In vivo photoacoustic imaging of tyrosinase expressing tumours in mice

Two human tumour cell lines (K562, 293T) were stably transfected to achieve the genetic expression of tyrosinase, which is involved in the production of the pigment eumelanin. The cells were injected subcutaneously into nude mice to form tumour xenografts, which were imaged over a period of up to 26 days using an all-optical photoacoustic imaging system. 3D photoacoustic images of the tumours and the surrounding vasculature were acquired at excitation wavelengths ranging from 600nm to 770nm. The images showed tumour growth and continued tyrosinase expression over the full 26 day duration of the study. These findings were confirmed by histological analysis of excised tumour samples.