Publications - 2024
Is ChatGPT ‘ready’ to be a learning tool for medical undergraduates and will it perform equally in different subjects? Comparative study of ChatGPT performance in tutorial and case-based learning questions in physiology and biochemistry |
| W. A. Nathasha V. Luke, Lee Seow Chong, Kenneth H. Ban, Amanda H. Wong, Chen Zhi Xiong, Lee Shuh Shing, Reshma Taneja, Dujeepa D. Samarasekera and Celestial T. Yap |
| Medical Teacher, 1–7. |
| Abstract |
| Generative AI will become an integral part of education in future. The potential of this technology in different disciplines should be identified to promote effective adoption. This study evaluated the performance of ChatGPT in tutorial and case-based learning questions in physiology and biochemistry for medical undergraduates. Our study mainly focused on the performance of GPT-3.5 version while a subgroup was comparatively assessed on GPT-3.5 and GPT-4 performances. |
BRD4 isoforms have distinct roles in tumour progression and metastasis in rhabdomyosarcoma |
| Dipanwita Das, Jia Yu Leung, Shivaranjani Balamurugan, Vinay Tergaonkar, Amos Hong Pheng Loh, Cheng-Ming Chiang and Reshma Taneja |
| Abstract |
| BRD4, a bromodomain and extraterminal (BET) protein, is deregulated in multiple cancers and has emerged as a promising drug target. However, the function of the two main BRD4 isoforms (BRD4-L and BRD4-S) has not been analysed in parallel in most cancers. This complicates determining therapeutic efficacy of pan-BET inhibitors. In this study, using functional and transcriptomic analysis, we show that BRD-L and BRD4-S isoforms play distinct roles in fusion negative embryonal rhabdomyosarcoma. BRD4-L has an oncogenic role and inhibits myogenic differentiation, at least in part, by activating myostatin expression. Depletion of BRD4-L in vivo impairs tumour progression but does not impact metastasis. On the other hand, depletion of BRD4-S has no significant impact on tumour growth, but strikingly promotes metastasis in vivo. Interestingly, BRD4-S loss results in the enrichment of BRD4-L and RNA Polymerase II at integrin gene promoters resulting in their activation. In fusion positive alveolar rhabdomyosarcoma, BRD4-L is unrestricted in its oncogenic role, with no evident involvement of BRD4-S. Our work unveils isoform-specific functions of BRD4 in rhabdomyosarcoma. |
PHF2 regulates genome topology and DNA replication in neural stem cells via cohesin |
| Derrick Sek Tong Ong |
| Nucleic Acids Res. 2024 Jul 8;52(12):7063-7080. doi: 10.1093/nar/gkae457. |
| Abstract |
| Cohesin plays a crucial role in the organization of topologically-associated domains (TADs), which influence gene expression and DNA replication timing. Whether epigenetic regulators may affect TADs via cohesin to mediate DNA replication remains elusive. Here, we discover that the histone demethylase PHF2 associates with RAD21, a core subunit of cohesin, to regulate DNA replication in mouse neural stem cells (NSC). PHF2 loss impairs DNA replication due to the activation of dormant replication origins in NSC. Notably, the PHF2/RAD21 co-bound genomic regions are characterized by CTCF enrichment and epigenomic features that resemble efficient, active replication origins, and can act as boundaries to separate adjacent domains. Accordingly, PHF2 loss weakens TADs and chromatin loops at the co-bound loci due to reduced RAD21 occupancy. The observed topological and DNA replication defects in PHF2 KO NSC support a cohesin-dependent mechanism. Furthermore, we demonstrate that the PHF2/RAD21 complex exerts little effect on gene regulation, and that PHF2's histone-demethylase activity is dispensable for normal DNA replication and proliferation of NSC. We propose that PHF2 may serve as a topological accessory to cohesin for cohesin localization to TADs and chromatin loops, where cohesin represses dormant replication origins directly or indirectly, to sustain DNA replication in NSC. |
A novel MTORC2-AKT-ROS axis triggers mitofission and mitophagy-associated execution of colorectal cancer cells upon drug-induced activation of mutant KRAS |
| Shazib Pervaiz |
| Autophagy. 2024 Jun;20(6):1418-1441. doi: 10.1080/15548627.2024.2307224. |
| Abstract |
| RAS is one of the most commonly mutated oncogenes associated with multiple cancer hallmarks. Notably, RAS activation induces intracellular reactive oxygen species (ROS) generation, which we previously demonstrated as a trigger for autophagy-associated execution of mutant KRAS-expressing cancer cells. Here we report that drug (merodantoin; C1)-induced activation of mutant KRAS promotes phospho-AKT S473-dependent ROS-mediated S616 phosphorylation and mitochondrial localization of DNM1L/DRP1 (dynamin 1 like) and cleavage of the fusion-associated protein OPA1 (OPA1 mitochondrial dynamin like GTPase). Interestingly, accumulation of the outer mitochondrial membrane protein VDAC1 (voltage dependent anion channel 1) is observed in mutant KRAS-expressing cells upon exposure to C1. Conversely, silencing VDAC1 abolishes C1-induced mitophagy, and gene knockdown of either KRAS, AKT or DNM1L rescues ROS-dependent VDAC1 accumulation and stability, thus suggesting an axis of mutant active KRAS-phospho-AKT S473-ROS-DNM1L-VDAC1 in mitochondrial morphology change and cancer cell execution. Importantly, we identified MTOR (mechanistic target of rapamycin kinsase) complex 2 (MTORC2) as the upstream mediator of AKT phosphorylation at S473 in our model. Pharmacological or genetic inhibition of MTORC2 abrogated C1-induced phosphorylation of AKT S473, ROS generation and mitophagy induction, as well as rescued tumor colony forming ability and migratory capacity. Finally, increase in thermal stability of KRAS, AKT and DNM1L were observed upon exposure to C1 only in mutant KRAS-expressing cells. Taken together, our work has unraveled a novel mechanism of selective targeting of mutant KRAS-expressing cancers via MTORC2-mediated AKT activation and ROS-dependent mitofission, which could have potential therapeutic implications given the relative lack of direct RAS-targeting strategies in cancer. |
Secretome from Magnetically Stimulated Muscle Exhibits Anticancer Potency: Novel Preconditioning Methodology Highlighting HTRA1 Action |
| Alfredo Franco-Obregón |
| Bioengineering 2024, 11(7), 637; |
| Abstract |
| Briefly (10 min) exposing C2C12 myotubes to low amplitude (1.5 mT) pulsed electromagnetic fields (PEMFs) generated a conditioned media (pCM) that was capable of mitigating breast cancer cell growth, migration, and invasiveness in vitro, whereas the conditioned media harvested from unexposed myotubes, representing constitutively released secretome (cCM), was less effective. Administering pCM to breast cancer microtumors engrafted onto the chorioallantoic membrane of chicken eggs reduced tumor volume and vascularity. Blood serum collected from PEMF-exposed or exercised mice allayed breast cancer cell growth, migration, and invasiveness. A secretome preconditioning methodology is presented that accentuates the graded anticancer potencies of both the cCM and pCM harvested from myotubes, demonstrating an adaptive response to pCM administered during early myogenesis that emulated secretome-based exercise adaptations observed in vivo. HTRA1 was shown to be upregulated in pCM and was demonstrated to be necessary and sufficient for the anticancer potency of the pCM; recombinant HTRA1 added to basal media recapitulated the anticancer effects of pCM and antibody-based absorption of HTRA1 from pCM precluded its anticancer effects. Brief and non-invasive PEMF stimulation may represent a method to commandeer the secretome response of muscle, both in vitro and in vivo, for clinical exploitation in breast and other cancers. |
Synergistic Cellular Responses Conferred by Concurrent Optical and Magnetic Stimulation Are Attenuated by Simultaneous Exposure to Streptomycin: An Antibiotic Dilemma |
| Alfredo Franco-Obregón |
| Bioengineering 2024, 11(7), 637; |
| Abstract |
| Concurrent optical and magnetic stimulation (COMS) combines extremely low-frequency electromagnetic and light exposure for enhanced wound healing. We investigated the potential mechanistic synergism between the magnetic and light components of COMS by comparing their individual and combined cellular responses. Lone magnetic field exposure produced greater enhancements in cell proliferation than light alone, yet the combined effects of magnetic fields and light were supra-additive of the individual responses. Reactive oxygen species were incrementally reduced by exposure to light, magnetics fields, and their combination, wherein statistical significance was only achieved by the combined COMS modality. By contrast, ATP production was most greatly enhanced by magnetic exposure in combination with light, indicating that mitochondrial respiratory efficiency was improved by the combination of magnetic fields plus light. Protein expression pertaining to cell proliferation was preferentially enhanced by the COMS modality, as were the protein levels of the TRPC1 cation channel that had been previously implicated as part of a calcium–mitochondrial signaling axis invoked by electromagnetic exposure and necessary for proliferation. These results indicate that light facilitates functional synergism with magnetic fields that ultimately impinge on mitochondria-dependent developmental responses. Aminoglycoside antibiotics (AGAs) have been previously shown to inhibit TRPC1-mediated magnetotransduction, whereas their influence over photomodulation has not been explored. Streptomycin applied during exposure to light, magnetic fields, or COMS reduced their respective proliferation enhancements, whereas streptomycin added after the exposure did not. Magnetic field exposure and the COMS modality were capable of partially overcoming the antagonism of proliferation produced by streptomycin treatment, whereas light alone was not. The antagonism of photon-electromagnetic effects by streptomycin implicates TRPC1-mediated calcium entry in both magnetotransduction and photomodulation. Avoiding the prophylactic use of AGAs during COMS therapy will be crucial for maintaining clinical efficacy and is a common concern in most other electromagnetic regenerative paradigms. |
Telomere shortening induces aging-associated phenotypes in hiPSC-derived neurons and astrocytes |
| Derrick Sek Tong Ong |
| Biogerontology. 2024 Apr;25(2):341-360. doi: 10.1007/s10522-023-10076-5. Epub 2023 Nov 21. |
| Abstract |
| Telomere shortening is a well-established hallmark of cellular aging. Telomerase reverse transcriptase (TERT) plays a crucial role in maintaining the length of telomeres, which are specialised protective caps at the end of chromosomes. The lack of in vitro aging models, particularly for the central nervous system (CNS), has impeded progress in understanding aging and age-associated neurodegenerative diseases. In this study, we aimed to explore the possibility of inducing aging-associated features in cell types of the CNS using hiPSC (human induced pluripotent stem cell) technology. To achieve this, we utilised CRISPR/Cas9 to generate hiPSCs with a loss of telomerase function and shortened telomeres. Through directed differentiation, we generated motor neurons and astrocytes to investigate whether telomere shortening could lead to age-associated phenotypes. Our findings revealed that shortened telomeres induced age-associated characteristics in both motor neurons and astrocytes including increased cellular senescence, heightened inflammation, and elevated DNA damage. We also observed cell-type specific age-related morphology changes. Additionally, our study highlighted the fundamental role of TERT and telomere shortening in neural progenitor cell (NPC) proliferation and neuronal differentiation. This study serves as a proof of concept that telomere shortening can effectively induce aging-associated phenotypes, thereby providing a valuable tool to investigate age-related decline and neurodegenerative diseases. |
Are Aminoglycoside Antibiotics TRPing Your Metabolic Switches? |
| Alfredo Franco-Obregón |
| Cells 2024, 13(15), 1273; |
| Abstract |
| Transient receptor potential (TRP) channels are broadly implicated in the developmental programs of most tissues. Amongst these tissues, skeletal muscle and adipose are noteworthy for being essential in establishing systemic metabolic balance. TRP channels respond to environmental stimuli by supplying intracellular calcium that instigates enzymatic cascades of developmental consequence and often impinge on mitochondrial function and biogenesis. Critically, aminoglycoside antibiotics (AGAs) have been shown to block the capacity of TRP channels to conduct calcium entry into the cell in response to a wide range of developmental stimuli of a biophysical nature, including mechanical, electromagnetic, thermal, and chemical. Paradoxically, in vitro paradigms commonly used to understand organismal muscle and adipose development may have been led astray by the conventional use of streptomycin, an AGA, to help prevent bacterial contamination. Accordingly, streptomycin has been shown to disrupt both in vitro and in vivo myogenesis, as well as the phenotypic switch of white adipose into beige thermogenic status. In vivo, streptomycin has been shown to disrupt TRP-mediated calcium-dependent exercise adaptations of importance to systemic metabolism. Alternatively, streptomycin has also been used to curb detrimental levels of calcium leakage into dystrophic skeletal muscle through aberrantly gated TRPC1 channels that have been shown to be involved in the etiology of X-linked muscular dystrophies. TRP channels susceptible to AGA antagonism are critically involved in modulating the development of muscle and adipose tissues that, if administered to behaving animals, may translate to systemwide metabolic disruption. Regenerative medicine and clinical communities need to be made aware of this caveat of AGA usage and seek viable alternatives, to prevent contamination or infection in in vitro and in vivo paradigms, respectively. |