Biology subjects

Troness, B.

Publications and source records attributed to Troness, B..

4 recordsLinked to original sources

bioRxiv2026

Endogenous APOBEC3B Promotes CHK1 Inhibitor Sensitivity

APOBEC3B (A3B) is a single-stranded DNA cytosine deaminase overexpressed in cancer, where it causes genomic DNA damage and mutations associated with tumor evolution. Enforced A3B overexpression triggers a dependency on the replication-stress response in different cellular models. However, whether endogenous A3B in cancer cells might yield a similar vulnerability is unclear. Here, we investigate how endogenous A3B expression and catalytic activity affect sensitivity to CHK1 inhibition, using two cancer cell lines, JHOC5 and U2OS. A3B-expressing cancer cells are sensitive to two chemically distinct CHK1 inhibitors, GDC-0575 and Prexasertib. CHK1 inhibitor sensitivity is reduced by A3B CRISPR knockout and restored by re-expressing wildtype A3B in knockout cells. Moreover, an endogenous A3B-E255A catalytic mutant generated by homology-directed repair phenocopies the reduced CHK1 inhibitor sensitivity of A3B-null cells, demonstrating a DNA deamination-dependent mechanism. CHK1 inhibition induces replication-associated DNA damage and cell-cycle perturbation dependent on A3B expression. As a result, A3B-expressing cells accumulate more pan-nuclear {gamma}H2AX, aberrant DNA-content profiles, and an expanded EdU-negative S-phase population, which are hallmarks of stalled DNA replication. In comparison, A3B-null and A3B-E255A cells retain defined cell-cycle distributions and are less sensitive to CHK1 inhibition. Together, these findings identify endogenous A3B-catalyzed deamination as a therapeutically actionable source of replication-associated DNA damage that renders tumor cells selectively dependent on CHK1 function. Statement of significanceAPOBEC3B causes mutations in cancer cells and simultaneously imposes DNA replication stress. This combines to sensitize tumor cells to chemical inhibitors of the DNA damage response kinase CHK1.

cancer biology↗

bioRxiv2025

Murine models for triple-negative breast cancer with differential responsiveness to immunotherapy

Breast cancer is the most common cancer diagnosis in women. Clinical studies with triple-negative breast cancer (TNBC) are encouraging for immunotherapy combined with chemotherapy (anti-PD-1 with paclitaxel and/or carboplatin). However, additional clinical advances may be pursued more rapidly with assistance from preclinical TNBC models including syngeneic mammary tumor cell lines. Here, we report two mammary tumor cell lines that exhibit differential responsiveness to immunotherapy in vivo. Spontaneous mammary tumors from C57BL/6J MMTV-Cre Trp53fl/+ animals were passaged serially in cell culture and in vivo in the mammary fat pad of fully wildtype animals. The resulting lines, MM001i and MM008i, lost Trp53 and formed 1000 mm3 tumors in the mammary fat pad within 21-28 days. Despite originating from the same genetic background, these lines exhibit differential responses to immunotherapy. For anti-PD-1 therapy, MM001i is poorly responsive and MM008i is strongly responsive with near-complete tumor regression. In comparison, both MM001i and MM008i respond rapidly to anti-CTLA-4 therapy. Both models express unique tumor antigens as evidenced by immunity to subsequent engraftments. Primary MM008i tumors exhibit greater T cell infiltration, and CD8-positive T lymphocytes are required for anti-PD-1 responses. These TNBC models are promising for further mechanistic studies and testing future single and combinatorial therapies.

cancer biology↗

bioRxiv2025

Modeling the role of urokinase plasminogen activator, uPA, and circulating Cancer-Associated Fibroblasts (cCAFS) in breast cancer cell extravasation

Circulating Cancer-Associated Fibroblasts (cCAFs) have been discovered in circulating tumor cell clusters from all stages of disease progression in breast cancer patients. We have shown that CAFs promote lung metastases in the mouse tail vein model when they are clustered with triple negative breast cancer (TNBC) MDA-MB231 cells. Following on this observation, we saw that MDA-MB231-luciferase labeled cells persist at higher levels when present in CAF23/MDA-MB231 co-clusters compared to MDA-MB231 mono-clusters within the first 3 days after tail vein injection. This prompted us to investigate whether CAFs aid cancer cell extravasation from capillary venules into the lung parenchyma, which would impart better survival and faster seeding of metastases. Ex vivo lung extravasation assays showed that within the first 8-24 hrs after tail vein injection, more cells from CAF23/MDA-MB231 co-clusters extravasated than cells from MDA-MB231 mono-clusters. Using in vitro endothelial binding assays, we determined that CAF/TNBC co-clusters bind to HUVEC endothelial cells better than TNBC mono-clusters. Single Cell RNA-seq identified several genes in the fibrinolysis pathway whose expression increases in TNBC cells when they are clustered with CAFs. One of these genes is PLAU, which encodes the urokinase-type plasminogen activator, uPA. siRNA knockdown of PLAU decreased in vitro TNBC-endothelial cell interactions and ex vivo extravasation of MDA-MB231 mono-clusters, revealing a role for uPA/PLAU in breast cancer cell extravasation. Our data helps to define the role of CAFs in breast cancer extravasation and highlights the importance of our previous work showing that CAFs promote tumor cell dissemination and metastasis.

cancer biology↗

bioRxiv2021

Hotspot ESR1 mutations are multimodal and contextual drivers of breast cancer metastasis

Constitutively active estrogen receptor- (ER/ESR1) mutations have been identified in approximately one third of ER+ metastatic breast cancer. Although these mutations are known mediators of endocrine resistance, their potential role in promoting metastatic disease has not yet been mechanistically addressed. In this study, we show the presence of ESR1 mutations exclusively in distant, but not local recurrences. In concordance with transcriptomic profiling of ESR1 mutant tumors, genome-edited Y537S and D538G cell models have a reprogrammed cell adhesive gene network via alterations in desmosome/gap junction genes and the TIMP3/MMP axis, which functionally confers enhanced cell-cell contacts while decreased cell-ECM adhesion. Context-dependent migratory phenotypes revealed co-targeting of Wnt and ER as vulnerability. Mutant ESR1 exhibits non-canonical regulation of several metastatic pathways including secondary transactivation and de novo FOXA1-driven chromatin remodeling. Collectively, our data supports evidence for ESR1 mutation-driven metastases and provides insight for future preclinical therapeutic strategies. SignificanceContext and allele-dependent transcriptome and cistrome reprogramming in genome-edited ESR1 mutation cell models elicit diverse metastatic phenotypes, including but not limited to alterations in cell adhesion and migration. The gain-of-function mutations can be pharmacologically targeted, and thus may be key components of novel therapeutic treatment strategies for ER-mutant metastatic breast cancer.

cancer biology↗