Related Experiment Videos
Magnetic resonance detects changes in phosphocholine associated with Ras activation and inhibition in NIH 3T3 cells
S M Ronen1, L E Jackson, M Beloueche
1Cancer Research Campaign (CRC) Clinical Magnetic Resonance Research Group, Institute of Cancer Research, Royal Marsden Hospital, Downs Road,Sutton, Surrey, SM2 5PT, UK.
Abstract:
Ras is frequently mutated in cancer, and novel therapies are being developed to target Ras signalling. To identify non-invasive surrogate markers of Ras activation and inhibition, we used(31)P magnetic resonance spectroscopy (MRS) and investigated NIH 3T3 cells compared to a mutant ras transfected counterpart. The MR spectra indicated that phosphocholine (PC) levels increased significantly from 3 +/- 2 fmol cell(-1)in NIH 3T3 cells to 13 +/- 4 fmol cell(-1)in the transfected cells. The PC/NTP ratio increased significantly from 0.3 +/- 0.1 to 0.7 +/- 0.3. This could not be explained by either a faster proliferation rate or by alterations in cell cycle distribution. Both cell lines were treated with simvastatin, 17-AAG and R115777, agents which inhibit Ras signalling. Cell proliferation was inhibited in both cell lines. The spectrum of NIH 3T3 cells was not affected by treatment. In contrast, in the ras transfected cells growth inhibition was associated with an average 35 +/- 5% drop in PC levels and a comparable drop in PC/NTP. Thus the MRS visible increase in phosphocholine is associated with Ras activation, and response to treatment is associated with partial reversal of phosphocholine increase in ras transfected cells. MRS might therefore be a useful tool in detecting Ras activation and its inhibition following targeted therapies.
Insights
Magnetic resonance spectroscopy (MRS) can detect increased phosphocholine (PC) levels in cells with activated Ras signaling. This MRS-detectable PC increase reverses upon targeted therapy, suggesting MRS as a tool for monitoring Ras pathway inhibition.
Area of Science:
- Oncology
- Biochemistry
- Medical Imaging
Background:
- Ras signaling pathways are frequently altered in various cancers.
- Targeted therapies aim to inhibit Ras signaling, but non-invasive markers for monitoring treatment response are needed.
Purpose of the Study:
- To investigate phosphocholine (PC) as a non-invasive surrogate marker for Ras activation and inhibition using (31)P magnetic resonance spectroscopy (MRS).
Main Methods:
- Comparison of NIH 3T3 cells with Ras-mutant transfected counterparts using (31)P MRS.
- Analysis of phosphocholine (PC) and PC/NTP ratios.
- Treatment of cell lines with Ras signaling inhibitors (simvastatin, 17-AAG, R115777).
Main Results:
- Ras-transfected cells showed significantly increased PC levels and PC/NTP ratios compared to control NIH 3T3 cells.
- Treatment with Ras inhibitors reduced PC levels and PC/NTP ratios in Ras-transfected cells, but not in control cells.
- Changes in PC levels were independent of proliferation rate and cell cycle distribution.
Conclusions:
- Elevated phosphocholine (PC) levels detected by MRS are associated with Ras activation.
- MRS can potentially monitor the inhibition of Ras signaling pathways in response to targeted therapies.