Estrogen receptor β‐mediated nuclear interaction between IRS‐1 and Rad51 inhibits homologous recombination directed DNA repair in medulloblastoma

Abstract

In medulloblastomas, which are highly malignant cerebellar tumors of the childhood genotoxic treatments such as cisplatin or γ-irradiation are frequently associated with DNA damage, which often associates with unfaithful DNA repair, selection of new adaptations and possibly tumor recurrences. Therefore, better understanding of molecular mechanisms which control DNA repair fidelity upon DNA damage is a critical task. Here we demonstrate for the first time that estrogen receptor beta (ERβ) can contribute to the development of genomic instability in medulloblastomas. Specifically, ERβ was found highly expressed and active in mouse and human medulloblastoma cell lines. Nuclear ERβ was also present in human medulloblastoma clinical samples. Expression of ERβ coincided with nuclear translocation of insulin receptor substrate 1 (IRS-1), which was previously reported to interfere with the faithful component of DNA repair when translocated to the nucleus. We demonstrated that ERβ and IRS-1 bind each other, and the interaction involves C-terminal domain of IRS-1 (aa 931–1233). Following cisplatin-induced DNA damage, nuclear IRS-1 localized at the sites of damaged DNA, and interacted with Rad51—an enzymatic component of homologous recombination directed DNA repair (HRR). In medulloblastoma cells, engineered to express HRR-DNA reporter plasmid, ER antagonist, ICI 182,780, or IRS mutant (931–1233) significantly increased DNA repair fidelity. These data strongly suggest that both molecular and pharmacological interventions are capable of preventing ERβ-mediated IRS-1 nuclear translocation, which in turn improves DNA repair fidelity and possibly counteracts accumulation of malignant mutations in actively growing medulloblastomas.

Inhibition of ERβ Induces Resistance to Cisplatin by Enhancing Rad51–Mediated DNA Repair in Human Medulloblastoma Cell Lines

“…Indeed, results in Fig. 6A (lower panel) confirmed that only a small fraction of nuclear IRS-1 was detected in Daoy cells treated together with cisplatin and ICI182,780, which according to our previous observation is expected to increase the fraction of Rad51, which in the absence of nuclear IRS-1 can be recruited more effectively to the sites of DSBs, supporting HRR [9], [36]. The results in Fig.…”

“…5), the cells treated with cisplatin in the presence of ICI182780 (Cis+ICI) show an increase in γH2AX nuclear foci (evaluated by γH2AX/DAPI co-localization), which may imply more effective recruitment of DNA repair proteins, including Rad51 [35]. Of note, we have previously reported that ICI182,780–mediated inhibition of ERβ prevented translocation of IRS-1 to the nucleus and the binding between IRS-1 and Rad51 after DNA damage [9]. Indeed, results in Fig.…”

“…To further analyze this possibility, we have selected human medulloblastoma cell lines, Daoy, D283Med and D384Med, which express high levels of ERβ in the absence of ERα [9], and asked if the effectiveness of cisplatin treatment could be enhanced by the ER antagonist, ICI182,780 [18], [19]. Surprisingly, our initial morphological evaluation, depicted in Fig.…”

Linking DNA Damage and Hormone Signaling Pathways in Cancer

“…In melanoma, the tumor suppressor gene MEN1 and ERα bind to the promoters of RAD51 and BRCA1, therein activating transcription [49]. Conversely, ERβ functions to place RAD51 into an inactive complex with insulin receptor substrate 1 (IRS1), thus diminishing HR function in medulloblastoma [50] Additionally, ERβ antagonism results in cisplatin resistance as a result of enhanced RAD51-associated DNA repair [51]. Although the opposite effects of ERα and ERβ demonstrate complexity, this is not without precedent as ERα has pro-proliferative capacity in BrCa, while ERβ is growth inhibitive in many cancer types [52, 53].…”

Investigação da participação do IRS1 na via de sinalização da β-catenina na leucemia linfoide aguda

“…A presença deste sítio pode explicar a translocação do IRS1 para o núcleo, após sua ativação pelo IGF1R induzida pelo IGF1 [91]. Além disso, a presença de IRS1 nuclear em células que expressam antígeno-T do vírus JCV humano, antígeno-T SV40, integrinas, receptor α de estrogênio (ERα) e receptor β de estrogênio (ERβ), indica que o mesmo pode ser translocado pela associação com outras proteínas equipadas com NLS [89,90,[92][93][94]. Adicionalmente, nossos resultados preliminares indicaram a presença de IRS1 no núcleo de células leucêmicas da linhagem linfoide (Jurkat) [95].…”