Arrange the steps in oncogenesis in the sequence: 1. increased activity of telomerase2. angiogenesis3. Evasion of host defense 4. Activation of proto-oncogene 5. Warburg effect
## Core Concept
Oncogenesis, the process of cancer development, involves a series of genetic and epigenetic alterations that lead to the transformation of normal cells into malignant cells. These steps include the activation of proto-oncogenes, evasion of host defense mechanisms, increased activity of telomerase, angiogenesis, and metabolic changes such as the Warburg effect.
## Why the Correct Answer is Right
The correct sequence of steps in oncogenesis starts with the **activation of proto-oncogenes (4)**, which are normal genes that can become oncogenic (cancer-causing) due to mutations or increased expression. This is often an early event. Next, **evasion of host defense (3)** occurs as cancer cells develop strategies to evade the immune system. The **increased activity of telomerase (1)** allows cancer cells to achieve immortality by maintaining their telomeres. As the tumor grows, **angiogenesis (2)** becomes crucial for providing the necessary blood supply. Finally, the **Warburg effect (5)**, a metabolic shift towards glycolysis even in the presence of oxygen, is a common feature of many cancer cells, supporting their rapid growth.
## Why Each Wrong Option is Incorrect
- **Option A:** This option suggests a sequence that does not logically fit the known steps of oncogenesis, particularly placing angiogenesis before evasion of host defenses and telomerase activation.
- **Option B:** This option incorrectly places the Warburg effect early in the sequence, before angiogenesis and telomerase activation, which does not align with the typical progression of oncogenic changes.
- **Option D:** This option incorrectly places increased telomerase activity before activation of proto-oncogenes, which contradicts the understanding that proto-oncogene activation is an early event.
## Clinical Pearl / High-Yield Fact
A key point to remember is that **telomerase activation** is a critical step that allows cancer cells to divide indefinitely, bypassing one of the hallmarks of cellular aging. This is a potential target for cancer therapy.
## Correct Answer Line
**Correct Answer: C.**