Evaluation of the optimal LNCaP prostate tumour developmental stage to be assessed by 99mTc-HYNIC-βAla-Bombesin(7–14) in an experimental model

Abstract

The lymph node carcinoma of the prostate (LNCaP) cell line is widely used in prostate cancer diagnostic studies. However, the optimal developmental stage during which to assess LNCaP prostate tumours by in vivo molecular imaging has not been established. This study aimed to assess LNCaP prostate tumours by scintigraphic imaging using technetium-99m (99mTc)-2-hydrazinonicotinamide (HYNIC)-beta-alanine (βAla)-Bombesin(7–14) at different stages of tumour development and to compare each developmental stage using histopathological analysis. 99mTc-HYNIC-βAla-Bombesin(7–14) (7.4 MBq) was injected into LNCaP prostate tumour-bearing mice after 15, 20 or 25 days of tumour inoculation. Scintigraphic images were obtained 1 and 4 h following radiopeptide injection and tumour tissues were obtained for histopathological analysis. Tumours were not observed by scintigraphic imaging after 15 days of inoculation, but after 20 and 25 days of inoculation, tumours were visualised, with a tumour-to-muscle ratio of 2.14 at 4 h after the radiopeptide injection into mice with 25-day tumours. Histopathological analysis showed that the amount of collagen fibres in the stroma was inversely proportional to the stage of tumour development, whereas the intensity of vascular proliferation was directly proportional to the tumour stage; this explains radiopeptide localisation in LNCaP cells and improved visualisation of the 25-day tumours. In conclusion, the results showed that 25-day tumours presented the most appropriate features for radiopeptide accumulation in LNCaP cells, suggesting that they are in the best stage of tumour development to be assessed by scintigraphic imaging using 99mTc-HYNIC-βAla-Bombesin(7–14).