James R. Miller

The gene expression signatures of melanoma progression

Because of the paucity of available tissue, little information has previously been available regarding the gene expression profiles of primary melanomas. To understand the molecular basis of melanoma progression, we compared the gene expression profiles of a series of nevi, primary melanomas, and melanoma metastases. We found that metastatic melanomas exhibit two dichotomous patterns of gene expression, which unexpectedly reflect gene expression differences already apparent in comparing laser-capture microdissected radial and vertical phases of a large primary melanoma. Unsupervised hierarchical clustering accurately separated nevi and primary melanomas. Multiclass significance analysis of microarrays comparing normal skin, nevi, primary melanomas, and the two types of metastatic melanoma identified 2,602 transcripts that significantly correlated with sample class. These results suggest that melanoma pathogenesis can be understood as a series of distinct molecular events. The gene expression signatures identified here provide the basis for developing new diagnostics and targeting therapies for patients with malignant melanoma.

Tumor Vascularity in the Prognostic Assessment of Primary Cutaneous Melanoma

PURPOSEnThe vascular supply of the primary tumor is recognized to play an important role in the progression of a number of solid tumors. However, the role of tumor vascularity in the prognostic assessment of melanoma remains unclear. The purpose of this study was to determine the prognostic impact of patterns of vascularity on the outcome associated with cutaneous melanoma.nnnPATIENTS AND METHODSnTumor vascularity was documented prospectively using routine histopathologic analysis of 417 primary cutaneous melanomas from the University of California at San Francisco Melanoma Center database. Four patterns of tumor vascularity were recorded: absent, sparse, moderate, and prominent.nnnRESULTSnIncreasing tumor vascularity significantly increased the risk of relapse and death associated with melanoma, corresponding to reduced relapse-free and overall survival. By multivariate analysis, tumor vascularity was the most important determinant of overall survival, surpassing tumor thickness. Increasing tumor vascularity was associated with increased incidence of ulceration in the primary tumor.nnnCONCLUSIONnTumor vascularity is an important prognostic factor in melanoma, rivaling tumor thickness. Increasing tumor vascularity is highly correlated with ulceration, possibly helping to explain the biologic basis of this known prognostic factor.

A multi-marker assay to distinguish malignant melanomas from benign nevi

The histopathological diagnosis of melanoma can be challenging. No currently used molecular markers accurately distinguish between nevus and melanoma. Recent transcriptome analyses have shown the differential expression of several genes in melanoma progression. Here, we describe a multi-marker diagnostic assay using 5 markers (ARPC2, FN1, RGS1, SPP1, and WNT2) overexpressed in melanomas. Immunohistochemical marker expression was analyzed in 693 melanocytic neoplasms comprising a training set (tissue microarray of 534 melanomas and nevi), and 4 independent validation sets: tissue sections of melanoma arising in a nevus; dysplastic nevi; Spitz nevi; and misdiagnosed melanocytic neoplasms. Both intensity and pattern of expression were scored for each marker. Based on the differential expression of these 5 markers between nevi and melanomas in the training set, a diagnostic algorithm was obtained. Using this algorithm, the lesions in the validation sets were diagnosed as nevus or melanoma, and the results were compared with the known histological diagnoses. Both the intensity and pattern of expression of each marker were significantly different in melanomas compared to nevi. The diagnostic algorithm exploiting these differences achieved a specificity of 95% and a sensitivity of 91% in the training set. In the validation sets, the multi-marker assay correctly diagnosed a high percentage of melanomas arising in a nevus, Spitz nevi, dysplastic nevi, and misdiagnosed lesions. The multi-marker assay described here can aid in the diagnosis of melanoma.

NF-κB in the Vascular Progression of Melanoma

Purpose To examine a model of melanoma progression based on vascular factors and the role of NF-κB in the vascular progression of melanoma. Patients and Methods A data set of 526 patients from the University of California San Francisco Melanoma Center with 2 years of follow-up or first relapse was studied. The impact of the presence or absence of various prognostic factors on overall survival of melanoma patients was assessed using Cox regression and Kaplan-Meier analysis. A matched-pair analysis of NF-κB expression was performed in cases with vascular involvement and increased tumor vascularity versus matched controls lacking these factors. Results Cox regression analysis of factors evaluated by the American Joint Committee on Cancer Melanoma Staging Committee reproduced the powerful impact of tumor thickness and ulceration in this data set. With the inclusion of vascular factors such as tumor vascularity and vascular involvement, ulceration was no longer significant in predicting overall survival. By mu...

Quantification of mutant huntingtin protein in cerebrospinal fluid from Huntington’s disease patients

BACKGROUNDnQuantification of disease-associated proteins in the cerebrospinal fluid (CSF) has been critical for the study and treatment of several neurodegenerative disorders; however, mutant huntingtin protein (mHTT), the cause of Huntingtons disease (HD), is at very low levels in CSF and, to our knowledge, has never been measured previously.nnnMETHODSnWe developed an ultrasensitive single-molecule counting (SMC) mHTT immunoassay that was used to quantify mHTT levels in CSF samples from individuals bearing the HD mutation and from control individuals in 2 independent cohorts.nnnRESULTSnThis SMC mHTT immunoassay demonstrated high specificity for mHTT, high sensitivity with a femtomolar detection threshold, and a broad dynamic range. Analysis of the CSF samples showed that mHTT was undetectable in CSF from all controls but quantifiable in nearly all mutation carriers. The mHTT concentration in CSF was approximately 3-fold higher in patients with manifest HD than in premanifest mutation carriers. Moreover, mHTT levels increased as the disease progressed and were associated with 5-year onset probability. The mHTT concentration independently predicted cognitive and motor dysfunction. Furthermore, the level of mHTT was associated with the concentrations of tau and neurofilament light chain in the CSF, suggesting a neuronal origin for the detected mHTT.nnnCONCLUSIONSnWe have demonstrated that mHTT can be quantified in CSF from HD patients using the described SMC mHTT immunoassay. Moreover, the level of mHTT detected is associated with proximity to disease onset and diminished cognitive and motor function. The ability to quantify CSF mHTT will facilitate the study of HD, and mHTT quantification could potentially serve as a biomarker for the development and testing of experimental mHTT-lowering therapies for HD.nnnTRIAL REGISTRATIONnNot applicable.nnnFUNDINGnCHDI Foundation Inc.; Medical Research Council (MRC) UK; National Institutes for Health Research (NIHR); Rosetrees Trust; Swedish Research Council; and Knut and Alice Wallenberg Foundation.

The Role of miR-18b in MDM2-p53 Pathway Signaling and Melanoma Progression

Background Although p53 is inactivated by point mutations in many tumors, melanomas infrequently harbor mutations in the p53 gene. Here we investigate the biological role of microRNA-18b (miR-18b) in melanoma by targeting the MDM2-p53 pathway. Methods Expression of miR-18b was examined in nevi (n = 48) and melanoma (n = 92) samples and in melanoma cell lines and normal melanocytes. Immunoblotting was performed to determine the expression of various proteins regulated by miR-18b. The effects of miR-18b overexpression in melanoma cell lines were investigated using assays of colony formation, cell viability, migration, invasion, and cell cycle and in a xenograft model (n = 10 mice per group). Chromatin immunoprecipitation and methylation assays were performed to determine the mechanism of microRNA silencing. Results Expression of miR-18b was substantially reduced in melanoma specimens and cell lines by virtue of hypermethylation and was reinduced (by 1.5- to 5.3-fold) in melanoma cell lines after 5-AZA-deoxycytidine treatment. MDM2 was identified as a target of miR-18b action, and overexpression of miR-18b in melanoma cells was accompanied by 75% reduced MDM2 expression and 2.5-fold upregulation of p53, resulting in 70% suppression of melanoma cell colony formation. The effects of miR-18b overexpression on the p53 pathway and on melanoma cell growth were reversed by MDM2 overexpression. Stable overexpression of miR-18b produced potent tumor suppressor activity, as evidenced by suppressed melanoma cell viability, induction of apoptosis, and reduced tumor growth in vivo. miR-18b overexpression suppressed melanoma cell migration and invasiveness and reversed epithelial-to-mesenchymal transition. Conclusions Our results demonstrate a novel role for miR-18b as a tumor suppressor in melanoma, identify the MDM2-p53 pathway as a target of miR-18b action, and suggest miR-18b overexpression as a novel strategy to reactivate the p53 pathway in human tumors.

Novel Role for RGS1 in Melanoma Progression

RGS1 (regulator of G protein signaling 1) encodes a member of the regulator of G protein family. Recently, RGS1 was found to be overexpressed in gene expression-profiling studies of melanoma. However, no analyses have been reported of its expression at the protein level in melanoma. In this study, the potential impact of RGS1 as a molecular prognostic marker for melanoma was assessed using immunohistochemical analysis of a melanoma tissue microarray containing primary cutaneous melanomas from 301 patients. High RGS1 expression was significantly correlated with increased tumor thickness (P=0.0083), mitotic rate (P=0.04), and presence of vascular involvement (P<0.02). Kaplan-Meier analysis demonstrated a significant association between increasing RGS1 expression and reduced relapse-free survival (P=0.0032) as well as disease-specific survival (DSS) (P=0.018) survival. Logistic regression analysis showed RGS1 overexpression to be significantly correlated to sentinel lymph node metastasis (P=0.04). Multivariate Cox regression analysis showed that increasing RGS1 immunostaining had an independent impact on the relapse-free survival (P=0.0069) and DSS (P=0.0077) of this melanoma cohort. In the analysis of DSS, RGS1 expression level was the most powerful factor predicting DSS. RGS1 immunostaining retained independent prognostic impact even when sentinel lymph node status was included in the prognostic model (P=0.0039). These results validate the role of RGS1 as a novel prognostic marker for melanoma given its impact on the survival associated with melanoma.

Prognostic significance of extent of ulceration in primary cutaneous melanoma.

Ulceration has been shown to be an adverse prognostic factor in primary cutaneous melanoma. However, the extent of ulceration required for histologic identification and biologic significance is unclear. We examined the impact of extent of ulceration on melanoma outcome in a cohort of 235 melanoma patients by evaluating the relationship between percentage of ulceration in the vertical growth phase of the primary tumor and 2 outcome parameters: sentinel lymph node status and overall survival. We measured the diameter of the ulcerated area in millimeters over the diameter of the entire vertical growth phase. There was a statistically significant relationship between increasing percentage of tumor ulceration and both sentinel lymph node status as well as overall survival, with a binary cut-off point of 2% for sentinel lymph node status and 5% for overall survival. The percentage of ulceration provides additional prognostic information in predicting sentinel lymph node status and in determining survival in melanoma patients. These results suggest that no more than minimal ulceration is required to have a prognostic impact on melanoma survival.

Analysis of sentinel lymph node positivity in patients with thin primary melanoma

BACKGROUNDnA minority of patients with T1 melanoma will have a positive sentinel lymph node (SLN) biopsy (SLNB) finding. Identifying who will develop metastatic disease is important in determining prognosis and treatment.nnnOBJECTIVEnWe sought to identify clinical and histologic features predictive of a positive SLNB result and determine its prognostic significance in patients with T1 melanoma.nnnMETHODSnClinical and histologic parameters were evaluated in 484 patients with T1 melanoma for their ability to predict a positive SLNB result. The impact of various factors on SLN positivity was evaluated. SLN status was examined as a predictor of overall survival.nnnRESULTSnIn all, 34 patients had a positive SLNB finding. Four factors predicted a higher risk of SLN positivity: age 43 years or younger, Breslow depth 0.8 mm or greater, tumors on the lower extremity and trunk, and tumor-infiltrating lymphocyte level. By multivariate analysis, low tumor-infiltrating lymphocytes (P = .0015) and decreasing age (P = .0058) independently predicted SLN positivity. If 0 to 2 of these factors were present, the rate of a positive SLNB result was 3%; this increased to 15% with 3 factors present and to 30% if all 4 factors were present (P < .002). SLN-positive patients had significantly decreased survival (P = .003), and SLN status was the most powerful predictor of survival (P = .009).nnnLIMITATIONSnOur data analysis includes patients from 1994 to 2007 and therefore information on mitotic rate, a recently defined T1b criterion, is not recorded for all patients.nnnCONCLUSIONSnCombining clinical and histologic prognostic factors may help identify subgroups of T1 patients at higher risk of SLN positivity. SLN status has significant prognostic impact in patients with thin melanomas.

Characterisation of immune cell function in fragment and full-length Huntington's disease mouse models.

Inflammation is a growing area of research in neurodegeneration. In Huntingtons disease (HD), a fatal inherited neurodegenerative disease caused by a CAG-repeat expansion in the gene encoding huntingtin, patients have increased plasma levels of inflammatory cytokines and circulating monocytes that are hyper-responsive to immune stimuli. Several mouse models of HD also show elevated plasma levels of inflammatory cytokines. To further determine the degree to which these models recapitulate observations in HD patients, we evaluated various myeloid cell populations from different HD mouse models to determine whether they are similarly hyper-responsive, as well as measuring other aspects of myeloid cell function. Myeloid cells from each of the three mouse models studied, R6/2, HdhQ150 knock-in and YAC128, showed increased cytokine production when stimulated. However, bone marrow CD11b+ cells did not show the same hyper-responsive phenotype as spleen and blood cells. Furthermore, macrophages isolated from R6/2 mice show increased levels of phagocytosis, similar to findings in HD patients. Taken together, these results show significant promise for these mouse models to be used to study targeting innate immune pathways identified in human cells, thereby helping to understand the role the peripheral immune system plays in HD progression.