Chapter 11: Cancer Biology

The core framework integrates the hallmarks of cancer, a conceptual model describing how malignant cells sustain proliferation through activated proto-oncogenes and dysregulated growth signaling, evade protective mechanisms by inactivating tumor suppressor genes like TP53 and RB, and accumulate genetic damage through defects in caretaker genes including BRCA1 and BRCA2. Cancer cells achieve unlimited replicative potential by upregulating telomerase to circumvent the Hayflick limit, reprogram metabolism toward aerobic glycolysis to support anabolic processes, and develop resistance to programmed cell death through multiple antiapoptotic mechanisms. The chapter explores how tumors manipulate their microenvironment by recruiting inflammatory cells and cancer-associated fibroblasts, induce blood vessel formation through angiogenic signals, and execute metastatic dissemination via epithelial-mesenchymal transition and invasion through tissue barriers. Clinical manifestations encompass constitutional symptoms such as cachexia and fatigue, local effects including pain and infection, and paraneoplastic phenomena arising from tumor-secreted substances or immune-mediated responses. Diagnostic approaches integrate histopathologic examination, molecular tumor markers, and staging systems that assess disease extent and guide prognosis. Treatment strategies have evolved from conventional modalities to precision approaches including tyrosine kinase inhibitors targeting specific oncogenic fusions, monoclonal antibodies blocking growth signaling pathways, and immunotherapeutic techniques that reactivate antitumor immunity through checkpoint inhibition and engineered T cell therapies, collectively enabling individualized therapeutic selection based on tumor biology.