The Role of Tumor Suppressor Genes PTEN and VHL on the Expression of HIF-1α under Hypocix Condition

The Role of Tumor Suppressor Genes PTEN and VHL on the Expression of HIF-1α under Hypocix Condition

The objective of this study was to determine the effect of hypoxic conditions on the expression of HIF- lu in LNCaP and LNCaP-MST cell lines containing tumor suppressor genes, such as P TEN and VHL. The degradation of HIF-lu is oxygen dependent and is facilitated by von hippel-lindau (VHL) protein. Under normoxic conditions, V HL gene recognizes HIF-lu and promotes its ubiquitination and lysosomal degradation. Under hypoxic conditions, the V HL is unable to bind to HIF-lu and therefore, the degradation is minimal. The phosphoinositide 3-kinase (P 13K) - Akt pathway regulates HIF I activity. Under normoxic conditions, PTEN decreases the effects of the P13K pathway. Therefore, loss of PTEN increases the expression of HIF- lu and consequently tumor angiogenesis. LNCaP and LNCaP- MST cells were grown in RPMI medium at 370C. After treatment, the total RNA was extracted and quantification was performed to determine the total yield. In order to compare, RT-PCR was carried out using Promega's Access Quick RT-PCR kit. Amplified cDNA was separated in a 1% agarose gel and then the band intensities were determined by densitometry scanning. Treatment of cells with hypoxia was found to increase the expression of HIF- lu in LNCaP and LNCaP-MST cells. The increase appears to be as a result of the stabilization of HIF-la. Under the hypoxic conditions, both PTEN and V HL levels were also increased which did not seem to affect the levels of HIF-lu. Under hypoxic condition, the expression of HIF-la increased although, both V HL and PTEN levels were elevated in our experimental conditions. This may be because under hypoxic conditions, V HL may not be able to recognize HIF-la and cause degradation. The reason for P TEN elevation under hypoxic condition is yet to be determined.