Inhibition of CD146 lessens uveal melanoma progression through reducing angiogenesis and vasculogenic mimicry.

PURPOSE: Anti-angiogenesis drug therapy is ineffective in treating uveal melanoma since it only targets angiogenesis leaving vasculogenic mimicry aside. There is no effective clinical strategy targeting vasculogenic mimicry, yet. We show here that CD146 is a novel target to inhibit uveal melanoma progression since it regulates both uveal melanoma angiogenesis and vasculogenic mimicry activity. METHODS: CD146 inhibition was achieved with its specific siRNAs or antibody AA98. Tube formation and migration of primary human retinal microvascular endothelial cells and tube-like structure formation, migration, invasion of uveal melanoma cells were evaluated after CD146 inhibition. The underlying mechanisms were investigated by Western blot and immunofluorescence. Finally, uveal melanoma cells were injected subretinally into the eyes of nude mice and AA98 was administrated. Tumor size was revealed by H&E staining, and angiogenesis and vasculogenic mimicry were evaluated with CD31-PAS staining. RESULTS: CD146 inhibition induced declines in tube formation and migration of primary human retinal microvascular endothelial cells and tube-like structure formation of uveal melanoma cells. CD146 mediated VEGFR/AKT/p38/NF-κB and FAK/VE-cadherin signal cascades were partially responsible for these biological effects. CD146 blockade by siRNA or AA98 also resulted in inhibition of migration and invasion as well as EMT process of uveal melanoma cells. The physiological relevance of such declines was confirmed by showing that AA98 treatment markedly suppressed the tumor growth, angiogenesis and vasculogenic mimicry induced by implantation of uveal melanoma cells into the eyes of nude mice. CONCLUSIONS: CD146 is a novel mediator of both angiogenesis and vasculogenic mimicry in uveal melanoma. Its antibody AA98 has the potency to be developed as a new antibody drug for treating uveal melanoma. Our results warrant further assessment of CD146 as a potential target to improve therapeutic management of uveal melanoma in a clinical setting.

Treatment of Hepatocellular Carcinoma by Intratumoral Injection of 125I-AA98 mAb and Its Efficacy Assessments by Molecular Imaging.

Objective: To investigate the therapeutic efficacy of intratumoral injection of 125I-AA98 mAb for hepatocellular carcinoma (HCC) and its therapy efficacy assessment by 99mTc-HYNIC-duramycin and 99mTc-HYNIC-3PRGD2 SPECT/CT imaging. Methods: HCC xenograft tumor mice models were injected intratumorally with a single dose of normal saline, 10 microcurie (µCi) 125I-AA98 mAb, free 125I, AA98 mAb, 80 µCi 125I-AA98 mAb, and 200 µCi 125I-AA98 mAb. 99mTc-HYNIC-duramycin and 99mTc-HYNIC-3PRGD2 micro-SPECT/CT imaging were performed on days 3 and 7, respectively. The T/M ratio for each imaging was compared with the corresponding immunohistochemical staining at each time point. The relative tumor inhibition rates were documented. Results: In terms of apoptosis, the 200 µCi group demonstrated the highest apoptotic index (11.8 ± 3.8%), and its T/M ratio achieved by 99mTc-HYNIC-duramycin imaging on day 3 was higher than that of the normal saline group, 80 µCi group, 10 µCi group and free 125I group on day 3, respectively (all P < 0.05). On day 3, there was a markedly positive correlation between T/M ratio from 99mTc-HYNIC-duramycin imaging and apoptotic index by TUNEL staining (r = 0.6981; P < 0.05). Moreover, the 200 µCi group showed the lowest T/M ratio on 99mTc-HYNIC-3PRGD2 imaging (1.0 ± 0.5) on day 7 (all P < 0.05) comparing to other groups. The T/M ratio on day 7 was not correlated with integrin ανß3 staining (P > 0.05). The relative inhibitory rates of tumor on day 14 in the AA98 mAb, 10 µCi, 80 µCi, free 125I, and 200 µCi groups were 26.3, 55.3, 60.5, 66.3, and 69.5%, respectively. Conclusion: 125I-AA98 mAb showed more effective apoptosis induced ability for CD146 high expression Hep G2 HCC cells and hold the potential for HCC treatment. Moreover, 99mTc-HYNIC-Duramycin (apoptosis-targeted) imaging and 99mTc-HYNIC-3PRGD2 (angiogenesis-targeted) imaging are reliable non-invasive methods to evaluate the efficacy of targeted treatment of HCC.