Chikara Ohyama

Chikara Ohyama


Research Focus & Metrics

Academic Career Length

11Years (2016-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

View All Publications
Verified
Journal Article
Open access
PDF file
TITomokazu Ishikawa
Tomokazu Ishikawa
TYTohru Yoneyama
Tohru Yoneyama
YTYuki Tobisawa
Yuki Tobisawa
SHShingo Hatakeyama
Shingo Hatakeyama
TKTatsuo Kurosawa
Tatsuo Kurosawa
COChikara Ohyama
Chikara Ohyama
The low specificity of the prostate-specific antigen (PSA) for early detection of prostate cancer (PCa) is a major issue worldwide. The aim of this study to examine whether the serum PCa-associated α2,3-linked sialyl N-glycan-carrying PSA (S2,3PSA) ratio measured by automated micro-total immunoassay systems (μTAS system) can be applied as a diagnostic marker of PCa. The μTAS system can utilize affinity-based separation involving noncovalent interaction between the immunocomplex of S2,3PSA and Maackia amurensis lectin to simultaneously determine concentrations of free PSA and S2,3PSA. To validate quantitative performance, both recombinant S2,3PSA and benign-associated α2,6-linked sialyl N-glycan-carrying PSA (S2,6PSA) purified from culture supernatant of PSA cDNA transiently-transfected Chinese hamster ovary (CHO)-K1 cells were used as standard protein. Between 2007 and 2016, fifty patients with biopsy-proven PCa were pair-matched for age and PSA levels, with the same number of benign prostatic hyperplasia (BPH) patients used to validate the diagnostic performance of serum S2,3PSA ratio. A recombinant S2,3PSA- and S2,6PSA-spiked sample was clearly discriminated by μTAS system. Limit of detection of S2,3PSA was 0.05 ng/mL and coefficient variation was less than 3.1%. The area under the curve (AUC) for detection of PCa for the S2,3PSA ratio (%S2,3PSA) with cutoff value 43.85% (AUC; 0.8340) was much superior to total PSA (AUC; 0.5062) using validation sample set. Although the present results are preliminary, the newly developed μTAS platform for measuring %S2,3PSA can achieve the required assay performance specifications for use in the practical and clinical setting and may improve the accuracy of PCa diagnosis. Additional validation studies are warranted.

19 March 2020 in International Urology and Nephrology
Verified
Journal Article
Closed access
PDF file
TOTeppei Okamoto
Teppei Okamoto
SHShingo Hatakeyama
Shingo Hatakeyama
AIAtsushi Imai
Atsushi Imai
HYHayato Yamamoto
Hayato Yamamoto
TYTohru Yoneyama
Tohru Yoneyama
COChikara Ohyama
Chikara Ohyama

Verified
Journal Article
Open access
PDF file
KHKazuhisa Hagiwara
Kazuhisa Hagiwara
YTYuki Tobisawa
Yuki Tobisawa
TKTakatoshi Kaya
Takatoshi Kaya
TKTomonori Kaneko
Tomonori Kaneko
SHShingo Hatakeyama
Shingo Hatakeyama
TYTohru Yoneyama
Tohru Yoneyama
Wisteria floribunda agglutinin (WFA) preferably binds to LacdiNAc glycans, and its reactivity is associated with tumor progression. The aim of this study to examine whether the serum LacdiNAc carrying prostate-specific antigen–glycosylation isomer (PSA-Gi) and WFA-reactivity of tumor tissue can be applied as a diagnostic and prognostic marker of prostate cancer (PCa). Between 2007 and 2016, serum PSA-Gi levels before prostate biopsy (Pbx) were measured in 184 biopsy-proven benign prostatic hyperplasia patients and 244 PCa patients using an automated lectin-antibody immunoassay. WFA-reactivity on tumor was analyzed in 260 radical prostatectomy (RP) patients. Diagnostic and prognostic performance of serum PSA-Gi was evaluated using area under the receiver-operator characteristic curve (AUC). Prognostic performance of WFA-reactivity on tumor was evaluated via Cox proportional hazards regression analysis and nomogram. The AUC of serum PSA-Gi detecting PCa and predicting Pbx Grade Group (GG) 3 and GG ≥ 3 after RP was much higher than those of conventional PSA. Multivariate analysis showed that WFA-reactivity on prostate tumor was an independent risk factor of PSA recurrence. The nomogram was a strong model for predicting PSA-free survival provability with a c-index ≥0.7. Serum PSA-Gi levels and WFA-reactivity on prostate tumor may be a novel diagnostic and pre- and post-operative prognostic biomarkers of PCa, respectively.

17 May 2020 in World Journal of Urology
Verified
Journal Article
Closed access
PDF file
TOTeppei Okamoto
Teppei Okamoto
SHShingo Hatakeyama
Shingo Hatakeyama
AIAtsushi Imai
Atsushi Imai
HYHayato Yamamoto
Hayato Yamamoto
TYTohru Yoneyama
Tohru Yoneyama
COChikara Ohyama
Chikara Ohyama

16 October 2020 in International Journal of Clinical Oncology
Verified
Journal Article
Closed access
PDF file
THTomoko Hamaya
Tomoko Hamaya
SHShingo Hatakeyama
Shingo Hatakeyama
MMMasaki Momota
Masaki Momota
TNTakuma Narita
Takuma Narita
HIHiromichi Iwamura
Hiromichi Iwamura
COChikara Ohyama
Chikara Ohyama

23 August 2018 in The International Journal of Medical Robotics and Computer Assisted Surgery
Verified
Journal Article
Open access
PDF file
TKTakuya Koie
Takuya Koie
COChikara Ohyama
Chikara Ohyama
TYTakahiro Yoneyama
Takahiro Yoneyama
HNHirotaka Nagasaka
Hirotaka Nagasaka
HYHayato Yamamoto
Hayato Yamamoto
YHYasuhiro Hashimoto
Yasuhiro Hashimoto
Background This study compared the surgical and urinary functional outcomes in patients with muscle‐invasive bladder cancer (MIBC) who underwent robot‐assisted radical cystectomy (RARC) followed by intracorporeal ileal neobladder reconstruction (ICNB) to those in patients who underwent minimum incision endoscopic radical cystectomy (MIE‐RC) followed by extracorporeal ileal neobladder reconstruction (ECNB). Materials and Methods This study reviewed the clinical records of 153 consecutive MIBC patients who underwent neoadjuvant chemotherapy followed by radical cystectomy and ileal neobladder reconstruction. Results The operative time in the ICNB group was significantly longer than that in the ECNB group. The median estimated blood loss was significantly less in the ICNB group than in the ECNB group. The neobladder capacity gradually increased in both groups. The maximum neobladder pressure and urethral closure pressure gradually improved in both groups. Conclusion Our initial experience with ICNB was favourable, with acceptable surgical and urinary functional outcomes.