The impact of hypoxia on differential expression of neurotensin receptors (NTR) in colorectal and prostate carcinoma cells

Background:

Recent studies showed increased expression of neurotensin receptors (NTR), particularly, NTR1 and NTR3, in various tumors, thus NTR is assumed a potential target for tumor imaging and therapy. However, the knowledge about the quantitative expression of NTR on mRNA and protein level, e.g., under hypoxic conditions is limited. The aim of this study was to develop a quantitative method for determination of absolute NTR mRNA amount in tumor and non-tumor cells and tissues. For method evaluation the NTR mRNA amounts in human colorectal (HT-29) and prostate (PC3) carcinoma cell lines under normoxic and hypoxic conditions in vitro were compared.

Material and methods:

A novel real-time RT-PCR method using an external standard was established. The elongation factor 1 alpha (EF1α) gene served as housekeeping gene and glucose transporter protein type 1 gene (GLUT1) was used as indicator for cellular hypoxic regulation effects. The derived standard curves allow for calculation of the number of specific mRNA molecules normalized to 1000 molecules of EF1α. Acute and chronic experimental hypoxia was induced by cultivation of cells at an oxygen concentration of 0.6% for 4 to 72 hours.

Results:

Both HT-29 cells and PC3 cells show high mRNA expression of NTR1 in normoxia. In acute hypoxia (

Conclusion:

A novel standardizable and reproducible quantitative method for measurement of NTR mRNA in cancer cells was established. The use of NTR1 as a target for imaging or therapy strongly depends on tumor cell type and tumor hypoxia. Ongoing investigations will compare quantitative mRNA expression with data on functional expression of NTR, e.g., protein synthesis and radioligand interaction, in human samples and rodent tumor (xenograft) models.