1222P - Detection of androgen-receptor splice variant 7 messenger RNA in circulating tumor cells of prostate cancer by in vitro assay

Background

Androgen-receptor splice variant 7 (AR-V7) is constitutively activated isoform of AR and has been associated with resistance towards AR targeting therapies and development into mCRPC. Confirmation of AR-V7 expression is important step in prostate cancer diagnosis and determining the drug, but the detection of AR-V7 with tissues has limitations such as clinical challenge to poorly accessible tumor tissues before and after treatment. Here, we developed the method of AR-V7 detection in circulating tumor cells (CTC) after isolation with CytoGen’s Smart Biopsy^TM CTC isolator by in vitro assay of qRT-PCR with high sensitivity and specificity, overcoming the limitations of tissue biopsy.

Methods

Nested qPCR method was developed for high sensitivity and specificity of detection of AR-V7. Sensitivity and specificity were tested using AR-V7 positive cells (VCaP) and negative cells (PC-3 and Raji cells). Limit of detection of AR-V7 of nested PCR was performed with VCaP (200 cells to 20 cells, 4 points) mixed with Raji cells (1x10ˆ5cells). Then, VCaP cells (200 cells to 20 cells, 4 points) was spiked into peripheral blood mononuclear cells of blood sample (5mL, healthy donor) to mimic CTC after isolation by CytoGen’s Smart Biopsy^TM CTC isolator, subsequently nested qPCR was carried out to detect of AR-V7 using each primer pairs. Non clinical sample were used.

Results

As a result of LoD test, AR-V7 expression was clearly detected even in the smallest VCaP sample and was not detected at all in the negative controls. The same clear result was also observed in the spiking test of VCaP into PBMCs isolated by CytoGen’s Smart Biopsy^TM CTC isolator, suggesting that clinical samples of prostate cancer could be applied with excellent sensitivity and specificity for AR-V7.

Conclusions

AR-V7 expresses only a part of cancer tissue, so it is difficult to accurately diagnose with traditional histological assays. Detection of AR-V7 in intact live CTC isolated by CytoGen’s Smart Biopsy^TM CTC isolator might overcome limitations of tissue biopsy. In this study, we developed a novel method of detection of AR-V7 in CTC with high sensitivity and specificity by in vitro assay and clinical test will be conducted for validation.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

Cytogen. Inc.

Funding

Cytogen. Inc.

Disclosure

H. Kang, J.H. Lee, S. Kim, J.B. Lee, S. Park, J. Choi, H. Lee, J.W. Kim: Financial Interests, Personal, Full or part-time Employment: Cytogen, Inc.