Effect of Erlotinib on proliferation and steriodogenesis in primary cultures of adrenocortical carcinoma

Background: Adrenocortical cancer (ACC) is a rare malignant endocrine tumour. Previously we found that erlotinib (inhibitor of EGFR) had an additive cytotoxic effect to standard therapy with mitotane in H295R cell line, especially after EGF stimulation. Primary cultures of ACC have been proven to be challenging to establish and maintain for further experiments, especially for assessing their steroid profile. Design: The aim of this study was to test the effect in the use of Erlotinib on primary ACC cultures. We successfully cultured 3 ACCs. In 2 ACC cases, radical surgery was a treatment of choice, whereas in the last case - surgery was after neo-adjuvant chemotherapy. Because last tumour was very heterogeneous, we cultured two samples from macroscopically different areas. Cell proliferation rate and the effect of the drugs were assessed by AlamarBlue assay. We used LCMS/MS to assess tumour steroids production from primary cultures derived from metastatic ACC cases. Results: Treatment with mitotane resulted in the decrease of cell proliferation (9%±2%) in all cases at 10uM and total death at 50μM. In one of radically operated ACCs, erlotinib (10μM) decreased proliferation by 24%, whereas in another it was not effective. Surprisingly, erlotinib has the opposite effect on cell proliferation in two samples from metastatic ACC; however its combination with low dose of mitotane (10μM) was sufficient to induce total death. Furthermore, the basal steroid production was different in those samples, and it changed in a different manner after treatment with mitotane and/or erlotinib (with or without EGF stimulation). Conclusion: Erlotinib can have an anti-proliferative effect on primary ACC cultures and can reduce mitotane effective concentration. For cases pre-treated with neo-adjuvant therapy, erlotinib may cause opposite responses in different parts of the same tumour; hence its clinical use needs further careful consideration. Different responses in steroidogenesis from different parts of the same ACC tumour has not been previously described underlines ACC heterogeneity.