Clinical features of anti-pituitary-specific transcription factor-1 (PIT-1) hypophysitis: a new aspect of paraneoplastic autoimmune condition

The pathogenesis of anti-pituitary-specific transcription factor-1 (PIT-1) hypophysitis was gradually revealed as cases emerged. Our comprehensive analysis, including all reported cases, identified a new instance of anti-PIT-1 hypophysitis postimmune checkpoint inhibitor therapy. All 9 patients exhibited extremely low growth hormone (GH), prolactin (PRL), and thyroid-stimulating hormone (TSH) levels; 2 had a slightly atrophic pituitary gland; 4 had thymoma, and 5 had malignant neoplasms of diffuse large B-cell lymphoma (DLBCL) and other origins. Patients with thymoma showed multiple autoimmune diseases. HLA-A*24:02 and/or A*02:06 were present in six and DR53 in 5 cases analyzed. High anti-PIT-1 antibody titers and ectopic PIT-1 expression in the cytosol and nucleus of the tumor tissues were observed in patients with thymoma or DLBCL, whereas it was exclusively observed in the nuclei of a bladder cancer patient. These findings provide new insights into the pathophysiology of paraneoplastic autoimmune hypophysitis.

Cytodifferentiation of pituitary tumors influences pathogenesis and cavernous sinus invasion

OBJECTIVE

Pituitary tumors (PTs) continue to present unique challenges given their proximity to the cavernous sinus, whereby invasive behavior can limit the extent of resection and surgical outcome, especially in functional tumors. The aim of this study was to elucidate patterns of cavernoinvasive behavior by PT subtype.

METHODS

A total of 169 consecutive first-time surgeries for PTs were analyzed; 45% of the tumors were functional. There were 64 pituitary transcription factor-1 (PIT-1)-expressing, 62 steroidogenic factor-1 (SF-1)-expressing, 38 T-box transcription factor (TPIT)-expressing, and 5 nonstaining PTs. The gold standard for cavernous sinus invasion (CSI) was based on histopathological examination of the cavernous sinus medial wall and intraoperative exploration.

RESULTS

Cavernous sinus disease was present in 33% of patients. Of the Knosp grade 3 and 4 tumors, 12 (19%) expressed PIT-1, 7 (11%) expressed SF-1, 8 (21%) expressed TPIT, and 2 (40%), were nonstaining (p = 0.36). PIT-1 tumors had a significantly higher predilection for CSI: 53% versus 24% and 18% for TPIT and SF-1 tumors, respectively (OR 6.08, 95% CI 2.86-13.55; p < 0.001). Microscopic CSI-defined as Knosp grade 0-2 tumors with confirmed invasion-was present in 44% of PIT-1 tumors compared with 7% and 13% of TPIT and SF-1 tumors, respectively (OR 11.72, 95% CI 4.35-35.50; p < 0.001). Using the transcavernous approach to excise cavernous sinus disease, surgical biochemical remission rates for patients with acromegaly, prolactinoma, and Cushing disease were 88%, 87%, and 100%, respectively. The granule density of PIT-1 tumors and corticotroph functional status did not influence CSI.

CONCLUSIONS

The likelihood of CSI differed by transcription factor expression; PIT-1-expressing tumors had a higher predilection for invading the cavernous sinus, particularly microscopically, compared with the other tumor subtypes. This elucidates a unique cavernoinvasive behavior absent in cells from other lineages. Innovative surgical techniques, however, can mitigate tumor behavior and achieve robust, reproducible biochemical remission and gross-total resection rates. These findings can have considerable implications on the surgical management and study of PT biology and behavior.

High-throughput splicing assays identify missense and silent splice-disruptive POU1F1 variants underlying pituitary hormone deficiency

Pituitary hormone deficiency occurs in ∼1:4,000 live births. Approximately 3% of the cases are due to mutations in the alpha isoform of POU1F1, a pituitary-specific transcriptional activator. We found four separate heterozygous missense variants in unrelated individuals with hypopituitarism that were predicted to affect a minor isoform, POU1F1 beta, which can act as a transcriptional repressor. These variants retain repressor activity, but they shift splicing to favor the expression of the beta isoform, resulting in dominant-negative loss of function. Using a high-throughput splicing reporter assay, we tested 1,070 single-nucleotide variants in POU1F1. We identified 96 splice-disruptive variants, including 14 synonymous variants. In separate cohorts, we found two additional synonymous variants nominated by this screen that co-segregate with hypopituitarism. This study underlines the importance of evaluating the impact of variants on splicing and provides a catalog for interpretation of variants of unknown significance in POU1F1.

Clinicopathological Features of Growth Hormone-producing Pituitary Adenomas and Correlation With Preoperative Laboratory Findings

BACKGROUND/AIM

The histopathological variability of each type of pituitary adenoma (PA) that causes growth hormone (GH) excess influences the phenotype, radiological characteristics and therapy response of acromegaly patients. We correlated the immunohistochemical (IHC) features of GH-secreting PAs with their clinical, laboratory and imaging data.

PATIENTS AND METHODS

We included 32 patients with documented acromegaly; tumour specimens were histologically and IHC examined: anterior pituitary hormones, pituitary-specific transcription factor-1 (PIT-1), Ki-67 labelling index were evaluated.

RESULTS

Macroadenomas represented 93.75%. Post-surgery disease control negatively correlated with the maximum initial tumour diameter (p=0.04). Ki-67 did not predict remission. No correlation was found between GH serum levels and IHC expression (p=0.45). PIT-1 was positive in all specimens, two had a weak expression. Four were considered PIT-1 positive plurihormonal adenomas and several had unusual IHC combinations.

CONCLUSION

PIT-1 accurately classifies GH-secreting PAs. The IHC classification as well as radiological dimensions and extent influence disease control, probably being the best prognosis factors.

Plurihormonal PIT-1-Positive Pituitary Adenomas: A Systematic Review and Single-Center Series

OBJECTIVE

The 2017 World Health Organization classification of pituitary adenomas identified the plurihormonal PIT-1-positive (PP1) adenoma as a distinct subtype. The reported data suggest that PP1 adenomas encompass the former class of silent subtype 3 (SS3) adenomas and might have an aggressive phenotype. In the present study, we summarized the current clinical data on PP1 and SS3 adenomas and compared the reported data with the data from a single institutional cohort.

METHODS

Medline and Google Scholar were searched from 1990 to 2020 for clinical series of PP1 and SS3 adenomas in accordance with the PRISMA (preferred reporting items for systematic reviews and meta-analyses) guidelines. Studies were included if they had reported pituitary pathology as PP1 or SS3 adenomas and had reported the clinical outcomes after surgical intervention. To better define the PP1 phenotype compared with non-PP1 adenomas, we also reviewed the adenomas treated surgically at our institution from 2012 to 2019.

RESULTS

Of all the tumors reported in the studies as PP1 or SS3, 99% were macroadenomas and 18% were giant adenomas (>4 cm). Of the reported patients, 31.8% had received radiotherapy, and 22.9% had undergone multiple surgeries for their pituitary tumor. In our single-center experience, 20 patients had an adenoma that met the criteria for a PP1 adenoma. Compared with the 1146 non-PP1 tumors, the PP1 tumors did not show statistically significant differences in the extent of resection, size, number of previous surgeries, future reoperations, rate of radiotherapy, p53 staining, or MIB-1 labeling index.

CONCLUSIONS

The findings from the present large, single-center study comparing PP1 and non-PP1 adenomas do not suggest that PP1 tumors are more aggressive. Further work is warranted to identify the pathologic subtypes of pituitary adenomas that are consistently more clinically aggressive.

Determination of Polymorphisms in Pituitary Genes of the Native Afghani Naked Neck Chicken

We investigated means to improve the production of the indigenous Naked Neck chicken in Afghanistan. Specifically, we analyzed single nucleotide polymorphisms (SNPs) in the prolactin (PRL) (24 bp indel), growth hormone (GH) (T185G), and pituitary specific transcript factor 1 (PIT-1) (intron 5) genes. Blood samples were collected from 52 birds and genomic DNA was extracted. Polymorphisms in the mentioned loci were analyzed by PCR, allele-specific PCR, and PCR-restriction fragment length polymorphism (RFLP) using TaqI and MspI endonucleases. Cloning followed by DNA sequencing was performed to ascertain the accuracy of the PCR-RFLP analysis for PIT-1.Two alleles were found for the PRL 24 bp indel, GH (T185G), and PIT-1/TaqI, with the following respective allelic frequencies: PRL-In 0.64 and PRL-Del 0.36, GH-T 0.91 and GH-G 0.09, and PIT-1-A 0.64 and PIT-1-B 0.36. Regarding the PIT-1/MspI polymorphism, three novel MspI recognition sites, as well as two reported MspI recognition sites, were detected in intron 5. Moreover, during sequence screening, two novel SNPs were found that generated restriction sites for MseI. Therefore, our results suggest that the PRL indel, GH T185G, and PIT-1/TaqI polymorphisms may be used as selection markers for Afghanistan Naked Neck chickens. Intron 5 of PIT-1 in the Afghani Naked Neck chicken was highly polymorphic compared to the reported Gallus gallus PIT-1 gene (GenBank accession no. NC_006088.4).