Ultraviolet-radiation-induced inflammation promotes angiotropism and metastasis in melanoma.

Intermittent intense ultraviolet (UV) exposure represents an important aetiological factor in the development of malignant melanoma. The ability of UV radiation to cause tumour-initiating DNA mutations in melanocytes is now firmly established, but how the microenvironmental effects of UV radiation influence melanoma pathogenesis is not fully understood. Here we report that repetitive UV exposure of primary cutaneous melanomas in a genetically engineered mouse model promotes metastatic progression, independent of its tumour-initiating effects. UV irradiation enhanced the expansion of tumour cells along abluminal blood vessel surfaces and increased the number of lung metastases. This effect depended on the recruitment and activation of neutrophils, initiated by the release of high mobility group box 1 (HMGB1) from UV-damaged epidermal keratinocytes and driven by Toll-like receptor 4 (TLR4). The UV-induced neutrophilic inflammatory response stimulated angiogenesis and promoted the ability of melanoma cells to migrate towards endothelial cells and use selective motility cues on their surfaces. Our results not only reveal how UV irradiation of epidermal keratinocytes is sensed by the innate immune system, but also show that the resulting inflammatory response catalyses reciprocal melanoma-endothelial cell interactions leading to perivascular invasion, a phenomenon originally described as angiotropism in human melanomas by histopathologists. Angiotropism represents a hitherto underappreciated mechanism of metastasis that also increases the likelihood of intravasation and haematogenous dissemination. Consistent with our findings, ulcerated primary human melanomas with abundant neutrophils and reactive angiogenesis frequently show angiotropism and a high risk for metastases. Our work indicates that targeting the inflammation-induced phenotypic plasticity of melanoma cells and their association with endothelial cells represent rational strategies to specifically interfere with metastatic progression.

Melanomas resist T-cell therapy through inflammation-induced reversible dedifferentiation.

Adoptive cell transfer therapies (ACTs) with cytotoxic T cells that target melanocytic antigens can achieve remissions in patients with metastatic melanomas, but tumours frequently relapse. Hypotheses explaining the acquired resistance to ACTs include the selection of antigen-deficient tumour cell variants and the induction of T-cell tolerance. However, the lack of appropriate experimental melanoma models has so far impeded clear insights into the underlying mechanisms. Here we establish an effective ACT protocol in a genetically engineered mouse melanoma model that recapitulates tumour regression, remission and relapse as seen in patients. We report the unexpected observation that melanomas acquire ACT resistance through an inflammation-induced reversible loss of melanocytic antigens. In serial transplantation experiments, melanoma cells switch between a differentiated and a dedifferentiated phenotype in response to T-cell-driven inflammatory stimuli. We identified the proinflammatory cytokine tumour necrosis factor (TNF)-α as a crucial factor that directly caused reversible dedifferentiation of mouse and human melanoma cells. Tumour cells exposed to TNF-α were poorly recognized by T cells specific for melanocytic antigens, whereas recognition by T cells specific for non-melanocytic antigens was unaffected or even increased. Our results demonstrate that the phenotypic plasticity of melanoma cells in an inflammatory microenvironment contributes to tumour relapse after initially successful T-cell immunotherapy. On the basis of our work, we propose that future ACT protocols should simultaneously target melanocytic and non-melanocytic antigens to ensure broad recognition of both differentiated and dedifferentiated melanoma cells, and include strategies to sustain T-cell effector functions by blocking immune-inhibitory mechanisms in the tumour microenvironment.

Kutane Sarkome.

Cutaneous sarcomas comprise a heterogeneous group of mesenchymal spindle cell tumors of the dermis and subcutis, one of the best-known entities being dermatofibrosarcoma protuberans. Other sarcomas addressed in this review include a typical fibroxanthoma, cutaneous undifferentiated pleomorphic sarcoma, leiomyosarcoma, liposarcoma, and angiosarcoma. With the exception of dermatofibrosarcoma protuberans, which has its peak incidence in middle-aged adults, cutaneous sarcomas usually occur in elderly individuals starting in the sixth or seventh decade of life. The pathogenesis of the various disease entities is not uniform and has not been definitively ascertained. Histology is the key to arriving at a correct diagnosis, and should always include ruling out other dermal neoplasms such as melanoma. In recent years, molecular genetic methods have provided greater insight into the pathogenesis, thus paving the way for new targeted therapies. Treatment of choice for cutaneous sarcomas is excision with sufficient surgical margins. Adjuvant and neoadjuvant therapeutic concepts include radiation therapy and the use of targeted therapies or chemotherapies. Local recurrences have frequently been reported in cutaneous sarcomas. Unlike soft tissue sarcomas, the prognosis in terms of survival - with the exception of angiosarcoma - is very good if treated adequately, a fact that should be emphasized to patients.

Cutaneous sarcomas.

Cutaneous sarcomas comprise a heterogeneous group of mesenchymal spindle cell tumors of the dermis and subcutis, one of the best-known entities being dermatofibrosarcoma protuberans. Other sarcomas addressed in this review include atypical fibroxanthoma, cutaneous undifferentiated pleomorphic sarcoma, leiomyosarcoma, liposarcoma, and angiosarcoma. With the exception of dermatofibrosarcoma protuberans, which has its peak incidence in middle-aged adults, cutaneous sarcomas usually occur in elderly individuals starting in the sixth or seventh decade of life. The pathogenesis of the various disease entities is not uniform and has not been definitively ascertained. Histology is the key to arriving at a correct diagnosis, and should always include ruling out other dermal neoplasms such as melanoma. In recent years, molecular genetic methods have provided greater insight into the pathogenesis, thus paving the way for new targeted therapies. Treatment of choice for cutaneous sarcomas is excision with sufficient surgical margins. Adjuvant and neoadjuvant therapeutic concepts include radiation therapy and the use of targeted therapies or chemotherapies. Local recurrences have frequently been reported in cutaneous sarcomas. Unlike soft tissue sarcomas, the prognosis in terms of survival - with the exception of angiosarcoma - is very good if treated adequately, a fact that should be emphasized to patients.

Neonatal UVB exposure accelerates melanoma growth and enhances distant metastases in Hgf-Cdk4(R24C) C57BL/6 mice.

Genetically engineered mouse models offer new opportunities to experimentally investigate the impact of UV on melanoma pathogenesis. Here we irradiated a cohort of newborn 15 Hgf-Cdk4(R24C) mice on the pigmented C57BL/6 background with one erythemogenic dose of 6 kJ/m(2) UVB and compared the development of nevi and melanoma with a cohort of 30 untreated Hgf-Cdk4(R24C) mice. Neonatal UVB exposure decreased the latency and accelerated the growth of primary melanomas resulting in a significantly decreased time from melanoma onset to melanoma-related death (61 days vs. 96 days). Interestingly, we did not observe differences in the development of melanocytic nevi. Histopathological investigations revealed that UVB irradiation shifted the spectrum of melanomas toward a more aggressive phenotype with increased tumor cell proliferation, invasive growth and enhanced angiogenesis. Accordingly, we observed distal melanoma metastases in the lungs more frequently in the UV-irradiated than in the untreated cohort of Hgf-Cdk4(R24C) mice (73% vs. 47%). UVB-induced melanomas only contained very few infiltrating immune cells and expressed very low levels of proinflammatory chemokines. Taken together, our results demonstrate that neonatal UVB exposure promoted the early appearance of rapidly enlarging primary melanomas in Hgf-Cdk4(R24C) C57BL/6 mice which showed enhanced invasive and metastatic behaviour without a persistent tumor-associated inflammatory response. The preferential impact of UVB irradiation on the progression of melanoma without an effect on the development of nevi supports the hypothesis that the molecular targets of UVB are involved in bypassing the proliferative arrest of transformed melanocytes without alerting a cellular immune response.

Imaging of fatty tumors: appearance of subcutaneous lipomas in optoacoustic images.

A wide variety of subcutaneous soft-tissue masses may be seen in clinical practice. Clinical examination based on palpation alone is often insufficient to identify the nature and exact origin of the mass, in which case imaging is necessary. We used handheld multispectral optoacoustic imaging technology (MSOT) in a proof-of-principle study to image superficial fatty tumors and compare the images with diagnostic ultrasound. Fatty tumors were clearly visualized by MSOT and exhibited a spectral signature which differed from normal fatty tissue or muscle tissue. Our findings further indicated that MSOT offers highly complementary contrast to sonography. Based on the performance achieved, we foresee a promising role for MSOT in the diagnosis and evaluation of subcutaneous soft-tissue masses. Picture: Pseudo-color representation of a cross-sectional multi-spectral optoacoustic slice through a subcutaneous lipoma. Multi-spectral information is encoded in color. The lipoma can clearly be distinguished from the surrounding tissue based on its color. Scalebar 1 cm.

MITF and c-Jun antagonism interconnects melanoma dedifferentiation with pro-inflammatory cytokine responsiveness and myeloid cell recruitment.

Inflammation promotes phenotypic plasticity in melanoma, a source of non-genetic heterogeneity, but the molecular framework is poorly understood. Here we use functional genomic approaches and identify a reciprocal antagonism between the melanocyte lineage transcription factor MITF and c-Jun, which interconnects inflammation-induced dedifferentiation with pro-inflammatory cytokine responsiveness of melanoma cells favouring myeloid cell recruitment. We show that pro-inflammatory cytokines such as TNF-α instigate gradual suppression of MITF expression through c-Jun. MITF itself binds to the c-Jun regulatory genomic region and its reduction increases c-Jun expression that in turn amplifies TNF-stimulated cytokine expression with further MITF suppression. This feed-forward mechanism turns poor peak-like transcriptional responses to TNF-α into progressive and persistent cytokine and chemokine induction. Consistently, inflammatory MITF(low)/c-Jun(high) syngeneic mouse melanomas recruit myeloid immune cells into the tumour microenvironment as recapitulated by their human counterparts. Our study suggests myeloid cell-directed therapies may be useful for MITF(low)/c-Jun(high) melanomas to counteract their growth-promoting and immunosuppressive functions.

Autochthonous primary and metastatic melanomas in Hgf-Cdk4 R24C mice evade T-cell-mediated immune surveillance.

Genetically engineered mouse models offer new opportunities to investigate the role of cell-mediated immunity in the natural progression of melanoma in an immunocompetent host. Here we report that Hgf-Cdk4(R24C) mice spontaneously develop a spectrum of primary melanomas with high penetrance during their first year of life. Malignant transformation proceeds in a stepwise manner from multiple melanocytic nevi to single nodular melanomas and disseminated metastases in most mice. Migrating melanoma cells invade the draining lymph nodes without activating the immune system. Autochthonous primary tumors are destroyed following experimental introduction of immune surveillance using an adoptive lymphocyte transfer approach. However, some tumor cells are able to survive, evade immune cell control, and recur both locally and systemically. Immune tolerance in recurring tumors may be supported by immunosuppressive Gr1(+) myeloid cells. Taken together, our results demonstrate that primary and metastatic melanomas developing spontaneously in Hgf-Cdk4(R24C) mice effectively evade cellular immune surveillance.

Complete regression of advanced primary and metastatic mouse melanomas following combination chemoimmunotherapy.

The development of therapeutic strategies which induce effective cellular antitumor immunity represents an important goal in cancer immunology. Here, we used the unique features of the genetically engineered Hgf-Cdk4(R24C) mouse model to identify a combination chemoimmunotherapy for melanoma. These mice develop primary cutaneous melanomas which grow progressively and metastasize in the absence of immunogenic foreign proteins such as oncogenes or antigens. Primary and metastatic tumors evade innate and adaptive immune defenses, although they naturally express melanocytic antigens which can be recognized by antigen-specific T cells. We found that primary melanomas continued to grow despite infiltration with adoptively transferred, in vivo-activated, tumor-specific CD8(+) T cells. To promote tumor immune defense, we developed a treatment protocol consisting of four complementary components: (a) chemotherapeutic preconditioning prior to (b) adoptive lymphocyte transfer and (c) viral vaccination followed by (d) adjuvant peritumoral injections of immunostimulatory nucleic acids. Lymphocyte ablation and innate antiviral immune stimulation cooperatively enhanced the expansion and the effector cell differentiation of adoptively transferred lymphocytes. The efficacy of the different treatment approaches converged in the tumor microenvironment and induced a strong cytotoxic inflammatory response enabling preferential recognition and destruction of melanoma cells. This combination chemoimmunotherapy caused complete regression of advanced primary melanomas in the skin and metastases in the lung with minimal autoimmune side effects. Our results in a clinically highly relevant experimental model provide a scientific rationale to evaluate similar strategies which unleash the power of innate and adaptive immune defense in future clinical trials.