Five to ten percent of individuals with melanoma have another affected family member, suggesting familial predisposition. Germ-line mutations in the cyclindependent kinase (CDK) inhibitor p16 have been reported in a subset of melanoma pedigrees, but their prevalence is unknown in more common cases of familial melanoma that do not involve large families with multiple affected members. We screened for germ-line mutations in p16 and in two other candidate melanoma genes, p19ARF and CDK4, in 33 consecutive patients treated for melanoma; these patients had at least one affected first or second degree relative (28 independent families). Five independent, definitive p16 mutations were detected (18%, 95% confidence interval: 6%, 37%), including one nonsense, one disease-associated missense, and three small deletions. No mutations were detected in CDK4. Disease-associated mutations in pl9ARF, whose transcript is derived in part from an alternative codon reading frame of p16, were only detected in patients who also had mutations inactivating p16. We conclude that germ-line p16 mutations are present in a significant fraction of individuals who have melanoma and a positive family history.

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Purpose. Molecular Radiotherapy (MRT) using 177 Lu-DOTATATE is a most effective therapy for the treatment of somatostatin receptor expressing neuroendocrine tumors (NETs). Despite its frequent and successful use in the clinic, little or no radiobiological considerations are taken into account at the time of treatment planning or delivery, and upon positive uptake of octreotide-based PET/SPECT imaging, treatment is usually administered as a standard dose and number of cycles without adjustment for peptide uptake, dosimetry, or radiobiological and DNA damage effects in the tumor. Here, we visualize and quantify the extent of DNA damage response following 177 Lu-DOTATATE therapy using SPECT imaging with 111 In-anti-γH2AX-TAT. This work is a proof-of-principle study of this in vivo non-invasive biodosimeter with beta-emitting therapeutic radiopharmaceuticals. Methods. Six cell lines were exposed to external beam radiotherapy (EBRT) or 177 Lu-DOTATATE, after which the number of γH2AX foci and clonogenic survival were measured. Mice bearing CA20948 somatostatin receptor positive tumor xenografts were treated with 177 Lu-DOTATATE or sham-treated, and co-injected with 111 In-anti-γH2AX-TAT, 111 In-IgG-TAT control, or vehicle. Results. Clonogenic survival following EBRT was cell line specific, indicating varying levels of intrinsic radiosensitivity. In vitro, cell lines treated with 177 Lu-DOTATATE, clonogenic survival decreased and γH2AX foci increased in cells expressing high levels of somatostatin receptor subtype 2 (SST2). Ex vivo measurements revealed a partial correlation between 177 Lu-DOTATATE uptake and γH2AX foci induction between different regions of CA20948 xenograft tumors, suggesting different parts of the tumor may react differentially to 177 Lu-DOTATATE irradiation. Conclusion. 111 In-anti-γH2AX-TAT allows monitoring of DNA damage following 177 Lu-DOTATATE therapy, and reveals heterogeneous damage responses.

Dense tumors are resistant to conventional chemotherapies due to the unique tumor microenvironment characterized by hypoxic regions that promote cellular dormancy. Bioreductive drugs that are activated in response to this hypoxic environment are an attractive strategy for therapy with anticipated lower harmful side effects in normoxic healthy tissue. Cobalt bioreductive pro-drugs that selectively release toxic payloads upon reduction in hypoxic cells have shown great promise as anticancer agents. However, the bioreductive response in the tumor microenvironment must be better understood, as current techniques for monitoring bioreduction to Co(II) such as X-ray absorption near-edge structure and extended X-ray absorption fine structure provide limited information on speciation and require synchrotron radiation sources. Here, we present magnetic resonance imaging (MRI) as an accessible and powerful technique to monitor bioreduction by treating the cobalt complex as an MRI contrast agent and monitoring the change in water signal induced by reduction from diamagnetic Co(III) to paramagnetic Co(II). Cobalt pro-drugs built upon the tris(2-pyridylmethyl)amine ligand scaffold with varying charge were investigated for distribution and activity in a 3D tumor spheroid model by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and MRI. In addition, paramagnetic H NMR spectroscopy of spheroids enabled determination of the speciation of activated Co(II)TPAx complexes. This study demonstrates the utility of MRI and associated spectroscopy techniques for understanding bioreductive cobalt pro-drugs in the tumor microenvironment and has broader implications for monitoring paramagnetic metal-based therapies.

Noteworthy  Targeted radionuclide therapy is growing in popularity for cancer treatment.  Efforts to improve targeted radionuclide therapy have led to increasing numbers of combination strategies being attempted.  Increasing our understanding of the radiobiology of targeted radionuclide therapy will help inform the successful implementation of combination strategies.

A cobalt tris(2-pyridylmethyl)amine complex cycles between stable paramagnetic Co(ii) and diamagnetic Co(iii) forms with corresponding changes in the MRI contrast.

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ParaSHIFT agents have shown promise in detecting chemical targets in biological systems by magnetic resonance, but few studies have used transition metal complexes for this purpose. Here we report our investigations into CoMetrenCl (tren = tris(2-aminoethyl)amine) as a paraSHIFT agent. The paramagnetic region of the H NMR spectrum shows characteristic spectral profiles in the presence of fluoride, acetate, lactate and citrate in aqueous solution. These distinctive NMR shifts of each anion are maintained even in mixtures of anions.