herein demonstrated a direct relationship between NRF2 and Endoplasmic Reticulum (ER) stress pathways in response to alkylating agents, which is coordinated by the availability of glutathione (GSH) pools. GSH is essential for both drug detoxification and protein thiol homeostasis within the ER, thus inhibiting ER stress induction and promoting survival, an effect independent of its antioxidant role. NRF2 accumulation induced by alkylating agents resulted in increased GSH synthesis via GCLC/GCLM enzyme, and interfering with this NRF2 response by either NRF2 knockdown or GCLC/GCLM inhibition with buthionine sulfoximine caused accumulation of damaged proteins within the ER, leading to PERK-dependent apoptosis. Conversely, upregulation of NRF2, through KEAP1 depletion or NRF2-myc overexpression, or increasing GSH levels with N-acetylcysteine or glutathione-ethyl-ester, decreased ER stress and abrogated alkylating agents-induced cell death. Based on these results, we identified a subset of lung and head-and-neck carcinomas with mutations in either KEAP1 or NRF2/NFE2L2 genes that correlate with NRF2 target overexpression and poor survival. In KEAP1-mutant cancer cells, NRF2 knockdown and GSH depletion increased cell sensitivity via ER stress induction in a mechanism specific to alkylating drugs. Overall, we show that the NRF2-GSH influence on ER homeostasis implicates defects in NRF2-GSH or ER stress machineries as affecting alkylating therapy toxicity. Mol Cancer Ther; 15(12); 3000-14. ©2016 AACR.

Prolactin confers resistance against cisplatin in breast cancer cells by activating glutathione-S-transferase

Resistance to chemotherapy is a major obstacle for successful treatment of breast cancer patients. Given that prolactin (PRL) acts as an anti-apoptotic/survival factor in the breast, we postulated that it antagonizes cytotoxicity by chemotherapeutic drugs. Treatment of breast cancer cells with PRL caused variable resistance to taxol, vinblastine, doxorubicin and cisplatin. PRL prevented cisplatin-induced G(2)/M cell cycle arrest and apoptosis. In the presence of PRL, significantly less cisplatin was bound to DNA, as determined by mass spectroscopy, and little DNA damage was seen by gamma-H2AX staining. PRL dramatically increased the activity of glutathione-S-transferase (GST), which sequesters cisplatin in the cytoplasm; this increase was abrogated by Jak and mitogen-activated protein kinase inhibitors. PRL upregulated the expression of the GSTmu, but not the pi, isozyme. A GST inhibitor abrogated antagonism of cisplatin cytotoxicity by PRL. In conclusion, PRL confers resistance against cisplatin by activating a detoxification enzyme, thereby reducing drug entry into the nucleus. These data provide a rational explanation for the ineffectiveness of cisplatin in breast cancer, which is characterized by high expression of both PRL and its receptor. Suppression of PRL production or blockade of its actions should benefit patients undergoing chemotherapy by allowing for lower drug doses and expanded drug options.

CYP2B6: new insights into a historically overlooked cytochrome P450 isozyme

Human CYP2B6 has been thought to account for a minor portion (<1%) of total hepatic cytochrome P450 (CYP) content and to have a minor function in human drug metabolism. Recent studies, however, indicate that the average relative contribution of CYP2B6 to total hepatic CYP content ranges from 2% to 10%. An increased interest in CYP2B6 research has been stimulated by the identification of an ever-increasing substrate list for this enzyme, polymorphic and ethnic variations in expression levels, and evidence for cross-regulation with CYP3A4, UGT1A1 and several hepatic drug transporters by the nuclear receptors pregnane X receptor and constitutive androstane receptor. Moreover, 20- to 250-fold interindividual variation in CYP2B6 expression has been demonstrated, presumably due to transcriptional regulation and polymorphisms. These individual differences may result in variable systemic exposure to drugs metabolized by CYP2B6, including the antineoplastics cyclophosphamide and ifosfamide, the antiretrovirals nevirapine and efavirenz, the anesthetics propofol and ketamine, the synthetic opioid methadone, and the anti-Parkinsonian selegiline. The potential clinical significance of CYP2B6 further enforces the need for a comprehensive review of this xenobiotic metabolizing enzyme. This communication summarizes recent advances in our understanding of this traditionally neglected enzyme and provides an overall picture of CYP2B6 with respect to expression, localization, substrate-specificity, inhibition, regulation, polymorphisms and clinical significance. Emphasis is given to nuclear receptor mediated transcriptional regulation, genetic polymorphisms, and their clinical significance.

Phase II feasibility and pharmacokinetic study of concurrent administration of trastuzumab and high-dose chemotherapy in advanced HER2+ breast cancer

PURPOSE

To evaluate the safety of concurrent treatment with trastuzumab and high-dose chemotherapy (HDC), using cyclophosphamide, cisplatin, and 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), with autologous hematopoietic progenitor cells support, in patients with HER2+ advanced breast cancer.

EXPERIMENTAL DESIGN

Patients with HER2-overexpressing high-risk primary breast cancer (HRPBC; defined as > or =4 involved nodes or inflammatory disease), or metastatic breast cancer (MBC) were eligible. Treatment consisted of a loading dose of trastuzumab at 4 mg/kg (day -5), HDC (days -5 to -2), autologous hematopoietic progenitor cells infusion on day 0, and weekly maintenance trastuzumab (2 mg/kg) from day +1 (minimum of 9 doses). Cardiac monitoring included serial left ventricular ejection fraction measurements before treatment and on days +20 and +65.

RESULTS

Thirty-three patients were prospectively enrolled (13 HRPBC, 20 MBC). Toxicity seemed similar to that expected with this HDC regimen alone. Neutrophils and platelets engrafted promptly. There were no cases of grade 4 or 5 toxicity. One patient experienced symptomatic grade 3 acute cardiac failure on day -4, responsive to treatment. Trastuzumab did not alter the pharmacokinetics of HDC. Eleven of twelve MBC patients with measurable disease (nine of them refractory to previous chemotherapy) experienced an objective response (9 complete and 2 partial responses). At median follow-up of 34 (13-58) months, all HRPBC patients remain alive and free of disease; the MBC group has event-free survival and overall survival rates of 45 and 70%, respectively.

CONCLUSIONS

Incorporation of trastuzumab into HDC (cyclophosphamide, cisplatin, and BCNU) is feasible, with no apparent increased toxicity or pharmacokinetic interactions.

Idiopathic pneumonia syndrome after high-dose chemotherapy and autologous hematopoietic stem cell transplantation for high-risk breast cancer

Our aim was to describe the incidence, clinical course, and risk factors for idiopathic pneumonia syndrome (IPS) after high-dose chemotherapy with cyclophosphamide, carmustine, and thiotepa followed by autologous stem cell transplantation for high-risk breast cancer. Charts for patients who underwent high-dose chemotherapy for high-risk breast cancer at a single center from 1992 to 2000 were retrospectively reviewed, and potential risk factors for development of IPS were sought with the log-rank test. Of 164 patients reviewed, 20 developed IPS at a median onset of 87 days after the transplant (range, 2-257 days). The actuarial incidence of IPS in the first 100 days after the transplant was 8%, and 95% of patients developed symptoms within the first 6 months after transplant. Patient age, smoking status, breast cancer stage at diagnosis, and pretransplant lung function did not predict development of IPS. Three patients died of progressive pulmonary failure and the IPS resolved in the other 17. We concluded that IPS is an important cause of morbidity and mortality in patients with high-risk breast cancer undergoing high-dose chemotherapy. Given the absence of predictive factors, any pulmonary symptoms appearing in the first year after the transplant should be evaluated carefully.

Methodologic guidelines for the design of high-dose chemotherapy regimens

PURPOSE

The objective of this report is to review the research methods that have been used in the design, analysis, and reporting of Phase I dose-escalation studies of high-dose chemotherapy (HDCT) with bone marrow or stem cell support and to propose new guidelines for such studies that incorporate emerging principles of pharmacology, toxicity assessment, statistical design, and long-term follow-up.

METHODS

We performed a search of original, English-language, peer-reviewed full-length reports of HDCT (with or without radiotherapy) and unmanipulated hematopoietic precursor support (autologous bone marrow or stem cells or allogeneic bone marrow) in which one or more drug doses were escalated to identify dose-limiting toxicities needed for the design of subsequent Phase II trials. We reviewed the design, execution, analysis, and reporting of these trials to develop a coherent set of guidelines for the initiation of new HDCT regimens. The primary elements included in our analysis were the technique of dose escalation, the choice and application of toxicity grading scale, and the pharmacologic correlates of dose escalation. We also evaluated the methods employed to define dose-limiting toxicities and to select the maximum tolerated dose and the dose recommended for further study. We then examined whether subsequent Phase II trials based on these definitions corroborated the findings from the prior Phase I studies and summarized the findings from pharmacologic analyses that were reported from a subset of these investigations.

RESULTS

Thirty-five reports met the criteria for our literature review. Two standard methods of dose escalation (fixed increments or modified Fibonacci increments) were described in detail and were employed in the majority (30/35) of the studies. In 5 studies, the details of dose escalation were either not provided or not adequately referenced. There was marked heterogeneity among toxicity grading methods; scales used included the National Cancer Institute Common Toxicity Criteria (or similar scales such as the United States cooperative group or World Health Organization scales) as well as substantially modified versions of those instruments. Wide variations in the methods used to identify dose-limiting toxicities were observed. Statistical considerations, applied to the identification of the maximum tolerated or Phase II recommended dose, were similarly heterogeneous. Phase II trial designs varied from a simple expansion of the Phase I trial to separate, formally conducted studies. Nine Phase I trials featured pharmacologic analyses, and these ranged from simple pharmacokinetic evaluations to more complex analyses of the relationship between drug dose and the molecular targets of drug action.

CONCLUSIONS

Phase I clinical trials in the HDCT setting have been designed, analyzed, and reported using heterogeneous methods that limited their application to Phase II and II investigations. Moreover, correlative pharmacologic analyses have not been routinely undertaken during this critical Phase I stage. We propose guidelines for the design of new Phase I studies of HDCT based on 4 essential elements: (1) rational preclinical and clinical pharmacologic foundation for the regimen and for the agent selected for dose escalation; (2) incorporation of analytical pharmacology in the design and analysis of the regimen under investigation; (3) clear, prospective definitions of the dose- or exposure-limiting toxicities that can be distinguished from modality-dependent toxicities; selection of an appropriate toxicity grading scale, including an assessment of cumulative, delayed, and long-term effects of HDCT, particularly when designing tandem or repetitive cycle regimens; and (4) statistical input into the design, execution, analysis, interpretation, and reporting of these studies.

Oxidative stress and inflammation contribute to lung toxicity after a common breast cancer chemotherapy regimen

Delayed pulmonary toxicity syndrome after high-dose chemotherapy (HDC) and autologous hematopoietic support occurs in up to 64% of women with advanced-stage breast cancer. Using a similar, but nonmyeloablative, HDC treatment regimen in mice, we found both immediate and persistent lung injury, coincident with marked decreases in lung tissue glutathione reductase activity and accompanied by increases in lung oxidized glutathione, bronchoalveolar lavage (BAL) lipid peroxidation, and BAL total cell counts. Most interestingly, at 6 wk, BAL total cell counts had increased fourfold, with lymphocyte cell counts increasing >11-fold. A single supplemental dose of glutathione prevented early lung injury at 48 h but showed no lung-protective effects at 6 wk, whereas single doses of other thiol-sparing agents (Ethyol and glutathione monoethyl ester) showed no benefit. These data suggest that this HDC regimen results in acute and persistent lung toxicity, induced in part by oxidative stress, that culminates with an acute lung cellular inflammatory response. Continuous glutathione supplementation and/or attenuation of the delayed pulmonary inflammatory response may prove beneficial in preventing lung toxicity after the use of these chemotherapeutic agents.

Prognostic model for relapse after high-dose chemotherapy with autologous stem-cell transplantation for stage IV oligometastatic breast cancer

PURPOSE

To study prognostic factors after high-dose chemotherapy (HDC) for patients with stage IV oligometastatic breast cancer.

PATIENTS AND METHODS

Sixty patients with minimal metastatic disease amenable to local therapy enrolled onto a prospective HDC trial were analyzed for potential prognostic factors. Tumor blocks were retrospectively collected from referring institutions.

RESULTS

Median follow-up was 62 months (range, 4 to 120 months). Median relapse-free survival (RFS) and overall survival (OS) times were 52 and 80 months, respectively. Five-year RFS and OS rates were 52% (95% confidence interval [CI], 39% to 64%) and 62% (95% CI, 49% to 74%), respectively. HER-2 expression, number of tumor sites, primary axillary nodal ratio (number of positive nodes divided by number of sampled nodes), number of positive axillary nodes, and delivery or omission of radiotherapy to metastases correlated with RFS. HER-2 overexpression and more than one site were independent adverse risk factors for RFS. HER-2 and the axillary nodal ratio were independent predictors of OS. The following prognostic categories for RFS were established (RFS rate, median RFS): good risk, no factors (77%, 80 months); intermediate risk, one factor (41%, 28 months); and poor risk, both factors (10%, 10 months).

CONCLUSION

Long-term results in patients with oligometastatic breast cancer are encouraging but need validation in prospective randomized studies. HER-2 expression, number of sites, and primary nodal ratio are independent outcome predictors. Confirmation of these observations in this selected population would imply the need for reevaluation of the current tenet that early detection of metastatic breast cancer recurrence is of no benefit.

Delayed pulmonary toxicity syndrome following high-dose chemotherapy and bone marrow transplantation for breast cancer

We have intensely followed 45 consecutive women who underwent high-dose chemotherapy (cyclophosphamide/cisplatin/BCNU) and autologous bone marrow transplant (HDC/ABMT) for primary breast cancer with pulmonary function testing and computed tomography at regular intervals up to 126 wk (median follow-up, 72 wk). Our results show a high incidence of interstitial pneumonitis requiring steroids (64%), but no deaths due to pulmonary toxicity. The DL(CO) reaches a nadir of 58.2 +/- SEM 3.4 (expressed as a percent of baseline value) 15-18 wk following HDC/ABMT, and marginally improves with time. To a much lesser extent, vital capacity is reduced with a parallel drop in FEV1, suggesting mild restrictive changes without significant obstruction. Patients who develop pulmonary symptoms of cough or dyspnea have a corresponding significantly greater and earlier decline in DL(CO). Chest computed tomography was neither sensitive nor specific for diagnosing pulmonary toxicity. For patients who received steroids for pulmonary toxicity, there was a subsequent improvement in DL(CO) of 17.1% (p = 0.0001). Because our patients do not fit with the recent definition of idiopathic pulmonary syndrome (IPS), we propose the term delayed pulmonary toxicity syndrome (DPTS) to better describe the milder form of lung toxicity seen in our patient population. We were unable to correlate the severity of DPTS with age, tobacco use, baseline pulmonary function, or systemic exposure to BCNU, cyclophosphamide, or cisplatin. These data suggest that factor(s) other than, or in addition to, chemotherapy systemic exposure can contribute to DPTS. Furthermore, early identification and institution of systemic corticosteroids may improve lung function.

Cyclophosphamide, cisplatin, and carmustine: pharmacokinetics of carmustine following multiple alkylating-agent interactions

Cyclophosphamide, cisplatin, and carmustine (CPA/cDDP/BCNU) constitute a combination alkylating-agent regimen commonly used with autologous marrow support. Its therapeutic effectiveness is accompanied by sporadic life-threatening and fatal toxicities, the most common of which is acute lung injury. We have previously shown that variation in the BCNU AUC can be correlated to the risk of pulmonary injury in patients receiving CPA/cDDP/BCNU. In an attempt to understand further the role of interpatient variation in drug pharmacokinetics (PK) with respect to pharmacodynamic outcomes, we evaluated the effect of pretreatment with CPA, cDDP, or both on BCNU PK in male Sprague-Dawley rats. The drug-administration pattern was designed to mimic that of the CPA/cDDP/BCNU regimen in patients. Each pretreatment increased both the absolute value of and the variation in BCNU AUC relative to the control values. These findings are consistent with an important rate-limiting elimination pathway for BCNU in rats and may explain the wide interpatient variability of BCNU AUC and the sporadic pulmonary toxicity seen in patients receiving CPA/cDDP/BCNU.