Laboratory
of
Sphingolipid Biology
Identifying and Establishing Sphingolipids and Gangliosides as Possible Diagnostic and Prognostic Biomarkers for Breast Cancer and Liver Disease Progression
In collaboration with clinicians, we use tumor tissues, biopsy, and plasma samples from patients undergoing treatment for breast cancer and liver diseases for LC-MS/MS based qualitative and quantitative analysis of various types and classes of lipids. We aim to develop and validate sphingolipid/ganglioside/phospholipid/glycerolipid-based diagnostic biomarkers for different subtypes of breast cancer and liver diseases that will be robust enough to overcome the heterogeneity of the disease, help in early detection, capable of better prognosis, and provide scope to be developed as therapeutic targets. Correlation of the lipid profile/s with clinicopathological data, disease recurrence, and disease-free survival status will allow us to determine the impact of temporal changes in the lipid signature/s with disease progression and patient response to treatments. The lipid signature/s will then be further validated in a larger patient cohort, and clinicopathological correlations will be established before they can be used for diagnosis or prognosis of the disease.
Elucidating the Role of Alternative Splicing of Sphingolipid Genes in Lipid Reprogramming during Breast Cancer Progression
Alternative splicing (AS) has emerged as a crucial post-transcriptional regulatory mechanism in many disease conditions including cancer. We identified AS events of sphingolipid and ganglioside genes in different breast cancer subtypes from The Cancer Genome Atlas (TCGA)-BRCA dataset. We successfully validated a Luminal B specific AS event in Ceramide Synthase 2 (CERS2) gene in breast cancer cell lines and tumor tissues in comparison to normal epithelial cells or adjoining normal tissue. We showed that AS of CERS2 reduces the functional protein and levels of very-long chain ceramides, and this imbalance contributes to increased cancer cell proliferation and migration (Pani et al. Cell Death Dis. 2021). We are currently validating and exploring the mechanism behind AS events in other genes of the sphingolipid/ganglioside pathway/s in representative cancer cell lines and clinical tissues. Differential isoform expression of these genes will be correlated to deregulation of corresponding sphingolipids and gangliosides as well as proliferation, migration, invasion, and drug response phenotypes of cancer cells. The empirical findings from this proposal will contribute to the knowledge of global regulation of post-transcriptional modifications in genes of sphingolipid/ganglioside pathway, and associate the altered sphingolipid/ganglioside metabolism to lipid reprogramming events in breast tumors.
Unravelling the Role of mTORC2 in Regulation of Sphingolipid and Ganglioside Metabolism in Cancer Progression
Current work from our laboratory revealed that mTORC2 regulates sphingolipid biosynthesis in breast cancer cells, and inhibition of RICTOR (one of the regulatory subunit of mTORC2 complex) alters the levels of sphingolipids and gangliosides (bioRxiv 2022.01.10.475595). We are now trying to validate the RICTOR-mediated transcriptional regulation of sphingolipid/ganglioside enzymes, and elucidate the role of epigenetic modulators like DNA methyltransferases, histone methyltransferases, and histone deacetylases responsible for these deregulations. Our aim is to establish gene-signaling-metabolite networks that coordinate key hallmark phenotypes of cancer progression.
Deciphering the Role of Sphingolipids and Gangliosides on Chemotherapy-mediated Unfolded Protein Response
Chemotherapy is a prime mode of treatment for cancer patients, and chemotherapeutic drugs cause numerous alterations in cellular signaling machinery like changes in sphingolipid and ganglioside metabolism, activation of unfolded protein response (UPR), generation of reactive oxygen species, and immunogenic cell death. In our earlier studies, we have shown that combination of doxorubicin with anti-angiogenic combretstatin-A4 and anti-inflammatory dexamethasone is highly effective in combating tumor progression by altering the sphingolipid metabolism through alternative splicing (Pal et al. ACS Central Sci., 2019). We also showed that combination of doxorubicin and the triterpenoid celastrol elevates expression of ceramide synthases with concurrent increase in the level of ceramides, thereby causing a synergistic apoptotic effect in a murine colon tumor model (Medatwal et al. Nanoscale 2020).
Independent studies have shown that deregulations in sphingolipids and gangliosides can activate the UPR during ER stress conditions, and this activation depends on nature of the lipid and cell type. UPR is also known to regulate the life-versus-death decision for cancer cells. Therefore, we are investigating the effect of chemotherapy-mediated alterations in sphingolipids/gangliosides on UPR. As chemotherapeutic drugs cause collateral damage by inducing apoptotic and immunogenic cell death, we aim to find the crucial mechanistic links between chemotherapy-mediated UPR and chemotherapy-mediated alterations in sphingolipid/ganglioside metabolism and identify key therapeutic targets that can be exploited further in combination with chemotherapeutic regimens.