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31P surface-coil NMR analysis of metabolic status in KHJJ tumors
Abstract:
Noninvasive monitoring of the effects of treatment on cancer tissue is fundamental to the development of rational radioimmunotherapy (RIT) schemes employing radiolabeled monoclonal antibodies or antibody fragments specific for human cancer. Recent advances in nuclear magnetic resonance spectroscopy make it an attractive candidate for sequential, topical monitoring by 31P NMR of metabolic events during RIT. Preliminary to this effort, we examined the metabolic competence of the well-characterized, murine KHJJ tumor in situ in BALB/c mice using 31P surface-coil NMR. The ATP/Pi ratio in tumor volumes ranging from 100 to 800 mm3 showed that tumors over this range of sizes were able to maintain high levels of ATP relative to Pi. As the tumor volume increased above 1 cm3, ATP/Pi levels indicated poor metabolic competence. This lack of metabolic competence was correlated with histological evidence of tissue necrosis and vascular disintegration. The T1 values of assigned phosphorus metabolites were established. Intracellular pH, as determined from the chemical shift of Pi, was found to vary in these tumors from 7.1 in rapidly metabolizing tissue to 6.6 in necrotic tumors.
Insights
Noninvasive monitoring of cancer metabolism using 31P NMR reveals that tumor size impacts metabolic competence. Larger tumors show decreased ATP/Pi ratios, indicating poor metabolic health and necrosis, crucial for radioimmunotherapy development.
Area of Science:
- Biophysics
- Oncology
- Biochemistry
Background:
- Noninvasive monitoring of cancer tissue is crucial for developing effective radioimmunotherapy (RIT).
- Nuclear magnetic resonance (NMR) spectroscopy, particularly 31P NMR, offers potential for sequential monitoring of metabolic events during RIT.
- The murine KHJJ tumor model is well-characterized and suitable for in situ studies.
Purpose of the Study:
- To assess the metabolic competence of murine KHJJ tumors in situ using 31P surface-coil NMR.
- To establish the relationship between tumor volume, metabolic state, and histological characteristics.
- To determine intracellular pH and T1 values of phosphorus metabolites in tumors.
Main Methods:
- Utilized 31P surface-coil NMR spectroscopy to examine KHJJ tumors in BALB/c mice.
- Measured the Adenosine Triphosphate (ATP)/Inorganic Phosphate (Pi) ratio in tumors of varying volumes.
- Correlated NMR data with histological analysis to assess tissue viability and vascular integrity.
- Determined T1 relaxation times for phosphorus metabolites and intracellular pH from the chemical shift of Pi.
Main Results:
- Tumors between 100 and 800 mm3 maintained high ATP/Pi ratios, indicating good metabolic competence.
- Tumor volumes exceeding 1 cm3 exhibited decreased ATP/Pi ratios, signifying poor metabolic competence.
- Histological examination revealed tissue necrosis and vascular disintegration in larger, metabolically compromised tumors.
- Intracellular pH ranged from 7.1 in metabolically active tissue to 6.6 in necrotic regions.
Conclusions:
- 31P NMR is a viable tool for noninvasively assessing tumor metabolic status and guiding RIT strategies.
- Tumor size is a critical factor influencing metabolic competence, with larger tumors showing signs of necrosis.
- Metabolic changes, including intracellular pH variations, correlate with tumor progression and histological findings.