Hormone-sensitive prostate cancer typically progresses to castration resistant prostate cancer (CRPC) after the androgen deprivation therapy. We investigated the impact of microRNAs (miRs) in the transition of prostate cancer to CRPC. MiR-221/-222 was highly expressed in bone metastatic CRPC tumor specimens. We previously demonstrated that transient overexpression of miR-221/-222 in LNCaP promoted the development of the CRPC phenotype. In current study, we show that stably overexpressing miR-221 confers androgen independent (AI) cell growth in LNCaP by rescuing LNCaP cells from growth arrest at G1 phase due to the lack of androgen. Overexpressing of miR-221 in LNCaP reduced the transcription of a subgroup of androgen-responsive genes without affecting the androgen receptor (AR) or AR-androgen integrity. By performing systematic biochemical and bioinformatical analyses, we identified two miR-221 targets, HECTD2 and RAB1A, which could mediate the development of CRPC phenotype in multiple prostate cancer cell lines. Downregulation of HECTD2 significantly affected the androgen-induced and AR-mediated transcription, and downregulation of HECTD2 or RAB1A enhances AI cell growth. As a result of the elevated expression of miR-221, expression of many cell cycle genes was altered and pathways promoting epithelial to mesenchymal transition/tumor metastasis were activated. We hypothesize that a major biological consequence of upregulation of miR-221 is reprogramming of AR signaling, which in turn may mediate the transition to the CRPC phenotype.

Ischemia-reperfusion injury is a common feature of ischemic stroke, which occurs when blood supply is restored after a period of ischemia. Reperfusion can be achieved either by thrombolysis using thrombolytic reagents such as tissue plasminogen activator (tPA), or through mechanical removal of thrombi. Spontaneous reperfusion also occurs after ischemic stroke. However, despite the beneficial effect of restored oxygen supply by reperfusion, it also causes deleterious effect compared with permanent ischemia. With the recent advancement in endovascular therapy including thrombectomy and thrombus disruption, reperfusion-injury has become an increasingly critical challenge in stroke treatment. It is therefore of extreme importance to understand the mechanisms of ischemia-reperfusion injury in the brain in order to develop effective therapeutics. Accumulating experimental evidence have suggested that the mechanisms of ischemia-reperfusion injury include oxidative stress, leukocyte infiltration, platelet adhesion and aggregation, complement activation, mitochondrial mediated mechanisms, and blood-brain-barrier (BBB) disruption, which altogether ultimately lead to edema or hemorrhagic transformation (HT) in the brain. Potential therapeutic strategies against ischemia-reperfusion injury may be developed targeting these mechanisms. In this review, we briefly discuss the pathophysiology and cellular and molecular mechanisms of cerebral ischemia-reperfusion injury, and potential therapeutic strategies.

ER+ breast cancers depend on ER signaling throughout disease progression, including after acquired resistance to existing endocrine agents, providing a rationale for further optimization and development of ER-targeting agents. Fulvestrant is unique amongst currently approved ER ligand therapeutics due to its classification as a full ER antagonist, which is thought to be achieved through degradation of ERα protein. However, the full clinical potential of fulvestrant is believed to be limited by poor physiochemical properties and exposure limitations due to its administration by intramuscular injection. Strategies to generate orally bioavailable molecules that retain fulvestrant's full antagonist profile but with considerably improved drug-like properties are thus being widely employed to identify next generation ER therapeutics. However, we find that therapeutic candidates that have recently emerged from prospective optimization of ER degradation, including GDC-0810 and GDC-0927, are not mechanistically equivalent. GDC-0810, GDC-0927, and fulvestrant display unique profiles in terms of ER degradation, transcriptional phenotypes and anti-proliferative potential across a panel of ER+ breast cancer cell lines. In HCI-011 (ER.WT) and HCI-013 (ER.Y537S) ER+ patient-derived breast cancer xenograft (PDX) models, GDC-0927 achieves more robust transcriptional suppression of ER than GDC-0810, and also and greater efficacy. Although displaying a more desirable mechanistic profile than GDC-0810, GDC-0927 has more rapid clearance and poor oral bioavailability, leading to a high pill burden and potential exposure limitation. Here, we describe for the first time GDC-9545, in which the distinct liabilities of GDC-0810, GDC-0927 and fulvestrant are addressed. GDC-9545 is a non-steroidal ER ligand that is highly potent in competing with estradiol for binding and in driving an antagonist conformation within the ER ligand binding domain. Like fulvestrant, and displaying some improvements over GDC-0927, GDC-9545 consistently induces ER turnover and drives deep transcriptional suppression of ER, resulting in robust in vitro anti-proliferative activity. GDC-9545 exhibits reduced metabolism and increased oral bioavailability relative to GDC-0927, resulting in an overall improved oral exposure in multiple species. As a result of both its mechanistic pharmacology and improved oral exposure, GDC-9545 can achieve the same degree of anti-tumor activity as GDC-0927 but at 100-fold lower doses in the HCI-013 PDX model. The in vivo efficacy of GDC-9545 in this model is greater than GDC-0810 and fulvestrant at clinically relevant exposures. The highly potent in vivo efficacy of GDC-9545 likely arises due to the particular combination of high binding potency, full suppression of ER signaling, and an improved DMPK profile when compared to GDC-0927 and fulvestrant. GDC-9545 is currently being evaluated in Phase 1 clinical trials (ClinicalTrials.gov Identifier: NCT03332797). Citation Format: Metcalfe C, Ingalla E, Blake RA, Chang J, Daemen A, De Bruyn T, Giltnane JM, Guan J, Hafner M, Hartman S, Kategaya L, Kleinheinz T, Liang J, Mody V, Nannini M, Oeh J, Ubhayakar S, Wertz I, Young A, Zbieg J, Zhou W, Sampath D, Friedman LS, Wang X. GDC-9545: A novel ER antagonist and clinical candidate that combines desirable mechanistic and pre-clinical DMPK attributes [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-04-07.