Biology subjects

Riggins, R. B.

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

16 recordsLinked to original sources

bioRxiv2026

Impact of Trastuzumab and Pertuzumab on HER2 Localization and the Estrogen Receptor Cistrome in ER+/HER2+ Breast Cancer

Background: Although anti-HER2 monoclonal antibody therapy with trastuzumab and pertuzumab is highly effective for HER2-positive breast cancer, co-expression of estrogen receptor (ER) significantly reduces pathologic complete response rates. Objective: We investigated how HER2-targeted inhibition affects HER2 cellular localization and ER genomic binding in ER-positive, HER2-positive breast cancer. Methods: We evaluated HER2 localization in a tissue microarray of treatment-naive patients. Using cellular fractionation, immunofluorescence, chromatin immunoprecipitation, and genome-wide profiling (CUT&RUN), we evaluated HER2 localization and ER genomic binding following acute anti-HER2 treatment and in models of treatment resistance. The treatment-induced ER-bound gene signature was assessed for associations with pathologic complete response and survival in breast cancer clinical cohorts. Results: In treatment-naive primary breast tumors, nuclear HER2 inversely correlated with ER levels. In cell models, treatment with trastuzumab and pertuzumab induced nuclear and chromatin accumulation of HER2. Concurrently, acute anti-HER2 treatment displaced ER from canonical estrogen response elements at classical target genes, yet genome-wide profiling revealed redistribution of ER binding toward non-canonical zinc finger motifs adjacent to pro-survival Wnt and RAGE pathway genes (FZD8, RELA). Expression of a drug-induced ER-bound gene signature was significantly higher in tumors of individuals who did not achieve pathologic complete response following neoadjuvant anti-HER2 therapy and significantly correlated with reduced distant metastasis-free survival in clinical cohorts. Conclusions: Anti-HER2 targeted therapy causes dynamic cistromic reprogramming of ER from classical estrogen pathways toward alternative pro-survival networks. These findings implicate ER redistribution as a possible mediator of resistance and highlight novel therapeutic targets in ER-positive, HER2-positive breast cancer.

cancer biology↗

bioRxiv2025

Probability Distribution for Rare Neutral Mutations in Cancers and Application to Dynamic Precision Medicine of Cancer

Cancers exhibit substantial genetic diversity between individual cells. Previous work shows greater overall diversity that also increases more quickly during a patients clinical course than heretofore expected. Rare subclones will harbor pre-existing resistance to any single agent and may cause medium to late term relapse, which may evolve further variants that have simultaneous resistance to non-cross resistant therapies. In this work, we present a probability distribution function (PDF) of the variant allele fraction (VAF), or prevalence, of a rare subclone, derived from previous evolutionary theory. We show that current clinical sequencing protocols fail to detect the vast majority of these rare subclones and that by the time of detection, simultaneous multiple resistance may already evolve. We apply the PDF to simulation of dynamic precision medicine (DPM), an evolutionary guided precision medicine paradigm that attempts to proactively eliminate singly-resistant subclones before they evolve multiple resistance, with significant potential to extend survival. We show the simulated benefit of DPM with perfect information is hampered by an inability to detect rare subclones if they are assumed to be absent when undetectable. However, the DPM benefit is restored if the PDF is used to calculate the likelihood of the subclone being present below the level of detection and incorporated into the DPM simulation and therapy recommendations in a probabilistic fashion. Two other common statistical distributions are less effective. This theoretical advance facilitates DPM and potentially other evolutionary guided approaches to precision cancer medicine in spite of the limitations of clinical sequencing. Significance StatementCancers contain many cells, each genetically unique. These variations can include pre-existing resistance to therapy, enabling relapse. DNA sequencing cannot detect minority cellular populations (subclones) below a certain size, by which time they may have already evolved simultaneous resistance to multiple therapies. We present a mathematical approach that assigns a risk that a subclone is present, and at what prevalence in the cellular population, even when undetected. We simulate applying this approach to dynamic precision medicine (DPM), which attempts to proactively eliminate singly resistant cells before they become resistant to multiple therapies. Using this probability distribution, we can retain the benefit of DPM even when most rare subclones are undetectable, in contrast to just assuming undetected subclones are absent.

systems biology↗

bioRxiv2025

Size-dependent invasion and therapeutic phenotype of 42MGBA glioblastoma spheroids

Glioblastoma (GBM) is one of the most common malignant brain tumors, with patient mortality driven by invasion into the surround brain microenvironment and drug resistance. Multicellular spheroids are increasingly a common model to study GBM invasion and drug response in engineered biomaterials. However, a key design feature of tumor spheroid studies is the size of each spheroid (number of cells, diameter). Given the heterogenous growth of GBM cells at the surgical margin, spheroids of different sizes may also have clinical relevance. Here, we define shifts in behavior and drug response of wild type and temozolomide (TMZ) resistant GBM spheroids as a function of initial spheroid size. GBM spheroids ranging from 100 to 12,000 cells in size were embedded into a methacrylamide-functionalized gelatin (GelMA) hydrogel. GBM spheroid size had an inverse relationship with the number of apoptotic cells. We observed significant spheroid size dependent effects on TMZ efficacy for both TMZ resistant and wild type cells. Interestingly, high single doses of TMZ were more effective in reducing three-dimensional migration from smaller spheroids than metronomic dosing while high single dose and metronomic dosing were equally effective in reducing invasion for large TMZ-resistant spheroids. Our study highlights the importance of considering and reporting spheroid size for cancer tissue engineering studies considering invasion and drug resistance. It also informs future studies of residual GBM at the tumor margins most responsible for patient relapse and mortality.

bioengineering↗

bioRxiv2025

Multicellular model of temozolomide resistance in glioblastoma reveals phenotypic shifts in drug response and migratory potential

Glioblastoma (GBM) is the most common and aggressive primary malignant brain tumor in adults, with limited survival outcomes due to tumor recurrence, mainly driven by GBM cell invasion and therapy resistance. Although temozolomide (TMZ) remains the standard-of-care chemotherapeutic, its long-term efficacy is often compromised by rapid emergence of acquired resistance, largely mediated by the DNA repair enzyme, methylguanine methyltransferase (MGMT). To investigate the interplay between tumor heterogeneity, drug resistance, and the extracellular matrix (ECM) microenvironment, we adapted a 3D methacrylamide-functionalized gelatin (GelMA) hydrogel model to study the behavior of mixed populations of TMZ-sensitive and TMZ-resistant GBM cells. Using both single-cell distributions and multicellular spheroids, we report the impact of heterogeneous cell populations and TMZ dosing regimens, including physiological, supraphysiological, and metronomic TMZ schedules, on drug response and migration. We show that the combination therapy of TMZ with an MGMT inhibitor, lomeguatrib, can modulate TMZ resistance in vitro. This hydrogel model enables systematic investigation of GBM heterogeneity, "go-or-grow" phenotypic plasticity, and therapeutic resistance in an ECM-rich microenvironment, offering a valuable platform for future translational research.

bioengineering↗

bioRxiv2024

Personalized cancer treatment strategies incorporating irreversible and reversible drug resistance mechanisms

Despite advances in targeted cancer therapy, the promise of precision medicine has been limited by resistance to these treatments. In this study, we propose a mathematical modelling framework incorporating cellular heterogeneity, genetic evolutionary dynamics, and non-genetic plasticity, accounting for both irreversible and reversible drug resistance. Previously we proposed Dynamic Precision Medicine (DPM), a personalized treatment strategy that designed individualized treatment sequences by simulations of irreversible genetic evolutionary dynamics in a heterogeneous tumor. Here we apply DPM to the joint model of reversible and irreversible drug resistance mechanisms, analyze the simulation results and compare the efficacy of various treatment strategies. The results indicate that this enhanced version of DPM results in superior patient outcomes compared with current personalized medicine treatment approaches. Our results provide insights into cancer treatment strategies for heterogeneous tumors with genetic evolutionary dynamics and non-genetic cellular plasticity, potentially leading to improvements in survival time for cancer patients.

systems biology↗

bioRxiv2024

Glutamate Transport Proteins and Metabolic Enzymes are Poor Prognostic Factors in Invasive Lobular Carcinoma

Invasive Lobular Carcinoma (ILC) is a subtype of breast cancer characterized by distinct biological features, and limited glucose uptake coupled with increased reliance on amino acid and lipid metabolism. Our prior studies highlight the importance of glutamate as a key regulator of ILC tumor growth and therapeutic response. Here we examine the expression of four key proteins involved in glutamate transport and metabolism - SLC3A2, SLC7A11, GPX4, and GLUD1/2 - in a racially diverse cohort of 72 estrogen receptor-positive (ER+) ILC and 50 ER+ invasive ductal carcinoma, no special type (IDC/NST) patients with primary disease. All four proteins associate with increased tumor size in ILC, with three showing stronger associations in Black women, but not in IDC/NST. Among these three proteins in ILC, GLUD1/2 uniquely associates with ER expression in all women, while GLUD1/2 and SLC3A2 are enriched in hypertensive women. GLUD1/2 and GPX4 are upregulated in endocrine therapy-resistant ILC cell lines, and pharmacological inhibition of GLUD1 reduces ER protein levels and cell viability. Together, these findings support a potentially important role for glutamate metabolism in ILC and suggest GLUD1 and other glutamate-handling proteins as candidate targets for therapeutic intervention in ILC.

cancer biology↗

bioRxiv2023

Acquired temozolomide resistance instructs patterns of glioblastoma behavior in gelatin hydrogels

Acquired drug resistance in glioblastoma (GBM) presents a major clinical challenge and is a key factor contributing to abysmal prognosis, with less than 15 months median overall survival. Aggressive chemotherapy with the frontline therapeutic, temozolomide (TMZ), ultimately fails to kill residual highly invasive tumor cells after surgical resection and radiotherapy. Here, we report a three-dimensional (3D) engineered model of acquired TMZ resistance using two isogenically-matched sets of GBM cell lines encapsulated in gelatin methacrylol hydrogels. We benchmark response of TMZ-resistant vs. TMZ-sensitive GBM cell lines within the gelatin-based extracellular matrix platform and further validate drug response at physiologically relevant TMZ concentrations. We show changes in drug sensitivity, cell invasion, and matrix-remodeling cytokine production as the result of acquired TMZ resistance. This platform lays the foundation for future investigations targeting key elements of the GBM tumor microenvironment to combat GBMs devastating impact by advancing our understanding of GBM progression and treatment response to guide the development of novel treatment strategies. TeaserA hydrogel model to investigate the impact of acquired drug resistance on functional response in glioblastoma.

bioengineering↗

bioRxiv2023

Unraveling Vulnerabilities in Endocrine Therapy-Resistant HER2+/ER+ Breast Cancer

BackgroundBreast tumors overexpressing human epidermal growth factor receptor (HER2) confer intrinsic resistance to endocrine therapy (ET), and patients with HER2/ estrogen receptor-positive (HER2+/HR+) breast cancer (BCa) are less responsive to ET than HER2-/ER+. However, real-world evidence reveals that a large subset of HER2+/ER+ patients receive ET as monotherapy, positioning this treatment pattern as a clinical challenge. In the present study, we developed and characterized two distinct in vitro models of ET-resistant (ETR) HER2+/ER+ BCa to identify possible therapeutic vulnerabilities. MethodsTo mimic ETR to aromatase inhibitors (AI), we developed two long-term estrogen-deprived (LTED) cell lines from BT-474 (BT474) and MDA-MB-361 (MM361). Growth assays, PAM50 molecular subtyping, genomic and transcriptomic analyses, followed by validation and functional studies, were used to identify targetable differences between ET-responsive parental and ETR-LTED HER2+/ER+ cells. ResultsCompared to their parental cells, MM361 LTEDs grew faster, lost ER, and increased HER2 expression, whereas BT474 LTEDs grew slower and maintained ER and HER2 expression. Both LTED variants had reduced responsiveness to fulvestrant. Whole-genome sequencing of the more aggressive MM361 LTED model system identified exonic mutations in genes encoding transcription factors and chromatin modifiers. Single-cell RNA sequencing demonstrated a shift towards non-luminal phenotypes, and revealed metabolic remodeling of MM361 LTEDs, with upregulated lipid metabolism and antioxidant genes associated with ferroptosis, including GPX4. Combining the GPX4 inhibitor RSL3 with anti-HER2 agents induced significant cell death in both the MM361 and BT474 LTEDs. ConclusionsThe BT474 and MM361 AI-resistant models capture distinct phenotypes of HER2+/ER+ BCa and identify altered lipid metabolism and ferroptosis remodeling as vulnerabilities of this type of ETR BCa.

cancer biology↗

bioRxiv2022

SGC-CLK-1 (CAF-170) a chemical probe for the Cdc2-Like kinases CLK1, CLK2, and CLK4

Small molecule modulators are important tools to study both basic biology and the complex signaling of protein kinases. The cdc2-like kinases (CLK) are a family of four kinases that have garnered recent interest for their involvement in a diverse set of diseases such as neurodegeneration, autoimmunity, and many cancers. Targeted medicinal chemistry around a CLK inhibitor hit identified through screening of a kinase inhibitor set against a large panel of kinases allowed us to identify a potent and selective inhibitor of CLK1, 2 and 4. Here, we present the synthesis, selectivity, and potential binding site of this compound - SGC-CLK-1. We further show CLK2 has the highest binding affinity, and high CLK2 expression correlates with a lower IC50 in a screen of multiple cancer cell lines. Finally, we show that SGC-CLK-1 not only reduces serine arginine rich (SR) protein phosphorylation, but also alters SR protein and CLK2 subcellular localization in a reversible way. Therefore, we anticipate that this compound will be a valuable tool for increasing our understanding of CLKs and their targets, SR proteins, at the level of phosphorylation and subcellular localization.

cancer biology↗

bioRxiv2022

WNT4 executes estrogen regulation of cellular metabolism via intracellular activity at the mitochondria

Wnt ligand WNT4 is critical in female reproductive tissue development, with WNT4 dysregulation linked to related pathologies including breast cancer (invasive lobular carcinoma, ILC) and gynecologic cancers. WNT4 signaling in these contexts is distinct from canonical Wnt signaling yet inadequately understood. We previously identified atypical intracellular activity of WNT4 (independent of Wnt secretion) regulating mitochondrial function, and herein examine intracellular functions of WNT4. We further examine how convergent mechanisms of WNT4 dysregulation impact cancer metabolism. In ILC, WNT4 is co-opted by estrogen receptor (ER) via genomic binding in WNT4 intron 1, while in gynecologic cancers, a common genetic polymorphism (rs3820282) at this ER binding site alters WNT4 regulation. Using proximity biotinylation (BioID), we show canonical Wnt ligand WNT3A is trafficked for secretion, but WNT4 is localized to the cytosol and mitochondria. We identified DHRS2, mTOR, and STAT1 as putative WNT4 cytosolic/mitochondrial signaling partners. Whole metabolite profiling, and integrated transcriptomic data, support that WNT4 mediates metabolic reprogramming via fatty acid and amino acid metabolism. Further, ovarian cancer cell lines with rs3820282 variant genotype are WNT4-dependent and have active WNT4 metabolic signaling. In protein array analyses of a cohort of 103 human gynecologic tumors enriched for patient diversity, germline rs3820282 genotype is associated with metabolic remodeling. Variant genotype tumors show increased AMPK activation and downstream signaling, with the highest AMPK signaling activity in variant genotype tumors from non-White patients. Taken together, atypical intracellular WNT4 signaling, in part via genetic dysregulation, regulate the distinct metabolic phenotypes of ILC and gynecologic cancers. SignificanceWNT4 regulates breast and gynecologic cancer metabolism via a previously unappreciated intracellular signaling mechanism at the mitochondria, with WNT4 mediating metabolic remodeling. Understanding WNT4 dysregulation by estrogen and genetic polymorphism offers new opportunities for defining tumor biology, precision therapeutics, and personalized cancer risk assessment.

cancer biology↗

bioRxiv2020

Riluzole suppresses growth and enhances response to endocrine therapy in ER+ breast cancer

BackgroundResistance to endocrine therapy in estrogen receptor-positive (ER+) breast cancer remains a significant clinical problem. Riluzole is FDA-approved for the treatment of amyotrophic lateral sclerosis. A benzothiazole-based glutamate release inhibitor with several context-dependent mechanism(s) of action, Riluzole has shown anti-tumor activity in multiple malignancies, including melanoma, glioblastoma, and breast cancer. We previously reported that the acquisition of Tamoxifen resistance in a cellular model of invasive lobular breast cancer is accompanied by the upregulation of GRM mRNA expression and growth inhibition by Riluzole. MethodsWe tested the ability of Riluzole to reduce cell growth, alone and in combination with endocrine therapy, in a diverse set of ER+ invasive ductal and lobular breast cancer-derived cell lines, primary breast tumor explant cultures, and the estrogen-independent, ESR1-mutated invasive lobular breast cancer patient-derived xenograft model HCI-013EI. ResultsSingle-agent Riluzole suppressed the growth of ER+ invasive ductal and lobular breast cancer cell lines in vitro, inducing a histologic subtype-associated cell cycle arrest (G0-G1 for ductal, G2-M for lobular). Riluzole induced apoptosis and ferroptosis and reduced phosphorylation of multiple pro-survival signaling molecules, including Akt/mTOR, CREB, and Src/Fak family kinases. Riluzole, in combination with either Fulvestrant or 4-hydroxytamoxifen, additively suppressed ER+ breast cancer cell growth in vitro. Single-agent Riluzole significantly inhibited HCI-013EI patient-derived xenograft growth in vivo, and the combination of Riluzole plus Fulvestrant significantly reduced proliferation in primary breast tumor explant cultures. ConclusionsRiluzole, alone or combined with endocrine therapy, may offer therapeutic benefits in diverse ER+ breast cancers, including lobular breast cancer.

cancer biology↗

bioRxiv2019

The orphan nuclear receptor estrogen-related receptor beta (ERRβ) in triple-negative breast cancer

PurposeTriple negative breast cancer (TNBC)/ basal-like breast cancer (BLBC) is a highly aggressive form of breast cancer prevalent in African-American (AA) women. We previously reported that a small molecule agonist ligand for the orphan nuclear receptor estrogen-related receptor beta (ERR{beta} or ESRRB) has growth inhibitory and anti-mitotic activity in TNBC cell lines. In this study, we evaluate the association of ESRRB mRNA, copy number levels, and protein expression with demographic, clinicopathological, and gene expression features in breast tumor clinical specimens.\n\nMethodsESRRB mRNA level expression and clinical associations were analyzed using RNAseq data. Array-based comparative genomic hybridization determined ESRRB copy number in AA and Caucasian women. Transcription factor activity was measured using promoter-reporter luciferase assays in TNBC cell lines. Semi-automatic quantification of immunohistochemistry measured ERR{beta} protein expression on a 150-patient tissue microarray series.\n\nResultsESRRB mRNA expression is significantly lower in TNBC/BLBC vs. other breast cancer subtypes. There is no evidence of ESRRB copy number loss. ESRRB mRNA expression is correlated with the expression of genes associated with neuroactive ligand-receptor interaction, metabolic pathways, and deafness. These genes contain G/C-rich transcription factor binding motifs. The ESRRB message is alternatively spliced into three isoforms, which we show have different transcription factor activity in basal-like vs. other TNBC cell lines. We further show that the ERR{beta}2 and ERR{beta}sf isoforms are broadly expressed in breast tumors at the protein level.\n\nConclusionsDecreased ESRRB mRNA expression, and distinct patterns of ERR{beta} isoform subcellular localization and transcription factor activity are key features in TNBC/BLBC.

cancer biology↗

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↗

bioRxiv2019

An evidence-based network approach to recommending targeted cancer therapies

In this work, we introduce CDGnet, an evidence-based network approach for recommending targeted cancer therapies, available as a user-friendly informatics tool. Our approach can be used to expand the range of options of targeted therapies for cancer patients who undergo molecular profiling. It considers biological pathway information specifically by looking at downstream targets of oncogenes and is personalized for individual patients via the user-inputted molecular alterations and cancer type. CDGnet integrates disparate sources of knowledge and provides results in a number of easily-accessible and usable forms, while separating targeted cancer therapies into categories in an evidence-based manner.

bioinformatics↗

bioRxiv2019

Estrogen-related receptor beta activation and isoform shifting by cdc2-like kinase inhibition restricts migration and intracranial tumor growth in glioblastoma

Glioblastoma (GBM; grade 4 glioma) is a highly aggressive and incurable tumor. GBM has recently been characterized as highly dependent on alternative splicing, a critical driver of tumor heterogeneity and plasticity. Estrogen-related receptor beta (ERR{beta}, ESRRB, NR3B2) is an orphan nuclear receptor expressed in the brain, where alternative splicing of the 3 end of the pre-mRNA leads to the production of three validated ERR{beta} protein products - ERR{beta} short form (ERR{beta}sf), ERR{beta}2, and ERR{beta} exon 10-deleted (ERR{beta}-{Delta}10). Our prior studies have shown the ERR{beta}2 isoform to play a role in G2/M cell cycle arrest and induction of apoptosis, in contrast to the function of the shorter ERR{beta}sf isoform in senescence and G1 cell cycle arrest. In this study, we sought to better define the role of the pro-apoptotic ERR{beta}2 isoform in GBM. We show that the ERR{beta}2 isoform is located in the nucleus, but also the cytoplasm. ERR{beta}2 suppresses GBM cell migration, interacts with the actin nucleation-promoting factor cortactin, and an ERR{beta} agonist is able to remodel the actin cytoskeleton and similarly suppress GBM cell migration. We further show that inhibition of the splicing regulatory cdc2-like kinases (CLKs) in combination with an ERR{beta} agonist shifts isoform expression in favor of ERR{beta}2 and potentiates inhibition of growth and migration in GBM cells and intracranial tumors. Financial SupportThis work was supported by R21 CA191444 (RBR), a Georgetown University Medical Center (GUMC) Dean for Researchs Toulmin Pilot Project Award (RBR), and a Partners in Research Breakthrough Award (RBR), as well as F99 CA234799 (DMT) and a student research grant from the Medical Center Graduate Student Organization (MCGSO, to DMT). Additional fellowship funding for DMT and MMH was provided by the Tumor Biology Training Grant (T32 CA009686, PI: Dr. Anna T. Riegel). Technical services were provided by the GUMC Animal Models, Flow Cytometry & Cell Sorting, Histopathology & Tissue, Microscopy & Imaging, and Tissue Culture Shared Resources, which are supported in part by Cancer Center Support Grant P30 CA051008 (PI: Dr. Louis M. Weiner). The Mayo Clinic Brain Tumor Patient-Derived Xenograft National Resource is supported in part by P50 CA108961 (JNS, PI: Dr. Patrick ONeill). The content of this article is the sole responsibility of the authors and does not represent the official views of the National Institutes of Health. Conflict of Interest and Author Contribution StatementThe authors declare no potential conflict of interest. DMT contributed to study design, performed experiments, analyzed data, and wrote the paper. SAK performed experiments, analyzed data, and wrote the paper. CJT performed experiments and analyzed data. MMH performed experiments. SDD performed experiments. JNS provided patient-derived xenograft samples. EG contributed to study design, and performed experiments. RBR contributed to study design, performed experiments, analyzed data, and wrote the paper. All authors reviewed, edited, and approved the manuscript.

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↗