| 其他摘要 | Prostate cancer is one of the most common malignant tumors in genitourinary system threatening the older men. The biggest obstacle of the treatment to clinical refractory prostate cancer is still unknown to the mechanisms mediating the conversion to androgen independent prostate cancer. Despite a lot of work have been done, the existing research results still cannot well interpret the androgen independent phenotype conversion mechanism. To this thorny clinical problem, we carried out our research in an LNCaP progression cell model (LNCaP/LNCaP-AI-F), so that we can escape the adverse effects from highly tumor heterogeneity. Using RNA-seq and comparative analysis the transcriptomes of both cell lines in gene expression, alternative splicing and fusion genes, we tried to find the potential mechanism mediating the conversion to androgen independent phenotype. The comparative analysis identified 788 differentially expressed genes (DEGs) and classed them into four categories according to functional related GO (gene ontology) annotation analysis, including: (1) Involved in neuroendocrine-like cell morphology and the associated functional activities; (2) Involved in chromatin assembly, lipids and steroids metabolism and the response to various stimuli; (3) Cell adhesion, migration, differentiation and proliferation-associated; (4) Involved in signal transduction pathways. Such as Notch, SAPK and IGF1 signaling pathways seemed to play important roles. Further IPA analysis of DEGs identified an AR and KLK3-centred network functionally related to cellular development, cellular proliferation, and organismal development, which may contribute to the emergence of androgen independent phenotype. In addition, some characteristic changes are of concern in the conversion to androgen-independent phenotype, such as neuroendocrine phenotype associated structural and functional changes, the ability to endure stress and surpressed response to various stimuli, and tumor stem cell-like characteristics. We identified 315 differentially alternative splicing events. Of particular note, AR not only upregulates its expression level, but also changes its variants and expands its CAG repeat length significantly. We also found 22 potential fusion genes and 8 LNCaP-AI-F specific fusion genes. Among these fusion genes, EIF2AK1-ATR and GLYR1-SLC9A8 are predicted to be cell damaging and oncogenic on function. Based on the critical roles of AR in tumorigenesis and progression of prostate cancer in previous studies, as well as the prominent role in LNCaP progression cell model, we identified the core role of AR in the conversion to androgen dependence. In addition, we conducted an in-depth analysis of AR CAG repeat expansion at mRNA level in androgen independent phenotype conversion, simultaneously we also investigated the GGC repeat, another important regulatory factor on AR function. Two representative androgen independent sublines were analyzed, and the altered AR CAG and GGC repeat length were identified in androgen independent phenotype conversion process, which highlight their potential roles in androgen independent phenotype conversion process. Finally, we have also unexpectedly identified a missing GA dinucleotide followed GGC repeat sequence, which presumably produce a highly truncated AR protein just retaining transcriptional activation domain and may play role in the occurrence of prostate cancer and androgen independent phenotype conversion. In conclusion, through comparative analysis of RNA-seq in an LNCaP progression cell model, we identified an AR-centered, involving in multiple changes of AR, including AR expression level, AR variants, AR T877A mutation, CAG and GGC repeat polymorphism and GA deletion, synergistically play role in androgen independent phenotype conversion. Especially, we firstly found significant changes of AR gene CAG and GGC repeat sequences’ polymorphisms in androgen independent phenotype conversion. We also firstly identified a GA deletion in prostate cancer cells，and the functional speculation suggested that this mutant AR may play role in prostate cancer tumorigenesis and androgen independent phenotype conversion. Further clinical validation is helpful to confirm the validity of these results and provide experimental and theoretical evidences to clinical diagnosis and treatment, and is also helpful to reveal the transformation mechanism of androgen independent phenotype. |
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