Biology subjects

Haddad, B. R.

Publications and source records attributed to Haddad, B. R..

3 recordsLinked to original sources

bioRxiv2019

Targeting destabilized DNA G-quadruplexes and aberrant splicing in drug-resistant glioblastoma

Temozolomide (TMZ) is a chemotherapeutic agent that has been the first-line standard of care for the aggressive brain cancer glioblastoma (GBM) since 2005. Though initially beneficial, TMZ- resistance is universal and second-line interventions are an unmet clinical need. Here we took advantage the mechanism of action of TMZ to target guanines (G) and investigated G-rich g- quadruplex (G4) and splice site changes that occur upon TMZ-resistance. We report TMZ-resistant GBM has guanine mutations that disrupt the G-rich DNA G4s and splice sites that lead to deregulated alternative splicing. These alterations create vulnerabilities, which are selectively targeted by either the G4 stabilizing drug TMPyP4 or a novel splicing kinase inhibitor of cdc2- like kinase. Finally, we show that the G4 and RNA-binding protein EWSR1 aggregates in the cytoplasm in TMZ-resistant GBM cells and patient samples. Together, our findings provide insight into targetable vulnerabilities of TMZ-resistant GBM and present cytoplasmic EWSR1 as a putative biomarker. TeaserTargeting temozolomide mutations in drug resistant glioma via g-quadruplex and splicing modulators with a putative biomarker.

cancer biology↗

bioRxiv2017

Alterations in Cell Motility, Proliferation, and Metabolism in Novel Models of Acquired Temozolomide Resistant Glioblastoma

Glioblastoma (GBM) is an aggressive and incurable tumor of the brain with limited treatment options. Current first-line standard of care is the DNA alkylating agent temozolomide (TMZ), but this treatment strategy adds only ~4 months to median survival due to the rapid development of resistance. While some mechanisms of TMZ resistance have been identified, they are not fully understood. There are few effective strategies to manage therapy resistant GBM, and we lack diverse preclinical models of acquired TMZ resistance in which to test therapeutic strategies on TMZ resistant GBM. In this study, we create and characterize two new GBM cell lines resistant to TMZ, based on the 8MGBA and 42MGBA cell lines. Analysis of the TMZ resistant (TMZres) variants in conjunction with their parental, sensitive cell lines shows that acquisition of TMZ resistance is accompanied by broad phenotypic changes, including increased proliferation, migration, chromosomal aberrations and secretion of cytosolic lipids. Importantly, each TMZ resistant model captures a different facet of the \"go\" (8MGBA-TMZres) or \"grow\" (42MGBA-TMZres) hypothesis of GBM behavior. These model systems will be important additions to the available tools for investigators seeking to define molecular mechanisms of acquired TMZ resistance.

cancer biology↗

bioRxiv2017

Expanding primary cells from mucoepidermoid and other salivary gland neoplasms for genetic and chemosensitivity testing

Restricted availability of cell and animal models is a rate-limiting step for investigation of salivary gland neoplasm pathophysiology and therapeutic response. Conditionally reprogrammed cell (CRC) technology enables establishment of primary epithelial cell cultures from patient material. This study tested a translational workflow for acquisition, expansion and testing of CRC-derived primary cultures of salivary gland neoplasms from patients presenting to an academic surgical practice. Results showed cultured cells were sufficient for epithelial cell-specific transcriptome characterization to detect candidate therapeutic pathways and fusion genes in addition to screening for cancer-risk-associated single nucleotide polymorphisms (SNPs) and driver gene mutations through exome sequencing. Focused study of primary cultures of a low-grade mucoepidermoid carcinoma demonstrated Amphiregulin-Mechanistic Target of Rapamycin-AKT/Protein kinase B (AKT) pathway activation, identified through bioinformatics and subsequently confirmed as present in primary tissue and preserved through different secondary 2D and 3D culture media and xenografts. Candidate therapeutic testing showed that the allosteric AKT inhibitor MK2206 reproducibly inhibited cell survival across different culture formats. In contrast, the cells appeared resistant to the adenosine triphosphate competitive AKT inhibitor GSK690693. Procedures employed here illustrate an approach for reproducibly obtaining material for pathophysiological studies of salivary gland neoplasms, and other less common epithelial cancer types, that can be executed without compromising pathological examination of patient specimens. The approach permits combined genetic and cell-based physiological and therapeutic investigations in addition to more traditional pathologic studies and can be used to build sustainable bio-banks for future inquiries.

cancer biology↗