A step forward on the in vitro and in vivo assessment of a novel nanomedicine against melanoma.

Melanoma is the most aggressive form of skin cancer, with increasing incidence and mortality rates. To overcome current treatment limitations, a hybrid molecule (HM) combining a triazene and a sulfur L-tyrosine analogue, was recently synthesized, incorporated in long blood circulating liposomes (LIP HM) and validated in an immunocompetent melanoma model. The present work constitutes a step forward in the therapeutic assessment of HM formulations. Here, human melanoma cells, A375 and MNT-1, were used and dacarbazine (DTIC), a triazene drug clinically available as first-line treatment for melanoma, constituted the positive control. In cell cycle analysis, A375 cells, after 24-h incubation with HM (60 µM) and DTIC (70 µM), resulted in a 1.2 fold increase (related to control) in the percentage of cells in G0/G1 phase. The therapeutic activity was evaluated in a human murine melanoma model (subcutaneously injected with A375 cells) to most closely resemble the human pathology. Animals treated with LIP HM exhibited the highest antimelanoma effect resulting in a 6-, 5- and 4-fold reduction on tumor volume compared to negative control, Free HM and DTIC groups, respectively. No toxic side effects were detected. Overall, these results constitute another step forward in the validation of the antimelanoma activity of LIP HM, using a murine model that more accurately simulates the pathology that occurs in human patients.

Preclinical validation of a new hybrid molecule loaded in liposomes for melanoma management.

The aggressiveness of melanoma and lack of effective therapies incite the discovery of novel strategies. Recently, a new dual acting hybrid molecule (HM), combining a triazene and a ʟ-tyrosine analogue, was synthesized. HM was designed to specifically be activated by tyrosinase, the enzyme involved in melanin biosynthesis and overexpressed in melanoma. HM displayed remarkable superior antiproliferative activity towards various cancer cell lines compared with temozolomide (TMZ), a triazene drug in clinical use, that acts through DNA alkylation. In B16-F10 cells, HM induced a cell cycle arrest at phase G0/G1 with a 2.8-fold decrease in cell proliferation index. Also, compared to control cells, HM led to a concentration-dependent reduction in tyrosinase activity and increase in caspase 3/7 activity. To maximize the therapeutic performance of HM in vivo, its incorporation in long blood circulating liposomes, containing poly(ethylene glycol) (PEG) at their surface, was performed for passively targeting tumour sites. HM liposomes (LIP HM) exhibited high stability in biological fluids. Preclinical studies demonstrated its safety for systemic administration and in a subcutaneous murine melanoma model, significantly reduced tumour progression. In a metastatic murine melanoma model, a superior antitumour effect was also observed for mice receiving LIP HM, with markedly reduction of lung metastases compared to positive control group (TMZ). Biodistribution studies using 111In-labelled LIP HM demonstrated its ability for passively targeting tumour sites, thus correlating with the high therapeutic effect observed in the two experimental murine melanoma models. Overall, our proposed nanotherapeutic strategy was validated as an effective and safe alternative against melanoma.

Sulfur Analogues of Tyrosine in the Development of Triazene Hybrid Compounds: A New Strategy against Melanoma.

Malignant melanoma is the major cause of death from skin cancer. Treatment of metastatic melanoma remains an enormous challenge. In this study we developed hybrid compounds and studied their potential use in malignant melanoma chemotherapy. They were designed to act by a double mechanism of action, being composed of two pharmacophores: the tyrosine sulfur analogue 4-S-cysteaminylphenol (4-S-CAP, 10), with immunomodulatory properties and specific melanocytotoxic activity, and triazene 4, with DNA alkylating properties. The design of these compounds aims to achieve selective activation by the enzyme tyrosinase overexpressed in melanoma cells. Compounds 11a-e, 13a, and 13b were found to be excellent tyrosinase substrates (0.5 min ≤ t 1/2 ≤ 3.7 min). Furthermore, derivatives 11 and 13 were evaluated for their molecular properties, hepatotoxicity, in vivo toxicity profile, and assessment of cytotoxic activity in melanoma and non-melanoma cell lines. The results were compared with those obtained for temozolomide, a triazene used in melanoma therapy. It was discovered that the hybrids are selective and effective drugs, representing a valuable model for the development of new multitarget melanoma therapy. In particular, compound 10 may be an important component for these strategies that use a metabolic pathway of melanin synthesis. Molecular hybridization of 10 with triazenes 4 renders the hybrids (11 and 13) unexpectedly devoid of hepatotoxicity while maintaining cytotoxic activity in malignant cells.

The selective cytotoxicity of new triazene compounds to human melanoma cells.

Metastatic melanoma still remains one the most difficult cancers to overcome. The aim of our research was the design of anti-tumour triazene compounds 3 for application to a melanoma-specific therapy. The strategy exploits the unique enzyme pathway of melanin biosynthesis for conversion of non-toxic prodrugs into toxic drugs in the melanoma cell. The compounds 3 were designed by coupling two active moieties, the alkylating triazenes and different tyrosinase substrates. All compounds 3 revealed to be chemically stable in isotonic phosphate buffer (PBS) at physiologic pH (t½≥48h), and most of them showed to be slowly hydrolysed in human plasma (1.5≤t½ (h)≤161). Compounds 3c-n revealed to be excellent tyrosinase substrates (0.74≤t½ (min)≤6) with the best tyrosinase substrate 3l releasing MMT 45s after tyrosinase activation. Structure-activity relationship studies allowed the identification of the better structural features for enzyme affinity. Furthermore, the derivatives 3l and 3m showed cell selectivity with significant cytotoxic effects (IC50 values of 46-65µM) against melanoma cell lines with tyrosinase overexpression MNT-1 and B16F10.