Retrospective Analysis of Rechallenge with Ipilimumab in Patients with Metastatic Melanoma.

BACKGROUND: Checkpoint inhibitors are effective in the treatment of several types of cancer, either being used separately or in combination. Ipilimumab pioneered the treatment of metastatic melanoma, and nowadays, it has been used more frequently in combination with anti-PD-1. Since the development of anti-PD1 for melanoma, rechallenge with ipilimumab has not been considered, although its use was considered in early trials. CASES: In this study, we analyzed 22 patients with metastatic melanoma who had benefited from the first treatment with ipilimumab, but eventually had progressive disease. They received ipilimumab at the same dose as the first treatment. Most of the patients received the second course after six months or more from the first treatment with ipilimumab. The median progression-free survival (mPFS) of the treatment with ipilimumab was 8.9 months, and the median progression-free survival of the second course was 6.3 months. CONCLUSION: There are limited data on rechallenge with ipilimumab addressing progression-free survival (PFS). In our analysis, twenty-two patients treated with a second course of ipilimumab were analyzed and most of them had a significant benefit. Despite the current alternatives for salvage therapies, rechallenging with ipilimumab might be an alternative to be considered in patients who had initial benefit.

Anthracyclines and taxanes in the neo/adjuvant treatment of breast cancer: does the sequence matter?

BACKGROUND: In early breast cancer, adjuvant chemotherapy decreases the risks of recurrence and breast cancer mortality, and neoadjuvant treatment leads to equivalent long-term outcomes. A large number of clinical trials have attempted to refine systemic therapeutic strategies in early breast cancer, but little attention has been paid to the sequence of anthracyclines and taxanes. Based on preclinical observations, there is limited rationale to administer the taxane before the anthracycline. METHODS: We searched PubMed, the American Society of Clinical Oncology website, and clinicaltrials.gov with the goal of identifying published or ongoing studies that aimed at comparing reverse sequences of anthracyclines and taxanes. Given the nature and the small number of studies identified, we did not attempt to quantitatively pool the study results. RESULTS: We retrieved seven studies in the adjuvant setting and eight in the neoadjuvant setting: 10 randomized trials (only 2 were phase IIII), 3 retrospective studies, and 2 ongoing phase II trials. A total of nearly 5000 patients were included in such studies. None of the clinical trials has shown disadvantages in terms of efficacy or toxicity for sequences in which the taxane was administered first. In the neoadjuvant setting, studies have collectively shown similar or increased pathological complete response rates for sequences in which the taxane was administered first. CONCLUSION: Given the available information, there seems to be sufficient evidence to suggest that a taxane followed by an anthracycline is a sequence option that can be incorporated into daily clinical practice.

Electrochemical therapy to treat cancer (in vivo treatment).

The aim of this paper is to present the evaluations and results attained by our research group from the clinical applications of Electrochemical Therapy (EChT in short) on tumors, specifically of cats and dogs. Our in vivo results indicate that EChT is an effective cancer treatment. Application of EChT in human beings was approved by National Health Surveillance Agency, which is linked to the Brazilian Ministry of Health. To make EChT available for cancer patients in the Brazil, basic studies were conducted and a Phase I clinical trial was started.

Practical guidelines for the management of biochemotherapy-related toxicity in melanoma.

The combination of cisplatin-based chemotherapy with interleukin 2 (IL-2) and IFN-alpha, referred to as biochemotherapy or chemoimmunotherapy, has shown promising antitumor activity in patients with metastatic melanoma. Phase II studies have reported overall response rates ranging from 40 to 60%, with durable complete remissions in approximately 10% of the patients. Toxicity, however, is often severe and can be life-threatening if the healthcare team is not familiar with toxicity management. In this report, we briefly describe the clinical results of the most effective biochemotherapy regimens and provide a detailed description and management of the most common toxic effects, with emphasis on the concurrent biochemotherapy program initially developed at M. D. Anderson Cancer Center and currently being tested in a slightly modified version in two large-scale Intergroup Phase III trials.

Final version of the American Joint Committee on Cancer staging system for cutaneous melanoma.

PURPOSE: To revise the staging system for cutaneous melanoma under the auspices of the American Joint Committee on Cancer (AJCC). MATERIALS AND METHODS: The prognostic factors analysis described in the companion publication (this issue), as well as evidence from the published literature, was used to assemble the tumor-node-metastasis criteria and stage grouping for the melanoma staging system. RESULTS: Major changes include (1) melanoma thickness and ulceration but not level of invasion to be used in the T category (except for T1 melanomas); (2) the number of metastatic lymph nodes rather than their gross dimensions and the delineation of clinically occult (ie, microscopic) versus clinically apparent (ie, macroscopic) nodal metastases to be used in the N category; (3) the site of distant metastases and the presence of elevated serum lactic dehydrogenase to be used in the M category; (4) an upstaging of all patients with stage I, II, and III disease when a primary melanoma is ulcerated; (5) a merging of satellite metastases around a primary melanoma and in-transit metastases into a single staging entity that is grouped into stage III disease; and (6) a new convention for defining clinical and pathologic staging so as to take into account the staging information gained from intraoperative lymphatic mapping and sentinel node biopsy. CONCLUSION: This revision will become official with publication of the sixth edition of the AJCC Cancer Staging Manual in the year 2002.

The changing prognosis of melanoma.

Cutaneous melanoma is a significant and increasing clinical problem. Knowing accurately the prognosis in a given patient is critical for treatment decisions and for optimal patient education. In this article we discuss the most current information regarding prognostic factors in early-stage and advanced malignant melanoma. Tumor thickness and ulceration are the most important predictors for primary melanoma. Number of positive lymph nodes is the most powerful predictor for stage III patients, and sites of disease and lactase dehydrogenase levels are the most useful predictors in metastatic disease.

Unexpected cytokines in serum of malignant melanoma patients during sequential biochemotherapy.

Biochemotherapy, which combines traditional chemotherapy with immune modulating biologicals, produces an unexpectedly high response rate (>50%) in advanced melanoma patients. We hypothesize that immunological mechanism(s) are responsible for the increased response rate, and particularly that macrophage activation is involved in tumor reduction. Patients were randomized to receive chemotherapy, composed of cisplatin, vinblastine, and dacarbazine (CVD), or biochemotherapy, which is CVD followed by interleukin (IL)-2 and IFN-alpha2b (CVD-BIO). Laboratory analysis was performed on sera from 41 patients from each arm. Measurements of macrophage activation (neopterin), nitric oxide production (nitrite), and tumor necrosis factor-alpha (TNF-alpha), IL-1alpha, IL-1beta, IFN-gamma, IL-6, IL-10, and soluble IL-2 receptor (sIL-2R) were performed. Six of the nine biological responses (nitrite, neopterin, IFN-gamma, IL-6, soluble IL-2R, and IL-10) significantly (P < 0.0002) increased in the CVD-BIO patients but not in the CVD patients. The increased IL-6 (P = 0.04) and IL-10 (P = 0.05) correlated with patient response, but only when the minor responders were included in the analysis. Evidence of macrophage activation was found in CVD-BIO patients and not in those receiving CVD alone. In addition, an unusual cytokine elaboration composed of IL-6, IFN-gamma, IL-10, nitrite, neopterin, and sIL-2R, but not the expected TNF-alpha and IL-1, was detected. A trend of higher increase in IL-6 and IL-10 in patients having clinical response was found, suggesting an incomplete Th2 pattern of cytokine elaboration. These data show that macrophage activation does not appear to be critical in the response to CVD-BIO, but that IL-10 and IL-6 induced by the BIO component of the CVD-BIO were associated with tumor regression, and that their biology should be pursued further in the analysis of mechanism(s) of response.

Clinical classification and staging.

The identification of increasingly powerful prognostic factors has led to sequential modifications of the cutaneous melanoma staging system. Changes in the staging system are anticipated as more refined prognostic factors are identified. This article provides an overview of the system, including a brief history and an introduction to recent advances in staging of patients with primary melanoma (i.e., sentinel lymphadenectomy). Practical recommendations for a stage-specific workup for the patient, which are especially important given the need for quality care in an increasingly cost-conscious environment, are provided.

A phase II study of "decrescendo" interleukin-2 plus interferon-alpha-2a in patients with progressive metastatic melanoma after chemotherapy.

BACKGROUND: The authors tested a biotherapy regimen involving recombinant interferon-alpha-2a (rIFN-alpha-2a) and recombinant human interleukin-2 (rhIL-2), given in a "decrescendo" schedule over 5 days, for its activity and toxicity in 21 patients who previously had received chemotherapy for advanced melanoma. METHODS: Patients (15 men and 6 women) were given intravenous rhIL-2 at a dose of 18 MIU/m(2) over 6 hours, followed by 18 MIU/m(2) over 12 hours, then 18 MIU/m(2) over 24 hours, and finally 4.5 MIU/m(2)/day for 3 consecutive days. rIFN-alpha-2a (10 MIU/m(2)) was given subcutaneously on Days 1-5. Courses were repeated every 4 weeks. Tumor sites were measured every 8 weeks. Toxicity was recorded using National Cancer Institute Common Toxicity Criteria. RESULTS: No major objective responses were noted. The median number of courses given was two. The median time to progression was 2 months and the median survival was 6 months (range, 2-25 months). However, 2 patients with melanoma involving >/= 2 visceral organs (1 with a high baseline serum lactate dehydrogenase level) and a third with soft tissue metastases achieved durable control of disease and were alive a median of 30+ months later. A fourth patient had a palliative response with reversal of melanosis and a survival of 7 months. This regimen was well tolerated and resulted in no serious long term adverse effects. CONCLUSIONS: The response rate for this regimen was no greater than 10% with Type I and II errors each not exceeding 10%. Nevertheless, occasional durable control of disease and the nonoverlapping toxicity profile with prior chemotherapy support consideration of this regimen in these patients who have limited second-line treatment options.

A new American Joint Committee on Cancer staging system for cutaneous melanoma.

The Melanoma Staging Committee of the AJCC has proposed major revisions of the melanoma TNM and stage grouping criteria. The committee members represent most of the major cooperative groups and cancer centers worldwide with a special interest in melanoma; the committee also collectively has had clinical experience with over 40,000 patients. The new staging system better reflects independent prognostic factors that are used in clinical trials and in reporting the outcomes of various melanoma treatment modalities. Major revisions include 1) melanoma thickness and ulceration, but not level of invasion, to be used in the T classification; 2) the number of metastatic lymph nodes, rather than their gross dimensions, the delineation of microscopic versus macroscopic lymph node metastases, and presence of ulceration of the primary melanoma to be used in the N classification; 3) the site of distant metastases and the presence of elevated serum LDH, to be used in the M classification; 4) an upstaging of all patients with Stage I,II, and III disease when a primary melanoma is ulcerated; 5) a merging of satellite metastases around a primary melanoma and in-transit metastases into a single staging entity that is grouped into Stage III disease; and 6) a new convention for defining clinical and pathologic staging so as to take into account the new staging information gained from intraoperative lymphatic mapping and sentinel lymph node biopsy. The AJC Melanoma Staging Committee invites comments and suggestions regarding this proposed staging system before a final recommendation is made.

Inducible nitric oxide synthase and nitrotyrosine in human metastatic melanoma tumors correlate with poor survival.

Despite recognition of the malignant potential of human melanomas, the mechanisms responsible for the pathobiological characteristics contributing to tumor growth, vascular invasiveness, and distant organ metastasis remain undefined. Recent studies have shown that various human tumors express an inducible form of nitric oxide synthase (iNOS) and nitrotyrosine (NT), which suggests a mechanistic role of tumor-associated nitric oxide (NO) in tumorigenesis. We investigated iNOS and NT expression by immunohistochemistry in 20 human metastatic melanoma tissue specimens specifically with respect to iNOS-expressing cell types in the tumor area, pathological and clinical response to systemic therapy, potential role as a prognostic indicator, and NT formation. Our results showed that melanoma cells from 12 of 20 tumors express iNOS, yet the expression of this molecule in the tumor did not correlate with pathological or clinical response to therapy. More importantly, iNOS and NT expression by the melanoma cells strongly correlated with poor survival in patients with stage 3 disease (P < 0.001 and P = 0.020, respectively), suggesting a pathway whereby iNOS might contribute to enhanced tumor progression. In conclusion, our findings strongly suggest that iNOS expression has potential to be considered as a prognostic factor and NO as a critical mediator of an aggressive tumor phenotype in human metastatic melanomas.

Classification and staging of melanoma.

Although a standardized and uniformly accepted cancer staging system is an essential and fundamental requirement to enable meaningful comparisons across patient populations, the sometimes capricious biologic behavior of melanoma makes developing such a staging system particularly difficult. Since the earliest well-documented attempts at classifying patients with cutaneous melanoma were described more than 50 years ago, the identification of increasingly powerful prognostic factors has led to sequential modifications of the cutaneous melanoma staging system. The current AJCC staging system is based on relatively well-established prognostic factors; however, several recent reports have identified additional prognostic factors not included in the current system, and other studies support the re-evaluation of some of the currently employed staging criteria. Some of the more controversial areas include the relevance of level of invasion versus tumor thickness, optimal cutoffs for tumor thickness, importance of ulceration, the grouping of satellites with in-transit metastases, the inclusion of microsatellites and local recurrences as a separate staging criterion, the replacement of size of nodal mass with number of positive nodes, the importance of nodal metastases in more than one nodal basin, and the prognostic significance of distant metastases. Future modifications of the staging system are anticipated to better incorporate these observations. Stage-specific staging recommendations for the patient with melanoma provide the clinician with a framework to most efficiently assess extent of disease in an era of cost-conscious clinical practice. In the asymptomatic patient with primary melanoma (stage I or II), we recommend a chest roentgenogram and evaluation of alkaline phosphatase and LDH levels; extensive radiologic evaluations are not indicated, because the rate of detection in this population is extremely low. Additional staging information should also be obtained by the technique of lymphatic mapping and sentinel lymphadenectomy. For patients with local-regional disease (stage III, satellites, and local recurrence), a selective approach to imaging studies is warranted. For this patient population, we recommend complete blood count, liver function tests including alkaline phosphatase and LDH, a chest roentgenogram, and a CT scan of the abdomen. Although the yield of these tests, particularly CT of the abdomen, in detecting distant metastases in asymptomatic patients is low, they may identify false-positive abnormalities and provide an important baseline for future studies in this high-risk population. For patients with disease below the waist or in the head and neck region, we recommend CT of the pelvis and CT of the neck, respectively. Additional studies should be done only if clinically indicated. Finally, patients with known systemic disease (stage IV) should be more comprehensively evaluated, because the likelihood of detecting asymptomatic metastases is higher. Accordingly, in addition to the work-up outlined previously for stage III patients, we also perform a CT scan of the chest and MR imaging of the brain; other studies (e.g., bone scan, gastrointestinal series) are performed on the basis of symptoms.

Follow-up recommendations for patients with American Joint Committee on Cancer Stages I-III malignant melanoma.

BACKGROUND: Guidelines for follow-up of melanoma patients are not established. In 1987, a follow-up protocol was instituted at the Yale Melanoma Unit to improve upon the detection of disease recurrence in patients with American Joint Committee on Cancer Stage I-III cutaneous melanoma. The follow-up protocol consists of a patient education program and a surveillance schedule based on stage of disease. METHODS: The authors retrospectively reviewed the records of 373 patients who were seen and followed according to the surveillance protocol in the Yale Melanoma Unit between January 1988 and December 1994 to determine 1) the time interval between the initial visit and recurrence; 2) the most common method of detecting recurrences; 3) whether the surveillance schedule or the patient detects more recurrences, i.e., asymptomatic recurrences versus symptomatic recurrences; 4) whether there is any survival difference between asymptomatic and symptomatic recurrences. RESULTS: The 5-year overall survival rates for Stage I, II, and III patients were 95%, 72%, and 52%, respectively. Of the 78 recurrences, 44 (56%) were detected by physician-directed surveillance examinations and 34 (44%) by patients. Most recurrences were found within the first (47%) or second (32%) year of follow-up. The estimated 6-month hazard rates for death or recurrence were 0.0044, 0.0088, and 0.0278 for Stage I, II, and III patients, respectively. The group of asymptomatic patients with recurrence had a survival advantage over the symptomatic recurrence group. In addition, patients with locoregional recurrence had better survival than those with distant recurrence. CONCLUSIONS: Although many recurrences arise rapidly and are recognized early by patients, in this study more than half were found by surveillance examinations before symptoms were manifest. Based on the hazard ratio for recurrences, the authors recommend the following surveillance schedules in addition to the patient education program for detection of recurrences: 1) Stage I, annually; 2) Stage II, every 6 months for Years 1-2 and annually thereafter; 3) Stage III, every 3 months for Year 1, every 4 months for Year 2, and every 6 months for Years 3-5; 4) at Year 6 and beyond, all patients should have surveillance annually, due to the risk of late recurrence and/or metachronous multiple primaries.

Pilot study of intra-arterial cisplatin and intravenous vinblastine and dacarbazine in patients with melanoma in-transit metastases.

For melanoma, in-transit metastases (ITMs) are a harbinger of systemic disease in over 70% of patients and thus warrant a systemic approach to management. In this study, previously untreated patients with ITMs (n=15) received a systemic regimen of 'CVD' in 21 day cycles (median, three cycles) as follows: dacarbazine 800 mg/m2 intravenously (i.v.) on day 1, vinblastine 1.6 mg/m2 i.v. on days 1-5, and cisplatin (CDDP) 100 mg/m2 by 24 h intra-arterial (i.a.) infusion in 1l of heparinized saline via the iliac or subclavian artery on day 3. There were three clinical complete responses (CRs) in patients with a modest burden of ITMs (< 3 cm in size) and seven partial responses (PRs), yielding a 67% response rate (95% confidence interval, 38-88%). One of the clinical CRs had microscopic residual disease at surgery (a pathological PR). The times to progression (TTP) for the CRs were 5, 21 and 38+ months; the median TTP for the PRs was 4.5 months (range, 2-10 months). Overall median survival was 31 months. Systemic toxicities were similar to those induced by i.v. CVD. However, patients noted more pronounced paraesthesia in the infused extremity. Also, two patients experienced severe CDDP-induced burns, one patient developed brachial plexopathy, and one patient had a haemorrhage in an occult brain metastasis. The high clinical activity of this regimen will have to be confirmed in more patients before a first-pass i.a. advantage can be claimed. Furthermore, the dose, schedule and technique of i.a. CDDP delivery must be further refined before it can be routinely incorporated in regimens as an alternative to isolated regional hyperthermic perfusion, which is technically more difficult and is not readily available in community-based hospitals.

Phase II trial of escalated dose of tirapazamine combined with cisplatin in advanced malignant melanoma.

A phase II study was undertaken to determine the efficacy of tirapazamine combined with cisplatin in patients with metastatic melanoma between April 1996 and April 1997. Tirapazamine 390 mg/m2, administered i.v. over 2 h, followed in 1 h by cisplatin 75 mg/m2 over 1 h, were used every 21 days to treat chemotherapy-naive patients with metastatic melanoma. Objective tumor measurements were used to assess efficacy of the regimen. NCI common toxicity criteria were used to grade toxicities. Forty-eight patients with metastatic melanoma of cutaneous or mucosal origin, none with symptomatic brain metastasis, were treated. Nine patients had a partial response, with an overall response rate of 20% (95% confidence interval: 9-33%). The median duration of response was 6 months. Grade 3 nausea, vomiting, anorexia, muscle cramps and fatigue occurred in fewer than 10% of patients. Neutropenia and thrombocytopenia were rare. This outpatient single-day administered tirapazamine-cisplatin regimen has definite activity in chemotherapy-naive patients with metastatic melanoma. Further studies in combination with other agents active against this disease are warranted.

Differential increase of Fas ligand expression on metastatic and thin or thick primary melanoma cells compared with interleukin-10.

Fas ligand (FasL), a cell surface molecule belonging to the tumour necrosis factor family, binds to its receptor Fas and thus induces apoptosis of Fas-bearing cells such as activated lymphocytes. In this paper, we report the expression of FasL on melanoma cell lines and patient tumour specimens, and compare it with the expression of interleukin-10 (IL-10), a putative immunosuppressive factor. Apoptosis of Fas-bearing Jurkat cells was increased after interferon-alpha treatment of the FasL-positive melanoma cell line A375, suggesting a regulation of FasL function. We also tested whether FasL and IL-10 were ever co-expressed. Immunohistochemistry studies showed that IL-10 expression was highly positive in the same tumour samples which expressed FasL. In the melanoma patients with thin primaries, 10 of the 12 primaries and six of the seven metastatic lesions were positive for IL-10. In the melanoma patients with thick primaries (> 0.75 mm), four of the five primary lesions and nine of the 10 metastatic lesions were positive for IL-10. In contrast, FasL was generally negative in primary tumours and positive in metastatic tumours. In the thin primary melanoma patients, two of the 12 primaries and five of the seven metastatic tumours were positive for FasL. From the thick melanomas, one of the five primaries and five of the 10 metastatic lesions were positive for FasL. The function of melanoma-derived FasL was confirmed by four different cytotoxicity assays.

Phase II trial of doxil for patients with metastatic melanoma refractory to frontline therapy.

Treatment options for patients with stage IV melanoma are limited. Based on differences in the toxicity and activity profiles of pegylated liposomal doxorubicin (doxil) compared to standard doxorubicin, we have conducted a phase II trial of doxil for patients with metastatic melanoma. Doxil was administered as a 60-90 min intravenous infusion every 21 days. The starting dose was 60 mg/m2 for the initial nine patients, but was subsequently reduced to 50 mg/m2 for the remainder due to toxicity issues. Thirty-two patients were enrolled in the trial. Ninety-one percent had received prior systemic therapy. There were no complete responses and two partial responses for an overall response rate of 6%. The dominant side effects included hand-foot syndrome, rash (occasionally severe), and stomatitis, consistent with reports from other trials using similar doses and schedules. We conclude that doxil does not demonstrate sufficient activity in metastatic melanoma to warrant further investigation into its use in this setting.

Classification and staging of melanoma.

Although a standardized and uniformly accepted cancer staging system is an essential and fundamental requirement to enable meaningful comparisons across patient populations, the sometimes capricious biologic behavior of melanoma makes developing such a staging system particularly difficult. Since the earliest well-documented attempts at classifying patients with cutaneous melanoma were described more than 50 years ago, the identification of increasingly powerful prognostic factors has led to sequential modifications of the cutaneous melanoma staging system. The current AJCC staging system is based on relatively well-established prognostic factors; however, several recent reports have identified additional prognostic factors not included in the current system, and other studies support the re-evaluation of some of the currently employed staging criteria. Some of the more controversial areas include the relevance of level of invasion versus tumor thickness, optimal cutoffs for tumor thickness, importance of ulceration, the grouping of satellites with in-transit metastases, the inclusion of microsatellites and local recurrences as a separate staging criterion, the replacement of size of nodal mass with number of positive nodes, the importance of nodal metastases in more than one nodal basin, and the prognostic significance of distant metastases. Therefore, future modifications of the staging system are anticipated to better incorporate these observations. Stage-specific staging recommendations for the patient with melanoma provide the clinician with a framework to most efficiently assess extent of disease in an era of cost-conscious clinical practice. In the asymptomatic patient with primary melanoma (stage I or II), we recommend a chest roentgenogram and evaluation of alkaline phosphatase and LDH levels; extensive radiologic evaluations are not indicated, because the rate of detection in this population is extremely low. Additional staging information should also be obtained by the technique of lymphatic mapping and sentinel lymphadenectomy. For patients with local-regional disease (stage III, satellites, and local recurrence), a selective approach to imaging studies is warranted. For this patient population, we recommend complete blood count, liver function tests including alkaline phosphatase and LDH, a chest roentgenogram, and a CT scan of the abdomen. Although the yield of these tests, particularly CT of the abdomen, in detecting distant metastases in asymptomatic patients is low, they may identify false-positive abnormalities and provide an important baseline for future studies in this high-risk population. For patients with disease below the waist or in the head and neck region, we recommend CT of the pelvis and CT of the neck, respectively. Additional studies should be done only if clinically indicated. Finally, patients with known systemic disease (stage IV) should be more comprehensively evaluated, because the likelihood of detecting asymptomatic metastases is higher. Accordingly, in addition to the work-up outlined previously for stage III patients, we also perform a CT scan of the chest and MR imaging of the brain; other studies (e.g., bone scan, gastrointestinal series) are performed on the basis of symptoms.

Melanin content and downregulation of glutathione S-transferase contribute to the action of L-buthionine-S-sulfoximine on human melanoma.

L-buthionine-S,R-sulfoximine (L-S,R-BSO) was enriched for the active L-buthionine-S-sulfoximine (L-S-BSO) diastereomer. Comparative analysis was performed to determine if this enriched form possessed an increased capacity to deplete glutathione (GSH), and to inhibit the proliferation of tumor cell lines and fresh human tumor samples. Increased activity was observed for the enriched preparation of L-S-BSO in direct proportion to its increased L-S-diastereomeric percentage. Significant antitumor activity towards melanoma, breast and ovarian carcinoma specimens was noted, with the greatest activity directed against malignant melanoma. The activity of BSO on melanoma specimens was found to be correlated with their melanin content, suggesting that free radicals generated during melanin synthesis may become cytotoxic after GSH-dependent scavenging has been eliminated by BSO treatment. The antimelanoma activity of melphalan and BCNU were found to be significantly enhanced in combination with L-S-BSO. With respect to the mechanism of L-S-BSO synergy with alkylators, L-S-BSO treatment of M14 and ZAZ human melanoma cell lines resulted in decreased GSH levels and glutathione S-transferase (GST) activity. Western and Northern blot analyses indicated that GST-mu was the predominant isozyme downregulated after L-S-BSO treatment. Both M14 and ZAZ cell lines selected for resistance to L-S-BSO also showed decreased levels of GST-mu expression. However, in drug free media GST enzyme activity returned to pre-treatment levels without altering the BSO-resistance status of the cell lines. We conclude that L-S-BSO may be an active agent in the treatment of melanoma, and that it may enhance alkylator activity on melanoma through depletion of GSH and down-regulation of GST expression. Purified L-S-BSO should be explored clinically as an active agent for the treatment of melanoma.