Chapters
4
Overview
After heart disease, cancer is the leading cause of death in North America. Broadly defined, it is a genetic disease, in which the normal controls governing cellular growth, differentiation, and behaviour are disordered. We can summarize the essential characteristics of cancer cells as follows (Figure 58):
Figure 58: Characteristics of cancer cells
Immortality refers to the fact that, unlike normal cells which replicate a finite number of times, cancer cells undergo mitosis indefinitely. Altered morphology refers to the fact that most cancer cells acquire different structural features and microscopic appearance. Finally, altered behaviour refers to loss of functions such as contact inhibition: when normal cells make contact with each other, they cease proliferating and growing, or enter cell cycle arrest (covered later in this unit). During malignant transformation, uncontrolled cell division occurs, resulting in solid tumour masses.
In this chapter, we will summarize the central paradigm of cell biology, that genes provide the blueprint for the building blocks of cellular activity. This will be followed by a description of the functional and structural differences between normal and cancerous cells, an exploration of the theories of cancer causation, and finally a summary of the systemic signs and symptoms of cancer.
Learning Outcomes
4.1: Articulate the basic structure of a gene, and how genes are translated and transcribed into proteins
4.2: Discuss the mechanisms regulating the cell cycle and cell differentiation
4.3: List the main features of benign and malignant neoplasia
4.4: Summarize some of the main mechanisms underlying carcinogenesis
4.5: Describe the tissue and systemic manifestations of cancer
Key Concepts
• Key features of cancer cells include immortality, altered morphology, and altered cell behaviour.
• Cell growth is regulated by growth factors which activate gene transcription and translation.
• Dysregulated cell growth is the result of genetic alterations in growth-inducing and growth-suppressing genes.
• Oncogenic stimuli include chemical, viral, and radiation-induced changes in DNA.
• Epigenetic modifications to DNA include methylation and histone modifications.
• Morphological changes in cancer cells include altered nuclear size and shape, altered and/or dedifferentiated cell shape, and high mitotic index.
• The most common sign of cancer is cachexia; the most common symptom is fatigue.
Learning Units
Unit 4.2 Dysregulated Cell Growth
Unit 4.3 Features of Cancer Cells and Tissues
Unit 4.4 Systemic Signs of Cancer and Cancer Biomarkers
Unit 4.1: Regulation of Cell Growth
The pathophysiology of cancer is fundamentally an alteration in cellular activity. As we begin this last chapter, it is helpful to briefly review how cellular growth and activity is regulated, starting with the central dogma of cell biology: that DNA (deoxyribonucleic acid) carries the genetic code or blueprint for proteins, which in turn