Sudhagar Selvaraju

The development of acquired resistance to tamoxifen poses a significant clinical challenge in breast cancer treatment. Tumour heterogeneity has emerged as a primary reason for the clinical implications of resistance, yet we still lack actionable targets to address this issue. Repurposing existing drugs has become an emerging trend to tackle demanding medical indications. Therefore, we aim to study the efficacy of the antipsychotic drug Thioridazine against both parental and tamoxifen-resistant breast cancer cells. In this study, we have demonstrated that Thioridazine induces phospholipid accumulation, followed by necroptosis in both parental and tamoxifen-resistant breast cancer cell lines. We have shown thioridazine-mediated cytostatic effects through analyses of cell viability, cell count, caspase activation, cell cycle, and p21 expression levels. Moreover, employing a pharmacometabolomics approach, we identified that Thioridazine induces phospholipid accumulation in breast cancer cells. We established that Thioridazine promotes the accumulation of phospholipids rather than neutral lipids in cells via lipid-specific fluorescent quantification and imaging analysis. The phospholipid accumulation triggers necroptosis, which was evaluated through a propidium iodide uptake assay. Thioridazine activates RIP signalling, facilitating the subsequent translocation of pore-forming MLKL to the plasma membrane to initiate necroptosis. The formation of MLKL-induced membrane pores was confirmed using scanning electron microscopy for cell surface visualisation. Furthermore, thioridazine co-treatment enhances the efficacy of tamoxifen in resistant breast cancer cells, augmenting its potential for combinatorial treatment. Altogether, Thioridazine induces phospholipid accumulation followed by necroptosis in both parental and tamoxifen-resistant breast cancer cell lines, highlighting its potential application in breast cancer treatment.

This study includes a novel chemo-herbal combination using biochanin A (BCA) and lenvatinib (LTB) to synergize each other's anti-cancer activities. Phenylboronic acid (PBA)-functionalized poly (lactic-co-glycolic acid) (PLGA) was employed to specifically target the sialic acid overexpressed in lung cancer. ATR, DSC, and NMR studies confirmed the successful synthesis of PBA-PLGA, which was further utilized for the development of BCA and LTB co-loaded PBA-PLGA nanoparticles (PBA-PLGA-BCA-LTB NPs). A higher in silico docking score between LTB and different proteins of endothelial growth factor receptors (EGFRs) and a combination index value H of −5.69 ± 0.183 (kcal mol⁻¹), ΔG of −4.98 (kcal mol⁻¹), and −TΔS of 0.706 (kcal mol⁻¹) using isothermal titration calorimetry (ITC) explained the enthalpy-driven specificity of PBA-PLGA towards sialic acid (Neu5AC). The prepared NPs showed physical stability at 4 ± 2 °C and were non-hemolytic and stable with plasma proteins. Significantly higher cytotoxicity and cellular uptake were observed for PBA-PLGA-BCA-LTB NPs in contrast to PLGA-BCA-LTB NPs and coarse-BCA-LTB. The PBA-PLGA-BCA-LTB NPs also exhibited anti-migration and invasion potential for A549 cells. In vivo pharmacokinetic studies indicated an increase in plasma half-life of the drugs and a decrease in hematological toxicities using PBA-PLGA-BCA-LTB NPs compared to free BCA-LTB. In summary, the PBA-PLGA-BCA-LTB NPs represent a biocompatible, potential, cancer-targeted, and effective treatment option for lung cancer treatment.

Branched‐chain amino acids (BCAA) are essential requirements for overall protein turnover, signalling and energy balance, and dysregulation of their metabolic pathway has been associated with many pathophysiological events. Despite the importance of BCAA in human health, our understanding of their metabolic regulation is limited. Here, we present evidence that G protein‐coupled oestrogen receptor (GPER) activation inhibits the key BCAA metabolic regulatory enzyme branched‐chain α‐keto acid dehydrogenase complex (BCKDH) by phosphorylating S293. Inhibition of BCKDH results in leucine, isoleucine and valine accumulation in cells. Interestingly, GPER did not alter the levels of the kinase BCKDK and the phosphatase PPM1K, which regulate BCKDH activity, but activated MAPK signalling. Using gene silencing, we identified that JNK intercedes GPER‐mediated BCKDH inhibition. Together, our results demonstrate that GPER inhibits BCAA metabolism through JNK signalling.

Purpose Rapid proliferation and nutrition starvation in the tumor microenvironment pose significant challenges to cellular protein homeostasis. The accumulation of misfolded proteins in the endoplasmic reticulum lumen induces stress on cells and causes irreversible damage to cells if unresolved. Emerging reports emphasize the influence of the tumor microenvironment on therapeutic molecule efficacy and treatment outcomes. Hence, we aimed to understand the influence of tamoxifen on the cellular adaptation to endoplasmic reticulum stress during metabolic stress in breast cancer cells. Methods Nutrition deprivation induces endoplasmic reticulum stress (ER stress), and the unfolded protein response (UPR) in breast cancer cells was confirmed by a Thioflavin B assay and western blotting. Tamoxifen-indued ER-phagy was studied using an MCD assay, confocal microscopy, and western blotting. Results Nutrition deprivation induces ER stress in breast cancer cells. Interestingly, tamoxifen modulates the nutrition deprivation-induced endoplasmic reticulum stress through enhancing the selective ER-phagy, a specialized autophagy. The tamoxifen-induced ER-phagy is mediated by AMPK activation. The pharmacological inhibition of AMPK blocks tamoxifen-induced ER-phagy and tamoxifen modulatory effect on ER stress during nutrition deprivation. Conclusion Tamoxifen modulates ER stress by inducing ER-phagy through AMPK, thereby, may support breast cancer cell survival during nutrition deprivation conditions.

The interaction of cancer cells with their tumor microenvironment determines key events in the progression of the disease, therapeutic efficacy, and the development of drug resistance. Here, we presented evidence that tamoxifen support breast cancer growth during nutrition deprivation by modulating mitochondrial dynamics through AMPK and MAPK signaling. Tamoxifen enhances mitochondrial fusion under nutrition‐deprived conditions by suppressing Drp1 ser616 phosphorylation and upregulating Mfn1 levels. Tamoxifen‐induced mitochondrial fusion is mediated by the activation of AMPK as evident by the pharmacological inhibition of AMPK reverse mitochondrial fusion. Interestingly, JNK activation by tamoxifen controls the mitochondrial fusion morphology by downregulating Mfn2. Collectively, tamoxifen support cell growth by enhancing mitochondrial fusion by regulating stress kinase signaling under nutrition deprivation condition.

ZSCAN4 is a transcription factor that plays a pivotal role during early embryonic development. It is a unique gene expressed specifically during the first tide of de novo transcription during the zygotic genome activation. Moreover, it is reported to regulate telomere length in embryonic stem cells and induced pluripotent stem cells. Interestingly, ZSCAN4 is expressed in approximately 5% of the embryonic stem cells in culture at any given time, which points to the fact that it has a tight regulatory system. Furthermore, ZSCAN4, if included in the reprogramming cocktail along with core reprogramming factors, increases the reprogramming efficiency and results in better quality, genetically stable induced pluripotent stem cells. Also, it is reported to have a role in promoting cancer stem cell phenotype and can prospectively be used as a marker for the same. In this review, the multifaceted role of ZSCAN4 in embryonic development, embryonic stem cells, induced pluripotent stem cells, cancer, and germ cells are discussed comprehensively. Graphical Abstract

Induced pluripotent stem cells (iPSCs) have vast biomedical potential concerning disease modeling, drug screening and discovery, cell therapy, tissue engineering, and understanding organismal development. In the year 2006, a groundbreaking study reported the generation of iPSCs from mouse embryonic fibroblasts by viral transduction of four transcription factors, namely, Oct4, Sox2, Klf4, and c-Myc. Subsequently, human iPSCs were generated by reprogramming fibroblasts as a starting cell source using two reprogramming factor cocktails [(i) OCT4, SOX2, KLF4, and c-MYC, and (ii) OCT4, SOX2, NANOG, and LIN28]. The wide range of applications of these human iPSCs in research, therapeutics, and personalized medicine has driven the scientific community to optimize and understand this reprogramming process to achieve quality iPSCs with higher efficiency and faster kinetics. One of the essential criteria to address this is by identifying an ideal cell source in which pluripotency can be induced efficiently to give rise to high-quality iPSCs. Therefore, various cell types have been studied for their ability to generate iPSCs efficiently. Cell sources that can be easily reverted to a pluripotent state are tissue-restricted stem cells present in the fetus and adult tissues. Tissue-restricted stem cells can be isolated from fetal, cord blood, bone marrow, and other adult tissues or can be obtained by differentiation of embryonic stem cells or trans-differentiation of other tissue-restricted stem cells. Since these cells are undifferentiated cells with self-renewal potential, they are much easier to reprogram due to the inherent characteristic of having an endogenous expression of few pluripotency-inducing factors. This review presents an overview of promising tissue-restricted stem cells that can be isolated from different sources, namely, neural stem cells, hematopoietic stem cells, mesenchymal stem cells, limbal epithelial stem cells, and spermatogonial stem cells, and their reprogramming efficacy. This insight will pave the way for developing safe and efficient reprogramming strategies and generating patient-specific iPSCs from tissue-restricted stem cells derived from various fetal and adult tissues.