Biology subjects

Alvarez, J. V.

Publications and source records attributed to Alvarez, J. V..

11 recordsLinked to original sources

bioRxiv2026

Adaptation of breast cancer cells to serum-free defined medium reveals changes in proliferation, adhesion, and lipid metabolism

Cancer cell metabolic dependencies are strongly influenced by nutrient availability, yet conventional culture conditions contain non-physiological nutrient concentrations and poorly defined serum components that may obscure metabolic vulnerabilities. Here, we investigated the adaptation of three breast cancer cell lines to physiologically relevant, serum-free defined medium (DM). Using a stepwise reduction in fetal bovine serum (FBS), we evaluated proliferation, adhesion, morphology, and transcriptional changes in HER2-positive SK-BR-3, triple-negative MDA-MB-231, and ER-positive/HER2-positive BT-474 cells. The three cell lines differed substantially in their ability to adapt to serum-free conditions. MDA-MB-231 cells adapted readily, maintaining proliferation and adhesion without exogenous substrate coatings. SK-BR-3 cells also achieved sustained proliferation in serum-free DM, but required a serum-derived coating to maintain adhesion. In contrast, BT-474 cells failed to sustain adhesion and proliferation following complete serum withdrawal, although they remained proliferative in medium containing 1% FBS. Adapted cells retained characteristic HER2 or vimentin expression despite changes in morphology and proliferation. RNA sequencing revealed extensive transcriptional remodeling, including reduced expression of cell-cycle-associated programs in SK-BR-3 cells and enrichment of cholesterol homeostasis gene sets in SK-BR-3 and MDA-MB-231 cells. Expression of cholesterol regulatory genes, including SREBF2, HMGCR, and LDLR, increased across all three lines. Together, these findings highlight cell-line-specific adhesion requirements and shared metabolic responses to serum withdrawal, establishing a framework for developing defined culture systems to investigate cancer metabolic dependencies through genetic screening.

cancer biology↗

bioRxiv2025

Recurrent Breast Cancer Cells Depend on De novo Pyrimidine Biosynthesis to Suppress Ferroptosis

Breast cancer recurrence remains a major clinical challenge, often associated with therapy resistance and altered metabolic states. To define metabolic vulnerabilities of recurrent disease, we performed a CRISPR knockout screen targeting 421 metabolic genes in paired primary and recurrent HER2-driven breast cancer cell lines. While both primary and recurrent tumors shared dependencies on core metabolic pathways, recurrent tumors exhibited selective essentiality for the de novo pyrimidine synthesis pathway, including Cad, Dhodh, and Ctps. Pharmacologic inhibition of the rate-limiting enzyme DHODH with BAY-2402234 selectively impaired the growth of recurrent tumor cells, while primary tumor cells were relatively resistant. BAY treatment robustly inhibited pyrimidine synthesis in all lines, but only recurrent cells underwent iron-dependent lipid peroxidation and ferroptotic cell death. Lipidomic profiling revealed enrichment of polyunsaturated ether phospholipids in recurrent cells, which may predispose them to ferroptosis. A sensitizer CRISPR screen in primary cells further identified nucleotide salvage and lipid metabolic pathways as modifiers of DHODH inhibitor sensitivity. Stable isotope tracing and nutrient depletion experiments showed that primary cells can compensate for DHODH inhibition through nucleotide salvage, whereas recurrent cells exhibit impaired salvage capacity, likely due to reduced expression of Slc28/Slc29 nucleoside transporters. Together, these findings reveal that breast cancer recurrence is associated with increased dependence on de novo pyrimidine synthesis to suppress ferroptosis, highlighting a therapeutically actionable metabolic vulnerability in recurrent disease.

cancer biology↗

bioRxiv2024

Endocrine persistence in ER+ breast cancer is accompanied by metabolic vulnerability in oxidative phosphorylation

Despite adjuvant treatment with endocrine therapies, estrogen receptor-positive (ER+) breast cancers recur in a significant proportion of patients. Recurrences are attributable to clinically undetectable endocrine-tolerant persister cancer cells that retain tumor-forming potential. Therefore, strategies targeting such persister cells may prevent recurrent disease. Using CRISPR-Cas9 genome-wide knockout screening in ER+ breast cancer cells, we identified a survival mechanism involving metabolic reprogramming with reliance upon mitochondrial respiration in endocrine-tolerant persister cells. Quantitative proteomic profiling showed reduced levels of glycolytic proteins in persisters. Metabolic tracing of glucose revealed an energy-depleted state in persisters where oxidative phosphorylation was required to generate ATP. A phase II clinical trial was conducted to evaluate changes in mitochondrial markers in primary ER+/HER2-breast tumors induced by neoadjuvant endocrine therapy (NCT04568616). In an analysis of tumor specimens from 32 patients, tumors exhibiting residual cell proliferation after aromatase inhibitor-induced estrogen deprivation with letrozole showed increased mitochondrial content. Genetic profiling and barcode lineage tracing showed that endocrine-tolerant persistence occurred stochastically without genetic predisposition. Mice bearing cell line- and patient-derived xenografts were used to measure the anti-tumor effects of mitochondrial complex I inhibition in the context of endocrine therapy. Pharmacological inhibition of complex I suppressed the tumor-forming potential of persisters and synergized with the anti-estrogen fulvestrant to induce regression of patient-derived xenografts. These findings indicate that mitochondrial metabolism is essential in endocrine-tolerant persister ER+ breast cancer cells and warrant the development of treatment strategies to leverage this vulnerability in the context of endocrine-sensitive disease. Statement of SignificanceEndocrine-tolerant persister cancer cells that survive endocrine therapy can cause recurrent disease. Persister cells exhibit increased energetic dependence upon mitochondria for survival and tumor re-growth potential.

cancer biology↗

bioRxiv2023

APOBEC3 activity promotes the survival and evolution of drug-tolerant persister cells during acquired resistance to EGFR inhibitors in lung cancer

APOBEC mutagenesis is one of the most common endogenous sources of mutations in human cancer and is a major source of genetic intratumor heterogeneity. High levels of APOBEC mutagenesis are associated with poor prognosis and aggressive disease across diverse cancers, but the mechanistic and functional impacts of APOBEC mutagenesis on tumor evolution and therapy resistance remain relatively unexplored. To address this, we investigated the contribution of APOBEC mutagenesis to acquired therapy resistance in a model of EGFR-mutant non-small cell lung cancer. We find that inhibition of EGFR in lung cancer cells leads to a rapid and pronounced induction of APOBEC3 expression and activity. Functionally, APOBEC expression promotes the survival of drug-tolerant persister cells (DTPs) following EGFR inhibition. Constitutive expression of APOBEC3B alters the evolutionary trajectory of acquired resistance to the EGFR inhibitor gefitinib, making it more likely that resistance arises through de novo acquisition of the T790M gatekeeper mutation and squamous transdifferentiation during the DTP state. APOBEC3B expression is associated with increased expression of the squamous cell transcription factor {Delta}Np63 and squamous cell transdifferentiation in gefitinib-resistant cells. Knockout of p63 in gefitinib-resistant cells reduces the expression of the {Delta}Np63 target genes IL1/{beta} and sensitizes these cells to the third-generation EGFR inhibitor osimertinib. These results suggest that APOBEC activity promotes acquired resistance by facilitating evolution and transdifferentiation in DTPs, and suggest that approaches to target {Delta}Np63 in gefitinib-resistant lung cancers may have therapeutic benefit.

cancer biology↗

bioRxiv2021

Context-dependent effects of whole-genome duplication during mammary tumor recurrence

Whole-genome duplication (WGD) generates polyploid cells possessing more than two copies of the genome and is among the most common genetic abnormalities in cancer. The frequency of WGD increases in advanced and metastatic tumors, and WGD is associated with poor prognosis in diverse tumor types, suggesting a functional role for polyploidy in tumor progression. Experimental evidence suggests that polyploidy has both tumor-promoting and suppressing effects, but how polyploidy regulates tumor progression remains unclear. Using a genetically engineered mouse model of Her2-driven breast cancer, we explored the prevalence and consequences of whole-genome duplication during tumor growth and recurrence. While primary tumors in this model are invariably diploid, nearly 40% of recurrent tumors undergo WGD. WGD in recurrent tumors was associated with increased chromosomal instability, decreased proliferation and increased survival in stress conditions. The effects of WGD on tumor growth were dependent on tumor stage. Surprisingly, in recurrent tumor cells WGD slowed tumor formation, growth rate and opposed the process of recurrence, while WGD promoted the growth of primary tumors. These findings highlight the importance of identifying conditions that promote the growth of polyploid tumors, including the cooperating genetic mutations that allow cells to overcome the barriers to WGD tumor cell growth and proliferation.

cancer biology↗

bioRxiv2021

APOBEC mutagenesis inhibits breast cancer growth through induction of a T cell-mediated antitumor immune response

The APOBEC family of cytidine deaminases is one of the most common endogenous sources of mutations in human cancer. Genomic studies of tumors have found that APOBEC mutational signatures are particularly enriched in the HER2 subtype of breast cancer and have been associated with immunotherapy response in diverse cancer types. However, the direct consequences of APOBEC mutagenesis on the tumor immune microenvironment have not been thoroughly investigated. To address this, we developed syngeneic murine mammary tumor models with inducible expression of APOBEC3B. We found that APOBEC activity induces an antitumor adaptive immune response and CD4+ T cell-mediated tumor growth inhibition. While polyclonal APOBEC tumors had a moderate growth defect, clonal APOBEC tumors were almost completely rejected by the immune system, suggesting that APOBEC-mediated genetic heterogeneity limits the antitumor adaptive immune response. Consistent with the observed immune infiltration in APOBEC tumors, APOBEC activity sensitized HER2-driven breast tumors to checkpoint inhibition. In human breast cancers, the relationship between APOBEC mutagenesis and immunogenicity varied by breast cancer subtype and the frequency of subclonal mutations. This work provides a mechanistic basis for the sensitivity of APOBEC tumors to checkpoint inhibitors and suggests a rationale for using APOBEC mutational signatures as a biomarker predicting immunotherapy response in HER2-positive breast cancers. SIGNIFICANCEAPOBEC mutational signatures are observed in many cancers, yet the consequences of these mutations on the tumor immune microenvironment are not well understood. Using a novel mouse model, we show that APOBEC activity sensitizes HER2-driven mammary tumors to checkpoint inhibition and could inform immunotherapy treatment strategies for HER2-positive breast cancer patients.

cancer biology↗

bioRxiv2020

Epithelial-to-mesenchymal transition activates Bcat1 expression to promote recurrent tumor growth

Branched-chain amino acid metabolism has emerged as a crucial regulator of tumor proliferation. In particular, the branched-chain amino acid transaminase 1 (BCAT1), which catalyzes the conversion of branched-chain amino acids to -keto acids in the cytoplasm, has been identified as a promising therapeutic target for several different cancer types, including gliomas and leukemias. BCAT1 expression has also been associated with resistance to anti-estrogen therapy in breast cancer, suggesting a role in therapeutic resistance and tumor progression. Yet a functional role for BCAT1 in promoting breast cancer recurrence has not been described. Further, BCAT1 expression is restricted to just a few specialized tissues, such as the testes and central nervous system, and the mechanism by which it becomes transcriptionally activated in tumors that arise from tissues that do not typically express BCAT1 is unclear. Here, we report that Bcat1 is upregulated in recurrent breast tumors to promote recurrent tumor growth. We find that Bcat1 is upregulated by the epithelial-to-mesenchymal transition (EMT) in mammary epithelial cells and breast cancer cells. Finally, we analyze human tumor datasets to show that BCAT1 expression is strongly correlated with epithelial-to-mesenchymal gene signatures, suggesting that EMT is the predominant regulator of BCAT1 expression in cancer. Because EMT is associated with therapy resistance, metastasis, and tumor recurrence, these findings suggest a broad clinical potential for BCAT1 inhibition.

cancer biology↗

bioRxiv2020

Adaptation and Selection Shape Clonal Evolution During Residual Disease and Recurrence

The survival of residual tumor cells following therapy and their eventual recurrence constitutes one of the biggest obstacles to obtaining cures in breast cancer, but it remains unclear how the clonal composition of tumors changes during tumor relapse. We used cellular barcoding to directly monitor clonal dynamics during tumor recurrence in a genetically engineered mouse model. We found that the clonal diversity of tumors progressively decreased during tumor regression, residual disease, and recurrence. Only a fraction of subclones survived oncogene withdrawal and persisted in residual tumors. The minimal residual disease phase itself was accompanied by a continued attrition of clones, suggesting an ongoing process of selection during dormancy. The reactivation of dormant residual cells into recurrent tumors followed several distinct evolutionary routes. Approximately half of the recurrent tumors exhibited a striking clonal dominance in which one or two subclones comprised the vast majority of the tumor. The majority of these clonal recurrent tumors exhibited evidence of de novo acquisition of Met amplification, and were sensitive to small-molecule Met inhibitors. A second group of recurrent tumors exhibited marked polyclonality, with thousands of subclones and a clonal architecture very similar to primary tumors. These polyclonal recurrent tumors were not sensitive to Met inhibitors, but were instead dependent upon an autocrine IL-6 - Stat3 pathway. These results suggest that the survival and reactivation of dormant tumors can proceed via multiple independent routes, producing recurrent tumors with distinct clonal composition, genetic alterations, and drug sensitivities.

cancer biology↗

bioRxiv2020

G9a Promotes Breast Cancer Recurrence Through Repression of a Pro-inflammatory Program

Epigenetic dysregulation is a common feature of cancer, and is thought to underlie many aspects of tumor progression. Using a genetically engineered mouse model of breast cancer recurrence, we show that recurrent mammary tumors undergo widespread epigenomic and transcriptional alterations, and acquire dependence on the G9a histone methyltransferase. Genetic ablation of G9a delays tumor recurrence, and pharmacologic inhibition of G9a slows the growth of recurrent tumors. Mechanistically, G9a activity is required to silence pro-inflammatory cytokines, including TNF, through H3K9 methylation at gene promoters. G9a inhibition induces re-expression of these cytokines, leading to p53 activation and necroptosis. Recurrent tumors upregulate receptor interacting protein kinase-3 (RIPK3) expression and are dependent upon RIPK3 activity. High RIPK3 expression renders recurrent tumors sensitive to necroptosis following G9a inhibition. These findings demonstrate that epigenetic rewiring - specifically G9a-mediated silencing of pro-necroptotic proteins - is a critical step in tumor recurrence and suggest that G9a is a targetable dependency in recurrent breast cancer.

cancer biology↗

bioRxiv2019

CCL5 promotes breast cancer recurrence through macrophage recruitment in residual tumors

Over half of breast cancer related deaths are due to recurrence five or more years after initial diagnosis and treatment. This latency suggests that a population of residual tumor cells can survive treatment and persist in a dormant state for many years. The role of the microenvironment in regulating the survival and proliferation of residual cells following therapy remains unexplored. Using a conditional mouse model for Her2-driven breast cancer, we identify interactions between residual tumor cells and their microenvironment as critical for promoting tumor recurrence. Her2 downregulation leads to an inflammatory program driven by TNF/NF{kappa}B signaling, which promotes immune cell infiltration in regressing and residual tumors. The cytokine CCL5 is elevated following Her2 downregulation and remains high in residual tumors. CCL5 promotes tumor recurrence by recruiting CCR5-expressing macrophages, which may contribute to collagen deposition in residual tumors. Blocking this TNF-CCL5-macrophage axis may be efficacious in preventing breast cancer recurrence.

cancer biology↗

bioRxiv2019

NRF2-dependent metabolic reprogramming is required for tumor recurrence following oncogene inhibition

Oncogenic signaling pathways both directly and indirectly regulate anabolic metabolism, and this is required for tumor growth. Targeted therapies that inhibit oncogenic signaling have dramatic impacts on cellular metabolism. However, it is not known whether the acquisition of resistance to these therapies is associated with - or driven by - alterations in cellular metabolism. To address this, we used a conditional mouse model of Her2-driven breast cancer to study metabolic adaptations following Her2 inhibition, during residual disease, and after tumor recurrence. We found that Her2 downregulation caused widespread changes in cellular metabolism, culminating in oxidative stress. Tumor cells adapted to this metabolic stress by upregulation of the antioxidant transcription factor, NRF2. Constitutive NRF2 expression persisted during residual disease and tumor recurrence, and NRF2 was both sufficient to promote tumor recurrence, and necessary for recurrent tumor growth. These results are supported by clinical data showing that the NRF2 transcriptional program is activated in recurrent breast tumors, and that NRF2 is associated with poor prognosis in patients with breast cancer. Mechanistically, NRF2 signaling in recurrent tumors induced metabolic reprogramming to re-establish redox homeostasis and upregulate de novo nucleotide synthesis. Finally, this NRF2-driven metabolic state rendered recurrent tumor cells sensitive to glutaminase inhibition, suggesting that NRF2-high recurrent tumors can be therapeutically targeted. Together, these data provide evidence that NRF2-driven metabolic reprogramming is required for breast cancer recurrence following oncogene inhibition.\n\nSignificanceAlthough tumor recurrence is the leading cause of mortality in breast cancer, the cellular properties that allow tumor cells to evade therapy and form recurrent tumors remain largely uncharacterized. Similarly, very little is known about how tumor metabolism changes following therapy, or whether alterations in cellular metabolism drive tumor recurrence. In this study, we identify the antioxidant transcription factor NRF2 as a critical positive regulator of breast cancer recurrence. We find that NRF2-dependent metabolic reprogramming is both sufficient and required to promote tumor recurrence. Additionally, we demonstrate that the NRF2-driven metabolic state renders recurrent tumors sensitive to glutaminase inhibitors, suggesting a novel therapeutic approach for the treatment of recurrent breast cancer.

cancer biology↗