MYC transcription activation mediated by OCT4 as a mechanism of resistance to 13-cisRA-mediated differentiation in neuroblastoma

Abstract

Despite the improvement in clinical outcome with 13-cis-retinoic acid (13-cisRA) + anti-GD2 antibody + cytokine immunotherapy given in first response ~40% of high-risk neuroblastoma patients die of recurrent disease. MYCN genomic amplification is a biomarker of aggressive tumors in the childhood cancer neuroblastoma. MYCN expression is downregulated by 13-cisRA, a differentiating agent that is a component of neuroblastoma therapy. Although MYC amplification is rare in neuroblastoma at diagnosis, we report transcriptional activation of MYC medicated by the transcription factor OCT4, functionally replacing MYCN in 13-cisRA-resistant progressive disease neuroblastoma in large panels of patient-derived cell lines and xenograft models. We identified novel OCT4-binding sites in the MYC promoter/enhancer region that regulated MYC expression via phosphorylation by MAPKAPK2 (MK2). OCT4 phosphorylation at the S111 residue by MK2 was upstream of MYC transcriptional activation. Expression of OCT4, MK2, and c-MYC was higher in progressive disease relative to pre-therapy neuroblastomas and was associated with inferior patient survival. OCT4 or MK2 knockdown decreased c-MYC expression and restored the sensitivity to 13-cisRA. In conclusion, we demonstrated that high c-MYC expression independent of genomic amplification is associated with disease progression in neuroblastoma. MK2-mediated OCT4 transcriptional activation is a novel mechanism for activating the MYC oncogene in progressive disease neuroblastoma that provides a therapeutic target.

Retinoic acid rewires the adrenergic core regulatory circuitry of childhood neuroblastoma

“…A subset of neuroblastoma cell lines that express high levels of MYC or MYCN do not respond to treatment with retinoids [32][33][34] . One example is NBL-S, which expresses high levels of MYCN but does not have a high MYCN copy number.…”

Development of cell‐based high throughput luminescence assay for drug discovery in inhibiting OCT4/DNA‐PKcs and OCT4–MK2 interactions

“…The stable cell line was prepared for immunoblotting and co‐immunoprecipitation by infecting NCI‐H82, a small cell lung cancer cell line, with a doxycycline‐inducible pCW57.1‐POU5F1‐mycDDK construct using a lentiviral system as previously described (Wei et al, 2020; Zhang et al, 2014). The cell lines were prepared for immunoblotting and co‐immunoprecipitation to validate the effect on kinase‐substrate binding as described previously (Kang et al, 2007).…”

Targeting MYCN in Molecularly Defined Malignant Brain Tumors

“…At another dimension which might be of importance for treatment resistance in MYCN-driven cancer, involves OCT4 phosphorylation at S111 via MAPKAP2 that can promote MYC expression ( Figure 3 ). This might help identifying a therapy-resistance mechanism in MYCN-driven NB, providing an escape route driven by OCT4-activated MYC ( 161 ) in recurrent tumors.…”