Project description:As a tumor suppressor, PTEN is frequently mutated in human cancers and PTEN mutants promote tumor progression and metastasis. PTEN mutations have been implicated in immune regulation, but the underlying mechanism is largely unknown. We report that PTENα, the isoform of PTEN, remains active in cancer bearing stop-gained PTEN mutations. Through counteraction of CD8+ T cell-mediated cytotoxicity, presence of PTENα leads to T cell dysfunction and accelerates immune-resistant cancer progression. Clinical analysis further uncovers that PTENα-active mutations suppress host immune responses and result in poor prognosis in cancer as relative to PTENα-inactive mutations. Furthermore, germline deletion of Ptenα in mice increases cell susceptibility to immune attack through augmenting stress granule formation and limiting synthesis of peroxidases, leading to massive oxidative cell death and severe inflammatory damage. We propose that PTENα protects tumor from T cell killing and thus PTENα is a potential target in antitumor immunotherapy.
Project description:As a tumor suppressor, PTEN is frequently mutated in human cancers and PTEN mutants promote tumor progression and metastasis. PTEN mutations have been implicated in immune regulation, but the underlying mechanism is largely unknown. We report that PTENα, the isoform of PTEN, remains active in cancer bearing stop-gained PTEN mutations. Through counteraction of CD8+ T cell-mediated cytotoxicity, presence of PTENα leads to T cell dysfunction and accelerates immune-resistant cancer progression. Clinical analysis further uncovers that PTENα-active mutations suppress host immune responses and result in poor prognosis in cancer as relative to PTENα-inactive mutations. Furthermore, germline deletion of Ptenα in mice increases cell susceptibility to immune attack through augmenting stress granule formation and limiting synthesis of peroxidases, leading to massive oxidative cell death and severe inflammatory damage. We propose that PTENα protects tumor from T cell killing and thus PTENα is a potential target in antitumor immunotherapy.
Project description:we report that USP9X and FBXW11 selectively regulate the stability of PTENα/β but not PTEN proteins by deubiqitination and ubiquitination respectively. USP9X promotes and FBXW11 suppresses tumorigenesis mediated by PTENα/β. In contrast to the current paradigm for PTEN as a tumor suppressor, PTENα/β promote tumorigenesis of cancer cells in a phosphatase-independent manner. Mechanistically, PTENα/β localized in the nucleus regulate expressions of tumor-promoting genes such as NOTCH3 in the similar way as the H3K4 presenter WDR5. Further, PTENα/β but not PTEN directly interact with WDR5 to promote trimethylation of H3K4 and maintain a tumor-promoting signature.
Project description:we report that USP9X and FBXW11 selectively regulate the stability of PTENα/β but not PTEN proteins by deubiqitination and ubiquitination respectively. USP9X promotes and FBXW11 suppresses tumorigenesis mediated by PTENα/β. In contrast to the current paradigm for PTEN as a tumor suppressor, PTENα/β promote tumorigenesis of cancer cells in a phosphatase-independent manner. Mechanistically, PTENα/β localized in the nucleus regulate expressions of tumor-promoting genes such as NOTCH3 in the similar way as the H3K4 presenter WDR5. Further, PTENα/β but not PTEN directly interact with WDR5 to promote trimethylation of H3K4 and maintain a tumor-promoting signature.
Project description:PTEN is frequently mutated in human cancers and PTEN mutants promote tumor progression and metastasis. PTEN mutations have been implicated in immune regulation, however, the underlying mechanism is largely unknown. Here, we report that PTENα, the isoform of PTEN, remains active in cancer bearing stop-gained PTEN mutations. Through counteraction of CD8+ T cell-mediated cytotoxicity, PTENα leads to T cell dysfunction and accelerates immune-resistant cancer progression. Clinical analysis further uncovers that PTENα-active mutations suppress host immune responses and result in poor prognosis in cancer as relative to PTENα-inactive mutations. Furthermore, germline deletion of Ptenα in mice increases cell susceptibility to immune attack through augmenting stress granule formation and limiting synthesis of peroxidases, leading to massive oxidative cell death and severe inflammatory damage. We propose that PTENα protects tumor from T cell killing and thus PTENα is a potential target in antitumor immunotherapy.
Project description:In contrast to the ubiquitous expression profile of PTEN, PTENα is predominantly expressed in brain. To study the biological function of PTENα in brain, we employed LCMV to induce murine viral encephalitis model. Through single cell RNA sequencing, we revealed the immunological function of PTENα during viral infection in the brain.
Project description:PTENα is the first isoform of tumor suppressor PTEN. To investigate the molecular mechanism by which PTENα modulates cell response to inflammation, we performed pull-down assays with FLAG-tagged proteins coupled with mass spectrometry under condition of H2O2 treatment.
Project description:PTENα is the first isoform of tumor suppressor PTEN. To investigate the molecular mechanism by which PTENα modulates cell response to inflammation, we performed pull-down assays with FLAG-tagged proteins coupled with mass spectrometry under condition of H2O2 treatment in B16 cells.
Project description:PTEN is frequently mutated in a wide range of malignancies. Beyond suppressing tumorigenesis, PTEN is involved in multiple biological processes, and the complexity of PTEN function is partially attributed to PTEN family members including PTENα and PTENβ. Here, we report the identification of PTENε (also named as PTEN5), a novel N-terminal-extended PTEN isoform that suppresses tumor invasion and metastasis. We show that the translation of PTENε is initiated from the CUG816 codon within the 5’UTR region of PTEN mRNA. PTENε mainly localizes in the cell membrane, and physically associates with and dephosphorylates VASP and ACTR2, which govern filopodia formation and cell motility. We found that endogenous depletion of PTENε promotes filopodia formation and enhances the metastasis capacity of tumor cells. Overall, we identify a new isoform of PTEN with distinct localization and function compared to the known members of the PTEN family. These findings enrich the PTEN family constitution and advance our current understanding of the importance and diversity of PTEN functions.
Project description:Beyond a function in hemostasis and thrombosis, platelets can regulate innate and adaptive immune responses. Hyperactive platelets are frequently associated with multiple human autoimmune diseases, yet their pathogenic functions in these diseases have not been fully established. Emerging studies show an essential function of the phosphatase and tensin homolog (PTEN) in maintenance of immune homeostasis. Here, we show that mice with platelet-specific deletion of Pten, develop age-related lymphoproliferative diseases and humoral autoimmunity not seen in wildtype animals. Platelet-specific Pten-deficient mice have aberrant T cell activation, excessive T follicular helper (Tfh) cell responses and accumulation of platelet aggregates in lymph nodes. Transferred Pten-deficient platelets are able to infiltrate into the peripheral lymphoid tissues and form more aggregates. Moreover, Pten-deficient platelets are hyperactive and overproduce multiple Tfh-promoting cytokines via activation of the PDK1/mTORC2-AKT-SNAP23 pathway. Pten-deficient platelets show enhanced interaction with CD4+ T cells and promote conversion of CD4+ T cells into Tfh cells. Our results implicate PTEN in platelet-mediated immune homeostasis, and provide evidence that hyperactive platelets function as an important mediator in autoimmune diseases using mouse models.