**Core Concept:** Tumor suppressor genes are a class of genes that normally prevent cells from dividing uncontrollably and form tumors. They act by detecting abnormal cell growth and inducing cell cycle arrest or apoptosis to maintain tissue homeostasis.

**Why the Correct Answer is Right:** PTEN (phosphatase and tensin homolog) is a well-known tumor suppressor gene. It is a phosphatase enzyme that has both lipid and protein phosphatase activities. Its primary function is to regulate cell growth, differentiation, and apoptosis by modulating the PI3K/AKT/mTOR signaling pathway.

**Why Each Wrong Option is Incorrect:**

A. This option is incorrect because it does not represent a known tumor suppressor gene.
B. Similarly, this option does not represent a well-known tumor suppressor gene.
C. PTEN is not the only tumor suppressor gene; other examples include p53 (tumor protein 53) and BRCA1/2 (breast cancer type 1/2). However, PTEN is a more specific example of a tumor suppressor gene.
D. This option is incorrect because it does not represent a known tumor suppressor gene.

**Clinical Pearl / High-Yield Fact:** The loss of PTEN function or activity is associated with various cancers, including glioblastoma, endometrial cancer, and certain types of leukemia. Understanding tumor suppressor genes like PTEN is essential for grasping the molecular basis of cancer development and progression.