My colleagues and I read with great interest the paper on magnetic resonance imaging of MYC mRNA in prostate cancer xenografts (1). This approach has great potential for noninvasive diagnosis of oncogene expression. We wonder whether some supplementary material is available concerning the chemical characterization of the starting materials and the oxidation products between the cysteine amide groups of TQVKIWFQNRRMKQKK-Cys-NH2 and Gd3+-complex-Lys(FITC)Lys-ATGCCCCTCAACGT-Cys-NH2, such as gel electrophoresis, reversed-phase liquid chromatography, yield, and mass spectroscopy. We would also like to know the structure of the complex that binds Gd3+. It is also remarkable that MYC mRNA could be visualized by magnetic resonance imaging in the prostate cancer xenografts when using a peptide nucleic acid (PNA) probe identical in sequence to the MYC mRNA in prostate cancer xenografts, as opposed to a complementary sequence. What mechanism could be hypothesized that could account for a sense probe hybridizing to a sense target? Notwithstanding these questions, it is most impressive to be able to visualize externally sites of probe hybridization to overexpressed MYC mRNA in tumors as early as 10 min after administration.

The Gd complex used by us (1) was based on Gd3+ [2-{[2-(carbamoylmethyl-carboxymethyl-amino)-ethyl]-carboxymethyl-amino}-ethyl)-carboxymethyl-amino]-acetic acid.

Because of ongoing patent applications, we had to reduce the chemical description to the term “complex.”

Furthermore, we would like to state that the signal intensity detected in magnetic resonance imaging was not completely understood.

At the moment, we discuss inner sphere effects of Gd and certain Micell formation effects.

Therefore, we would be grateful for hints leading to understanding this increase in intensity.

In addition, we tested a possible imaging property of the “complex” with respect to the hints in the literature demonstrating the existence of complementary RNA sequences to n-MYC.