Biology subjects

Weichselbaum, R. R.

Publications and source records attributed to Weichselbaum, R. R..

4 recordsLinked to original sources

bioRxiv2026

Programmable genetic control of tumor-colonizing Bifidobacterium longum for intratumoral therapeutic delivery and biocontainment

Engineered bacteria offer a distinct modality for cancer therapy by exploiting the ability of certain species to colonize tumors and deliver therapeutic payloads. Improving their efficacy and safety requires control over bacterial activity after tumor colonization, yet few microbial chassis permit it. Bifidobacterium longum, a probiotic with intrinsic tumor-targeting and antitumor activity, is a promising chassis but lacks such control. Here, we develop a genetic control system that regulates B. longum activity within tumors, from gene expression to bacterial abundance. A human-isolate-derived replicon supports plasmid maintenance without antibiotic selection, and promoter and ribosome-binding-site libraries provide [~]150-fold and [~]48-fold expression ranges, respectively. Signal peptides enable secretion of structurally diverse therapeutic payloads and B. longum secreting CCL21 or an anti-PD-L1 nanobody reduces tumor growth relative to PBS controls. Anhydrotetracycline delivered in drinking water induces transgene expression in tumor-resident bacteria and reduces intratumoral bacterial load through CRISPRi targeting essential genes. Together, these results establish a tumor-homing probiotic as an externally controllable therapeutic chassis.

synthetic biology↗

bioRxiv2024

A new universal chimeric-antigen receptor (CAR)- fragment antibody binder (FAB) split system for cancer immunotherapy

Chimeric antigen receptor T (CAR-T) cell therapy has shown extraordinary results in treating hematological cancer. However, many patients relapse because of heterogeneous antigen expression and outgrowth of antigen lost variants. Other problems include on-target-off-tumor toxicity and the requirement for manufacturing of complex cellular products. Universal and modular CAR constructs offer significantly improved flexibility, safety and cost-effectiveness over conventional CAR constructs. Here we present a new chimeric-antigen receptor (CAR)-fragment antibody binder (Fab) platform based on an engineered protein G variant (GA1) and Fab scaffolds that present exquisite specificity and selectivity on antibody capture. The expression of GA1CAR on human CD8+T cells leads to antigen recognition and T cell effector function that can be modulated according to the affinity of the CAR for the Fab scaffold and of the Fab for the target. GA1CAR-T cells can recognize multiple Fab-antigen pairs on breast and ovarian cancer cell lines. Adoptive transfer of GA1CAR-T cells/Fabs in breast cancer xenograft models leads to effective tumor control. Rapid re-direction of the CAR-T cells to a new target can be achieved by using different Fabs. GA1CAR expression confers favorable phenotypic properties to T cells including a higher effector function upon exposure to antigen as compared to conventional scFv CAR-T cells. This highly versatile "plug and play" CAR-T platform has potential for application in personalized therapy, preventing antigen loss variant escape, decreasing toxicity and increasing access.

bioengineering↗

bioRxiv2021

Chromosomal instability mediates immune exclusion and response to cytotoxic chemotherapy in colorectal liver metastases

The genomic drivers of immune exclusion in colorectal cancer liver metastases (CRCLM) remain poorly understood. Chromosomal instability (CIN), resulting in aneuploidy and genomic rearrangements, is the central pathway of mismatch repair-proficient colorectal cancer pathogenesis; however, it is unknown whether CIN impacts the outcomes of patients with limited spread of CRCLM treated with curative intent cytotoxic chemotherapy and surgery. Herein, we examined the relationship between CIN and the molecular subtypes of CRCLM, immune signaling, treatment sensitivity, and patient outcomes in three independent CRCLM patient cohorts. We established that a previously developed 70-gene CIN signature (CIN70) is a reliable measure of CIN, encompassing features of both aneuploidy and cellular proliferation. We demonstrated that tumors with the canonical subtype of CRCLM exhibit elevated levels of CIN and aneuploidy. Genomically unstable tumors were associated with an immune-depleted tumor microenvironment, and patients with genomically unstable tumors were at increased risk for disease progression in adverse metastatic sites, resulting in poor progression-free and overall survival. However, high-CIN tumors were particularly susceptible to DNA-damaging chemotherapies, including topoisomerase inhibitors, as well as radiation therapy. Treatment with genotoxic agents depleted CIN-rich cell populations, which resulted in a concomitant increase in intratumoral CD8+ T-cells in patients with primary rectal, breast, and bladder cancer. Taken together, we propose a mechanistic explanation for why cytotoxic chemotherapy can augment anti-tumor immunity and improve outcomes in patients with genomically unstable cancers.

cancer biology↗

bioRxiv2018

Pancreatic adenocarcinoma human organoids share structural and genetic features with primary tumors

Patient-derived pancreatic ductal adenocarcinoma (PDAC) organoid systems show great promise for understanding the biological underpinnings of disease and advancing therapeutic precision medicine. Despite the increased use of organoids, the fidelity of molecular features, genetic heterogeneity, and drug response to the tumor of origin remain important unanswered questions limiting their utility. To address this gap in knowledge, we created primary tumor- and PDX-derived organoids, and 2D cultures for in-depth genomic and histopathological comparisons to the primary tumor. Histopathological features and PDAC representative protein markers showed strong concordance. DNA and RNA sequencing of single organoids revealed patient-specific genomic and transcriptomic consistency. Single-cell RNAseq demonstrated that organoids are primarily a clonal population. In drug response assays, organoids displayed patient-specific sensitivities. Additionally, we examined the in vivo PDX response to FOLFIRINOX and Gemcitabine/Abraxane treatments, which was recapitulated in vitro by organoids. The patient-specific molecular and histopathological fidelity of organoids indicate that they can be used to understand the etiology of the patients tumor and the differential response to therapies and suggests utility for predicting drug responses.

cancer biology↗