Patient's question:
Differences and characteristics between cancer cells and normal cellsDoctor's answer:
Cancer cells have three significant basic characteristics: immortality, metastasis, and loss of contact inhibition. Recommendations: Cancer cells differ from normal cells in the following physiological, biochemical, and morphological aspects:(1) Morphological characteristics of cancer cells
Cancer cells vary in size and shape, typically being larger than their source cells, with a significantly higher nuclear-to-cytoplasmic ratio than normal cells. The nuclei are irregular in shape and may exhibit giant nuclei, binucleation, or multinucleation. The chromosomes within the nucleus are aneuploid, with some chromosomes missing and others having increased numbers. In normal cells, abnormal changes in chromosomes trigger apoptosis, but in cancer cells, the signaling pathways related to apoptosis are impaired, meaning cancer cells exhibit immortality.
(2) Physiological characteristics of cancer cells
Loss of control over the cell cycle. Like microorganisms residing in the body, cancer cells are not regulated by normal growth control systems and can continue to divide and proliferate.
Migration ability. Mutations or deletions in components related to cell adhesion and connection, as well as blocked signaling pathways, cause cells to lose connections with each other and the extracellular matrix, making it easier for them to detach from the tumor. Many cancer cells have the ability to move and can produce enzymes that pierce the basal lamina and connective tissues, facilitating migration to other tissues.
Loss of contact inhibition. Normal cells in vitro exhibit anchorage-dependent growth, stopping proliferation after forming a monolayer, a phenomenon known as contact inhibition. However, cancer cells can still grow even when piled up in clusters.
Loss of anchorage dependence. Most normal eukaryotic cells, except mature blood cells, must adhere to a specific extracellular matrix to survive by inhibiting apoptosis, a condition called anchorage dependence. Cancer cells lose this dependence and can grow on substrates such as agar or methylcellulose.
Dedifferentiation. It is known that cancer cells express over 20 fetal homologous enzymes. Fetal alpha-fetoprotein is unique to fetuses but is expressed in liver cancer cells, making it a marker for early liver cancer diagnosis.
Reduced requirement for growth factors. Cancer cells cultured in vitro require significantly less growth factor than normal cells. Some cancer cells can also release angiogenic factors, promoting the growth of blood vessels toward the tumor, allowing cancer cells to obtain the nutrients needed for rapid proliferation.
High metabolism. The activity of DNA and RNA polymerases in tumor tissues is higher than in normal tissues, while the degradation of nucleic acids is significantly reduced, leading to higher levels of DNA and RNA. Protein synthesis and catabolism are both enhanced, but synthesis exceeds decomposition, even to the extent of stealing protein breakdown products from normal tissues, resulting in severe wasting syndrome in the body.
Mitochondrial dysfunction. Even under sufficient oxygen supply, energy is primarily obtained through glycolysis.
Transmissibility. Normal cells transplanted into a host body are often rejected due to immune responses and rarely survive. However, cancer cells are transmissible, such as human cancer cells being transplanted into rodents to form transplanted tumors.