Current screening methods for cervical cancer have several disadvantages and vaccination programs cover only parts of the population for varying reasons. Furthermore, the vaccins are not effective against all HPV types. Specific and sensitive biomarkers may therefore pave the way for a diagnostic test that may further optimize prevention of cervical cancer.
The CervicoVaginal Fluid (CVF) is composed of secretions originating from organs that are part of the female genital tract, including vagina, cervix, endometrium and ovaries; hence the proteome of this fluid contains a wealth of information concerning the physiological status of all of these organs. Since many studies have proven CVF self-sampling as a good sample collection method for subsequent assays, CVF may very well be suited for the development of a simple bedside assay for triage of suspected cases or screening in remote areas.
Therefore, proteomics studies were undertaken to search for suitable protein biomarkers that could be used in the development of an ELISA-like assay.
In a differential proteomics study, six CVF samples from healthy and six samples from precancerous women were run over a 2D-LC-MS/MS platform and quantified by spectral counting. ELISA was used to validate the results on more samples. Differentially expressed proteins were than introduced into Ingenuity Pathway Analysis (IPA) in order to find cervical cancer-related pathways.
We identified one protein, alpha-actinin-4 (ACTN4), that was present and absent in all CVF samples originating from precancerous and healthy women, respectively. We also found four proteins that showed > 3x up- or downregulation in one of the two conditions. ACTN4 followed appearance or clearance of the virus in longitudinal CVF samples. Further testing with ELISA showed that the protein could discriminate between the healthy and (pre)cancerous state with a sensitivity and specificity of both 80%. Furthermore, IPA analysis showed that, unlike CVF from healthy women, CVF from precancerous women contains many interconnected proteins involved in (cervical) cancer from which some could be valuable biomarkers too.
These results show that CVF is a body fluid that may contain several biomarkers for detection or follow-up of cervical precancerous women. With the set of potential CVF biomarkers it may become possible to determine a cervical (pre)cancer biomarker combination with increased discriminative power, compared to ACTN4 alone. Therefore, quantification of several biomarkers from this list by ELISA or mass spectrometry (Multiple Reaction Monitoring, MRM) is currently ongoing in order to optimize sensitivity and specificity of the assay.
Van Raemdonck, G., Tjalma, W., Coen, E., Depuydt, C. and Van Ostade, X.. Identification of protein biomarkers for cervical cancer using human cervicovaginal fluid. PLoS One. 9:e106488 (2014).