155P - Exploring the utility of serum anti-tNASP antibodies as a screening biomarker in prostate, pancreatic, and ovarian cancer

Background

Nuclear auto-antigenic sperm protein (NASP) is a histone chaperone and a facilitator of chromatin assembly. One of two NASP splice variants, tNASP, is specific to the testis, where it is sequestered by the blood-testis barrier and also present in cancer cells. Exposure of tNASP from the cancer cells to the immune system induces a robust humoral immune response. We hypothesized that the autoantibodies produced against tNASP may be used as a supplementary diagnostic marker for prostate, pancreatic, and ovarian cancer.

Methods

Sera from patients with pancreatic cancer (74), prostate cancer (63), and ovarian cancer (19) were tested for the presence of antibodies against tNASP using enzyme-linked immunosorbent assay (ELISA) with a recombinant tNASP fragment as bait. Correlation analysis was used to determine correlations between anti-tNASP antibody level and the age, ethnicity, TMN staging, and diagnostic marker levels (PSA in the prostate cancer and CA19-9 in pancreatic cancer).

Results

Level of anti-tNASP antibody in prostate cancer patients ranged from 426 to 3810 μg/mL and was significantly higher compared to healthy individuals (p<0.01). The cutoff for anti-tNASP antibody thus was established at 400 μg/mL. Combined analysis of anti-tNASP and PSA tests demonstrated that 18% of PC patients with PSA higher than 4 ng/mL had a low level of anti-tNASP antibody (false positive PSA, supported by negative biopsy); 11.4% of PC patients with PSA lower than 4 ng/mL had high levels of anti-tNASP antibodies (false negative PSA, proved histologically). Level of anti-tNASP antibody in pancreatic cancer patients ranged from 564 to 2751 μg/mL and was significantly higher compared to healthy individuals (p<0.01). Correlations between expression of tNASP antibody and levels of CA19-9 are not conclusive. There is a significant difference in tNASP antibody concentrations between serum from patients with ovarian cancer and serum from the control group of patients.

Conclusions

Expression of serum anti-tNASP antibody is not a specific screening marker for prostate, pancreatic, or ovarian cancer. Combined use of PSA with anti-tNASP antibody analysis reveals significant elimination of false positive and false negative PSA test results.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Campbell University, USA.

Disclosure

All authors have declared no conflicts of interest.