eng Oriental Scientific Publishing Company Biomedical and Pharmacology Journal 0974-6242 2023-03-21 16 1 389 398 10.13005/bpj/2620 47885 article Nosheen Mahmood 1 Qamar Jamal 2 Reem Al- Kahtani 1 Shamim Mustaq 2 Humera Akhlaq 3 Saima Aamir 1 Department of Basic Medical Sciences King Saud bin Abdulaziz University for Health Sciences, Riyadh, 14611, Kingdom of Saudi Arabia. Department of Pathology, Ziauddin University, Karachi, 75600, Pakistan Department of Oral Pathology, Jinnah Sind Medical University, Karachi, 75510, Pakistan MicroRNA-21, an oncomiR, plays a pivotal role in carcinogenesis and is upregulated in many cancers including oral squamous cell carcinoma (OSCC). Use of smokeless tobacco (ST) products and cigarettes smoking in causation of OSCC is well established. This study sought to reconnoiter miR-21 expression in relation to smoking and chewing habits among subjects with oral cancer. Methods After gaining approval from IRB of Ziauddin University, analysis of miR-21 expression was conducted in 100 biopsy proven OSCC cases and 100 controls. All participants gave informed written consent after which venous blood sample was collected. qRT-PCR (Quantitative real-time Polymerase chain reaction) was performed to check miR-21 expression. SPSS Version 24 was used for analyzing the data. Results Consumption of ST was reported by 85 % and 63% were smoking cigarettes. miR-21 expression was significantly higher among smokers and those addicted to ST products, p<0.001. Subjects addicted to gutka chewing and those using more than one chewable product showed significant upregulation of miR-21, p<0.05.  Amount of ST product use and smoking cigarettes was found to be positively correlated with miR-21expression. Conclusion Our study provides the evidence that use of ST products and cigarette smoking trigger miR-21 which in turn potentiate carcinogenesis in OSCC. https://biomedpharmajournal.org/vol16no1/deciphering-the-link-between-chewing-habits-and-microrna-21-dysregulation-in-oral-squamous-cell-carcinoma-a-potential-cancerous-blend/ Head and neck cancer  MicroRNA-21 Oral Cancer  Smokeless tobacco