Manganese-enhanced MRI (MEMRI) in breast and prostate cancers: Preliminary results exploring the potential role of calcium receptors

Abstract

Procedures: To preliminary assess the relationship between Manganese Enhanced Magnetic Resonance Imaging (MEMRI) and the expression of calcium receptors in human prostate and breast cancer animal models.

Methods: NOD/SCID mice were inoculated with MDA-MB-231 breast cancer cells and prostate PC3 cancer cells to develop orthotopic or pseudometastatic cancer animal models. Mice were studied on a clinical 3T scanner by using a prototype birdcage coil before and after intravenous injection of MnCl2. Assessment of receptor's status was carried out after the MR images acquisition by immunohistochemistry on excised tumours.

Results: Manganese contrast enhancement in breast or prostate cancer animal models well correlated with CaSR expression (p<0.01), whereas TRPV6 expression levels appeared not relevant to the Mn uptake.

Conclusion: Our preliminary results suggest that MEMRI appears an efficient tool to characterize human breast and prostate cancer animal models in the presence of different expression level of calcium receptors.

Fig 1. Manganese Enhanced MR Imaging (MEMRI) of orthotopic human breast cancer xenografts and CaSR/TRPV6 receptors levels.

AB. Tumour diameter 5 mm. Upon comparing T1-weighted gradient echo images (T1 WI) recorded before and 90 minutes after Mn²⁺ administration, the tumour showed manganese uptake (red circles). CD. Immunohistochemistry (IHC) of CaSR and TRPV6: both receptors are detected (score 4) with a homogenous intense staining. Scale bar = 100μ. EF. Tumour diameter 5 mm. Upon comparing T1-weighted gradient echo images (T1 WI) recorded before and 90 minutes after Mn2+ administration, no changes in tumour signal enhancement was appreciated (red circles). GH. Immunohistochemistry (IHC) showed no evidence for CaSR and TRPV6 expression (score 0). Scale bar = 100μ.

Fig 2. Manganese Enhanced MR Imaging (MEMRI) of orthotopic human prostate cancer xenografts and CaSR/TRPV6 receptors levels.

Tumour diameter 10 mm. On T2-weighted MR image a high signal intensity multilobulated prostatic tumour is detected (red arrow). BC. On T1-weighted gradient echo MR images (T1 WI) recorded before and 90 minutes after Mn²⁺ administration, no changes in tumour signal enhancement was appreciated (red arrows). DE. Immunohistochemistry (IHC) of CaSR and TRPV6: both receptors were not detected in tumour cells (score 0) showing a negative staining. Scale bar = 100μ. F. Tumour diameter 6 mm. On T2-weighted image a high signal intensity extra-capsular prostatic tumour is detected (red arrow). GH. On T1-weighted gradient echo images (T1 WI) recorded before and 90 minutes after Mn2+ administration, no changes in tumour signal enhancement was appreciated (red arrows). IL. Immunohistochemistry (IHC) of CaSR and TRPV6: both receptors displayed a very low positive staining in tumour cells (score 1). Scale bar = 100μ.

Fig 3. Manganese Enhanced MR Imaging (MEMRI) of the intraosseous human breast cancer xenotransplant model and CaSR/TRPV6 receptors levels.

A. Tumor diameter 10 mm. On T2-weighted MR image a low signal intensity solid tumor is detected at the left leg of the mouse (red arrow). BC. On T1-weighted gradient echo MR images (T1 WI) recorded before and 90 minutes after Mn²⁺ administration, no changes in tumor enhancement was appreciated (red arrows). D. X-Ray imaging of the left leg of the mouse showed multiple lytic areas within the tibia in keeping with the tumor transplantation (red circle). E. Hematoxylin and eosin staining displaying the intraosseous tumor. FG. Immunohistochemistry (IHC) of CaSR and TRPV6: both receptors were not detected in tumor cells (score 0) showing a negative staining. Scale bar = 100μ.

Fig 4. Manganese Enhanced MR Imaging (MEMRI) of the pseudometastatic prostate cancer animal model and CaSR/TRPV6 receptors levels.

A. Multiple tumours with diameter from 3 to 10 mm. T2-weighted MR images showed multiple high intensity nodules with intra-abdominal ascites. B-Q. T1-weighted gradient echo MR images (T1 WI) recorded before and 90 minutes after Mn²⁺ administration: B-G. No manganese uptake by the liver metastases was detected (red arrows); L-Q. An increase in signal enhancement after manganese administration, respectively, within a diaphragmatic (LM) and mediastinal nodules (PQ) is appreciated (red arrows). D-S. Immunohistochemistry (IHC) of CaSR and TRPV6: D-I. A rare positive staining of CaSR was detected in tumour cells (score 1), while TRPV6 receptors displayed intense staining (score 4); N-S. Non-uniform weak/intense expression of CaSR was detected in tumour cells (score 3), while TRPV6 receptors ranged from strong uniform (score 4) to rare positive (score 2). Scale bar = 100μ.

Fig 5. Manganese Enhanced MR Imaging (MEMRI) of pseudo-metastatic prostate cancer animal model and CaSR/TRPV6 receptors levels.

A. Multiple peritoneal nodules with diameter of 3 mm (the same mouse of Fig 4). In T2-weighted MR image multiple high intensity peritoneal nodules with ascites are detected. BC. This slice shows the peritoneal nodules in T1-weighted gradient echo images (T1 WI) recorded before and 90 minutes after Mn²⁺ administration. No manganese uptake is detected (red arrows); D-G. Immunohistochemistry (IHC) of CaSR and TRPV6: A rare positive staining of both receptors was detected in tumour cells (score 1). Scale bar = 100μ.

Fig 6. Dependence of MR signal enhancement (SE%) from the score of CaSR (black square) and TRPV6 (red circles) expression.

The Mn-induced enhancement increases with CaSR expression; the expression level of TRPV6 appears not relevant for the increase of the MR signal.