Advances in gene therapy for malignant melanoma

Enhanced gene transfection and induction of apoptosis in melanoma cells by branched poly(β-amino ester)s with uniformly distributed branching units

Melanoma, one of the most devastating forms of skin cancer, currently lacks effective clinical treatments. Delivery of functional genes to modulate specific protein expression to induce melanoma cell apoptosis could be a promising therapeutic approach. However, transfecting melanoma cells using non-viral methods, particularly with cationic polymers, presents significant challenges. In this study, we synthesized three branched poly(β-amino ester)s (HPAEs) with evenly distributed branching units but varying space lengths through a two-step "oligomer combination" strategy. The unique topological structure enables HPAEs to condense DNA to form nano-sized polyplexes with favorable physiochemical properties. Notably, HPAEs, especially HPAE-2 with intermediate branching unit space length, demonstrated significantly higher gene transfection efficiency than the leading commercial gene transfection reagent, jetPRIME, in human melanoma cells. Furthermore, HPAE-2 efficiently delivered the Bax-encoding plasmid into melanoma cells, leading to a pronounced pro-apoptotic effect without causing noticeable cytotoxicity. This study establishes a potent non-viral platform for gene transfection of melanoma cells by harnessing the distribution of branching units, paving the way for potential clinical applications of gene therapy in melanoma treatment.

Survivin Promoter-Driven DFF40 Gene Expression Sensitizes Melanoma Cancer Cells to Chemotherapy

Downregulation of the apoptotic protein DNA fragmentation factor 40 (DFF40) is correlated with poor overall survival in some malignancies, including melanoma. In this study, DFF40 gene expression driven by survivin promoter, a tumor-specific promoter, was used to selectively induce cytotoxicity in melanoma cells. The activity and strength of survivin promoter were examined in B16F10 murine melanoma, and L929 murine normal fibroblast cell lines using enhanced green fluorescent protein reporter assay and reverse transcription polymerase chain reaction. The effect of expression of DFF40 under the control of cytomegalovirus (CMV) or survivin promoter on viability of cancerous and normal cells was determined by MTT [3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide] assay. Apoptosis induction by expression of DFF40 was evaluated using Annexin-V/propidium iodide staining. Our findings showed high activity of survivin promoter comparable to the control promoter (ie, CMV) in melanoma cells, while survivin activity in normal cells was negligible. Survivin promoter-derived DFF40 gene expression led to selective inhibition of cell viability and induction of apoptosis in cancerous cells. Low and sublethal concentrations of a chemotherapeutic drug, dacarbazine, significantly enhanced the growth inhibitory effect of DFF40 gene therapy. Combination of survivin-driven gene therapy and chemotherapy could be considered as a potential therapeutic treatment for melanoma and possibly other malignancies with similar features.

Curcumin plays a synergistic role in combination with HSV-TK/GCV in inhibiting growth of murine B16 melanoma cells and melanoma xenografts

Melanoma is a global concern and accounts for the major mortality of skin cancers. Herpes simplex virus thymidine kinase gene with ganciclovir (HSV-TK/GCV) is a promising gene therapy for melanoma. Despite its low efficiency, it is well known for its bystander effect which is mainly mediated by gap junction. In this study, we found that curcumin reduced B16 melanoma cell viability in both time- and dose-dependent manner. Further study showed that curcumin improved the gap junction intercellular communication (GJIC) function, and upregulated the proteins essential to gap junction, such as connexin 32 and connexin 43, indicating the potential role in enhancing the bystander effect of HSV-TK/GCV. By co-culturing the B16^TK cells, which stably expressed TK gene, with wildtype B16 (B16^WT) cells, we found that co-treatment of curcumin and GCV synergistically inhibited B16 cell proliferation, but the effect could be eliminated by the gap junction inhibitor AGA. Moreover, curcumin markedly increased apoptosis rate of B16^WT cells, suggesting its effect in enhancing the bystander effect of HSV-TK/GCV. In the in-vivo study, we established the xenografted melanoma model in 14 days by injecting mixture of B16^TK and B16^WT cell in a ratio of 3:7. The result demonstrated that, co-administration of curcumin and GCV significantly inhibited the xenograft growth, as indicated by the smaller size and less weight. The combinational effect was further confirmed as a synergistic effect. In conclusion, the results demonstrated that curcumin could enhance the killing effect and the bystander effect of HSV-TK/GCV in treating melanoma, which might be mediated by improved gap junction. Our data suggested that combination of HSV-TK/GCV with curcumin could be a potential chemosensitization strategy for cancer treatment.

Dioscin augments HSV-tk-mediated suicide gene therapy for melanoma by promoting connexin-based intercellular communication

Suicide gene therapy is a promising strategy against melanoma. However, the low efficiency of the gene transfer technique can limit its application. Our preliminary data showed that dioscin, a glucoside saponin, could upregulate the expression of connexins Cx26 and Cx43, major components of gap junctions, in melanoma cells. We hypothesized that dioscin may increase the bystander effect of herpes simplex virus thymidine kinase/ganciclovir (HSV-tk/GCV) through increasing the formation of gap junctions. Further analysis showed that dioscin indeed could increase the gap junctional intercellular communication in B16 melanoma cells, resulting in more efficient GCV-induced bystander killing in B16^tk cells. By contrast, overexpression of dominant negative Cx43 impaired the cell-cell communication of B16 cells and subsequently weakened the bystander effect of HSV-tk/GCV gene therapy. In vivo, combination treatment with dioscin and GCV of tumor-bearing mice with 30% positive B16^tk cells and 70% wild-type B16 cells caused a significant reduction in tumor volume and weight compared to treatment with GCV or dioscin alone. Taken together, these results demonstrated that dioscin could augment the bystander effect of the HSV-tk/GCV system through increasing connexin-mediated gap junction coupling.

TGF beta secreted by B16 melanoma antagonizes cancer gene immunotherapy bystander effect

Tumor-targeted delivery of immune stimulatory genes, such as pro-inflammatory cytokines and suicide genes, has shown to cure mouse models of cancer. Total tumor eradication was also found to occur despite subtotal tumor engineering; a phenomenon coined the "bystander effect". The bystander effect in immune competent animals arises mostly from recruitment of a cancer lytic cell-mediated immune response to local and distant tumor cells which escaped gene modification. We have previously described a Granulocyte-Macrophage Colony Stimulating Factor (GM-CSF) and Interleukin 2 (IL2) fusokine (aka GIFT2) which serves as a potent anticancer cytokine and it here served as a means to understand the mechanistic underpinnings to the immune bystander effect in an immune competent model of B16 melanoma. As expected, we observed that GIFT2 secreted by genetically engineered B16 tumor cells induces a bystander effect on non modified B16 cells, when admixed in a 1:1 ratio. However, despite keeping the 1:1 ratio constant, the immune bystander effect was completely lost as the total B16 cell number was increased from 10(4) to 10(6) which correlated with a sharp reduction in the number of tumor-infiltrating NK cells. We found that B16 secrete biologically active TGFbeta which in turn inhibited GIFT2 dependent immune cell proliferation in vitro and downregulated IL-2R beta expression and IFN gamma secretion by NK cells. In vivo blockade of B16 originating TGFbeta significantly improved the immune bystander effect arising from GIFT2. We propose that cancer gene immunotherapy of pre-established tumors will be enhanced by blockade of tumor-derived TGFbeta.

Short and highly efficient synthetic promoters for melanoma-specific gene expression

Here, we report the construction and functional analysis of synthetic promoters designed for gene therapy applications requiring strong and specific gene expression in melanoma cell lines. We have analysed the transcriptional activity of different combinations of two transcriptional regulatory modules, a melanocyte-specific element from the human tyrosinase promoter and a cell-cycle-specific element from the human alpha-fetoprotein promoter. Transient expression assays in different cell lines show that several of these composite synthetic promoters can drive a strong and selective expression of a reporter gene in melanoma cell, providing us with a new powerful tool for gene therapy of melanomas.

Retargeting of adenoviral infection to melanoma: combining genetic ablation of native tropism with a recombinant bispecific single-chain diabody (scDb) adapter that binds to fiber knob and HMWMAA

Gene therapy is an emerging and promising modality for the treatment of malignant melanoma and other neoplasms for which conventional therapies are inadequate. Various therapeutic genes have shown promise for tumor cell killing. However, successful gene therapy depends on the development of efficient and targeted gene transfer vectors. Here we describe a novel strategy for targeting of adenovirus-mediated gene transfer to melanoma cells. This strategy combines genetic ablation of native adenoviral tropism with redirected viral binding to melanoma cells via a bispecific adapter molecule, a bacterially expressed single-chain diabody, scDb MelAd, that binds to both the adenoviral fiber protein and to the high molecular weight melanoma-associated antigen (HMWMAA). This antigen is widely and specifically expressed on the surface of melanoma cells and its expression is associated with tumor development and progression. Our results showed specific and strong binding of the anti-HMWMAA scFv RAFT3 and the bispecific adapter scDb MelAd to melanoma cells. In adenoviral infection experiments, we demonstrated i) substantially (>50-fold) reduced infectivity of capsid mutant adenoviruses, ii) restored (up to 367-fold increase), CAR-independent and HMWMAA-mediated infectivity of these mutant viruses by scDb MelAd specifically in melanoma cells, and iii) higher levels of transgene expression in melanoma cells by fiber mutant virus complexed with scDbMelAd, relative to a vector with wild-type fibers. We confirmed the utility of this targeting strategy with human primary melanoma cells that represent clinically relevant substrates. These experiments established that the retargeting strategy mediates up to 54-fold increased adenoviral gene transfer to CAR-negative melanoma cells compared to the vector with native tropism. Hence, the HMWMAA-targeted adenoviral vector lacking native tropism exhibits both enhanced specificity and augmented infectivity of gene transfer to melanoma cells, suggesting that it is feasible to use this vector to improve gene therapy for malignant melanoma.

Apoptosis and melanoma chemoresistance

Melanoma is the most aggressive form of skin cancer and is notoriously resistant to all current modalities of cancer therapy. A large set of genetic, functional and biochemical studies suggest that melanoma cells become 'bullet proof' against a variety of chemotherapeutic drugs by exploiting their intrinsic resistance to apoptosis and by reprogramming their proliferation and survival pathways during melanoma progression. In recent years, the identification of molecules involved in the regulation and execution of apoptosis, and their alteration in melanoma, have provided new insights into the molecular basis for melanoma chemoresistance. With this knowledge in hand, the challenge is now to devise strategies potent enough to compensate or bypass these cell death defects and improve the actual poor prognosis of patients at late stages of the disease.

Diagnosis and management of high-risk and metastatic melanoma

OBJECTIVES

To identify treatment modalities and corresponding nursing implications for the high-risk and metastatic melanoma patient.

DATA SOURCES

Texbooks, research articles, and professional experience.

CONCLUSIONS

Recent advances in the field of melanoma include identification of prognostic factors, refinement of surgical techniques, and identification of effective adjuvant therapy. Novel therapies are currently under investigation.

IMPLICATIONS FOR NURSING PRACTICE

Nurses play a vital role in the treatment of melanoma patients through education regarding their disease and treatment options, patient identification for clinical trials, and intensive monitoring and management for treatment-related side effects.

Rational approaches to human cancer immunotherapy

Over most of the 20th century, immunotherapy for cancer was based on empiricism. Interesting phenomena were observed in the areas of cancer, infectious diseases, or transplantation. Inferences were made and extrapolated into new approaches for the treatment of cancer. If tumors regressed, the treatment approaches could be refined further. However, until the appropriate tools and reagents were available, investigators were unable to understand the biology underlying these observations. In the early 1990s, the first human tumor T cell antigens were defined and dendritic cells were discovered to play a pivotal role in antigen presentation. The current era of cancer immunotherapy is one of translational research based on known biology and rationally designed interventions and has led to a rapid expansion of the field. The beginning of the 21st century brings the possibility of a new era of effective cancer immunotherapy, combining rational, immunological treatments with conventional therapies to improve the outcome for patients with cancer.