https://dspace.nii.res.in//https://dspace.nii.res.in/handle/123456789/84 Mon, 27 Apr 2026 15:40:43 GMT 2026-04-27T15:40:43Z https://dspace.nii.res.in//https://dspace.nii.res.in/handle/123456789/1539 Title: Ponatinib delays the growth of solid tumours by remodelling immunosuppressive tumour microenvironment through the inhibition of induced PD-L1 expression Authors: Barnwal, Anjali; Tamang, Rohini; Das, Sanjeev; Bhattacharyya, Jayanta Abstract: Background: Therapeutic modalities including chemo, radiation, immunotherapy, etc. induce PD-L1 expression that facilitates the adaptive immune resistance to evade the antitumour immune response. IFN-γ and hypoxia are some of the crucial inducers of PD-L1 expression in tumour and systemic microenvironment which regulate the expression of PD-L1 via various factors including HIF-1α and MAPK signalling. Hence, inhibition of these factors is crucial to regulate the induced PD-L1 expression and to achieve a durable therapeutic outcome by averting the immunosuppression. Methods: B16-F10 melanoma, 4T1 breast carcinoma, and GL261 glioblastoma murine models were established to investigate the in vivo antitumour efficacy of Ponatinib. Western blot, immunohistochemistry, and ELISA were performed to determine the effect of Ponatinib on the immunomodulation of tumour microenvironment (TME). CTL assay and flow cytometry were such as p-MAPK, p-JNK, p-Erk, and cleaved caspase-3 carried out to evaluate the systemic immunity induced by Ponatinib. RNA sequencing, immunofluorescence and Western blot analysis were used to determine the mechanism of PD-L1 regulation by Ponatinib. Antitumour immunity induced by Ponatinib were compared with Dasatinib. Results: Here, Ponatinib treatment delayed the growth of tumours by inhibiting PD-L1 and modulating TME. It also downregulated the level of PD-L1 downstream signalling molecules. Ponatinib enhanced the CD8 T cell infiltration, regulated Th1/Th2 ratio and depleted tumour associated macrophages (TAMs) in TME. It induced a favourable systemic antitumour immunity by enhancing CD8 T cell population, tumour specific CTL activity, balancing the Th1/Th2 ratio and lowering PD-L1 expression. Ponatinib inhibited FoxP3 expression in tumour and spleen. RNA sequencing data revealed that Ponatinib treatment downregulated the genes related to transcription including HIF-1α. Further mechanistic studies showed that it inhibited the IFN-γ and hypoxia induced PD-L1 expression via regulating HIF-1α. Dasatinib was used as control to prove that Ponatinib induced antitumour immunity is via PD-L1 inhibition mediated T cell activation. Conclusions: RNA sequencing data along with rigorous in vitro and in vivo studies revealed a novel molecular mechanism by which Ponatinib can inhibit the induced PD-L1 levels via regulating HIF-1α expression which leads to modulation of tumour microenvironment. Thus, our study provides a novel therapeutic insight of Ponatinib for the treatment of solid tumours where it can be used alone or in combination with other drugs which are known to induce PD-L1 expression and generate adaptive resistance. Sun, 01 Jan 2023 00:00:00 GMT https://dspace.nii.res.in//https://dspace.nii.res.in/handle/123456789/1539 2023-01-01T00:00:00Z https://dspace.nii.res.in//https://dspace.nii.res.in/handle/123456789/1524 Title: HDAC5 modulates SATB1 transcriptional activity to promote lung adenocarcinoma Authors: Sharma, Shalakha; Tyagi, Witty; Tamang, Rohini; Das, Sanjeev Abstract: Background: Dysregulation of histone deacetylases has been linked to diverse cancers. HDAC5 is a histone deacetylase belonging to Class IIa family of histone deacetylases. Limited substrate repertoire restricts the understanding of molecular mechanisms underlying its role in tumorigenesis. Methods: We employed a biochemical screen to identify SATB1 as HDAC5-interacting protein. Coimmunoprecipitation and deacetylation assay were performed to validate SATB1 as a HDAC5 substrate. Proliferation, migration assay and xenograft studies were performed to determine the effect of HDAC5-SATB1 interaction on tumorigenesis. Results: Here we report that HDAC5 binds to and deacetylates SATB1 at the conserved lysine 411 residue. Furthermore, dynamic regulation of acetylation at this site is determined by TIP60 acetyltransferase. We also established that HDAC5-mediated deacetylation is critical for SATB1-dependent downregulation of key tumor suppressor genes. Deacetylated SATB1 also represses SDHA-induced epigenetic remodeling and anti-proliferative transcriptional program. Thus, SATB1 spurs malignant phenotype in a HDAC5-dependent manner. Conclusions: Our study highlights the pivotal role of HDAC5 in tumorigenesis. Our findings provide Sun, 01 Jan 2023 00:00:00 GMT https://dspace.nii.res.in//https://dspace.nii.res.in/handle/123456789/1524 2023-01-01T00:00:00Z https://dspace.nii.res.in//https://dspace.nii.res.in/handle/123456789/1499 Title: Repurposing Ponatinib as a PD-L1 Inhibitor Revealed by Drug Repurposing Screening and Validation by In Vitro and In Vivo Experiments Authors: Das, Sanjeev; Barnwal, Anjali; Bhattacharyya, Jayanta Abstract: Cancer treatment by inhibiting the PD-1/PD-L1 pathway using monoclonal antibodies has made great advances as it showed long-lasting antitumor responses in a wide range of cancers. However, antibodies exhibit several disadvantages, which include low permeability, immune-related adverse effects, complex synthetic procedures, and high treatment costs. Hence, small-molecule inhibitors can be used as alternatives; however, no small molecule with in vivo activity has been reported. In addition, there are many challenges in developing a new drug, including the timeline and escalating cost. Therefore, repurposing an approved drug offers advantages over the development of an entirely new drug. Herein, we identify an FDA-approved small-molecule drug, Ponatinib, as a PD-L1 inhibitor via virtual drug screening of the ZINC database. Ponatinib showed stable binding with PD-L1, with the highest binding energy among all of the screened FDA-approved drugs. The binding of Ponatinib with PD-L1 was supported by a fluorescence quenching assay and immunofluorescence study. Further, we compared the in vivo antitumor efficacy of Ponatinib with a commercially available anti-PD-L1 antibody in the murine melanoma model. Ponatinib was found to be more efficient in delaying tumor growth than the anti-PD-L1 antibody. Furthermore, Ponatinib also reduced the expression of PD-L1 in tumors and increased the T-cell population. Interestingly, splenocytes isolated from Ponatinib-treated mice showed enhanced cytotoxic T-cell (CTL) activity against B16-F10 cells. However, Ponatinib itself did not have any direct toxic effect on cancer cells in vitro. These findings suggest that Ponatinib can be used as a potent small-molecule inhibitor of PD-L1 to overcome the disadvantages associated with antibodies. Sun, 01 Jan 2023 00:00:00 GMT https://dspace.nii.res.in//https://dspace.nii.res.in/handle/123456789/1499 2023-01-01T00:00:00Z https://dspace.nii.res.in//https://dspace.nii.res.in/handle/123456789/1414 Title: SIRT6 deacetylates PKM2 to suppress its nuclear localization and oncogenic functions Authors: Das, Sanjeev Abstract: SIRT6 (sirtuin 6) is a member of sirtuin family of deacetylases involved in diverse processes including genome stability, metabolic homeostasis, and tumorigenesis. However, the role of SIRT6 deacetylase activity in its tumor-suppressor functions is not well understood. Here we report that SIRT6 binds to and deacetylates nuclear PKM2 (pyruvate kinase M2) at the lysine 433 residue. PKM2 is a glycolytic enzyme with nonmetabolic nuclear oncogenic functions. SIRT6-mediated deacetylation results in PKM2 nuclear export. We further have identified exportin 4 as the specific transporter mediating PKM2 nuclear export. As a result of SIRT6-mediated deacetylation, PKM2 nuclear protein kinase and transcriptional coactivator functions are abolished. Thus, SIRT6 suppresses PKM2 oncogenic functions, resulting in reduced cell proliferation, migration potential, and invasiveness. Furthermore, studies in mouse tumor models demonstrate that PKM2 deacetylation is integral to SIRT6-mediated tumor suppression and inhibition of metastasis. Additionally, reduced SIRT6 levels correlate with elevated nuclear acetylated PKM2 levels in increasing grades of hepatocellular carcinoma. These findings provide key insights into the pivotal role of deacetylase activity in SIRT6 tumor-suppressor functions. Fri, 01 Jan 2016 00:00:00 GMT https://dspace.nii.res.in//https://dspace.nii.res.in/handle/123456789/1414 2016-01-01T00:00:00Z