MEMRI and tumors: a method for the evaluation of the contribution of Mn(II) ions in the extracellular compartment

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

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.

Manganese-Enhanced Magnetic Resonance Imaging for Detection and Characterization of Colorectal Cancers

Here, we investigated the diagnostic performance of manganese (Mn)-enhanced magnetic resonance imaging (MEMRI) in colorectal cancer (CRC). The ability of CRC cell lines SW620 and SW480 to uptake Mn was evaluated and compared with a normal colon cell using MEMRI. Subcutaneous xenografts in nude mice underwent MRI examination at tumor sizes of 5, 10, and 15 mm. Contrast enhancement was compared between gadolinium (Gd)- and Mn-enhanced MRI. SW620 and SW480 cell lines took up more Mn²⁺ than normal cells, resulting in 4.5 and 2 times greater T1 value shortening than normal cell using in vitro MEMRI (P < .001). Most xenografts (17/23) enhanced markedly on MEMRI. A heterogeneous enhancement pattern invariably noted whether Mn or Gd agents were administered, but tumors imaged using MEMRI showed a greater degree of enhancement with a larger extent of enhanced area than those imaged using Gd-enhanced MRI. The numbers of markedly Mn-enhanced cases were more in the 5-mm-size tumor group than in 10- or 15-mm-size tumor groups. Overall, MEMRI could enhance CRCs and it showed potential in detecting early small lesions and markedly enhancing tumors that had minimal Gd enhancement.

Manganese-enhanced MRI for the detection of metastatic potential in colorectal cancer

Background

To study manganese superoxide dismutase (MnSOD) expression, manganese-enhanced magnetic resonance imaging (MEMRI) appearance and its relation to metastatic potential in colorectal cancer (CRC).

Methods

CRC cells SW620, HCT116, LoVo, SW480, DLD-1, HCT15, Caco-2 and their normal counterpart CCD841 CoN were chosen, based on differential aggressiveness, to undergo Western blot analysis for assessment of MnSOD expression, reported as proportion of readings to internal reference (glyceraldehyde-3-phosphate-dehydrogenase). Based on the results of the invasion assay, HCT15, DLD-1, LoVo and SW620 cells and corresponding xenografts underwent MEMRI. The differences of average T1-value shortening were compared.

Results

MnSOD expression in SW620, HCT116, LoVo, SW480, DLD-1, HCT15, Caco-2 and CCD841 CoN cells (0.255 ± 0.018 (mean ± standard deviation), 0.289 ± 0.028, 0.438 ± 0.028, 0.337 ± 0.025, 0.777 ± 0.031, 1.045 ± 0.038, 0.163 ± 0.035 and 0.185 ± 0.038, respectively) was not correlated with Invasion Index (22.6 ± 0.7, 17.0 ± 0.6, 20.9 ± 0.6, 9.7 ± 0.4, 7.5 ± 0.3, 8.3 ± 0.2, 12.6 ± 0.5 and 0) (r = − 0.204, p = 0.627). In highly aggressive cells (SW620, LoVo), T1 shortening (289.33 ± 0.57, 268.45 ± 6.87 ms, respectively) was greater than that in lower counterparts (148.68 ± 3.99 ms in DLD-1, 128.60 ± 1.96 in HCT15) (p < 0.001). Both 5- and 10-mm group SW620 and/or LoVo tumours showed greater T1 shortening (≥600 ms) than DLD-1 and HCT15 (≤350 ms) (p < 0.001, p = 0.005, p = 0.010).

Conclusions

MEMRI has the potential to noninvasively distinguish different metastatic potential CRCs. However, the MnSOD expression is not correlated to malignant potential in CRC cells.

In vivo MEMRI characterization of brain metastases using a 3D Look-Locker T1-mapping sequence

Although MEMRI (Manganese Enhanced MRI) informations were obtained on primary tumors in small animals, MEMRI data on metastases are lacking. Thus, our goal was to determine if 3D Look-Locker T1 mapping was an efficient method to evaluate Mn ions transport in brain metastases in vivo. The high spatial resolution in 3D (156 × 156 × 218 μm) of the sequence enabled to detect metastases of 0.3 mm³. In parallel, the T1 quantitation enabled to distinguish three populations of MDA-MB-231 derived brain metastases after MnCl2 intravenous injection: one with a healthy blood-tumor barrier that did not internalize Mn²⁺ ions, and two others, which T1 shortened drastically by 54.2% or 24%. Subsequent scans of the mice, enabled by the fast acquisition (23 min), demonstrated that these T1 reached back their pre-injection values in 24 h. Contrarily to metastases, the T1 of U87-MG glioma remained 26.2% shorter for one week. In vitro results supported the involvement of the Transient Receptor Potential channels and the Calcium-Sensing Receptor in the uptake and efflux of Mn²⁺ ions, respectively. This study highlights the ability of the 3D Look-Locker T1 mapping sequence to study heterogeneities (i) amongst brain metastases and (ii) between metastases and glioma regarding Mn transport.