PTEN coordinates G(1) arrest by down-regulating cyclin D1 via its protein phosphatase activity and up-regulating p27 via its lipid phosphatase activity in a breast cancer model.
PTEN frequently shows loss of heterozygosity in breast and prostate cancers, and mutations in this gene are responsible for Cowden disease, a rare Mendelian syndrome that includes breast cancer as part of its phenotype.
PTEN is an ubiquitously expressed tumor suppressor which plays a prominent role in the pathogenesis of many types of sporadic solid tumors, including breast cancer, as well as hematologic malignancies.
PTEN deletion increased PI(3,4)P<sub>2</sub> levels in a mouse model of prostate cancer, and it inversely correlated with PI(3,4)P<sub>2</sub> levels across several EGF-stimulated prostate and breast cancer lines.
A large-scale RNA interference screen to discover genes involved in trastuzumab resistance in breast cancer identified only PTEN as a modulator of drug sensitivity.
A new tumor suppressor gene PTEN/MMAC1 was recently isolated at chromosome 10q23 and found to be inactivated by point mutation or homozygous deletion in glioma, prostate and breast cancer.
A total of 360 paired breast carcinoma and adjacent normal tissue samples from 180 sporadic breast cancer patients were included in the present study and examined for PTEN promoter methylation status by methylation-specific polymerase chain reaction.
A total of 44 samples of invasive human breast cancer, 5 breast cancer cell lines and 16 samples of normal human breast tissue from young and elderly women were studied for methylation of the PTEN promoter by methylation-specific PCR and PTEN protein expression by immunohistochemistry.
Additionally, we summarized breast cancer risk associated with the following genetic factors: breast cancer susceptibility high-penetrance genes (BRCA1, BRCA2, p53, PTEN, ATM, NBS1 or LKB1) and low-penetrance genes such as cytochrome P450 genes (CYP1A1, CYP2D6, CYP19), glutathione S-transferase family (GSTM1, GSTP1), alcohol and one-carbon metabolism genes (ADH1C and MTHFR), DNA repair genes (XRCC1, XRCC3, ERCC4/XPF) and genes encoding cell signaling molecules (PR, ER, TNFalpha or HSP70).