Expression profiling of O(6) methylguanine-DNA-methyl transferase in prolactinomas: a correlative study of promoter methylation and pathological features in 136 cases

Update in Pathogenesis, Diagnosis, and Therapy of Prolactinoma

Simple Summary

This review updates recent advances in the pathogenesis, diagnosis, and therapy of prolactinoma. Prolactinomas, comprising 30–50% of all pituitary neuroendocrine tumors, frequently occur in females aged 20 to 50 and cause hypogonadism and infertility. In typical cases, female patients exhibit galactorrhea and amenorrhea due to serum prolactin (PRL) elevation, and during pregnancy, they should be carefully treated. During diagnosis, other causes of hyperprolactinemia must be excluded, and an MRI is useful for detecting pituitary neuroendocrine tumors. For the treatment of prolactinoma, dopamine agonists are effective in decreasing PRL levels and shrinking tumor size in most patients. Surgical treatment is recommended for patients who are resistant or intolerant to dopamine agonists. This review also discusses giant and malignant prolactinomas, prolactinoma-associated pregnancy, and new therapeutic approaches.

Abstract

Prolactinomas comprise 30–50% of all pituitary neuroendocrine tumors, frequently occur in females aged 20 to 50, and cause hypogonadism and infertility. In typical cases, female patients exhibit galactorrhea and amenorrhea due to serum prolactin (PRL) elevation, and patients during pregnancy should be carefully treated. During diagnosis, other causes of hyperprolactinemia must be excluded, and an MRI is useful for detecting pituitary neuroendocrine tumors. For treating prolactinoma, dopamine agonists (DAs) are effective for decreasing PRL levels and shrinking tumor size in most patients. Some DA-resistant cases and the molecular mechanisms of resistance to a DA are partially clarified. The side effects of a DA include cardiac valve alterations and impulse control disorders. Although surgical therapies are invasive, recent analysis shows that long-term remission rates are higher than from medical therapies. The treatments for giant or malignant prolactinomas are challenging, and the combination of medication, surgery, and radiation therapy should be considered. Regarding pathogenesis, somatic SF3B1 mutations were recently identified even though molecular mechanisms in most cases of prolactinoma have not been elucidated. To understand the pathogenesis of prolactinomas, the development of new therapeutic approaches for treatment-resistant patients is expected. This review updates the recent advances in understanding the pathogenesis, diagnosis, and therapy of prolactinoma.

Clinical Efficacy of Temozolomide and Its Predictors in Aggressive Pituitary Tumors and Pituitary Carcinomas: A Systematic Review and Meta-Analysis

Background: A growing number of evidences suggest that TMZ applications can generate impressive benefits for APT and PC patients. However, the definite role of TMZ for individuals remains unclarified due to the variation between studies. And the predictive factors to alter its efficacy remain debatable.

Objective: To evaluate the long-term effectiveness and safety profile of TMZ in the treatment of pituitary malignancies, and delineate the predictors during its clinical employment.

Results: A literature retrieval was conducted from online databases for studies published up to December 31, 2020. Twenty one studies involving 429 patients were identified. TMZ exhibited 41% radiological overall response rate (rORR). The biochemical response rate was determinate in 53% of the functioning subset. Two-year and 4-year survival rate were 79 and 61%, respectively. TMZ prolonged the median PFS and OS as 20.18 and 40.24 months. TMZ-related adverse events occurred in 19% of patients. Regarding predictors of TMZ response, rORR was dramatically improved in patients with low/intermediate MGMT expression than those with high-MGMT (>50%) (p < 0.001). The benefit of TMZ varied according to functioning subtype of patients, with greater antitumor activities in functioning subgroups and fewer activities in non-functioning sets (p < 0.001). Notably, the concomitant therapy of radiotherapy and TMZ significantly increased the rORR (p = 0.007).

Conclusion: TMZ elicits clinical benefits with moderate adverse events in APT and PC patients. MGMT expression and clinical subtype of secreting function might be vital predictors of TMZ efficacy. In the future, the combination of radiotherapy with TMZ may further improve the clinical outcomes than TMZ monotherapy.

Ki67 in endocrine neoplasms: to count or not to count, this is the question! A systematic review from the English language literature

BACKGROUND

Endocrine neoplasms are generally slow-growing tumors that can show hormonal activity and give metastases. In most cases they are benign and clearly malignant forms are easy to diagnose. However, borderline forms may occur and be, for the pathologists, very difficult to classify. In these cases, there is a strong need to identify factors that may aid. Official classification systems for endocrine neoplasms are based on the evaluation of proliferation and, in most cases, they rely on mitotic count. In support, the study of Ki67 is carried out which, however, has not yet been included in any official classification system, except for neuroendocrine neoplasms of the gastro-entero-pancreatic tract.

PURPOSE

The aim of the present study was to investigate the proven or unproven role of Ki67 in endocrine neoplasms, in different districts, in order to bring to light the substantial differences, in terms of proliferation, existing between neoplasms so similar, but at the same time, so different.

METHODS

A thorough search of English language literature was performed, looking for articles concerning Ki67 in five endocrine neoplasms (pituitary adenomas, thyroid neoplasms, adrenocortical neoplasms, pheochromocytomas and paragangliomas).

RESULTS

From 2170, 236 articles were selected and it was seen that the endocrine neoplasm in which Ki67 was most studied was the pituitary, where it still shows a controversial role. In other neoplasms different roles were identified.

CONCLUSION

The pathologist should be aware of the contribution that this proliferative marker can give to the diagnosis and, sometimes, to the therapy selection, for the clinician.

Tumor suppressor miR-145-5p sensitizes prolactinoma to bromocriptine by downregulating TPT1

PURPOSE

Prolactinoma is the most commonly seen secretory tumor of pituitary glands, which accounts for approximately up to 40% of total pituitary adenomas. Due to its high drug resistance, dopamine agonist, such as bromocriptine, has limited effect on the treatment of patients with prolactinoma. Recent discoveries have revealed that multiple miRNAs were involved in regulating drug resistance. In this research, we explored the relationship between miR-145-5p expression as well as bromocriptine sensitivity both in vitro and in vivo.

METHODS

To study the role of miR-145-5p in drug resistance of prolactinoma, the expression levels of miR-145-5p in bromocriptine-resistant prolactinoma cell line MMQ/BRC and its parental cell line MMQ cells, 24 bromocriptine-resistant as well as eight sensitive clinical samples were measured by qRT-PCR. Moreover, CCK8, flow cytometry and immunofluorescence were performed to identify the biological characteristics of MMQ/BRC and MMQ. TPT1 was predicted as a direct target gene of miR-145-5p by bioinformatic methods. In addition, qRT-PCR, western blot and immunohistochemistry were used to detect the expression level of TPT1 in clinical specimens and cell lines. Xenograft mouse model was constructed to analyze whether miR-145-5p could reverse bromocriptine resistance in prolactinoma in vivo.

RESULTS

In our study, bromocriptine-resistant prolactinoma clinical samples and cell line had decreased miR-145-5p levels and expressed high levels of TPT1 compared with their sensitive counterparts. Bioinformatic methods and our preliminary dual luciferase reporter assay were utilized to elucidate that TPT1 was a direct target gene of miR-145-5p. Furthermore, introducing miR-145-5p mimic into MMQ cells led to a decrease of IC50 along with upregulation of TPT1; nevertheless, transfecting the corresponding inhibitor into MMQ cells resulted in an upregulation of IC50 as well as reduction of TPT1.

CONCLUSIONS

Collectively, our findings elucidated the role of miR-145-5p as an important regulator of drug resistance in prolactinoma by controlling TPT1, and implicated the potential application of miR-145-5p in cancer therapy as well.

Effects of Some Growth Factors and Cytokines on the Expression of the Repair Enzyme MGMT and Protein MARP in Human Cells In Vitro : Effect of Some Growth Factors and Cytokines

The inducible repair enzyme O⁶-methylguanine-DNA methyltransferase (MGMT) eliminates O⁶-methylguanine adducts in DNA and protects the cells from damaging effects of alkylating agents. We have found that anti-MGMT antibodies recognize both the MGMT protein with a mol. weight ~ 24 kDa and a protein with a mol. weight ~ 48 kDa, which was named MARP (anti-methyltransferase antibody recognizable protein). A number of growth factors and cytokines were shown to regulate the expression of MGMT and MARP proteins. The ranges of concentrations of several growth factors and cytokines that caused increasing or decreasing protein amounts in human cell cultures were determined. The results of special biological experiments have allowed us to assume a possible role of MARP in the repair of alkyl adducts in human cells.

Is there a role for early chemotherapy in the management of pituitary adenomas?

Pituitary adenomas are benign intracranial neoplasms that are frequently well-controlled with standard treatments that include surgical resection, radiotherapy, and agents that modulate hormonal excess. Unfortunately, a subset of patients remains uncontrolled or develops complications from these interventions. For these patients, chemotherapy is an additional treatment option that could improve outcomes. Temozolomide is an oral chemotherapy with a favorable side-effect profile that has shown activity against pituitary adenomas. Its non-overlapping toxicity and ability to induce rapid tumor regression renders it a potentially important adjunctive treatment. In patients with tumors that cannot be optimally addressed with standard treatments, there may be a role for early initiation of temozolomide.