Unveiling Metabolic Signatures as Potential Biomarkers in Common Cancers: Insights from Lung, Breast, Colorectal, Liver, and Gastric Tumours.

Reprogramming is a hallmark of cancer, enabling tumour cells to sustain rapid proliferation, resist cell death, and adapt to hostile microenvironments. This review explores the expression profiles of key metabolic enzymes and transporters involved in glucose, amino acid, and lipid metabolism across the five most deadly cancers worldwide: lung, breast, colorectal, liver, and gastric cancers. Through a comparative analysis, we identify consistent upregulation of glycolytic enzymes such as LDHA, PKM2, and HK2, as well as nutrient transporters like GLUT1, ASCT2, and LAT1, which contribute to cancer progression, metastasis, and therapy resistance. The role of enzymes involved in glutaminolysis (e.g., GLS1, GDH), one-carbon metabolism (e.g., SHMT2, PHGDH), and fatty acid synthesis (e.g., FASN, ACLY) is also examined, with emphasis on their emerging relevance as diagnostic, prognostic, and predictive biomarkers. While several metabolic proteins show strong potential for clinical translation, only a few, such as tumour M2-pyruvate kinase (TuM2-PK) and serum LDH measurement, have progressed into clinical use or trials. This review addresses some of the challenges in biomarker development. Ultimately, our findings underscore the importance of metabolic proteins not only as functional drivers of malignancy but also as promising candidates for biomarker discovery. Advancing their clinical implementation could significantly enhance early detection, treatment stratification, and personalized oncology.