Stefano Sodi

Melanoma × macrophage hybrids with enhanced metastatic potential

Studies were conducted on the hypothesis that melanoma metastasis might be initiated through the gener-ation of hybrids comprised of cells of the primary tumor and tumor-infiltrating leukocytes. Fusion hybrids were generated in vitro between weakly metastatic Cloudman S91 mouse melanoma cells and normal mouse or human macrophages. Hybrids were implanted s.c. in the tail and mice were monitored for metastases. Controls included parental S91 cells, autologous S91 × S91 hybrids, and B16F10 melanoma cells. Of 35 hybrids tested, most were more aggressive than the parental melanoma cells, producing metastases sooner and in more mice. A striking characteristic was heterogeneity amongst hybrids, with some lines producing no metastases and others producing metastases in up to 80% of mice. With few exceptions, hybrids with the highest metastatic potential also had the highest basal melanin content whereas those with the lowest metastatic potential were basally amelanotic, as were t he parental melanoma cells. A spontaneous in vivo supermelanotic hybrid between an S91 tumor cell and DBA/2J host cell was one of the most metastatic lines. Hybrids with the highest metastatic potential also exhibited markedly higher chemotaxis to fibroblast-conditioned media. Histologically, the metastatic hybrids demonstrated vascular invasion and spread to distant organs similar to that of metastatic melanomas in mice and humans. Thus previous findings of enhanced metastasis in leukocyte × lymphoma hybrids can now be extended to include leukocyte × melanoma hybrids. Whether such hybridization is a natural cause of metastasis in vivo remains to be determined; however the fusion hybrids with genetically-matched parents described herein so closely resembled naturally- occurring metastatic melanoma cells that they could serve as useful new models for studies of this complex and deadly phenomenon.

Genetic variants of Nogo-66 Receptor with possible association to schizophrenia block myelin inhibition of axon growth

In schizophrenia, genetic predisposition has been linked to chromosome 22q11 and myelin-specific genes are misexpressed in schizophrenia. Nogo-66 receptor 1 (NGR or RTN4R) has been considered to be a 22q11 candidate gene for schizophrenia susceptibility because it encodes an axonal protein that mediates myelin inhibition of axonal sprouting. Confirming previous studies, we found that variation at the NGR locus is associated with schizophrenia in a Caucasian case-control analysis, and this association is not attributed to population stratification. Within a limited set of schizophrenia-derived DNA samples, we identified several rare NGR nonconservative coding sequence variants. Neuronal cultures demonstrate that four different schizophrenia-derived NgR1 variants fail to transduce myelin signals into axon inhibition, and function as dominant negatives to disrupt endogenous NgR1. This provides the first evidence that certain disease-derived human NgR1 variants are dysfunctional proteins in vitro. Mice lacking NgR1 protein exhibit reduced working memory function, consistent with a potential endophenotype of schizophrenia. For a restricted subset of individuals diagnosed with schizophrenia, the expression of dysfunctional NGR variants may contribute to increased disease risk.

UV Light and MSH Receptors

ABSTRACT: Ultraviolet B (UVB) radiation in the skin induces pigmentation that protects cells from further UVB damage and reduces photocarcinogenesis. Although the mechanisms are not well understood, our laboratory has shown that UVB radiation causes increased MSH receptor activity by redistributing MSH receptors from internal pools to the external surface, with a resultant increase in cellular responsiveness to MSH. By this means, UVB and MSH act synergistically to increase melanin content in the skin of mice and guinea pigs. In humans, MSH causes increased skin pigmentation, predominantly in sun‐exposed areas. We have shown recently that UVB irradiation and exposure to MSH or to dbcAMP, stimulates production of mRNAs for both αMSH receptors and POMC in human melanocytes and keratinocytes. This indicates that at least one action of UVB on the pigmentary system is mediated through increased MSH receptor production, as well as through the production of the signal peptides, MSH and ACTH, that can further activate MSH receptors. The results add support to the hypothesis that the effects of UVB on cutaneous melanogenesis are mediated through a series of coordinated events in which MSH receptors and POMC‐derived peptides play a central role.

Antitumour effects of genetically engineered Salmonella in combination with radiation.

The antitumour efficacy of lipid A mutant Salmonella was evaluated alone and in combination with X-rays in mice bearing B16F10 or Cloudman S91 melanomas. Each treatment alone slowed tumour growth and prolonged survival, and the combined treatments produced supra-additive antitumour effects. That is, in dose-response studies with single doses of Salmonella and increasing doses of radiation, the two agents together caused suppression of tumour growth that was greater than that calculated for additivity. The results suggest that the combination of these genetically engineered Salmonella with radiotherapy could be a new and beneficial treatment for solid tumours.

Salmonella pathogenicity island-2 and anticancer activity in mice

Salmonella enterica servovar Typhimurium is capable of targeting, colonizing, and eliciting growth suppression of tumors in mice. We examined the effects of mutations on this anticancer phenotype in two Salmonella virulence gene clusters. Salmonella pathogenicity island (SPI)-1 genes promote systemic invasion from the intestine, whereas SPI-2 genes support systemic survival within macrophages and other cells. Disabling SPI-1 (prgH−) strongly reduced invasion in vitro, but had no effect on tumor growth suppression in vivo. However, disabling SPI-2 (ssaT−) ablated tumor growth suppression. In addition to ssaT−, mutations in SPI-2 genes sseA, sseB, sseC, sscA, and ssrA also eliminated antitumor activity, whereas mutations in sseF or sseG yielded partial loss of function. Impaired tumor amplification was seen in three SPI-2 mutants tested after intravenous or intratumoral injection. A SPI-2− strain was unable to suppress tumor growth in CD18-deficient mice with defective macrophages and neutrophils, suggesting that loss of tumor growth suppression in wild-type mice by SPI-2 mutants was not solely a function of increased susceptibility to immune attack. Thus, SPI-2 is essential for the Salmonella antitumor effects, perhaps by aiding bacterial amplification within tumors, and is the first identified genetic system for this Salmonella phenotype.

Enhancement of the depigmenting effect of hydroquinone by cystamine and buthionine sulfoximine

Glutathione (GSH) performs several important biological functions, including quenching of reactive oxygen species, and protection of cells from toxic compounds such as quinones. The first step in the synthesis of GSH is catalysed by γ‐glutamylcysteine synthetase, an enzyme which is inhibited by cystamine and buthionine sulfoximine (BSO). In this study, we examined the possibility that the effect of hydroquinone (HQ) on pigmentation could be potentiated by inhibiting the production of GSH. In vitro studies using melanoma cell lines demonstrated that both cystamine and BSO could potentiate the inhibitory effects of HQ on tyrosinase activity and melanin content. A synergistic decrease in hair pigmentation was observed when a combination of HQ (2 or 4%) and BSO (5%) was applied to the dorsal skin of C57BL mice. In black hairless guinea‐pigs, the application of HQ plus either BSO or cystamine resulted in a significant decrease in epidermal pigmentation when compared with any of the agents alone. The possibility exists that in the future a combination of HQ plus cystamine or BSO could be used to treat disorders such as melasma and post‐Inflammatory hyperpigmentation.