Relevance: Increased incidence of lung cancer globally and in Kazakhstan, lack of screening in hereditary cases, high mortality, and low survival of patients necessitate the study of the molecular genetic causes of the disease. At present, gene mutation studies for lung cancer diagnostics are expanding. However, many gene mutations revealed remain undercovered in the scientific literature, and there is not enough data on their prognostic and diagnostic value. The purpose of the study was to

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... over the specifics of the р53 gene mutations and reveal the EGFR exon 19 deletions and exon 21 L858R mutations in malignant tumors of the lung of various histogenesis. Methods: The mutations were studied in tumors (200 samples) and adjacent tissue (200 samples) of patients with lung cancer (squamous cell carcinoma (SCC) and adenocarcinoma (ADC) of the lung) by polymerase chain reaction (PCR), electrophoresis, and EcoR1- and Pst1-restriction of samples after p53 gene fragments and cDNA amplification and mRNA revertase treatment. Another 263 lung cancer samples were evaluated by real-time PCR for EGFR exon 19 deletions and EGFR exon 21 L858R mutations. Results: The p53 gene was not expressed in 50% of SCC and adenocarcinoma of the lung samples. Restriction revealed p53 mRNA mutations in 100% of SCC and 75% of ADC samples. p53 exon-intron 5-6 was mutated in 50% of ADC and 70% of SCC samples, exon-intron 7-9 – in 60% of SCC cases. EGFR exons 19 and 21 mutations found in 65 of 263 lung tumor samples were associated with increased sensitivity to EGFR tyrosine kinase inhibitors. Conclusion: The p53 gene mutations revealed in most samples of SCC and ADC of the lung could be used to diagnose lung cancer and predict its severity. The identified EGFR mutations allow predicting the effectiveness of targeted therapy