Disturbed alternative splicing of growth hormone is associated with increased expression of SF2/ASF oncogene in pituitary adenoma
A. Piekielko-Witkowska1, H. Kedzierska1, B. Rybicka1, P. Nauman2, Z. Bonicki3 & A. Nauman1
Introduction: Pituitary adenomas account for 1025% of all intracranial tumours. Although rarely malignant, they are associated with high morbidity due to severe endocrine effects and difficult surgical access. Alternative splicing (AS) consists in selective removal of non-coding regions from pre-mRNA and joining of coding regions to produce mRNA variants that may be further translated. AS is regulated by splicing factors and is often disturbed in cancer. AS of growth hormone (GH) leads to synthesis of five transcript variants. Variant 3 encodes a 17.5 kDa protein which is a dominant negative and blocks secretion of biologically active GH proteins encoded by variants 1 and 2. AS of GH is regulated by splicing factors SF2/ASF and SC35. SF2/ASF is an oncogenic protein. In this study we hypothesized that AS of GH may be disturbed in pituitary tumours.
Methods: The study involved 28 human pituitary adenomas (21 gonadotroph adenomas and 7 other types adenomas) and five non-neoplastic pituitary tissue specimens obtained with the permission of local Bioethics Committee. The used methods were: RNA isolation, reverse transcription, PCR using primers designed to detect GH splice variants, cloning using pGEM-Teasy vector, sequencing, and real-time PCR.
Results: Using GH-specific PCR we found that while in control samples only transcript variant 1 was expressed, in adenoma samples variants 1, 2, and 3 were present. This was confirmed by cloning and sequencing of all three variants. Variant 3 was expressed in 20 (71%) of analyzed adenoma specimens. This was associated with statistically significantly increased expression of SF2/ASF and SC35 mRNAs in gonadotroph adenomas when compared with control samples.
Conclusion: Alternative splicing of GH is disturbed in pituitary adenomas, possibly due to impaired expression of splicing factors SF2/ASF and SC35. Altered splicing of GH may possibly serve as a neoplastic marker in pituitary adenomas.
Supported by NCN grant NN401532140.
Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.
Funding: This work was supported, however funding details unavailable.