Biology subjects

van Diest, P. J.

Publications and source records attributed to van Diest, P. J..

4 recordsLinked to original sources

bioRxiv2026

DDX3 Regulates the Innate Immune Response to Bone Sarcomas

Osteosarcoma (OS) and Ewing sarcoma (EWS) are the most common malignant bone tumors in children and adolescents, with survival rates around 25% in metastatic disease and few advances in treatment in decades. High DDX3 expression has been reported across various sarcoma subtypes. Depending on the context, DDX3 appears to have opposing roles in regulating the tumor immune microenvironment. Within macrophages, DDX3 promotes inflammatory cytokine expression and supports immune cell function. In contrast, in tumor cells DDX3 suppresses a pro-inflammatory state by unwinding dsRNAs, preventing a Type I interferon response. We show that inhibiting DDX3 with RK-33 leads to dsRNA accumulation, inducing a Type I interferon response and broader inflammatory gene expression changes across multiple sarcoma models, shifting macrophage polarization toward a pro-inflammatory M1-like phenotype. To evaluate whether this innate immune microenvironmental remodeling could translate into clinical benefit, we assessed the therapeutic efficacy of RK-33 alone or in combination with mifamurtide, an immunostimulant, in immune competent mouse models of osteosarcoma, with metastatic burden as the primary outcome. We found that in the absence of MYC over-expression, the combination treatment significantly reduced metastatic spread. These findings support targeting DDX3 as a novel innate immune based therapeutic strategy and highlight that the tumors molecular landscape critically influences therapeutic responsiveness.

cancer biology↗

bioRxiv2023

Somatic mutation of Afadin leads to anchorage independent survival and metastatic growth of breast cancer through alpha E-catenin dependent destabilization of the adherens junction

Loss of E-cadherin (CDH1) and the adherens junction (AJ) drive development and progression of invasive lobular breast cancer (ILC). However, approximately 40% retain wild type CDH1 alleles, indicating that modulation of other genes attenuates the AJ during ILC etiology. To identify alternative drivers, we performed targeted sequencing in CDH1 wild type samples, based on a defined set of 100 AJ, tight junction, and desmosome genes we designated as the Adhesome. In 146 ILC samples, we identified 62 cases (43%) with wild type CDH1 alleles in which we detected a total of 284 mutations in 36 Adhesome genes. After selection based on occurrence and potential loss of function, we identified an inactivating frameshift mutation in Afadin (AFDN; p.Lys630fs). Functional studies in E-cadherin-expressing breast cancer cells showed that Afadin knockout leads to immature AJs, and a non-cohesive phenotype accompanied by actomyosin dependent anoikis resistance, which are classical ILC hallmarks. Afadin reconstitutions show that F-actin organization critically depends on the E-catenin binding CC domain. Afadin loss in intraductal xenograft mouse breast cancer models leads to ILC-type morphologies and overt lung metastases. AFDN truncate reconstitutions revealed that deletion of the C-terminal E-catenin binding CC domain is sufficient to drive metastatic ILC. In conclusion, we identified and functionally coupled a somatic frameshift AFDN mutation in breast cancer to destabilization the epithelial AJ and the development of ILC hallmarks such as actomyosin-dependent anoikis resistance and single cell invasion. As such, Afadin represents a candidate tumor suppressor for E-cadherin-positive ILC development and progression.

cancer biology↗

bioRxiv2023

RNA Helicase DDX3 Regulates RAD51 Localization and DNA Damage Repair in Ewing Sarcoma

We previously demonstrated that RNA helicase DDX3X (DDX3) can be a therapeutic target in Ewing sarcoma (EWS), but its role in EWS biology remains unclear. The present work demonstrates that DDX3 plays a unique role in DNA damage repair (DDR). We show that DDX3 interacts with several proteins involved in homologous recombination, including RAD51, RECQL1, RPA32, and XRCC2. In particular, DDX3 colocalizes with RAD51 and RNA:DNA hybrid structures in the cytoplasm of EWS cells. Inhibition of DDX3 RNA helicase activity increases cytoplasmic RNA:DNA hybrids, sequestering RAD51 in the cytoplasm, which impairs nuclear translocation of RAD51 to sites of double-stranded DNA breaks thus increasing sensitivity of EWS to radiation treatment, both in vitro and in vivo. This discovery lays the foundation for exploring new therapeutic approaches directed at manipulating DDR protein localization in solid tumors.

cancer biology↗

bioRxiv2020

Heterogeneity in signaling pathway activity within primary and between primary and metastatic breast cancer

BackgroundTargeted drug treatment aims to block tumor driving signaling pathways, and is generally based on analysis of one primary tumor (PT) biopsy. Phenotypic heterogeneity within primary and between primary and metastatic lesions was investigated. MethodsActivity of androgen and estrogen receptor, PI3K-FOXO, Hedgehog, TGF{beta}, and Wnt signaling pathways was measured in breast cancer samples using a novel mRNA-based assay platform. Macro-scale heterogeneity analysis was performed on multiple spatially distributed PT tissue blocks from 17 luminal A-like, 9 luminal B-like, and 9 ER-negative primary breast cancers; micro-scale heterogeneity analysis was performed on four "quadrant" samples of a single tissue block of respectively 9, 4, and 4 matched PT. Samples from 6 PT with matched lymph node (LN, n=23) and 9 PT with distant metastatic sites (DS, n=12) were analyzed. Statistical variance analysis was performed with linear mixed models. A "checkerboard" model was introduced to explain the observed heterogeneity in PT. ResultsWithin PT, macro-scale heterogeneity in signaling pathway activity was similar to micro-scale heterogeneity, with a possible exception of the PI3K pathway. Variation was significantly higher on microscale for Hedgehog and TGF{beta} pathways. While pathway activity scores correlated significantly between different locations in the PT, positive correlations decreased between PT and LN, and even more between PT and DS metastases, including the emergence of a negative correlation for the ER pathway. ConclusionWith a possible exception of the PI3K pathway, variation in signaling pathway activity within a single PT tissue block was generally representative for the whole PT, but not for DS or LN metastases. The higher variation in TGF{beta} and HH pathway activity on microscale suggested the presence of multiple small cancer cell clones. While analysis of multiple sub-samples of a single biopsy block may be sufficient to predict PT response to some targeted therapies, such as hormonal therapy, metastatic breast cancer treatment requires analysis of metastatic biopsies. The findings on phenotypic intra-tumor heterogeneity are compatible with currently emerging ideas on a Big Bang type of cancer evolution.

cancer biology↗