The role of taxanes in the treatment of metastatic melanoma

The management of patients with metastatic malignant melanoma remains difficult. Conventional chemotherapy has been disappointingly ineffective. Dacarbazine (DTIC) is considered to be one of the most active single agents with a response rate of approximately 15-20%. Many patients who initially respond to treatment subsequently relapse. Clearly, there is a need for improvement, and the evaluation of new agents is warranted. This article reviews current phase II studies of single-agent taxanes and their combinations in patients with metastatic melanoma, and examines the likely impact of taxanes on treatment strategies. Response rates from phase II trials with single-agent taxanes vary from 3.3% to 17%. Prolonged durations of disease control are observed. Combinations of taxanes with DTIC, temozolomide, cisplatin, carboplatin and tamoxifen have demonstrated response rates from 12% to 41%, suggesting that they are at least as effective as various other combination regimens. Encouraging results have been produced in the second-line metastatic setting. Taxanes, both as single agents and in combinations, may be a treatment option for some patients with metastatic melanoma, especially in the second-line setting.     

Genetic polymorphisms in DNA repair and oxidative stress pathways associated with malignant melanoma susceptibility

Background

Base excision repair (BER) and nucleotide excision repair (NER) pathways eliminate a wide variety of DNA damage, including UV photoproducts. The ability of each individual to repair DNA damage following different causes might explain at least in part the variability in cancer susceptibility. Moreover, inflammatory response to UV exposure may further contribute to skin carcinogenesis by oxidative stress mechanisms. Single nucleotide polymorphisms in genes encoding various DNA-repair enzymes and oxidative stress factors may be candidate low-penetrance variants with a role in susceptibility to different cancers, particularly in those with aetiologies linked to environmental exposure, such as malignant melanoma (MM).

Methods

In this case-control study, 684 Spanish sporadic MM patients and 406 cancer-free control subjects were included and the role of 46 polymorphisms belonging to 16 BER and NER genes as well as 11 genes involved in oxidative stress processes were investigated.

Results

One polymorphism was identified to be individually associated with MM in the Spanish population. The variant was found in the NOS1 oxidative stress gene (rs2682826; p-value = 0.01). These results suggest a putative role of oxidative stress processes in the genetic predisposition to melanoma.

Conclusion

To the authors’ knowledge, this is the largest DNA repair-related SNP study in melanoma risk conducted in the Spanish population up to now. Furthermore, it also represents a comprehensive genetic study of several oxidative stress polymorphisms tested in relation to MM susceptibility.     

The role of surgery for patients with metastatic melanoma

When deciding to perform a resection for metastatic melanoma one should first decide whether the intent of the procedure is curative or palliative. When the resection is palliative, the success of surgical treatment will depend on the presence of identifiable symptoms, the morbidity of the procedure, the course of the disease, and the ability to communicate the treatment goals among surgeon, patient, and family. When the resection is curative, survival will depend on the ability of the surgeon to select patients with a pattern of recurrence suggestive of less aggressive tumor biology. Factors generally found predictive of improved survival, and therefore reflective of tumor biology, include longer disease-free interval, fewer numbers of metastases, and the ability to obtain a complete resection. Resection of metastases in patients who recur within one-year, who present with multiple lesions, and who present with disease that cannot be completely resected, will not result in long-term survival.     

The role of endogenous and exogenous factors in the etiology of skin melanoma]

The results of case-control study of skin melanoma carried out in Moscow are presented. They point to considerable influence of endogenous factors on the relative risk of melanoma. The risk of melanoma is increased by such factors as light color of the skin, presence of freckles and moles. Exposure to UV-radiation raised the risk of melanoma, however, after relevant adjustment for the said factors relative risk was reduced. Consumption of greens and high blood levels of alpha-tocopherol significantly decreased the risk of melanoma. Female users of oral contraceptives had significantly lower risk of skin melanoma.     

Antiapoptotic role of endogenous nitric oxide in human melanoma cells

The role of endogenous NO on cell survival was investigated in human melanoma cells and melanocytes. Inducible NO synthase (iNOS) was always expressed in a panel of melanoma cell lines from metastatic lesions and in normal adult melanocytes. iNOS was also detected by immunohistochemistry in melanoma cells from metastases. Release of NO by tumor cells and melanocytes was inhibited by a specific iNOS inhibitor, aminoguanidine (AMG). Inhibition of endogenous NO synthesis did not affect cell cycle progression of melanoma cells but led to cell death by apoptosis, as indicated by Annexin V/propidium iodide and terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling assays. By contrast, iNOS inhibition by AMG did not promote apoptosis in normal adult melanocytes. A mitochondrial pathway was involved in melanoma apop tosis, as indicated by altered mitochondrial membrane potential (delta psi(m)) and down-regulation of Bcl-2 protein level after iNOS inhibition. AMG treatment triggered release of caspase-1, enzymatic activation of caspase-3, and degradation of poly(ADP-ribose) polymerase, one of the main caspase-3 substrates. Melanoma cell apoptosis induced by iNOS inhibition was completely blocked by peptide inhibitors of caspase-1 and caspase-3 (Ac-DEVD-CHO and AC-YVAD-CHO) or by an exogenous NO donor, sodium nitroprusside, or by addition of serum. Finally, comparison of control and AMG-treated melanoma cells by pathway-specific gene array analysis indicated that inhibition of NO synthesis led, before induction of apoptosis, to up-regulation of mRNA levels of genes involved in the apoptosis pathway such as Bax, caspase-1, caspase-3, caspase-6, gadd45beta, mdm2, and TRAIL. Taken together, these results indicate that melanoma cell survival is regulated by endogenous NO resulting from iNOS activity.     

The role of radiotherapy in recurrent and metastatic malignant melanoma: a clinical radiobiological study

A review of the literature and our data has been completed to analyze the clinical radiobiology of malignant melanoma. Six hundred eighteen radiotherapy-treated malignant melanoma lesions were analyzed with regard to radiobiological parameters such as total dose, dose per fraction, treatment time, tumor volume, and various fractionation models. Forty-eight per cent of the treated tumors achieved complete response, which was persistent in 87% after 5 years. Neither total dose, treatment time, nor various modifications of the NSD concept showed any well-defined correlation with response. There was, however, a significant relationship between dose per fraction and response, and a high dose per fraction yielded a significantly better response (59% CR for doses greater than 4 Gy versus 33% CR for doses per fraction less than or equal to 4 Gy). The lack of treatment time influence allowed analysis of the data according to the linear-quadratic model, resulting in an alpha/beta ratio of 2.5 Gy. Using this ratio, an iso-effect for different fractionation schedules could be estimated by the extrapolated total-dose (ETD). The ratio was further improved when corrected for the tumor volume. Thus, an iso-effect formula for malignant melanoma could be calculated as: ETDvol (Gy) = D X [d + 2.5)/2.5) X M-.33, where D and d are total dose and dose per fraction in Gy, respectively, and M is the mean tumor diameter in cm. Based on a logit analysis, a complete response level of 50% appeared at an ETDvol value of 83 Gy. The formula is currently the best way to determine an optimal radiation schedule for an effective radiation treatment of malignant melanoma. The tumor response was further improved in 134 additional cases receiving adjuvant hyperthermia. Here, a thermal enhancement ratio (TER) of 2.0 was observed. In a group of 131 patients with only local or regional disease, a 5 year survival rate of 49% was observed in 77 patients with persistent local tumor control, but only 3% survived among the 54 patients in whom local therapy failed. It is therefore, highly important to the probability of survival in recurrent melanoma that proper local treatment be performed.     

Tumour growth rate and DNA flow cytometry parameters as prognostic factors in metastatic melanoma.

The prognostic value of flow cytometric parameters and tumour growth rate of melanoma metastases under the mouse renal capsule was investigated for tumours from 117 consecutive patients referred to the Helsinki University Central Hospital Melanoma Team. DNA flow cytometry (FCM) was interpretable for the tumours of 114 patients, and growth rate analysis for 82 patients, both results being available from 79 patients. Thirty-six percent of the tumours were DNA diploid and 64% DNA aneuploid. Tumour ploidy and S-phase fraction were shown by multivariate Cox model analysis to be independent prognostic variables and major determinants of survival after first recurrence. Patients with DNA diploid or aneuploid tumours survived a median 16 and 27 months, respectively. A high growth rate of tumour sample in vivo under the mouse renal capsule tended to be a sign of poor prognosis, although not reaching statistical significance. Combining the results of FCM, tumour growth rate and TNM stage, we propose a highly efficient prognostic scoring method. Patients with a score above 0.75 had a median survival of 11 months compared to 30 months among patients scoring under 0.75 (P less than 0.0001). This score was the most significant (P less than 0.0001) prognostic factor in the Cox model when TNM stage, age, ploidy, SPF, and tumour growth rate were analysed as covariates.     

The role of oxidative stress on breast cancer development and therapy

Reactive oxygen species (ROS) are produced by both enzymatic and non-enzymatic systems within eukaryotic cells and play important roles in cellular physiology and pathophysiology. Although physiological concentrations are crucial for ensuring cell survival, ROS overproduction is detrimental to cells, and considered key-factors for the development of several diseases, such as neurodegenerative diseases, cardiovascular disorders, and cancer. Cancer cells are usually submitted to higher ROS levels that further stimulate malignant phenotype through stimulus to sustained proliferation, death evasion, angiogenesis, invasiveness, and metastasis. The role of ROS on breast cancer etiology and progression is being progressively elucidated. However, less attention has been given to the development of redox system-targeted strategies for breast cancer therapy. In this review, we address the basic mechanisms of ROS production and scavenging in breast tumor cells, and the emerging possibilities of breast cancer therapies targeting ROS homeostasis.     

Comparison of nuclear DNA content in primary and metastatic papillary thyroid carcinoma

Nuclear DNA values were determined in 40 primary papillary thyroid carcinomas, as well as in 52 corresponding local recurrences and metastases were observed either at the time of diagnosis or up to 20 years later. The patient population consisted of 34 survivors and 6 nonsurvivors. In survivors, both the primary tumors and their recurrences and metastases exhibited a majority of cells with DNA values within the normal diploid region, whereas nonsurvivors showed increased and scattered DNA values. In all cases, the primary tumors and the corresponding recurrences and metastases showed similar DNA distribution patterns even if many years had passed between the detection of the primary tumor and the metastases. The results indicate that in papillary thyroid carcinomas, the DNA distribution patterns in the primary tumor and the corresponding recurrences or metastases are generally similar throughout the entire period of disease.     

The role of gap junction communication in metastatic B16 melanoma in C57BL mice

The study is concerned with the effects of non-specific blocking gap junction communication with oleamide as well as genesis and spreading of melanoma B16 metastases to the lung in mice C57B1. The blocking exerted no distinct influence on primary tumorigenesis but had a marked effect on metastatic spread. Oleamide treatment during tumor growth led to an increase in area covered by metastases. A correlation was established between metastatic frequency and dosage: 1 mg/kg was followed by an upsurge in frequency of secondary lung tumors while 10 mg/kg--by a drop.     

N-acetylcysteine protects melanocytes against oxidative stress/damage and delays onset of ultraviolet-induced melanoma in mice.

PURPOSE: UV radiation is the major environmental risk factor for melanoma and a potent inducer of oxidative stress, which is implicated in the pathogenesis of several malignancies. We evaluated whether the thiol antioxidant N-acetylcysteine (NAC) could protect melanocytes from UV-induced oxidative stress/damage in vitro and from UV-induced melanoma in vivo. EXPERIMENTAL DESIGN: In vitro experiments used the mouse melanocyte line melan-a. For in vivo experiments, mice transgenic for hepatocyte growth factor and survivin, shown previously to develop melanoma following a single neonatal dose of UV irradiation, were given NAC (7 mg/mL; mother's drinking water) transplacentally and through nursing until 2 weeks after birth. RESULTS: NAC (1-10 mmol/L) protected melan-a cells from several UV-induced oxidative sequelae, including production of intracellular peroxide, formation of the signature oxidative DNA lesion 8-oxoguanine, and depletion of free reduced thiols (primarily glutathione). Delivery of NAC reduced thiol depletion and blocked formation of 8-oxoguanine in mouse skin following neonatal UV treatment. Mean onset of UV-induced melanocytic tumors was significantly delayed in NAC-treated compared with control mice (21 versus 14 weeks; P = 0.0003). CONCLUSIONS: Our data highlight the potential importance of oxidative stress in the pathogenesis of melanoma and suggest that NAC may be useful as a chemopreventive agent.     

Ferritin contributes to melanoma progression by modulating cell growth and sensitivity to oxidative stress.

PURPOSE: Employing an in vitro model system of human melanoma progression, we previously reported ferritin light chain (L-ferritin) gene overexpression in the metastatic phenotype. Here, we attempted to characterize the role of ferritin in the biology of human melanoma and in the progression of this disease. EXPERIMENTAL DESIGN: Starting from the LM human metastatic melanoma cell line, we engineered cell clones in which L-ferritin gene expression was down-regulated by the stable expression of a specific antisense construct. These cells were then assayed for their growth capabilities, chemoinvasive properties, and sensitivity to oxidative stress. Additionally, ferritin protein content in primary and metastatic human melanomas was determined by immunohistochemistry. RESULTS: Artificial L-ferritin down-regulation in the LM cells strongly inhibited proliferation and chemoinvasion in vitro and cell growth in vivo. In addition, L-ferritin down-regulated cells displayed enhanced sensitivity to oxidative stress and to apoptosis. Concurrently, immunohistochemical analysis of a human melanoma tissue array revealed that ferritin expression level in metastatic lesions was significantly higher (P < 0.0001) than in primary melanomas. Furthermore, ferritin expression was constantly up-regulated in autologous lymph node melanoma metastases when compared with the respective primary tumors in a cohort of 11 patients. CONCLUSIONS: These data suggest that high ferritin expression can enhance cell growth and improve resistance to oxidative stress in metastatic melanoma cells by interfering with their cellular antioxidant system. The potential significance of these findings deserves to be validated in a clinical setting.     

The prognostic role of CD4+ and CD8+ lymphocytes during chemoimmunotherapy in metastatic melanoma

We have observed that an early increase in the CD4+/CD8+ ratio of metastatic melanoma patients during chemoimmunotherapy is the most favourable independent prognostic factor. In this study, 87 patients with metastatic melanoma were monitored for peripheral blood lymphocyte subsets (CD4+ and CD8+) before and during chemoimmunotherapy (dacarbazine, vinblastine, lomustine and bleomycin or dacarbazine alone plus interferon-alpha) to confirm our previous observation. Blood samples were systematically obtained from patients who received either of these chemoimmunotherapies. The frequencies of peripheral blood lymphocyte subsets were monitored by flow cytometry using monoclonal antibodies OKT4 (CD4+, T-helper cells) and OKT8 (CD8+, T-suppressor cells). The overall response rate was 46.5%, and the median overall survival was 9.3 months. Patients with pre-treatment CD4+ levels above the mean level, who later responded to therapy, had a median survival of 28.1 months vs. 10.2 months for responders with low pre-treatment CD4+ levels (P=0.053, log-rank test). Responders with decreasing CD8+ levels had a median survival of 27.8 months vs. 10.8 months for responders with increasing CD8+ levels (P=0.04, log-rank test). Similarly, responding patients with an increasing CD4+/CD8+ ratio had a median survival of 28.1 months vs. 10.5 months for those with decreasing ratios (P=0.002, log-rank test). Non-responders showed no difference in median survival irrespective of low or high pre-treatment CD4+ lymphocytes, increasing or decreasing CD8+ levels, or increasing or decreasing CD4+/CD8+ ratios. This follow-up study confirms that the monitoring of CD4+ and CD8+ lymphocytes may provide important predictive and prognostic information in metastatic melanoma patients receiving chemoimmunotherapy.