自噬在卡麦角林治疗中的作用及新机制探索

Prolactinoma is the most common type of functioning pituitary adenomas and cabergoline (CAB) is the first-line choice of treatment. Previous studies mainly demonstrated that CAB induced the apoptosis of tumor cells and the decrease of PRL secretion through activating dopamine 2 receptor. However, the mechanisms of CAB involving in the regulation of autophagy remain largely unclear. Recent studies indicated that majority of chemotherapeutic drugs could induce autophagy. Our preliminary experiment demonstrated that CAB induced autophagy by inhibiting mTOR signal pathway, moreover, knockdown of autophagy-relative gene p62 could reduce the sensitivity of pituitary adenoma cells to CAB treatment. In order to investigate the function and novel mechanism of autophagy in CAB treatment, we will further confirm in this proposed study ① whether regulation of autophagy-relative genes can change the sensitivity of pituitary adenoma cells to CAB treatment in vitro and in vivo; ② the relationship between tumor cell autophagy and apoptosis induced by CAB; ③ the approach of autophagy induced by CAB; ④ the differential expression of key autophagy-relative genes between clinically sensitive- and resistant- prolactinomas in order to guide the drug therapy. This proposed study for the first time investigates the function and novel mechanism of autophagy in cabergoline treatment and regulation of the autophagy level sensitizes the pituitary tumor cells to CAB treatment. If successful, the findings from this study will give us insight into the novel mechanism of CAB treatment to prolactinomas and provide us a new avenue for treatment of clinical dopamine-resistant prolactinomas, which has far-reaching clinical significance and academic value.

垂体泌乳素腺瘤是最常见的功能性垂体腺瘤，卡麦角林(CAB)为首选治疗。以往针对CAB的作用机制研究集中在激活多巴胺2型受体诱导肿瘤细胞凋亡和PRL分泌减少上，而除此之外的机制仍然不详。目前研究表明，大多数肿瘤化疗药物能诱导自噬。我们前期预实验证实CAB通过抑制mTOR通路诱导垂体肿瘤细胞发生自噬，敲低自噬相关基因p62的表达能减弱CAB的治疗效果。为了明确自噬在CAB治疗中的作用及机制，本课题将进一步在细胞水平和在体水平调控自噬相关基因的表达来观察CAB治疗效果；阐明细胞自噬和凋亡之间的关系；CAB诱导自噬的作用途径；同时，在临床标本上验证关键自噬相关基因的差异表达，指导临床用药。本课题首次研究自噬在CAB治疗中的作用及机制，以及调节自噬用以增强CAB的治疗效果。如果实验成功，将从全新的角度阐明CAB的作用机制，同时将有助于解决耐药泌乳素腺瘤的临床治疗难题，具有深远的临床意义和学术价值。

卡麦角林（CAB）是治疗垂体泌乳素腺瘤的首选药物，主要为多巴胺2型受体激动剂，能促进肿瘤细胞凋亡和泌乳素分泌减少，然而其作用机制不清楚；而且，临床上对于耐药的泌乳素腺瘤，缺乏有效的治疗手段。该课题在我们以往两项国自然（30800347和81271523）发现的基础上，进一步阐明了药物作用的全新机制，主要是自噬在其中的作用，重要发现有如下三点：①CAB通过抑制mTOR通路诱导垂体肿瘤细胞发生自噬，同时抑制溶酶体的功能，阻滞了自噬潮，表现为p62的集聚，从而发生自噬依赖性死亡机制（oncotarget，2016）。②氯喹作为自噬抑制剂，在临床上常作为化疗增敏剂。我们发现，氯喹联合卡麦角林可明显促进细胞死亡，抑制肿瘤生长，尤其对耐药的病例，可以逆转耐药治疗（JCEM，2017）。并以此为基础，建立了卡麦角林联合氯喹治疗耐药泌乳素瘤的多中心临床研究中心（NCT03400865），以期基础研究向临床的有效转化。③卡麦角林主要通过激活多巴胺受体D5，抑制SOD1活性，导致ROS水平增加，从而抑制mTOR信号通路，诱导细胞自噬性死亡；同时，在体内水平上证实了卡麦角林可抑制肿瘤细胞的生长（autophagy，2017）。该课题从自噬这一全新的角度阐明CAB治疗垂体泌乳素腺瘤的作用机制，补充和完善了过去对于药物作用的认识；另外，氯喹联合卡麦角林治疗加强了药物对肿瘤细胞的杀伤作用，对于临床上解决耐药泌乳素腺瘤的治疗难题，具有重大的临床意义。