Endocrine Abstracts

Adrenocortical carcinoma (ACC) is a rare and highly aggressive endocrine neoplasm, with limited therapeutic option. Activating β-catenin somatic mutations are observed in ACC and associated with a poor outcome. Activation of the Wnt/β-catenin signaling pathway seems to play a major role in ACC aggressiveness, and might be a promising therapeutic target. The H295 cell line derived from an ACC harbors an activating β-catenin mutation. We herein assess the in vitro and in vivo effect of β-catenin inactivation using doxycyclin (dox) inducible sh-RNA plasmid in H295R adrenocortical cancer cells line (clones named H295R-shβ).

In vitro: a dramatic reduction in β-catenin expression was detectable in H295R-shβ after dox treatment compared to control clones (−82%, P<0.005). Accordingly, we observed a transcriptional Wnt/β-catenin-dependent luciferase reporter activity decrease (−62%, P<0.05) as well as a decreased expression of an ubiquitous target gene, AXIN2 (−76%, P<0.0001). β-catenin silencing led to a decreased cell proliferation (−46%, P<0.05) and cell cycle alterations with cell accumulation in the G1 phase (+10%, P<0.05) and increased apoptosis (+67%, P<0.05).

In vivo: after subcutaneous induction of tumor xenografts in athymic nude mice, 9 days dox administration was associated with a significant decrease in intra-tumoral β-catenin (−89%, P=0.007) and AXIN2 (−87% P<0.005) expression in H295R-shβ grafted mice while mice grafted with control H295R clone remained unaffected. Long-term dox administration, starting 3 days after tumor cell inoculation, was associated with a total absence of tumor growth in the H295R-shβ group while tumors were present in all the mice of the control group (median tumor weight after sacrifice 67.4 mg vs 0 mg, P<0.001).

In summary, these experiments provide evidences that Wnt/β-catenin pathway inhibition in ACC is a promising therapeutic target.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This work was supported, however funding details unavailable.