Netrin-1 receptor loss in colon tissue is associated with what potential outcome?

• A. Improved tissue repair
• B. Tumor formation
• C. Decreased cell turnover only
• D. No cancer risk

Answer: (B)

The concept being tested is how netrin-1 receptors can act as dependence receptors in colon tissue. These receptors promote cell survival when bound by netrin-1, but in the absence of the ligand they can trigger apoptosis, helping to eliminate abnormal cells and prevent tumor development. When the netrin-1 receptor is lost, that apoptotic safeguard is removed, so cells with damage or oncogenic mutations are more likely to survive and accumulate, increasing the chance of tumor formation. This fits with evidence that the DCC receptor, a netrin-1 receptor, functions as a tumor suppressor in colorectal tissue.

So, losing the receptor is associated with tumor formation because it removes an important pro-apoptotic checkpoint that would otherwise help eliminate potentially cancerous cells. The idea of improved tissue repair or no cancer risk doesn’t align with the loss of this tumor-suppressing apoptotic pathway, and decreased cell turnover contradicts the tendency for damaged cells to escape death and proliferate.