Repair of DNA damage induced by the novel nucleoside analogue CNDAG through homologous recombination

We postulate that the deoxyguanosine analogue CNDAG [9-(2-C-cyano-2-deoxy-1-β-d-arabino-pentofuranosyl)guanine] likely causes a single-strand break after incorporation into DNA, similar to the action of its cytosine congener CNDAC, and that subsequent DNA replication across the unrepaired nick would generate a double-strand break. This study aimed at identifying cellular responses and repair mechanisms for CNDAG prodrugs, 2-amino-9-(2-C-cyano-2-deoxy-1-β-d-arabino-pentofuranosyl)-6-methoxy purine (6-OMe) and 9-(2-C-cyano-2-deoxy-1-β-d-arabino-pentofuranosyl)-2,6-diaminopurine (6-NH2). Each compound is a substrate for adenosine deaminase, the action of which generates CNDAG. Growth inhibition assay, clonogenic survival assay, immunoblotting, and cytogenetic analyses (chromosomal aberrations and sister chromatid exchanges) were used to investigate the impact of CNDAG on cell lines. The 6-NH2 derivative was selectively potent in T cell malignant cell lines. Both prodrugs caused increased phosphorylation of ATM and its downstream substrates Chk1, Chk2, SMC1, NBS1, and H2AX, indicating activation of ATM-dependent DNA damage response pathways. In contrast, there was no increase in phosphorylation of DNA-PKcs, which participates in repair of double-strand breaks by non-homologous end-joining. Deficiency in ATM, RAD51D, XRCC3, BRCA2, and XPF, but not DNA-PK or p53, conferred significant clonogenic sensitivity to CNDAG or the prodrugs. Moreover, hamster cells lacking XPF acquired remarkably more chromosomal aberrations after incubation for two cell cycle times with CNDAG 6-NH2, compared to the wild type. Furthermore, CNDAG 6-NH2 induced greater levels of sister chromatid exchanges in wild-type cells exposed for two cycles than those for one cycle, consistent with increased double-strand breaks after a second S phase. CNDAG-induced double-strand breaks are repaired mainly through homologous recombination.     

Effects of α1-adrenergic receptor antagonists on the development and progression of urothelial cancer

We recently demonstrated that silodosin, a selective α₁-blocker often prescribed for the symptomatic treatment of benign prostatic hyperplasia (BPH), could inactivate a c-fos proto-oncogene regulator ELK1 in bladder cancer cells possessing a functional androgen receptor (AR). However, the clinical impact of α₁-blockers on the development and progression of bladder cancer remained poorly understood. In the present study, we investigated if α₁-blockers clinically used, including silodosin, tamsulosin, and naftopidil, could prevent the neoplastic/malignant transformation and cell growth, using non-neoplastic urothelial SVHUC sublines with carcinogen/MCA challenge and bladder cancer lines, respectively. Bladder cancers in men treated with silodosin, tamsulosin, or naftopidil for their BPH were then compared. Silodosin at 1-10 µM significantly inhibited the neoplastic transformation of MCA-SVHUC-AR cells, but not that of AR-negative MCA-SVHUC-control cells. In MCA-SVHUC-AR, silodosin significantly reduced the expression levels of oncogenes (c-fos/NF-κB1) and induced those of tumor suppressors (p27/PTEN). However, tamsulosin (up to 1 µM) or naftopidil (up to 10 µM) failed to significantly inhibit the neoplastic transformation of AR-positive or AR-negative urothelial cells. Similarly, cell proliferation/migration of AR-positive bladder cancer lines was considerably inhibited only by silodosin. Meanwhile, the incidence of bladder cancer in patients with silodosin [49/540 (9.1%)] was marginally lower, compared to those with tamsulosin [64/523 (12.2%); P=0.094] or tamsulosin or naftopidil [64+28/523+236 (12.1%); P=0.082]. There were no significant differences in tumor grade/stage among the 3 cohorts. Outcome analysis revealed lower risks for disease progression of non-muscle-invasive bladder tumors in the silodosin group than in the naftopidil group (P=0.011) or tamsulosin+naftopidil groups (P=0.035). Similarly, silodosin patients with muscle-invasive tumor had lower risks for disease progression, compared with tamsulosin (P=0.006) or tamsulosin+naftopidil (P=0.028) patients. Multivariate analysis further showed that silodosin treatment in those with non-muscle-invasive tumor was associated with improved progression-free survival, compared with naftopidil (hazard ratio=0.086; 95% confidence interval=0.008-0.905; P=0.041) or tamsulosin/naftopidil (hazard ratio=0.128; 95% confidence interval=0.016-1.036; P=0.054) treatment. Our in vitro studies thus indicate that both urothelial tumorigenesis and tumor growth are inhibited by silodosin, but not by tamsulosin or naftopidil. Clinical data further suggest that even pharmacological doses (e.g. 0.1 µM) of silodosin contribute to preventing bladder cancer progression.     

Quantitative analysis of the intra-beam respiratory motion with baseline drift for respiratory-gating lung stereotactic body radiation therapy

This study aimed to quantitatively clarify the baseline drift for each respiratory cycle in two respiratory-gating methods using the intra-beam respiratory motion data of lung cancer patients. The residual motion and dose distribution were calculated based on intra-beam respiratory motion data with the baseline drift. To quantify the baseline drift during irradiation, it was defined as the inclination between the detected expiration point and the expiration point in the next cycle in the anterior–posterior (AP), cranial–caudal (CC) and left–right (LR) directions obtained using an in-house programme. The baseline drift value reached up to 0.74 mm/s in the CC direction as per the respiratory motion data of 10 patients. The homogeneity index (HI) of the phase-gating method tended to increase because the target was irradiated even when the amplitude position of the target differed from period to period. In contrast, the amplitude-gating method enabled irradiation considering the amplitude position of the target because the gating window was set considering the amplitude position of the respiratory motion. The respiratory-gating methods and respiratory phase in respiratory-gating lung stereotactic body radiation therapy (SBRT) must be determined based on the respiratory motion of the patients.     

Subtle disruption of the middle cerebellar peduncles in patients with schizophrenia

Diffusion tensor imaging (DTI) was used to investigate subtle disruption in the middle cerebellar peduncles in patients with schizophrenia. Fractional anisotropy (FA) was measured in 25 patients with schizophrenia and 21 healthy subjects using DTI. The FA of the right and left middle cerebellar peduncles was significantly lower in the schizophrenic patients compared to healthy subjects. FA in the left middle cerebellar peduncles was significantly correlated with the dosage of neuroleptics in patients with schizophrenia. There were no significant differences of mean diffusivity in the right and left middle cerebellar peduncles between patients with schizophrenia and healthy subjects. The findings of the study suggest that antipsychotics may improve the subtle disruption in the middle cerebellar peduncles in patients with schizophrenia.     

Conservative treatment of ruptured vertebrobasilar dissecting aneurysm

Ruptured vertebrobasilar dissecting aneurysm is usually treated surgically because rebleeding negatively affects outcome. However, the risk of rebleeding decreases markedly once several hours have passed from the initial bleeding. Moreover, surgery-related complications are not rare. We describe seven patients with ruptured vertebrobasilar dissecting aneurysm. To prevent rebleeding during the acute stage, we treated all seven patients conservatively with fentanyl instead of emergency surgery. During the follow-up period (mean 20 months), no patient suffered rebleeding. Conservative treatment with fentanyl administration may be a good option for management of ruptured vertebrobasilar dissecting aneurysm during the acute stage.