Impact of delayed lymphoscintigraphy for sentinel lymphnode biopsy for breast cancer.

BACKGROUND: Despite universal adoption of sentinel lymph node biopsy (SLNB) for breast cancer, there remains no standardized protocol for preoperative lymphoscintographic assessment of sentinel nodes. Both immediate and delayed lymphoscintigraphy are currently utilized, although it is unclear how delayed imaging impacts SLN identification. METHODS: Among patients diagnosed with breast cancer who underwent SLNB at Duke from 2011 to 2012, two protocols for preoperative lymphoscintigraphy were used: protocol A included both immediate and delayed lymphoscintigraphy (n = 152), while protocol B involved immediate lymphoscintigraphy only (n = 103). RESULTS: The overall intraoperative SLN identification rate was 98.4% and did not differ between groups. A lower number of SLN were visualized on the immediate scan using protocol A compared to protocol B (P < 0.001). Although a greater total number of nodes was excised using protocol A, this result was not statistically significant (P = 0.08). Moreover, there was no significant difference in the number of negative SLN between groups (P = 0.51). CONCLUSIONS: We found no significant impact on identification rate or number of SLN excised with the use of delayed versus immediate imaging. These findings support abandoning delayed lymphoscintographic imaging, except in those cases where aberrant drainage is suspected.

Leukotriene C4 induces migration of human monocyte-derived dendritic cells without loss of immunostimulatory function.

Generation of human monocyte-derived dendritic cells (DCs) for cancer vaccination involves ex vivo maturation in the presence of proinflammatory cytokines and prostaglandin E(2) (PGE(2)). Although the inclusion of PGE(2) during maturation is imperative for the induction of DC migration, PGE(2) has unfavorable effects on the immunostimulatory capacity of these cells. Like PGE(2), leukotrienes (LTs) are potent mediators of DC migration. We therefore sought to characterize the migratory and immunologic properties of DCs that matured in the presence of LTB(4), LTC(4), LTD(4), and PGE(2). Here, we demonstrate that DCs matured in the presence of LTC(4), but not LTB(4) or LTD(4), are superior to PGE(2)-matured DCs in stimulating CD4(+) T-cell responses and in inducing antigen-specific cytotoxic T lymphocytes (CTLs) in vitro without concomitant induction or recruitment of regulatory T cells (Tregs). LTC(4)-matured DCs migrate efficiently through layers of extracellular matrix and secrete higher levels of immunostimulatory IL-12p70 while producing reduced levels of immune-inhibitory IL-10, IL12p40, indoleamine-2,3-dioxidase, and TIMP-1 (tissue inhibitor of matrix metalloproteinases). Intracellular calcium mobilization and receptor antagonist studies reveal that, in contrast to LTD(4), LTC(4) did not signal through CysLTR(1) in DCs. Collectively, our data suggest that LTC(4) represents a promising candidate to replace PGE(2) in DC maturation protocols for cancer vaccination.

Contribution of tumour and immune cells to PD-L1 expression as a predictive biomarker in metastatic triple-negative breast cancer: exploratory analysis from KEYNOTE-119.

The efficacy of pembrolizumab monotherapy versus chemotherapy increased with increasing programmed death ligand 1 (PD-L1) expression, as quantified by combined positive score (CPS; PD-L1 expression on both tumour cells and immune cells) in patients with previously treated metastatic triple-negative breast cancer (mTNBC) in the phase 3 KEYNOTE-119 study. This exploratory analysis was conducted to determine whether the expression of PD-L1 on tumour cells contributes to the predictive value of PD-L1 CPS in mTNBC. PD-L1 expression in tumour samples was assessed using PD-L1 IHC 22C3 pharmDx and quantified using both CPS and tumour proportion score (TPS; PD-L1 expression on tumour cells alone). Calculated immune cell density (CID) was defined as CPS minus TPS. The ability of each scoring method (CPS, TPS, and CID) to predict clinical outcomes with pembrolizumab was evaluated. With pembrolizumab, the area under the receiver operating characteristic curve was 0.69 (95% CI = 0.58-0.80) for CPS, 0.55 (95% CI = 0.46-0.64) for TPS, and 0.67 (95% CI = 0.56-0.77) for CID. After correction for cutoff prevalence, CPS performed as well as, if not better than, CID with respect to predicting objective response rate, progression-free survival, and overall survival. Data from this exploratory analysis suggest that, although PD-L1 expression on immune cells alone is predictive of response to programmed death 1 blockade in mTNBC, adding tumour PD-L1 expression assessment (i.e. CPS, which combines immune cell and tumour cell PD-L1 expression) may improve prediction. PD-L1 CPS thus remains an effective and broadly applicable uniform scoring system for enriching response to programmed death 1 blockade with pembrolizumab in mTNBC as well as other tumour types.

Impact of anti-CD25 monoclonal antibody on dendritic cell-tumor fusion vaccine efficacy in a murine melanoma model.

BACKGROUND: A promising cancer vaccine involves the fusion of tumor cells with dendritic cells (DCs). As such, a broad spectrum of both known and unidentified tumor antigens is presented to the immune system in the context of the potent immunostimulatory capacity of DCs. Murine studies have demonstrated the efficacy of fusion immunotherapy. However the clinical impact of DC/tumor fusion vaccines has been limited, suggesting that the immunosuppresive milieu found in patients with malignancies may blunt the efficacy of cancer vaccination. Thus, novel strategies to enhance fusion vaccine efficacy are needed. Regulatory T cells (Tregs) are known to suppress anti-tumor immunity, and depletion or functional inactivation of these cells improves immunotherapy in both animal models and clinical trials. In this study, we sought to investigate whether functional inactivation of CD4+CD25+FoxP3+ Treg with anti-CD25 monoclonal antibody (mAb) PC61 prior to DC/tumor vaccination would significantly improve immunotherapy in the murine B16 melanoma model. METHODS: Treg blockade was achieved with systemic PC61 administration. This blockage was done in conjunction with DC/tumor fusion vaccine administration to treat established melanoma pulmonary metastases. Enumeration of these metastases was performed and compared between experimental groups using Wilcoxon Rank Sum Test. IFN-gamma ELISPOT assay was performed on splenocytes from treated mice. RESULTS: We demonstrate that treatment of mice with established disease using mAb PC61 and DC/tumor fusion significantly reduced counts of pulmonary metastases compared to treatment with PC61 alone (p=0.002) or treatment with control antibody plus fusion vaccine (p=0.0397). Furthermore, IFN-gamma ELISPOT analyses reveal that the increase in cancer immunity was mediated by anti-tumor specific CD4+ T-helper cells, without concomitant induction of CD8+ cytotoxic T cells. Lastly, our data provide proof of principle that combination treatment with mAb PC61 and systemic IL-12 can lower the dose of IL-12 necessary to obtain maximal therapeutic efficacy. CONCLUSIONS: To our knowledge, this is the first report investigating the effects of anti-CD25 mAb administration on DC/tumor-fusion vaccine efficacy in a murine melanoma model, and our results may aide the design of future clinical trials with enhanced therapeutic impact.

Plasma cytokine analysis in patients with advanced extremity melanoma undergoing isolated limb infusion.

BACKGROUND: Preprocedure clinical and pathologic factors have failed to consistently differentiate complete response (CR) from progressive disease (PD) in patients after isolated limb infusion (ILI) with melphalan for unresectable in-transit extremity melanoma. METHODS: Multiplex immunobead assay technology (Milliplex MAP Human Cytokine/Chemokine Magnetic Bead Panel, Millipore Corp., Billerica, MA; and Magpix analytical test instrument, Luminex Corp., Austin, TX) was performed on pre-ILI plasma to determine concentrations of selected cytokines (MIP-1α, IL-1Rα, IP-10, IL-1ß, IL-1α, MCP-1, IL-6, IL-17, EGF, IL-12p40, VEGF, GM-CSF, and MIP-1ß) on a subset of patients (n = 180) who experienced CR (n = 23) or PD (n = 24) after ILI. Plasma from normal donors (n = 12) was also evaluated. RESULTS: Of 180 ILIs performed, 28 % (95 % confidence interval 22-35, n = 50) experienced a CR, 14 % (n = 25) experienced a partial response, 11 % (n = 21) had stable disease, 34 % (n = 61) had PD, and 13 % (n = 23) were not evaluable for response. Tumor characteristics and pharmacokinetics appeared similar between CR (n = 23) and PD (n = 24) patients who underwent cytokine analysis. Although there were no differences in cytokine levels between CR and PD patients, there were differences between the melanoma patients and controls. MIP-1α, IL-1Rα, IL-1ß, IL-1α, IL-17, EGF, IL-12p40, VEGF, GM-CSF, and MIP-1ß were significantly higher in normal controls compared to melanoma patients, while IP-10 was lower (p < 0.001) in controls compared to melanoma patients. CONCLUSIONS: Patients with unresectable in-transit melanoma appear to have markedly decreased levels of immune activating cytokines compared to normal healthy controls. This further supports a potential role for immune-targeted therapies and immune monitoring in patients with regionally advanced melanoma.

Melanoma, version 2.2013: featured updates to the NCCN guidelines.

The NCCN Guidelines for Melanoma provide multidisciplinary recommendations on the clinical management of patients with melanoma. This NCCN Guidelines Insights report highlights notable recent updates. Foremost of these is the exciting addition of the novel agents ipilimumab and vemurafenib for treatment of advanced melanoma. The NCCN panel also included imatinib as a treatment for KIT-mutated tumors and pegylated interferon alfa-2b as an option for adjuvant therapy. Also important are revisions to the initial stratification of early-stage lesions based on the risk of sentinel lymph node metastases, and revised recommendations on the use of sentinel lymph node biopsy for low-risk groups. Finally, the NCCN panel reached clinical consensus on clarifying the role of imaging in the workup of patients with melanoma.

Local secretion of IL-12 augments the therapeutic impact of dendritic cell-tumor cell fusion vaccination.

BACKGROUND: The development of dendritic cell (DC)-tumor fusion vaccines is a promising approach in cancer immunotherapy. Using fusion vaccines allows a broad spectrum of known and unidentified tumor-associated antigens to be presented in the context of MHC class I and class II molecules, with potent co-stimulation provided by the DCs. Although DC-tumor fusion cells are immunogenic, murine studies have shown that effective immunotherapy requires a third signal, which can be provided by exogenous interleukin 12 (IL-12). Unfortunately, systemic administration of IL-12 induces severe toxicity in cancer patients, potentially precluding clinical use of this cytokine to augment fusion vaccine efficacy. To overcome this limitation, we developed a novel approach in which DC-tumor fusion cells locally secrete IL-12, then evaluated the effectiveness of this approach in a murine B16 melanoma model. MATERIALS AND METHODS: Tumor cells were stably transduced to secrete murine IL-12p70. These tumor cells were then electrofused to DC to form DC-tumor heterokaryons. These cells were used to treat established B16 pulmonary metastases. Enumeration of these metastases was performed and compared between experimental groups using Wilcoxon rank sum test. Interferon γ enzyme-linked immunosorbent spot assay was performed on splenocytes from treated mice. RESULTS: We show that vaccination with DCs fused to syngeneic melanoma cells that stably express murine IL-12p70 significantly reduces counts of established lung metastases in treated animals when compared with DC-tumor alone (P = 0.029). Interferon γ enzyme-linked immunosorbent spot assays suggest that this antitumor response is mediated by CD4(+) T cells, in the absence of a tumor-specific CD8(+) T cell response, and that the concomitant induction of antitumor CD4(+) and CD8(+) T cell responses required exogenous IL-12. CONCLUSIONS: This study is, to the best of our knowledge, the first report that investigates the impact of local secretion of IL-12 on antitumor immunity induced by a DC-tumor fusion cell vaccine in a melanoma model and may aid the rational design of future clinical trials.

Enhancement of anti-tumor immunity through local modulation of CTLA-4 and GITR by dendritic cells.

Cancer vaccines have now demonstrated clinical efficacy, but immune modulatory mechanisms that prevent autoimmunity limit their effectiveness. Systemic administration of mAbs targeting the immune modulatory receptors CTLA-4 and glucocorticoid-induced TNFR-related protein (GITR) on Treg and effector T cells augments anti-tumor immunity both experimentally and clinically, but can induce life-threatening autoimmunity. We hypothesized that local delivery of anti-CTLA-4 and anti-GITR mAbs to the sites where T cells and tumor antigen-loaded DC vaccines interact would enhance the induction of anti-tumor immunity while avoiding autoimmunity. To achieve this goal, DCs transfected with mRNA encoding the H and L chains of anti-mouse CTLA-4 and GITR mAbs were co-administered with tumor antigen mRNA-transfected DCs. We observed enhanced induction of anti-tumor immunity and significantly improved survival in melanoma-bearing mice, without signs of autoimmunity. Using in vitro assays with human DCs, we demonstrated that DCs transfected with mRNA encoding a humanized anti-CTLA-4 mAb and mRNA encoding a soluble human GITR-L fusion protein enhance the induction of anti-tumor CTLs in response to DCs transfected with mRNAs encoding either melanoma or breast cancer antigens. Based on these results, this approach of using local delivery of immune modulators to enhance vaccine-induced immunity is currently being evaluated in a phase I clinical cancer immunotherapy trial.

The effect of metastatic site and decade of diagnosis on the individual burden of metastatic melanoma: contemporary estimates of average years of life lost.

OBJECTIVES: Metastatic melanoma (MM) is a leading cause of years of life lost due to malignancy. This study aimed to identify the average years of life lost (AYLL) in MM patients. METHODS: MM patients were identified from a prospectively maintained database, and a linear model predicting AYLL was developed. RESULTS: Between 1970 and 1999, 4,774 patients diagnosed with MM died. The AYLL was 23.2 years. AYLL remained stable across three decades. CONCLUSIONS: AYLL for MM is greater than 20 years, and has not improved. This burden underscores the need for continued research and access to funding for this disease.

Experimental Medicine Study to Measure Immune Checkpoint Receptors PD-1 and GITR Turnover Rates In Vivo in Humans.

Development of monoclonal antibodies (mAbs) targeting immune-checkpoint receptors (IMRs) for the treatment of cancer is one of the most active areas of investment in the biopharmaceutical industry. A key decision in the clinical development of anti-IMR mAbs is dose selection. Dose selection can be challenging because the traditional oncology paradigm of administering the maximum tolerated dose is not applicable to anti-IMR mAbs. Instead, dose selection should be informed by the pharmacology of immune signaling. Engaging an IMR is a key initial step to triggering pharmacologic effects, and turnover (i.e., the rate of protein synthesis) of the IMR is a key property to determining the dose level needed to engage the IMR. Here, we applied the stable isotope labeling mass spectrometry technique using 13 C6 -leucine to measure the in vivo turnover rates of IMRs in humans. The 13 C6 -leucine was administered to 10 study participants over 15 hours to measure 13 C6 -leucine enrichment kinetics in 2 IMR targets that have been clinically pursued in oncology: GITR and PD-1. We report the first measurements of GITR and PD-1 median half-lives associated with turnover to be 55.6 and ≥ 49.5 hours, respectively. The approach outlined here can be applied to other IMRs and, more generally, to protein targets.

Inhibition of poly(ADP-ribose) polymerase enhances the effect of chemotherapy in an animal model of regional therapy for the treatment of advanced extremity malignant melanoma.

BACKGROUND: Poly(ADP-ribose) polymerase (PARP) is an important regulator of programmed cell death in response to alkylating agents such as temozolomide (TMZ). The goal of this study was to determine if a systemically administered PARP-inhibitor (INO-1001) could augment the efficacy of TMZ in a rat model of extremity malignant melanoma. MATERIALS AND METHODS: PARP activity was measured in vitro across a panel of 5 human malignant melanoma-derived cell lines. To evaluate tumor response to PARP inhibition in combination with regional isolated limb infusion (ILI) therapy with TMZ, two TMZ-resistant malignant melanoma cell lines were grown as xenografts in the hind limb of rats. INO-1001 (400 mg/kg) was injected intraperitoneally 7 times every 8 hours prior to ILI. Tumor volume was measured for up to 40 days. RESULTS: In vitro inhibition of PARP activity by INO-1001 ranged from 25.5% to 65.6%. In a mismatch repair (MMR)-deficient xenograft, treatment with INO-1001 prior to ILI significantly (P < .04) increased the efficacy of TMZ. The increase in tumor volume at day 40 following TMZ-ILI with INO-1001 was only 22.6% compared with 322.8% with TMZ-ILI alone. In a xenograft that was MMR-proficient and had high levels of O(6)-methylguanine-DNA methyltransferase (MGMT) activity, there was little improvement in TMZ efficacy with INO-1001 treatment. CONCLUSION: The PARP-inhibitor, INO-1001, can enhance the response of TMZ-resistant, MMR-deficient, malignant melanoma xenografts to intra-arterially administered TMZ in a regional treatment model of advanced extremity malignant melanoma.

Association of programmed death ligand 1 expression with prognosis among patients with ten uncommon advanced cancers.

AIM: PD-L1 expression and high levels of microsatellite instability (MSI-H) may predict response to checkpoint inhibitors, but their prevalence and prognostic value are unknown in many cancers. METHODS: We retrospectively evaluated PD-L1 combined positive score (CPS) and MSI-H and their association with clinical outcomes among patients with ten advanced uncommon cancers. RESULTS: 398 of 426 patients (93%) had a valid PD-L1 result; most (242; 61%) had CPS ≥1. Prevalence of MSI-H tumors was 8/360. Median overall survival was shorter among patients with PD-L1 CPS ≥1 tumors after first-line treatment (23.0 vs 39.7 months, p = 0.014). CONCLUSION: PD-L1 was commonly expressed in solid tumors, and CPS ≥1 was associated with shorter overall survival. Prevalence of MSI-H was low.

Efficacy of Pembrolizumab in Patients With Noncolorectal High Microsatellite Instability/Mismatch Repair-Deficient Cancer: Results From the Phase II KEYNOTE-158 Study.

PURPOSE: Genomes of tumors that are deficient in DNA mismatch repair (dMMR) have high microsatellite instability (MSI-H) and harbor hundreds to thousands of somatic mutations that encode potential neoantigens. Such tumors are therefore likely to be immunogenic, triggering upregulation of immune checkpoint proteins. Pembrolizumab, an anti‒programmed death-1 monoclonal antibody, has antitumor activity against MSI-H/dMMR cancer. We report data from the phase II KEYNOTE-158 study of pembrolizumab in patients with previously treated, advanced noncolorectal MSI-H/dMMR cancer. PATIENTS AND METHODS: Eligible patients with histologically/cytologically confirmed MSI-H/dMMR advanced noncolorectal cancer who experienced failure with prior therapy received pembrolizumab 200 mg once every 3 weeks for 2 years or until disease progression, unacceptable toxicity, or patient withdrawal. Radiologic imaging was performed every 9 weeks for the first year of therapy and every 12 weeks thereafter. The primary end point was objective response rate per Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1, as assessed by independent central radiologic review. RESULTS: Among 233 enrolled patients, 27 tumor types were represented, with endometrial, gastric, cholangiocarcinoma, and pancreatic cancers being the most common. Median follow up was 13.4 months. Objective response rate was 34.3% (95% CI, 28.3% to 40.8%). Median progression-free survival was 4.1 months (95% CI, 2.4 to 4.9 months) and median overall survival was 23.5 months (95% CI, 13.5 months to not reached). Treatment-related adverse events occurred in 151 patients (64.8%). Thirty-four patients (14.6%) had grade 3 to 5 treatment-related adverse events. Grade 5 pneumonia occurred in one patient; there were no other treatment-related fatal adverse events. CONCLUSION: Our study demonstrates the clinical benefit of anti-programmed death-1 therapy with pembrolizumab among patients with previously treated unresectable or metastatic MSI-H/dMMR noncolorectal cancer. Toxicity was consistent with previous experience of pembrolizumab monotherapy.

Efficacy and Safety of Pembrolizumab in Previously Treated Advanced Cervical Cancer: Results From the Phase II KEYNOTE-158 Study.

PURPOSE: KEYNOTE-158 ( ClinicalTrials.gov identifier: NCT02628067) is a phase II basket study investigating the antitumor activity and safety of pembrolizumab in multiple cancer types. We present interim results from patients with previously treated advanced cervical cancer. PATIENTS AND METHODS: Patients received pembrolizumab 200 mg every 3 weeks for 2 years or until progression, intolerable toxicity, or physician or patient decision. Tumor imaging was performed every 9 weeks for the first 12 months and every 12 weeks thereafter. The primary end point was objective response rate (ORR), assessed per Response Evaluation Criteria in Solid Tumors (version 1.1) by independent central radiologic review. Safety was a secondary end point. RESULTS: Ninety-eight patients were treated. Median age was 46.0 years (range, 24 to 75 years), and 65.3% of patients had Eastern Cooperative Oncology Group performance status of 1. Eighty-two patients (83.7%) had programmed death-ligand 1 (PD-L1)-positive tumors (combined positive score ≥ 1), 77 having previously received one or more lines of chemotherapy for recurrent or metastatic disease. Median follow-up was 10.2 months (range, 0.6 to 22.7 months). ORR was 12.2% (95% CI, 6.5% to 20.4%), with three complete and nine partial responses. All 12 responses were in patients with PD-L1-positive tumors, for an ORR of 14.6% (95% CI, 7.8% to 24.2%); 14.3% (95% CI, 7.4% to 24.1%) of these responses were in those who had received one or more lines of chemotherapy for recurrent or metastatic disease. Median duration of response was not reached (range, ≥ 3.7 to ≥ 18.6 months). Treatment-related adverse events occurred in 65.3% of patients, and the most common were hypothyroidism (10.2%), decreased appetite (9.2%), and fatigue (9.2%). Treatment-related grade 3 to 4 adverse events occurred in 12.2% of patients. CONCLUSION: Pembrolizumab monotherapy demonstrated durable antitumor activity and manageable safety in patients with advanced cervical cancer. On the basis of these results, the US Food and Drug Administration granted accelerated approval of pembrolizumab for patients with advanced PD-L1-positive cervical cancer who experienced progression during or after chemotherapy.

Isolated limb infusion for in-transit malignant melanoma of the extremity: a well-tolerated but less effective alternative to hyperthermic isolated limb perfusion.

BACKGROUND: Isolated limb infusion (ILI) is a recently described minimally invasive technique developed in Australia for delivering regional chemotherapy. This study examined the efficacy and toxicity of ILI, compared to hyperthermic isolated limb perfusion (HILP), in treating extremity in-transit melanoma. METHODS: Variables from a prospective single institution database of 120 regionally treated melanoma patients (1995-2007) were compared using chi-square analysis. This included 61 consecutive ILI treatments in 58 patients and 59 HILP treatments in 54 patients. Response was defined at 3 months using the response evaluation criteria in solid tumors (RECIST). ILI was performed using melphalan (LPAM) and dactinomycin for 30 min after limb temperature reached 37 degrees C. HILP was performed using LPAM for 60 min after limb temperature reached 38.5 degrees C. RESULTS: For ILI (n = 61), the complete response (CR) rate was 30%, the partial response (PR) rate was 14%, and there was no response (NR) in 56% of patients. The median duration of CR was 12 months and 18% of patients experienced (grade >or=3) toxicity. HILP (n = 59) was associated with a better (P < 0.001) response rate (CR 57%, PR 31%, and NR 12%) however, more patients (32%) experienced grade >or=3 toxicity (P = 0.037). The dose of LPAM was corrected for ideal body weight (IBW) in 40 out of 61 ILI procedures, and 13 of 59 HILP procedures. This dosing modification was associated with decreased toxicity (P = 0.024) without diminishing response. CONCLUSION: ILI was found to be a well-tolerated alternative to HILP. While ILI does not appear to be as effective as HILP, it does seem to be associated with less morbidity.

Defining regional infusion treatment strategies for extremity melanoma: comparative analysis of melphalan and temozolomide as regional chemotherapeutic agents.

Five different human melanoma xenografts were used in a xenograft model of extremity melanoma to evaluate the variability of tumor response to regionally administered melphalan or temozolomide and to determine if various components of pertinent drug resistance pathways for melphalan [glutathione S-transferase (GST)/glutathione] and temozolomide [O(6)-alkylguanine DNA alkyltranferase (AGT)/mismatch repair (MMR)] could be predictive of tumor response. Xenograft-bearing rats underwent regional isolated limb infusion with either melphalan (90 mg/kg) or temozolomide (2,000 mg/kg). The levels of AGT activity, GST activity, glutathione level, and GST/AGT expression were examined in this group of xenografts and found to be quite heterogeneous. No correlation was identified between melphalan sensitivity and the GST/glutathione cellular detoxification pathway. In contrast, a strong correlation between the levels of AGT activity and percentage increase in tumor volume on day 30 (r = 0.88) was noted for tumors treated with temozolomide. Regional therapy with temozolomide was more effective when compared with melphalan for the xenograft with the lowest AGT activity, whereas melphalan was more effective than temozolomide in another xenograft that had the highest AGT activity. In three other xenografts, there was no significant difference in response between the two chemotherapy agents. This study shows that AGT activity may be useful in predicting the utility of temozolomide-based regional therapy for advanced extremity melanoma tumors. Our observations also point out the limited ability of analysis of the GST/glutathione pathway to predict response to chemotherapies like melphalan whose resistance is primarily mediated through a complex mechanism of detoxification.

Optimizing a novel regional chemotherapeutic agent against melanoma: hyperthermia-induced enhancement of temozolomide cytotoxicity.

PURPOSE: Previous preclinical studies have shown that regional temozolomide therapy via isolated limb infusion is more effective than melphalan, the current drug of choice for regional chemotherapy for advanced extremity melanoma. The aim of this study was to determine whether hyperthermia could further augment the efficacy of temozolomide, an alkylating agent, against melanoma and improve its therapeutic index in a rat model of isolated limb infusion. EXPERIMENTAL DESIGN: Athymic rats bearing s.c. human melanoma xenografts (DM6) in their hind limbs were randomized to a 15-minute isolated limb infusion procedure with or without temozolomide at room temperature, normothermic (37.5 degrees C), or hyperthermic (43 degrees C) conditions. RESULTS: The concomitant administration of hyperthermia during an infusion with temozolomide led to the greatest increase in tumor growth delay, decreased proliferative index, and increased cell death. Isolated limb infusion treatment with a low dose (350 mg/kg) of temozolomide was ineffective at producing tumor growth delay (P = 0.07). Similarly, temozolomide infusion under normothermia yielded minimal tumor growth delay (P = 0.08). In contrast, the combination of hyperthermia plus temozolomide treatment produced marked tumor growth delay of 10.4 days (P = 0.02) with minimal toxicity. The addition of heat to temozolomide treatment yielded the smallest proliferative index (P = 0.001), while markedly increasing the level of apoptosis 48 hours after isolated limb infusion. CONCLUSION: This study, the first to examine the interaction between hyperthermia and temozolomide, shows a strong, synergistic antitumor effect when hyperthermia is combined with temozolomide for regional treatment of melanoma confined to an extremity. The mechanism of this synergy seems to be through an augmentation, by hyperthermia, of the antiproliferative and proapoptotic effects of temozolomide.

Modulation of chemotherapy resistance in regional therapy: a novel therapeutic approach to advanced extremity melanoma using intra-arterial temozolomide in combination with systemic O6-benzylguanine.

This study investigated whether the therapeutic index of regional melanoma therapy using parenteral temozolomide could be improved by chemomodulation with O6-benzylguanine (O6BG), an inhibitor of the DNA repair enzyme O6-alkylguanine-DNA alkyltransferase (AGT). Using a nude rat s.c. human melanoma xenograft model of the extremity, tumors were analyzed for AGT level 2 to 3 hours after the i.p. injection of 3.5 to 70.0 mg/kg O6BG to inhibit AGT activity. Survival studies were conducted using animals that were treated with a 15-minute isolated limb infusion with 10% DMSO in PBS (control), temozolomide alone, or temozolomide in conjunction with single or multiple doses of i.p. O6BG. Tumor volume and toxicity level were monitored every other day. Administration of 3.5 mg/kg O6BG depleted tumor AGT activity by 93.5% (P < 0.01). Groups treated with regional temozolomide alone (350 mg/kg), systemic temozolomide with O6BG, or vehicle combined with O6BG showed no significant tumor responses compared with controls. Whereas use of regional temozolomide alone at a higher dose (750 mg/kg) showed some degree of tumor response, regional temozolomide given in conjunction with multiple dosages of O6BG showed a marked (P < 0.01) reduction in tumor growth with minimal toxicity. Our findings suggest that AGT modulation by the administration of O6BG in combination with temozolomide regional chemotherapy leads to a significant improvement in melanoma antitumor responses. Clinical trials using chemotherapy modulation may improve response rates in future regional infusion and perfusion drug trials.

The role of hyperthermia in regional alkylating agent chemotherapy.

The role of hyperthermia during regional alkylating agent chemotherapy is controversial. The aim of this study was to determine the exact contribution of hyperthermia to tumor response during isolated limb infusion with l-phenylalanine mustard. Rats bearing rodent fibrosarcoma on the hindlimb underwent isolated limb infusion with saline, saline plus heat, l-phenylalanine mustard, l-phenylalanine mustard under conditions of normothermia, or l-phenylalanine mustard plus hyperthermia. Heat was administered locally using an in-line hot water circulation loop. Treatment with l-phenylalanine mustard at a concentration of 15 or 50 micrograms/mL was ineffective at producing tumor growth delay (P = 0.24 and 0.41, respectively). Furthermore, thermal enhancement of l-phenylalanine mustard activity was not seen at 15 micrograms/mL. However, administration of high-dose l-phenylalanine mustard, 50 micrograms/mL, with increasing amounts of heat yielded increasing tumor growth delay, increased regressions, and decreased proliferative index. Although l-phenylalanine mustard infusion under normothermia yielded a tumor growth delay of 7.1 days, combination l-phenylalanine mustard + hyperthermia treatment produced tumor growth delay of 27.0 days (P < 0.01; with two of five animals showing a complete response). Four hours after isolated limb infusion, 50.9% of cells in tumor treated with l-phenylalanine mustard + hyperthermia experienced apoptosis, whereas only 18.1, 16, and 4.4% of cells underwent apoptosis after treatment with l-phenylalanine mustard, saline + hyperthermia, or saline. The mean concentration of l-phenylalanine mustard within tumor relative to perfusate following isolated limb infusion was found to be similar among all groups at 0.023, 0.025, and 0.032 in animals undergoing isolated limb infusion with l-phenylalanine mustard, l-phenylalanine mustard + normothermia, and l-phenylalanine mustard + hyperthermia, respectively. These data indicate a synergistic cytotoxic effect of l-phenylalanine mustard + hyperthermia in isolated limb infusion, which is not attributable to enhanced tumor drug uptake.