A Novel Mutation of Aryl Hydrocarbon Receptor Interacting Protein Gene Associated with Familial Isolated Pituitary Adenoma Mediates Tumor Invasion and Growth Hormone Hypersecretion.

BACKGROUND:Germline mutations in the aryl hydrocarbon receptor-interacting protein (AIP) gene were identified in nearly 20% of families with familial isolated pituitary adenoma. Some variants of AIP have been confirmed to induce tumor cell proliferation and invasiveness; however, the mechanism is still unclear. METHODS:A novel missense mutation (c.512C>T, p.T171I) was discovered in 3 patients from a Chinese family with familial isolated pituitary adenoma. In silico and multiplex ligation-dependent probe amplification analysis predicted the mutation to be pathogenic. GH3 and 293FT cell lines were used to verify the variant's effect on cell proliferation (Cell Counting Kit-8), invasiveness (Transwell) and growth hormone (GH) secretion (enzyme-linked immunosorbent assay) by transfection with different vectors: control, blank vector, wild-type AIP, p.T171I variant (experimental group), p.Q315* variant, and AIP small interfering RNA. Furthermore, Zac1, Sstr2, interleukin (IL)-6, and Stat3/phosphorylation-Stat3 expression (reverse transcription polymerase chain reaction, Western blot) in each group was also evaluated. RESULTS:The experimental group, p.Q315* variant group, and AIP small interfering RNA-overexpressing group promoted cell proliferation at 24 and 48 hours, respectively (compared with the control group; P < 0.01 for both). Similarly, the cells in the experimental group manifested more invasion and GH secretion compared with the control group (P < 0.01 and P < 0.05, respectively). Furthermore, the experimental group cells expressed less Sstr2 (a prerequisite for the responsiveness to somatostatin analogues) and Zac1 (tumor suppressor gene), but more IL-6 and phosphorylated-Stat3 (GH-secretion related). CONCLUSIONS:The novel AIP mutation c.512C>T (p.T171I) is a pathogenic variant that promoted cell proliferation, invasiveness, and GH secretion through regulation of Sstr2, Zac1, and IL-6/phosphorylated-Stat3 expression.

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