Hiromichi Ishiyama

The kinetochore protein Bub1 participates in the DNA damage response

The DNA damage response (DDR) and the spindle assembly checkpoint (SAC) are two critical mechanisms by which mammalian cells maintain genome stability. There is a growing body of evidence that DDR elements and SAC components crosstalk. Here we report that Bub1 (budding uninhibited by benzimidazoles 1), one of the critical kinetochore proteins essential for SAC, is required for optimal DDRs. We found that knocking-down Bub1 resulted in prolonged H2AX foci and comet tail formation as well as hypersensitivity in response to ionizing radiation (IR). Further, we found that Bub1-mediated Histone H2A Threonine 121 phosphorylation was induced after IR in an ATM-dependent manner. We demonstrated that ATM phosphorylated Bub1 on serine 314 in response to DNA damage in vivo. Finally, we showed that ATM-mediated Bub1 serine 314 phosphorylation was required for IR-induced Bub1 activation and for the optimal DDR. Together, we elucidate the molecular mechanism of DNA damage-induced Bub1 activation and highlight a critical role of Bub1 in DDR.

Spontaneous Regression of Thoracic Metastases While Progression of Brain Metastases After Stereotactic Radiosurgery and Stereotactic Body Radiotherapy for Metastatic Renal Cell Carcinoma: Abscopal Effect Prevented by the Blood-Brain Barrier?

Department of Radiation Oncology, The Methodist Hospital, Research Institute, ouston, TX Department of Radiation Oncology, The Methodist Hospital, Houston, TX Department of Radiology and Radiation Oncology, Kitasato University School of edicine, Sagamihara, Kanagawa, Japan Department of Radiation Oncology, Cancer Hospital (Institute), Chinese Academy f Medical Sciences, Peking Union Medical College, Beijing, China Department of Radiology, The Methodist Hospital, Houston, TX Medical Branch, The University of Texas, Houston, TX Division of Oncology, The University of Texas, Health Science Center, Memorial ermann Cancer Center, Houston, TX

The alkylphospholipid, perifosine, radiosensitizes prostate cancer cells both in vitro and in vivo

BackgroundPerifosine is a membrane-targeted alkylphospholipid developed to inhibit the PI3K/Akt pathway and has been suggested as a favorable candidate for combined use with radiotherapy. In this study, we investigated the effect of the combined treatment of perifosine and radiation (CTPR) on prostate cancer cells in vitro and on prostate cancer xenografts in vivo.MethodsHuman prostate cancer cell line, CWR22RV1, was treated with perifosine, radiation, or CTPR. Clonogenic survival assays, sulforhodamine B cytotoxity assays and cell density assays were used to assess the effectiveness of each therapy in vitro. Measurements of apoptosis, cell cycle analysis by flow cytometry and Western blots were used to evaluate mechanisms of action in vitro. Tumor growth delay assays were used to evaluate radiation induced tumor responses in vivo.ResultsIn vitro, CTPR had greater inhibitory effects on prostate cancer cell viability and clonogenic survival than either perifosine or radiation treatment alone. A marked increase in prostate cancer cell apoptosis was noted in CTPR. Phosphorylation of AKT-T308 AKT and S473 were decreased when using perifosine treatment or CTPR. Cleaved caspase 3 was significantly increased in the CTPR group. In vivo, CTPR had greater inhibitory effects on the growth of xenografts when compared with perifosine or radiation treatment alone groups.ConclusionsPerifosine enhances prostate cancer radiosensitivity in vitro and in vivo. These data provide strong support for further development of this combination therapy in clinical studies.

Is there an increase in genitourinary toxicity in patients treated with transurethral resection of the prostate and radiotherapy? A systematic review.

Purpose:Transurethral resection of the prostate (TURP) is considered by some as a risk factor for genitourinary (GU) toxicity after radiotherapy (RT). However, there are conflicting results regarding the interaction between RT and TURP with respect to GU toxicity. The purpose of this report is to review the published data concerning TURP before or after RT and its effect on urinary complication. Methods and Materials:A systematic literature review based on database searches in MEDLINE, EMBASE, Pubmed, Ovid, and Chochrane Library. The eligibility criteria of final review were (1) definitive RT for prostate cancer is reported; (2) comparison of GU toxicities between patients with and without TURP is reported; (3) minimum 5 patients after TURP are included. Results:Twelve articles regarding overall GU toxicity, 15 articles regarding urinary incontinence, and 13 articles regarding urinary or bladder neck stricture met eligibility criteria, and they were included in the final review. A quantitative synthesis from the data of selected articles was impossible because of variable grading systems and variable definitions in their comparisons between patients with and without TURP. However, most published articles demonstrated the increased risk of GU toxicity with TURP in patients treated with RT. Conclusions:Our systematic review strongly suggests that TURP is one of the risk factors of GU toxicity after RT. This needs to be taken seriously when prostate cancer patients with TURP are considered for RT either external beam or brachytherapy.

Stereotactic body radiation therapy for prostate cancer

Stereotactic body radiation therapy (SBRT) is a promising treatment option for prostate cancer. Hypofractionation regimens, such as SBRT, may be more advantageous compared with conventional regimens because low α:β ratio of prostate cancer has high sensitivity to dose per fraction. In addition, a smaller and tighter margin with SBRT is expected to provide a low toxicity rate without reducing tumor control. The purpose of this article is to examine radiobiological, technical and clinical aspects of SBRT for prostate cancer.

Salvage intensity modulated radiotherapy using endorectal balloon after radical prostatectomy: Clinical outcomes

To evaluate biochemical non‐evidence of disease and adverse events of salvage intensity‐modulated radiotherapy using an endorectal balloon for prostate cancer patients after radical prostatectomy.

Stereotactic body radiotherapy (SBRT)/stereotactic ablative body radiotherapy (SABR) for “radioresistant” renal cell carcinoma (RCC)

Stereotactic body radiation therapy (SBRT) developed as a result of technological advances in image-guided radiotherapy (IGRT), treatment planning, body stereotaxis, and motion management allows precise delivery of biologically potent dose to the tumor targets. Preclinical and clinical studies of SBRT have now demonstrated very promising results without significant toxicity in the treatment of primary and metastatic renal cell carcinoma (RCC) lesions. The additional benefit of SBRT may be the abscopal (distant bystander) effect, mediated by an immunological response. In addition, high single-dose radiation such as SBRT may overcome radioresistance of RCC caused by the von Hippel-Lindau (VHL) tumor-suppressor gene mutation and hypoxia-inducible factor-1 (HIF-1). As radiotherapy is not considered as a definitive treatment of RCC, a combination of radiotherapy and various systemic therapies has not been examined. However, SBRT could change the role of radiotherapy for RCC, and the development of combination therapy needs to be explored in the future trials. This review focused on the role of SBRT in the treatment of primary and metastatic RCC.

Schedule-dependent interactions between perifosine and radiotherapy in prostate cancer

ObjectivePerifosine was developed as a membrane-targeted alkylphospholipid that inhibits the PI3K/AKT pathway and has been suggested as a favorable candidate for combined use of radiotherapy. To better define the optimal schedule for this combination, we investigated schedule-dependent cytotoxic effects of perifosine and radiotherapy against prostate carcinoma cell lines in vitro.MethodsHuman prostate cancer cell line CWR22RV1 and LNCaP were incubated with perifosine (5, 20, 40xa0μM) and treated with radiation (2, 4, 6, 8xa0Gy). Three different schedules were used: simultaneous treatment (Ru2009+u2009P), perifosine followed by radiotherapy (Pu2009→u2009R), and vice versa (Ru2009→u2009P). Cell growth inhibition was determined by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay. The effects of drug combinations at the concentration producing 80xa0% cell growth inhibition were analyzed by the isobologram method (Steel and Peckham). Colony formation assay was also conducted to confirm the result of MTS assay. Western blot analysis was used to explore the molecular mechanism of action for the combination of perifosine and irradiation.ResultsThe Ru2009→u2009P schedule showed the most significant cell growth inhibition when compared to other schedules (pu2009<u20090.01). This schedule produced an additive effect for CWR22RV1 and a supra-additive effect for LNCaP. The reverse sequence produced a protective effect for CWR22RV1 and an additive/sub-additive effect for LNCaP. Ru2009+u2009P schedule showed intermediate effect between Ru2009→u2009P and Pu2009→u2009R schedules. Western blot analysis showed that phosphorylation of AKT (indicative of anti-apoptosis activity) was inhibited by this combination therapy except for Pu2009→u2009R schedule.ConclusionOur new findings suggest that Ru2009→u2009P would be the optimal schedule for this combination treatment strategy. The finding is also important as it explains the negative outcomes of several previously reported trials combining radiotherapy and perifosine in the treatment of various tumors. Applications of this schedule-dependent approach might be beneficial for the treatment of prostate cancer and other tumors.

Serum testosterone level after intensity-modulated radiotherapy in low-risk prostate cancer patients: does testicular dose correlate with testosterone level?

PurposeThe purpose of this study is to evaluate the relationship between testicular dose and serum testosterone (TE) level in low-risk prostate cancer patients treated with intensity-modulated radiotherapy (IMRT).Methods and materialsThis study was conducted as a subset analysis of a previously published prospective clinical trial combining IMRT and gene therapy. To the best of our knowledge, this gene therapy had no significant effect on patient’s TE level. Twenty-nine patients with low-risk prostate cancer, who underwent combined treatment of 76xa0Gy in 35 fractions and gene therapy without any androgen deprivation, were included in this study. No pelvic irradiation was used. TE levels were examined before, during, and after IMRT. The relationship between mean testicular dose and post-treatment TE levels was assessed.ResultsMean testicular dose was 5.3xa0Gy (range, 1.7 to 10.7xa0Gy). Mean baseline TE level was 310xa0ng/dl (range, 113 to 530xa0ng/dl). Before treatment, 66% of the patients already had hypogonadism. The mean TE levels were significantly decreased at 12, 24, 30, 36xa0months after treatment when compared to those at baseline (Pu2009<u20090.05). A relatively weak correlation was seen between testicular dose and ratio of post-treatment TE level to baseline. However, this correlation was statistically significant only at 4xa0months after treatment. There was no significant relationship between TE levels and PSA values.ConclusionOur study showed decreased post-treatment TE levels of prostate cancer patients after IMRT. A relatively weak correlation was seen between testicular dose and ratio of post-treatment TE level to baseline.