PDGFRα up-regulation mediated by sonic hedgehog pathway activation leads to BRAF inhibitor resistance in melanoma cells with BRAF mutation

Control of BRAF(V600E) metastatic melanoma by BRAF inhibitor (BRAF-I) is limited by intrinsic and acquired resistance. Growth factor receptor up-regulation is among the mechanisms underlying BRAF-I resistance of melanoma cells. Here we demonstrate for the first time that PDGFRα up-regulation causes BRAF-I resistance. PDGFRα inhibition by PDGFRα-specific short hairpin (sh)RNA and by PDGFRα inhibitors restores and increases melanoma cells' sensitivity to BRAF-I in vitro and in vivo. This effect reflects the inhibition of ERK and AKT activation which is associated with BRAF-I resistance of melanoma cells. PDGFRα up-regulation is mediated by Sonic Hedgehog Homolog (Shh) pathway activation which is induced by BRAF-I treatment. Similarly to PDGFRα inhibition, Shh inhibition by LDE225 restores and increases melanoma cells' sensitivity to BRAF-I. These effects are mediated by PDGFRα down-regulation and by ERK and AKT inhibition. The clinical relevance of these data is indicated by the association of PDGFRα up-regulation in melanoma matched biopsies of BRAF-I +/- MEK inhibitor treated patients with shorter time to disease progression and less tumor regression. These findings suggest that monitoring patients for early PDGFRα up-regulation will facilitate the identification of those who may benefit from the treatment with BRAF-I in combination with clinically approved PDGFRα or Shh inhibitors

New CXCR4 Antagonist Peptide R (Pep R) Improves Standard Therapy in Colorectal Cancer

he chemokine receptor CXCR4 is overexpressed and functional in colorectal cancer. To investigate the role of CXCR4 antagonism in potentiating colon cancer standard therapy, the new peptide CXCR4 antagonist Peptide R (Pep R) was employed. Human colon cancer HCT116 xenograft-bearing mice were treated with chemotherapeutic agents (CT) 5-Fluorouracil (5FU) and oxaliplatin (OX) or 5FU and radio chemotherapy (RT-CT) in the presence of Pep R. After two weeks, CT plus Pep R reduced by 4-fold the relative tumor volume (RTV) as compared to 2- and 1.6-fold reductions induced, respectively, by CT and Pep R. In vitro Pep R addition to CT/RT-CT impaired HCT116 cell growth and further reduced HCT116 and HT29 clonal capability. Thus, the hypothesis that Pep R could target the epithelial mesenchyme transition (EMT) process was evaluated. While CT decreased ECAD and increased ZEB-1 and CD90 expression, the addition of Pep R restored the pretreatment expression. In HCT116 and HT29 cells, CT/RT-CT induced a population of CD133+CXCR4+ cells, supposedly a stem-resistant cancer cell population, while Pep R reduced it. Taken together, the results showed that targeting CXCR4 ameliorates the effect of treatment in colon cancer through inhibition of cell growth and reversal of EMT treatment-induced markers, supporting further clinical studies

Translational Research in Cutaneous Melanoma: New Therapeutic Perspectives

Melanoma is an aggressive form of skin cancer characterized by poor prognosis and high mortality. The development of targeted agents based on the discovery of driver mutations as well as the implementation of checkpoint inhibitor-based immunotherapy represent a major breakthrough in the treatment of metastatic melanoma. However, in both cases the development of drug resistance and immune escape mechanisms as well as the lack of predictive biomarkers limit their extraordinary clinical efficacy. In this article, we summarize the available therapeutic options for patients with metastatic melanoma, outline the mechanisms implicated in the resistance to both targeted agents and immunotherapy, discuss potential predictive biomarkers and outline future therapeutic approaches under investigation

Antitumor activity of BRAF inhibitor and IFNÃ\u97alpha; Combination in BRAF-mutant melanoma

Background: BRAFV600E-mediated MAPK pathway activation is associated in melanoma cells with IFNAR1 downregulation. IFNAR1 regulates melanoma cell sensitivity to IFNÃ\u97alpha;, a cytokine used for the adjuvant treatment of melanoma. These findings and the limited therapeutic efficacy of BRAF-I prompted us to examine whether the efficacy of IFNÃ\u97alpha; therapy of BRAFV600E melanoma can be increased by its combination with BRAF-I.Methods: BRAF/NRAS genotype, ERK activation, IFNAR1, and HLA class I expression were tested in 60 primary melanomatumors from treatment-naive patients. The effect of BRAF-I on IFNAR1 expression was assessed in three melanoma cell lines and in four biopsies of BRAFV600E metastases. The antiproliferative, pro-apoptotic and immunomodulatory activity of BRAF-I and IFNÃ\u97alpha; combination was tested in vitro and in vivo utilizing three melanoma cell lines, HLA class I-MA peptide complex-specific T-cells and immunodeficient mice (5 per group for survival and 10 per group for tumor growth inhibition). All statistical tests were two-sided. Differences were considered statistically significant when the P value was less than .05. Results: The IFNAR1 level was statistically significantly (P Ã\u97lt; .001) lower in BRAFV600E primary melanoma tumors than in BRAF wild-type tumors. IFNAR1 downregulation was reversed by BRAF-I treatment in the three melanoma cell lines (P Ã\u97le; .02) and in three out of four metastases. The IFNAR1 level in the melanoma tumors analyzed was increased as early as 10 to 14 days following the beginning of the treatment. These changes were associated with: 1) an increased susceptibility in vitro of melanoma cells to the antiproliferative (P Ã\u97le; .04), pro-apoptotic (P Ã\u97le; .009) and immunomodulatory activity, including upregulation of HLA class I antigen APM component (P Ã\u97le; .04) and MA expression as well as recognition by cognate T-cells (P Ã\u97lt; .001), of BRAF-I and IFNÃ\u97alpha; combination and 2) an increased survival (P Ã\u97gt; .001) and inhibition of tumor growth of melanoma cells (P Ã\u97lt; .001) in vivo by BRAF-I and IFNÃ\u97alpha; combination. Conclusions: The described results provide a strong rationale for the clinical trials implemented in BRAFV600E melanoma patients with BRAF-I and IFNÃ\u97alpha; combination

Hierarchical graph representations in digital pathology

Cancer diagnosis, prognosis, and therapy response predictions from tissue specimens highly depend on the phenotype and topological distribution of constituting histological entities. Thus, adequate tissue representations for encoding histological entities is imperative for computer aided cancer patient care. To this end, several approaches have leveraged cell-graphs, capturing the cell-microenvironment, to depict the tissue. These allow for utilizing graph theory and machine learning to map the tissue representation to tissue functionality, and quantify their relationship. Though cellular information is crucial, it is incomplete alone to comprehensively characterize complex tissue structure. We herein treat the tissue as a hierarchical composition of multiple types of histological entities from fine to coarse level, capturing multivariate tissue information at multiple levels. We propose a novel multi-level hierarchical entity graph representation of tissue specimens to model the hierarchical compositions that encode histological entities as well as their intra-and inter-entity level interactions. Subsequently, a hierarchical graph neural network is proposed to operate on the hierarchical entity-graph and map the tissue structure to tissue functionality. Specifically, for input histology images, we utilize well-defined cells and tissue regions to build HierArchical Cell-to-Tissue ( HACT ) graph representations, and devise HACT-Net, a message passing graph neural network, to classify the HACT representations. As part of this work, we introduce the BReAst Carcinoma Subtyping (BRACS) dataset, a large cohort of Haematoxylin & Eosin stained breast tumor regions-of-interest, to evaluate and benchmark our proposed methodology against pathologists and state-of-the-art computer-aided diagnostic approaches. Through comparative assessment and ablation studies, our proposed method is demonstrated to yield superior classification results compared to alternative methods as well as individual pathologists. The code, data, and models can be accessed at https://github.com/histocartography/hact-net . (c) 2021 Elsevier B.V. All rights reserved