OBJECTIVETo explore the role of aquaporin-1 (AQP1) gene in erythroid differentiation of erythroleukemia K562 cells induced by retinoic acid (RA).

METHODSK562 cells were cultured in the presence of 1 µmol/L RA for varying lengths of time, and γ-globin mRNA expression and hemoglobin content in the cells were detected by real-time PCR (RT-PCR) and ultraviolet spectrophotometry, respectively, to evaluate the erythroid differentiation of K562 cells. RT-PCR and Western blotting were used to examine AQP1 expression in the cells following RA treatment. A retroviral expression vector of AQP1 small interfering RNA (pSUPER-retro-puro-shAQP1) was constructed and transfected into K562 cells to establish a K562 cell line with stable AQP1 down-regulation (K562-shAQP1), in which the changes in γ-globin and hemoglobin expressions after RA treatment were detected.

RESULTSRA treatment significantly increased γ-globin and hemoglobin expressions in K562 cells (P<0.01), causing also significantly enhanced AQP1 mRNA and protein expressions over time (P<0.01). Transfection with the recombinant plasmids pSuper-retro-puro-shAQP1 resulted in stable AQP1 suppression in K562 cells (P<0.01), which showed markedly reduced γ-globin and hemoglobin expressions after RA induction as compared to the control K562 cells (P<0.01).

CONCLUSIONK562 cells show a significant increase of AQP1 expression after RA-induced erythroid differentiation, and suppression of AQP1 expression can partially block the effect of RA, suggesting the important role of AQP1 in RA-induced erythroid differentiation of K562 cells.

Aquaporin 1 ; antagonists & inhibitors ; metabolism ; Cell Differentiation ; drug effects ; Humans ; K562 Cells ; Leukemia, Erythroblastic, Acute ; metabolism ; RNA, Messenger ; genetics ; RNA, Small Interfering ; genetics ; Tretinoin ; pharmacology

PURPOSE: Renal cell carcinoma (RCC) and melanoma have been considered ‘radioresistant’ due to the fact that they do not respond to conventionally fractionated radiation therapy. Stereotactic radiosurgery (SRS) provides high-dose radiation to a defined target volume and a limited number of studies have suggested the potential effectiveness of SRS in radioresistant histologies. We sought to determine the effectiveness of SRS for the treatment of patients with radioresistant brain metastases.MATERIALS AND METHODS: We performed a retrospective review of our institutional database to identify patients with RCC or melanoma brain metastases treated with SRS. Treatment response were determined in accordance with the Response Evaluation Criteria in Solid Tumors.RESULTS: We identified 53 radioresistant brain metastases (28% RCC and 72% melanoma) treated in 18 patients. The mean target volume and coverage was 6.2 ± 9.5 mL and 95.5% ± 2.9%, respectively. The mean prescription dose was 20 ± 4.9 Gy. Forty lesions (75%) demonstrated a complete/partial response and 13 lesions (24%) with progressive/stable disease. Smaller target volume (p < 0.001), larger SRS dose (p < 0.001), and coverage (p = 0.008) were found to be positive predictors of complete response to SRS.CONCLUSION: SRS is an effective management option with up to 75% response rate for radioresistant brain metastases. Tumor volume and radiation dose are predictors of response and can be used to guide the decision-making for patients with radioresistant brain metastases.
Brain ; Carcinoma, Renal Cell ; Humans ; Melanoma ; Neoplasm Metastasis ; Prescriptions ; Radiosurgery ; Response Evaluation Criteria in Solid Tumors ; Retrospective Studies ; Tumor Burden

Although the epigenetic regulatory protein histone deacetylase 6 (HDAC6) has been recently implicated in the etiology of Alzheimer's disease (AD), little is known about the role of HDAC6 in the etiopathogenesis of AD and whether HDAC6 can be a potential therapeutic target for AD. Here, we performed positron emission tomography (PET) imaging in combination with histopathological analysis to better understand the underlying pathomechanisms of HDAC6 in AD. We first developed [¹⁸F]PB118 which was demonstrated as a valid HDAC6 radioligand with excellent brain penetration and high specificity to HDAC6. PET studies of [¹⁸F]PB118 in 5xFAD mice showed significantly increased radioactivity in the brain compared to WT animals, with more pronounced changes identified in the cortex and hippocampus. The translatability of this radiotracer for AD in a potential human use was supported by additional studies, including similar uptake profiles in non-human primates, an increase of HDAC6 in AD-related human postmortem hippocampal tissues by Western blotting protein analysis, and our ex vivo histopathological analysis of HDAC6 in postmortem brain tissues of our animals. Collectively, our findings show that HDAC6 may lead to AD by mechanisms that tend to affect brain regions particularly susceptible to AD through an association with amyloid pathology.