Study of glycosylation of prostate-specific antigen secreted by cancer tissue-originated spheroids reveals new candidates for prostate cancer detection

Abstract

Prostate-specific antigen (PSA) is the most frequently used biomarker for the screening of prostate cancer. Understanding the structure of cancer-specific glycans can help us improve PSA assay. In the present study, we analysed the glycans of PSA obtained from culture medium containing cancer tissue-originated spheroids (CTOS) which have similar characteristics as that of the parent tumour to explore the new candidates for cancer-related glycoforms of PSA. The glycan profile of PSA from CTOS was determined by comparing with PSA from normal seminal plasma and cancer cell lines (LNCaP and 22Rv1) using lectin chromatography and mass spectrometry. PSA from CTOS was mostly sialylated and the content of Wisteria floribunda agglutinin reactive glycan (LacdiNAc) was similar to that of PSA derived from seminal plasma and 22Rv1. Conversely, concanavalin A (Con A)-unbound PSA was definitely detected from the three cancer origins but was almost negligible in seminal PSA. Two novel types of PSA were elucidated in the Con A-unbound fraction: one is a high molecular weight PSA with highly branched N-glycans, and the other is a low molecular weight pSA without N-glycans. Furthermore, the existence of Lewis X antigen group on PSA was indicated. These PSAs will be candidates for new cancer-related markers.Prostate-specific antigen (PSA) is a glycoprotein that is exclusively produced by the prostate gland. PSA is normally found in semen, but men with prostate cancer often have a higher amount of PSA in the blood. PSA test is a screening test for prostate cancer; it measures the concentration of PSA in blood. The PSA levels also increase during non-cancerous conditions such as prostatitis (inflammation of the prostate), or benign prostatic hyperplasia (BPH, enlargement of the prostate). Men with PSA levels between 4 and 10 ng/ml have a 25% chance of developing prostate cancer, and this concentration range is known as the diagnostic grey zone. Therefore, a precise diagnosis that can distinguish cancer and inflammatory diseases is required.Numerous studies have reported that aberrant glycosylation occurs in cancer cells rather than in normal cells 1,2 . These cancer-associated modifications of glycans are expected to help in a more precise diagnosis of cancer. Therefore, if aberrant glycans on PSA of cancer origin are present, they are attractive targets and several studies to determine them have been conducted 3 . Peracaula et al. 4 analysed the glycans released from PSA in conditioned medium of LNCaP cancer cell line. The glycans were not sialylated, but they contained a Fucα1-2Gal residue and a high amount of GalNAcβ1-4GlcNAc (LacdiNAc). However, the glycans on PSA from the sera of prostate cancer patients were mostly sialylated and the glycan profiles are not the same as in the LNCaP cell 5,6 . It is well known that cell lines often acquire substantial bias and lose several characteristics of parental tumours during culture establishment and passage 7,8 ; thus, the glycan profiles of such cells may have often changed from primary ...

Clinical Assay for the Early Detection of Colorectal Cancer Using Mass Spectrometric Wheat Germ Agglutinin Multiple Reaction Monitoring

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