Deep tissue imaging of B16 melanoma in mice by Multispectral Optoacoustic Tomography

Melanoma is an extremely aggressive form of skin cancer that will be diagnosed approximately 192,000 times in 2019. Of these, more than half will be the invasive variety. The 5‐year survival rates for a patient with invasive disease drops from ~98% to ~23%. Although cancer aggressiveness is mostly a consequence of patient specific environmental factors and cancer cell mutations, early detection remains a key determinant for improved patient’s outcomes. In this study, we used Multispectral Optoacoustic Tomography (MSOT), a novel diagnostic imaging tool with improved sensitivity and selectivity. MSOT imaging uses the optoacoustic properties of host tissue to provide structural information and in case of melanoma, a potent contrast agent for the detection of metastatic disease. In brief, cells constitutively expression of melanin provides a signal in MSOT that can be monitored over days to weeks. We studied both intradermal and intravenous models of melanoma and performed MSOT imaging every five days to monitor tumor formation and psuedotumor metastases. In our intradermal experiment, tumors were visible starting at day seven, but no metastasis were detected. However, we did detect metastatic disease in intravenous injected B16‐BL6 mice by MSOT imaging. In several animals, we also detected bilateral adrenal tumor, which is similar to the end‐stage human disease. Hematoxylin and eosin staining verified the presence of melanoma cells in the mice at both primary and distal sites. These findings validate the use of MSOT for the preclinical detection of melanoma in vivo and demonstrates the feasibility of using MSOT in the diagnosis of melanoma. Support or Funding Information Auburn University, Auburn, AL USATaibah University, Madinah, KSA