Biology subjects

Bharambe, H. S.

Publications and source records attributed to Bharambe, H. S..

3 recordsLinked to original sources

bioRxiv2025

Collagen remodeling promotes a GPCR-mediated mechanosensory immune checkpoint in ADGRG1+ CD8+ T cells and serves as a spatial biomarker of response to immunotherapy

Accessibility of immune cells to the tumor microenvironment (TME) in many solid tumors can be influenced by extracellular matrix (ECM) deposition, organization, and remodeling within tumor stroma. Specifically, lysyl hydroxylase-2 (LH2)-catalyzed lysine hydroxylation in type-I collagen telopeptides leads to formation of intermolecular collagen cross-links creating a stiffened and proteolytically resistant, stable ECM. Advanced head and neck squamous cell carcinomas (HNSCC) frequently exhibit desmoplasia with elevated LH2 expression, and Immune-checkpoint (ICI) therapy is effective in only <20% patients, suggesting that ECM remodeling mechanistically governs the composition and function of TME infiltrates. We show that elevated LH2 and collagen alignment promotes stromal accumulation of CD8 T-cells, and poor response to ICI in HPV-HNSCCs. Integration of clinical biopsies, transcriptomic datasets, and an immunocompetent syngeneic mouse model revealed that aligned collagen spatially restricts adhesion G protein-coupled receptor positive (ADGRG1) CD8 T-cells to activate a non-canonical GPCR-mediated mechanosensory program that drives dysfunction and exhaustion. Statement of significanceDesmoplasia is common in solid tumors, and immune checkpoint inhibitors benefit only some patients. Current biomarkers like PD-L1 and TMB have limited value. Our findings reveal a previously unrecognized collagen-ADGRG1 mechanosensory immune checkpoint, offering a clinically tractable, spatially resolved biomarker to better stratify patients for immunotherapy.

cancer biology↗

bioRxiv2025

Adaptive Responses Directed by CREB Control Epithelial-Mesenchymal Plasticity in Cancer

Cellular plasticity plays essential roles in development including organogenesis and tissue homeostasis. The epithelial-to-mesenchymal transition (EMT) is no longer considered a binary switch but rather a dynamic process characterized by a continuum of metastable intermediates having unique features. This epithelial-mesenchymal (E/M) plasticity can be co-opted by cancer cells to promote dedifferentiation that results in hybrid E/M states which increase tumor heterogeneity and generate distinct molecular and phenotypic adaptations that promote drug resistance, dormancy, recurrence, and/or cell invasion and metastasis. The mechanisms that coordinate and maintain metastable hybrid E/M states are poorly understood, and here we report they are controlled by the master transcription factor CREB which regulates adaptive response genes necessary for E/M plasticity. Specifically, a CREB-dependent head and neck cancer model validated the role of CREB in cancer cell plasticity and revealed that it controls a non-canonical EMT gene signature. Moreover, analyses of this signature across cancer types identified the transcriptional regulators VGLL3 and KLF3 as core PanCancer mediators of hybrid E/M states, and gain- and loss-of-function studies established that CREB regulates E/M plasticity by coordinating VGLL3 and KLF3 to drive metastasis.

cell biology↗

bioRxiv2023

Medulloblastoma-associated DDX3X mutants are oncogenic having a defect in translation-promoting activity but functional in stress granule formation and interferon signaling

DDX3X, a DEAD box-containing RNA helicase, is known to play diverse roles in RNA metabolism, stress response, innate immunity, and cancer. Medulloblastoma is the single most common malignant brain tumor in children. DDX3X is recurrently mutated in the WNT and SHH subgroups of medulloblastoma. CRISPR-Cas9 mediated DDX3X knockout was successful in the HEK293FT cells but generated only non-truncating indels in the medulloblastoma cells suggesting DDX3X is necessary for the viability of the cells. Downregulation of DDX3X expression using shRNA also brought about a considerable reduction in proliferation, clonogenic potential, and anchorage-independent growth of the medulloblastoma cells. Thus, DDX3X expression was found to be essential for the survival, growth, and malignant potential of the medulloblastoma cells consistent with the non-truncating nature of medulloblastoma-associated DDX3X mutations. The medulloblastoma-associated DDX3X mutants were found to be defective in their ability to drive the translation of mRNAs with complex 5-UTR that is dependent on the ATP-dependent helicase activity of DDX3X. These helicase defective DDX3X mutants could restore the expression of interferon signaling genes and malignant potential lost upon DDX3X knockdown in medulloblastoma cells. Their N-terminal domain is intact and was found to be functional in stress granule formation. DDX3X mutants upregulated expression of malignancy-related genes suggesting tumor suppressive role for the helicase activity in the medulloblastoma pathogenesis. Inhibitors of the N-terminal domain of DDX3X which is essential for the viability of medulloblastoma cells could have therapeutic potential in the treatment of WNT and SHH subgroup medulloblastomas.

cancer biology↗