Monitoring mammary tumor progression and effect of tamoxifen treatment in MMTV-PymT using MRI and magnetic resonance spectroscopy with hyperpolarized [1-13C]pyruvate

PURPOSE

To use dynamic magnetic resonance spectroscopy (MRS) of hyperpolarized (13)C-pyruvate to follow the progress over time in vivo of breast cancer metabolism in the MMTV-PymT model, and to follow the response to the anti-estrogen drug tamoxifen.

METHODS

Tumor growth was monitored by anatomical MRI by measuring tumor volumes. Dynamic MRS of hyperpolarized (13)C was used to measure an "apparent" pyruvate-to-lactate rate constant (kp) of lactate dehydrogenase (LDH) in vivo. Further, ex vivo pathology and in vitro LDH initial reaction velocity were evaluated.

RESULTS

Tamoxifen significantly halted the tumor growth measured as tumor volume by MRI. In the untreated animals, kp correlated with tumor growth. The kP was somewhat but not significantly lower in the treated group. Studies in vitro confirmed the effects of tamoxifen on tumor growth, and here the LDH reaction velocity was reduced significantly in the treated group.

CONCLUSION

These hyperpolarized (13)C MRS findings indicate that tumor metabolic changes affects kP. The measured kp did not relate to treatment response to the same extent as did tumor growth, histological evaluation, and in vitro determination of LDH activity.

Multi-sample measurement of hyperpolarized pyruvate-to-lactate flux in melanoma cells

Hyperpolarized [1-13 C] pyruvate can be used to examine the metabolic state of cancer cells, highlighting a key metabolic characteristic of cancer: the upregulated metabolic flux to lactate, even in the presence of oxygen (Warburg effect). Thus, the rate constant of 13 C exchange of pyruvate to lactate, kPL , can serve as a metabolic biomarker of cancer presence, aggressiveness and therapy response. Established in vitro hyperpolarized experiments dissolve the probe for each cell sample independently, an inefficient process that consumes excessive time and resources. Expanding on our previous development of a microcoil with greatly increased detection sensitivity (103 -fold) compared with traditional in vitro methods, we present a novel microcoil equipped with a 10-μL vertical reservoir and an experimental protocol utilizing deuterated dissolution buffer to measure metabolic flux in multiple mass-limited cell suspension samples using a single dissolution. This method increases efficiency and potentially reduces the methodological variability associated with hyperpolarized experiments. This technique was used to measure pyruvate-to-lactate flux in melanoma cells to assess BRAF-inhibition treatment response. There was a significant reduction of kPL in BRAFV600E cells following 24 and 48 hours of treatment with 2 μM vemurafenib (P ≤ .05). This agrees with significant changes observed in the pool sizes of extracellular lactate (P ≤ .05) and glucose (P ≤ .001) following 6 and 48 hours of treatment, respectively, and a significant reduction in cell proliferation following 72 hours of treatment (P ≤ .01). BRAF inhibition had no significant effect on the metabolic flux of BRAFWT cells. These data demonstrate a 6-8-fold increase in efficiency for the measurement of kPL in cell suspension samples compared with traditional hyperpolarized in vitro methods.

Hereditary Pancreatic Cancer: Advances in Genetic Testing, Early Detection Strategies, and Personalized Management

Background: Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal malignancy with a five-year survival rate of approximately 13% for advanced stages. While the majority of PDAC cases are sporadic, a significant subset is attributable to hereditary and familial predispositions, accounting for approximately 25% of cases. This article synthesizes recent advancements in the understanding, detection, and management of hereditary pancreatic cancer (PC). Results: Our review highlights the critical role of genetic testing (GT) in identifying high-risk individuals (HRIs), with germline pathogenic variants (PVs) found in up to 20% of hereditary PDAC cases. Since the implementation of next-generation sequencing (NGS) panels in 2014, detection capabilities have been significantly enhanced. HRIs can be included in screening programs that facilitate the early detection of PDAC. Early detection strategies, including the use of microribonucleic acid (miRNAs) signatures and novel imaging techniques like hyperpolarized 13C-magnetic resonance spectroscopy (MRS) have shown promising results. The identification of germline pathogenic variants (PVs) or mutations in homologous recombination (HR) genes plays a predictive role in the response to various treatments, prolonging patient survival. Discussion: Universal germline testing for PDAC, as recommended by the National Comprehensive Cancer Network (NCCN), is now a standard practice, facilitating the identification of at-risk individuals and enabling targeted surveillance and intervention. Multidisciplinary management, integrating genetic counseling, imaging, and gastrointestinal services, is essential for optimizing outcomes. Conclusions: Advances in genetic testing and biomarker research are transforming the landscape of hereditary PC management. Early detection and personalized treatment strategies are pivotal in improving survival rates. Ongoing multi-institutional research efforts are crucial for validating biomarkers and developing preventive measures, ultimately aiming to reduce the burden of this aggressive cancer.

Imaging biomarkers of TERT or GABPB1 silencing in TERT-positive glioblastoma

BACKGROUND

TERT promoter mutations are observed in 80% of wild-type IDH glioblastoma (GBM). Moreover, the upstream TERT transcription factor GABPB1 was recently identified as a cancer-specific therapeutic target for tumors harboring a TERT promoter mutation. In that context, noninvasive imaging biomarkers are needed for the detection of TERT modulation.

METHODS

Multiple GBM models were investigated as cells and in vivo tumors and the impact of TERT silencing, either directly or by targeting GABPB1, was determined using 1H and hyperpolarized 13C magnetic resonance spectroscopy (MRS). Changes in associated metabolic enzymes were also investigated.

RESULTS

1H-MRS revealed that lactate and glutathione (GSH) were the most significantly altered metabolites when either TERT or GABPB1 was silenced, and lactate and GSH levels were correlated with cellular TERT expression. Consistent with the drop in lactate, 13C-MRS showed that hyperpolarized [1-13C]lactate production from [1-13C]pyruvate was also reduced when TERT was silenced. Mechanistically, the reduction in GSH was associated with a reduction in pentose phosphate pathway flux, reduced activity of glucose-6-phosphate dehydrogenase, and reduced NADPH. The drop in lactate and hyperpolarized lactate were associated with reductions in glycolytic flux, NADH, and expression/activity of GLUT1, monocarboxylate transporters, and lactate dehydrogenase A.

CONCLUSIONS

Our study indicates that MRS-detectable GSH, lactate, and lactate production could serve as metabolic biomarkers of response to emerging TERT-targeted therapies for GBM with activating TERT promoter mutations. Importantly these biomarkers are readily translatable to the clinic, and thus could ultimately improve GBM patient management.