Targeting Prolyl Peptidases in Tamoxifen Resistant Breast Cancer

 说明(申请人提供)乳腺癌是最常见的女性癌症，大约70-75%的病例表达雌激素受体α(ERα)。他莫昔芬()是一种雌激素受体拮抗剂，是绝经前ERα阳性乳腺癌的标准内分泌治疗药物。不幸的是，几乎所有晚期肿瘤都会对内分泌治疗产生抵抗。Pro-羧基肽酶(PRCP)及其家族成员Pro-endopeptidase(PREP)是Pro-肽酶家族的成员。这些酶裂解神经肽G蛋白偶联受体(GPCR)激动剂来调节GPCR信号。PrCP是在MCF7细胞中促进耐药的因素的遗传筛选中被鉴定出来的。初步数据显示，PRCP的高表达与乳腺癌患者的预后不良相关。PrCP过表达增加AKT-mTOR激活，促进耐药，诱导MCF7移植瘤的自发转移。我们确定了一种有效的PRCP抑制剂，并将其命名为Y-OX。PRCP/PREP耗竭或Y-OX抑制可破坏IRS-1的稳定性，并抑制AKT-mTOR。由于PRCP和PREP裂解GPCR激动剂，我们测试了PRCP/PREP是否以GPCR依赖的方式调节IRS-1和AKT-mTOR通路。我们的数据支持一种模型，在该模型中，PRCP/PREP增加了CaMK2(钙/钙调蛋白激活激酶2)依赖于GPCR的激活，并激活了CaMK2，然后通过抑制AMPK来稳定IRS-1。最后，我们发现Y-OX破坏了雷帕霉素处理的细胞中IRS-1的稳定并抑制了AKT的反馈激活，并且与雷帕霉素联合使用增加了对耐药细胞的杀伤率。基于这些结果，我们推测：1)PRCP/PREP以依赖于gpr和CaMK2的方式维持IRS-1和AKT/mTOR通路，导致耐药和转移；2)原发乳腺肿瘤中PRCP、PREP和/或CaMK2的表达将与耐药和预后不良相关；3)联合抑制PRCP/PREP和mTOR将减少PI3K/AKT的反馈激活，从而改善内分泌耐药和转移性乳腺肿瘤的治疗。

 DESCRIPTION (provided by applicant) Breast cancer is the most common female cancer and approximately 70-75% of cases express estrogen receptor alpha (ERα). Tamoxifen (TAM) is an estrogen receptor antagonist and the standard endocrine therapy for premenopausal women with ERα positive breast cancer. Unfortunately, resistance to endocrine therapy develops in almost all advanced tumors. Prolylcarboxypeptidase (PRCP) and its family member prolylendopeptidase (PREP) are members of the prolyl- peptidase family. These enzymes cleave neuropeptide G-protein coupled receptor (GPCR) agonists to regulate GPCR signaling. PRCP was identified in a genetic screen for factors that promote TAM resistance in MCF7 cells. Preliminary data show high PRCP expression is correlated with worse prognosis in breast cancer patients. PRCP over-expression increased AKT-mTOR activation, promoted TAM resistance, and induced spontaneous metastasis in MCF7 tumor xenografts. We identified a potent inhibitor of PRCP and PREP termed Y-ox. PRCP/PREP depletion or inhibition by Y-ox destabilized IRS-1 and inhibited AKT-mTOR. Because PRCP and PREP cleave peptide GPCR agonists, we tested if PRCP/PREP regulate IRS-1 and the AKT-mTOR pathway in a GPCR-dependent manner. Our data support a model in which PRCP/PREP increase GPCR-dependent activation of CaMK2 (calcium/calmodulin activated kinase 2), and activated CaMK2 then stabilizes IRS-1 by inhibiting AMPK. Finally, we showed Y-ox destabilized IRS-1 and inhibited feedback activation of AKT in rapamycin treated cells and, in combination with rapamycin increased killing of TAM- resistant cells. Based on these results, we hypothesize 1) PRCP/PREP maintain IRS-1 and the AKT/mTOR pathway in a GPCR and CaMK2-dependent manner, leading to TAM resistance and metastasis, 2) PRCP, PREP, and/or CaMK2 expression in primary breast tumors will correlate with TAM resistance and poor prognosis, 3) combined inhibition of PRCP/PREP and mTOR will reduce feedback activation of the PI3K/AKT and consequently improve treatment of endocrine resistant and metastatic breast tumors.