Portrait of Dr. AraiDr. Arai had been working in academic hospitals in Japan as a urologist and has performed clinical and basic research on urological cancers, especially castration-resistant prostate cancer (CRPC). To further understand the molecular basis of CRPC and pursue his career as a surgeon-scientist, he joined the Balk Lab in 2014. Since then, he has dedicated himself to discovering novel therapies for lethal prostate cancer (PCa), primarily targeting the apoptosis pathway. During his time in the Balk Lab, Dr. Arai has also successfully generated a series of patient-derived PCa xenografts (PD Xs), including a BRCA2-deficient model. Using these valuable PDX models he is investigating novel personalized therapies for patients with lethal PCa.

Email Dr. Arai


Postdoctoral Training: Beth Israel Deaconess Medical Center: 2014-present

Ph.D.: Medical Science (Analytical Chemistry), Gunma University (Japan): 2006-2010

M.D.: Gunma University (Japan): 1997-2003

Grant Support

Grant-in-Aid for Young Scientists (25861411), Japan Society for the Promotion of Science: 2013-2015

Research Promotion Grant, The Japanese Foundation for Prostate Research: 2013


  1. Russo JW, Gao C, Bhasin SS, Voznesensky OS, Calagua C, Arai S, Nelson PS, Montgomery B, Mostaghel EA, Corey E, Taplin ME, Ye H, Bhasin M, Balk SP. Downregulation of Dipeptidyl Peptidase 4Accelerates Progression to Castration-Resistant Prostate Cancer. Cancer Res. 2018 Nov 15;78(22):6354-6362. PMID: 30242112.
  2. Arai S, Jonas O, Whitman MA, Corey E, Balk SP, Chen S. Tyrosine Kinase Inhibitors Increase MCL1 Degradation and in Combination with BCLXL/BCL2 Inhibitors Drive Prostate Cancer Apoptosis.Clin Cancer Res. 2018 Nov 1;24(21):5458-5470. PMID: 30021909.
  3. Oki R, Ito K, Suzuki R, Fujizuka Y, Arai S, Miyazawa Y, Sekine Y, Koike H, Matsui H, Shibata Y, Suzuki K. Long-term longitudinal changes in baseline PSA distribution and estimated prevalence of prostate cancer in male Japanese participants of population-based PSA screening.Int J Cancer. 2018 Apr 26. PMID: 29696637.
  4. Oba A, Nakaya N, Saito-Nakaya K, Hasumi M, Takechi H, Arai S, Shimizu N. Psychological distress in men with prostate cancer and their partners before and after cancer diagnosis: a longitudinal study.Jpn J Clin Oncol. 2017 Aug 1;47(8):735-742. PMID: 28505354.
  5. Shibata Y, Arai S, Miyazawa Y, Shuto T, Nomura M, Sekine Y, Koike H, Matsui H, Ito K, Suzuki K. Effects of Steroidal Antiandrogen or 5-alpha-reductase Inhibitor on Prostate Tissue Hormone Content. 2017 May;77(6):672-680. PMID: 28145028.
  6. Shibata Y, Arai S, Honma S. Methodological approach to the intracrine study and estimation of DHEA and DHEA-S using liquid chromatography-tandem mass spectrometry (LC-MS/MS).J Steroid Biochem Mol Biol. 2015 Jan;145:193-9. PMID: 24794825.
  7. Arai S, Matsui H, Ohki R, Miyazawa Y, Koike H, Hashita T, Katsuyama Y, Sekine Y, Nomura M, Shibata Y, Hatori M, Ito K, Yamamoto K, Ohmori S, Suzuki K. Suicide attempt with an overdose of sunitinib.Br J Clin Pharmacol. 2014 Oct;78(4):933-5. PMID: 24645902.
  8. Oba A, Nakaya N, Hasumi M, Ono-Yanaba K, Saito-Nakaya K, Takechi H, Arai S, Shimizu N. Psychosocial longitudinal study profile and distress of couples in relation to the conduct of prostate biopsy.Jpn J Clin Oncol. 2014 May;44(5):463-71. PMID: 24643291.
  9. Shibata Y, Suzuki K, Arai S, Miyoshi Y, Umemoto S, Masumori N, Kamiya N, Ichikawa T, Kitagawa Y, Mizokami A, Sugimura Y, Nonomura N, Sakai H, Honma S, Kubota Y. Impact of pre-treatment prostate tissue androgen content on the prediction of castration-resistant prostate cancer development in patients treated with primary androgen deprivation therapy. 2013 May;1(3):505-11. PMID: 23444052.
  10. Arai S, Shibata Y, Nakamura Y, Kashiwagi B, Uei T, Tomaru Y, Miyashiro Y, Honma S, Hashimoto K, Sekine Y, Ito K, Sasano H, Suzuki K. Development of prostate cancer in a patient with primary hypogonadism: intratumoural steroidogenesis in prostate cancer tissues. 2013 Jan;1(1):169-74. PMID: 23258647.
  11. Arai S, Hasumi M, Shimizu N. Long-term survival and onset of granulomatous pneumonia after lung metastasectomy in a patient with non-muscle-invasive bladder cancer.Int Urol Nephrol. 2012 Oct;44(5):1383-7. PMID: 22653723.
  12. Arai S, Miyashiro Y, Shibata Y, Tomaru Y, Kobayashi M, Honma S, Suzuki K. Effect of castration monotherapy on the levels of adrenal androgens in cancerous prostatic tissues. 2011 Feb;76(3):301-8. PMID: 21147140.
  13. Arai S, Miyashiro Y, Shibata Y, Kashiwagi B, Tomaru Y, Kobayashi M, Watanabe Y, Honma S, Suzuki K. New quantification method for estradiol in the prostatic tissues of benign prostatic hyperplasia using liquid chromatography-tandem mass spectrometry. 2010 Jan;75(1):13-9. PMID: 19766667.
  14. Arai S, Makino T, Okugi H, Hasumi M, Shibata Y, Hatori M, Suzuki K. A case of emphysematous pyelonephritis in a renal allograft. 2006 Jan 27;81(2):296-7. PMID: 16436977.
  15. Shibata Y, Kashiwagi B, Arai S, Fukabori Y, Suzuki K, Honma S, Yamanaka H. Direct regulation of prostate blood flow by vascular endothelial growth factor and its participation in the androgenic regulation of prostate blood flow in vivo. 2004 Oct;145(10):4507-12. PMID: 15231711.