Carcinogenesis and Oncogenes

A 52-year-old man from Delhi presents with a 3-month history of progressive dysphagia and retrosternal chest pain. Upper endoscopy reveals a 4 cm ulcerated mass in the mid-esophagus with biopsy confirming squamous cell carcinoma. Molecular analysis shows amplification of the CCND1 gene (cyclin D1). Which of the following best explains the oncogenic mechanism in this patient?

The RAS gene is mutated in approximately what percentage of human cancers, making it the most frequently altered oncogene?

Which of the following oncogenes, when activated, primarily functions as a growth factor receptor tyrosine kinase?

Which of the following best describes the mechanism by which the BCR-ABL fusion protein (Philadelphia chromosome) drives chronic myeloid leukemia?

A 55-year-old man with newly diagnosed gastrointestinal stromal tumor (GIST) harboring a KIT mutation is referred for systemic therapy. What is the drug of choice for first-line treatment?