ARID1A is a subunit of the mammalian SWI/SNF complex, which is thought to regulate gene expression through restructuring chromatin structures. Its gene ARID1A is frequently mutated and ARID1A levels are lowered in several human cancers, especially gynecologic ones. A functional ARID1A loss may have prognostic or predictive value in terms of therapeutic strategies but has not been proposed based on a quantitative method. Hardly any literature is available on ARID1A levels in tumor samples. We developed an indirect enzyme-linked immunosorbent assay (ELISA) for ARID1A based on the current EMA and FDA criteria. We demonstrated that our ELISA provides the objective, accurate, and precise quantification of ARID1A concentrations in recombinant protein solutions, cell culture standards, and tissue lysates of tumors. A standard curve analysis yielded a ‘goodness of fit’ of R² = 0.99. Standards measured on several plates and days achieved an inter-assay accuracy of 90.26% and an inter-assay precision with a coefficient of variation of 4.53%. When tumor lysates were prepared and measured multiple times, our method had an inter-assay precision with a coefficient of variation of 11.78%. We believe that our suggested method ensures a high reproducibility and can be used for a high sample throughput to determine the ARID1A concentration in different tumor entities. The application of our ELISA on various tumor and control tissues will allow us to explore whether quantitative ARID1A measurements in tumor samples are of predictive value.

Background/Objectives: Loss of heterozygosity (LOH) in meningioma has been known for more than two decades. It has been shown that LOH on chromosome 1p36 is an independent marker of meningioma recurrence and progression. ARID1A, a tumor suppressor gene located on chromosome 1p36.11, is part of the chromatin-regulating SWI/SNF complex whose subunits are altered in 20% of cases across all tumor entities. Methods: Using our newly developed indirect enzyme-linked immunosorbent assay (ELISA), we investigated whether tumors with or without LOH 1p differ in ARID1A expression in 61 meningiomas. To study possible links between ARID1A and ARID1B, we tested for LOH 6q in association with LOH 1p using a PCR-based microsatellite approach. ARID1B, another member of the SWI/SNF complex, is located on 6q25.3. Additionally, we compared our ELISA results with immunohistochemistry data staining of ARID1A in tissue sections known to harbor LOH 1p. Results: Our results indicate that meningiomas harboring LOH 1p have significantly lower ARID1A levels compared to tumors without LOH 1p. In free nuclear protein fractions, reductions were up to 32% (CI: 6–58.7%). Interestingly, we found that ARID1A levels were significantly lower in tumors with recurrence and/or multiple localizations. In addition, our analysis of chromosome 6q uncovered a significantly strong correlation between LOH 1p and LOH 6q (p < 0.0001). Conclusions: These results highlight the importance of ARID1A in meningioma malignization and indicate for the first time functional evidence for LOH 1p.