Cancer biology research

DNA Methylation and Gene Silencing👇

✅DNA methylation is a key epigenetic mechanism that regulates gene expression without altering the DNA sequence. This process involves the addition of a methyl group (CH₃) to the cytosine base, converting it into 5-methylcytosine. The reaction is catalyzed by DNA methyltransferases (DNMTs), which specifically target cytosine residues in CpG dinucleotides.

✅CpG islands are regions rich in cytosine and guanine nucleotides, often located in gene promoter regions. When these CpG islands are unmethylated, the chromatin remains open and accessible to transcription factors, allowing gene expression to occur. In this state, genes are considered transcriptionally active (ON).

✅In contrast, when CpG islands become methylated, multiple methyl groups accumulate along the DNA. This leads to chromatin condensation and the recruitment of repressive protein complexes. As a result, transcription is inhibited, and the gene is effectively silenced (OFF).

✅DNA methylation plays a crucial role in normal cellular processes such as development, genomic imprinting, and X-chromosome inactivation. However, abnormal methylation patterns are frequently observed in diseases such as cancer, where tumor suppressor genes can be silenced through hypermethylation.
💡Savic, B.; Savic, B.; Stanojlovic, S. Epigenetic DNA Methylation Under the Influence of Low-Dose Ionizing Radiation, and Supplementation with Vitamin B12 and Folic Acid: Harmful or Beneficial for Professionals? Epigenomes 2025, 9, 17. https://doi.org/10.3390/epigenomes9020017

Metabolic Reprogramming in Cancer Cells👇

✅Cellular metabolism is tightly regulated by signaling pathways that control how nutrients such as glucose, glutamine, and fatty acids are utilized. In cancer cells, these pathways are frequently reprogrammed to support rapid growth and proliferation. Oncogenic signaling molecules including PI3K/AKT, MYC, RAS, YAP/TAZ, and HIF-1 enhance the uptake of nutrients and stimulate the expression of metabolic enzymes, thereby promoting anabolic processes.

✅Glucose metabolism is strongly upregulated in cancer cells through increased glycolysis and activation of the pentose phosphate pathway (PPP). Key enzymes such as HK2, PFK, G6PD, and PGD are stimulated to enhance energy production and generate biosynthetic precursors. The PPP also produces NADPH, which is essential for redox balance and lipid synthesis. In parallel, glycolytic intermediates are diverted into pathways like serine and nucleotide synthesis.

✅Within the mitochondria, metabolic intermediates derived from glucose and glutamine fuel the tricarboxylic acid (TCA) cycle. Glutamine metabolism plays a critical role by supplying carbon and nitrogen for biosynthesis. Enzymes such as GLS1/2 and GLUD convert glutamine into intermediates that sustain the TCA cycle and support the production of amino acids like aspartate. Oxidative phosphorylation (OXPHOS) further contributes to ATP generation.

✅Fatty acid metabolism is also enhanced in cancer cells. Citrate exported from the mitochondria is converted into acetyl-CoA by ACLY, which is then used for fatty acid synthesis via enzymes such as ACC and FASN. These lipids are essential for membrane production and energy storage. Regulatory proteins like SREBP coordinate the expression of lipogenic genes, while transporters and binding proteins such as FABP3 facilitate lipid handling.

✅Tumor suppressor pathways act as metabolic checkpoints. Proteins such as p53, AMPK, SIRT4, GSK3, and miR-23 inhibit key metabolic processes, limiting cell growth under stress conditions. For example, AMPK suppresses anabolic pathways during energy stress, while p53 downregulates glycolysis and promotes metabolic balance.

✅Finally, several therapeutic agents target cancer metabolism by inhibiting critical steps in these pathways. Drugs such as 2-deoxyglucose (2-DG) inhibit glycolysis, while others like CB-839 and BPTES target glutaminolysis. Inhibitors of fatty acid synthesis and mitochondrial metabolism are also being explored, highlighting metabolism as a promising target in cancer therapy.
💡 Park, J.H.; Pyun, W.Y.; Park, H.W. Cancer Metabolism: Phenotype, Signaling and Therapeutic Targets. Cells 2020, 9, 2308. https://doi.org/10.3390/cells9102308

Mechanisms of Autophagy: An Overview👇

✅Macroautophagy is the most well-characterized form of autophagy and involves the formation of a double-membrane structure called the autophagosome. This process begins with the initiation step, regulated by the ULK1 complex, which is tightly controlled by nutrient-sensing pathways involving mTORC1 and AMPK. Under stress or nutrient deprivation, this regulation shifts to activate autophagy.

✅During nucleation and elongation, key autophagy-related proteins such as ATG5, ATG12, and ATG16 contribute to the expansion of the autophagosomal membrane. LC3 is incorporated into the membrane and plays a critical role in cargo recognition and autophagosome maturation. The fully formed autophagosome then fuses with the lysosome, a step mediated by SNARE proteins, leading to degradation of the enclosed cellular material.

✅Microautophagy, in contrast, is a simpler and more direct process. Instead of forming a separate vesicle, the lysosomal membrane itself invaginates to engulf cytoplasmic material. This allows for continuous and non-selective degradation of cellular components, contributing to cellular homeostasis.

✅Chaperone-mediated autophagy (CMA) is a highly selective process that targets specific proteins containing a recognition motif. These proteins are identified by the chaperone HSC70 and delivered to the lysosomal membrane. There, they bind to the receptor LAMP2A, unfold, and are translocated directly into the lysosome for degradation.

✅Together, these three pathways—macroautophagy, microautophagy, and CMA—coordinate the controlled breakdown and recycling of cellular material, ensuring proper cellular function and adaptation to stress.
💡 Yang, H.; Li, X.; Wang, K.; Zou, Y.; Shi, Q.; Yang, Y.; Zhao, Q.; Zou, W. Autophagy: From Molecular Mechanisms to Disease Regulation and Therapeutic Strategies. Curr. Issues Mol. Biol. 2026, 48, 285. https://doi.org/10.3390/cimb48030285

Insulin Signaling Mechanism👇

✅This diagram illustrates the mechanism of insulin action, a key process that regulates glucose uptake and metabolism in target cells such as muscle and adipose tissue.

✅Insulin Receptor Activation
Insulin binds to its specific insulin receptor on the cell surface, triggering receptor autophosphorylation. This leads to the activation of intracellular adaptor proteins, mainly insulin receptor substrate (IRS) and Shc, initiating downstream signaling pathways.

✅Intracellular Signaling Cascade
Activated IRS recruits and stimulates key signaling molecules, including PI3K, AKT (Protein Kinase B), PDK1, and p85. These molecules form a signaling cascade that regulates multiple cellular processes such as protein synthesis, cell growth, and glycogen production.

✅GLUT4 Translocation
One of the most important outcomes of insulin signaling is the translocation of GLUT4 vesicles to the plasma membrane. Through exocytosis, GLUT4 transporters are inserted into the membrane, increasing the cell’s capacity to import glucose.

✅Glucose Uptake and Utilization
Once GLUT4 is present on the membrane, glucose enters the cell via facilitated diffusion. The glucose is then used for energy production (metabolism) or stored as glycogen or fat, depending on the body’s needs.

✅Physiological Significance
This tightly regulated mechanism ensures efficient glucose homeostasis. Impairment in insulin signaling or GLUT4 translocation can lead to insulin resistance and metabolic disorders such as type 2 diabetes.
💡 Mahgoub, M.O.; Ali, I.I.; Adeghate, J.O.; Tekes, K.; Kalász, H.; Adeghate, E.A. An Update on the Molecular and Cellular Basis of Pharmacotherapy in Type 2 Diabetes Mellitus. Int. J. Mol. Sci. 2023, 24, 9328. https://doi.org/10.3390/ijms24119328