The necessity of native human proteins in the search for the most promising biomarkers

Native human proteins

Biomarker discovery with native human proteins

Whether looking at diagnosis, prognosis, or prediction of therapy effectiveness, biomarkers are integral to monitoring health and disease. Biomarkers can be genetic, translational, or proteomic in nature, but protein biomarkers garner much interest as they become easier to discover and profile. Advances in proteomics technologies continue to expand our understanding and application of proteins, including comprehensive protein characterization and an in-depth view into biological and pathogenic processes. In fact, protein biomarkers can be more reliable predictors of a disease state or therapeutic outcome due to their functional role in a given pathway.

However, the more we learn about proteins, the more their complexity becomes apparent. Deciphering the dynamic range of candidate proteins, with their native isoforms, new isoforms associated with a disease, both regular and aberrant protein modifications, and formation of various complexes, further complicates the evaluation of whether a protein is of clinical relevance. Some post-translational modifications, or PTMs, (phosphorylation, methylation, glycosylation, acetylation, and proteolysis), for example, might be key to regular function and contribute to proteome diversity, but when altered, create non-functional proteins or cause changes in target interactions. These subtle differences could become significant to clinical diagnosis and potential therapeutic approaches.

Protein biomarkers detected in easily accessible clinical samples, such as blood, urine, or saliva, are incredibly useful for non-invasive disease detection and classification, especially when a panel of proteins is available. And while the introduction of recombinant proteins has enabled easy access to proteins necessary for therapeutic, industrial, and commercial applications, generating these proteins is highly complex. Furthermore, they are difficult to apply to biomarker research and development due to the heterogeneity, modifications, and specificity of active sites on target proteins. Thus, native proteins provide the opportunity to definitively observe and analyze potential biomarkers as they appear in vivo.

Native proteins are typically isolated from organisms or tissues for preservation of protein functionality. The native state of a protein can be defined as the collection of stable and active conformations resulting from folding conditions in vivo. Since these proteins maintain their natural structure and functional activity, native proteins are commonly used in a wide range of applications such as protein functional assays, ELISAs, Western Blot, and Immunoprecipitation.

ELISAs have evolved to be so sensitive and practical that they can detect biomarkers at the earliest stage of diagnosis, discriminating a disease state biomarker from its healthy isoform. Mass spectrometry platforms are robust profiling tools for native proteins with clinical potential. Additionally, advances in detection and enhancements in sensitivity are enabling a more comprehensive search for not only single biomarkers but patterns that can form biomarker signatures. These approaches combined with the utility of native human proteins help to further proteomic research and take the steps necessary to move protein biomarkers to the clinic.

Supporting biomarker identification and development

Once biomarker candidates have been identified, they must be qualified, verified, and validated in order to be implemented into clinical practice. Due to the high number of candidates typically identified in the discovery phase, a targeted selection can be tested based on protein folding variations between health and disease states, the role of the protein within pathological mechanisms, and capabilities for target specificity.

In order to successfully progress through these phases, in-depth knowledge of the possible isoforms of the target protein in a defined matrix is important. Certain proteins, particularly those involved in cell signaling, regulation, and growth, can reflect various stages of disease progression, and thus are significant for biomarker screens and discovery. Here, we discuss some common native human proteins used for protein biomarker discovery and development that span applications from monitoring growth and development to cancer diagnosis and prognosis testing.

Growth and development

Human Alpha-Fetoprotein (AFP) is a diagnostic biomarker for fetal anomalies, such as neural tube defects and Down’s syndrome, and certain carcinomas. It is produced by the embryo and crosses into maternal blood circulation. Elevated levels of the protein signify higher risk of neural tube defects, while low levels indicate risk of Down’s syndrome. AFP synthesis can resume in adulthood with liver pathologies and carcinomas. Further study of AFP has revealed its principal role in female fertility and development.

Human Chorionic Gonadotropin (hCG) is a key protein in the maintenance of pregnancy, and as such, is known as a biomarker measured in serum or urine to monitor pregnancy and issues related to pregnancy, as well as diagnosis of gynecological cancers. hCG active sites have been well characterized, allowing monoclonal antibody assays to be designed with targeted hCG epitope specificity. Two defined epitopes are regularly used in biomarker assays, detecting elevated levels of hCG associated with preeclampsia, Down’s syndrome, and gestational trophoblastic disease.

Human Luteinizing Hormone (LH) works synergistically with follicle-stimulating hormone in regulating certain aspects of reproduction. Elevated levels of LH are associated with pituitary disease and the diagnosis and treatment of infertility. Studies on LH variants are investigating their effects on FSH sensitivity, infertility, and hypogonadism.

Human Growth Hormone (GH), as a biomarker, detects GH abuse in sports, monitors the effects of GH replacement for GH deficiency, and is used in the diagnosis and management of acromegaly (GH excess). Continued research into GH detection and therapies has shown progress in faster and more accessible GH biomarker testing and improved disease control.

Cancer biomarkers

Native Human Carcinoembryonic Antigen (CEA) is one of the more significant biomarkers for colorectal cancers, and is expressed in a majority of colorectal, gastric, and pancreatic carcinomas as well as in breast cancers and non-small cell lung cancers. Studies of CEA have shown it to be an important factor in cancer prognosis, where elevated levels associate with poor prognosis and treatment failure.

Native Human Prostate Specific Antigen (PSA) is the biomarker of choice in prostate cancer diagnosis. However, current tests have a high rate of false positives. Research into improving molecular diagnosis is examining characteristics unique to PSA and PSA variants for more precise detection and identification of prostate cancer.

Native Human Thyroid Stimulating Hormone (TSH), a biomarker of thyroid function and autoimmunity, can help predict thyroid cancer risk and assess thyroid function. Thyroid hormones impact normal nervous system development, and so decreased levels of TSH in children are associated with neurological anomalies. In adults, high levels of TSH are associated with increased blood pressure and deficient blood lipid profiles, which can lead to cardiovascular disease.

Native Human Prolactin is a protein synthesized primarily in the pituitary, implicated in the development and progression of cancers in the female reproductive system. Research into variants of the protein could enhance further functional studies into both health and disease states as well as investigate the potential clinical value to cancer diagnostics.

Cell Sciences offers native human proteins, including those listed above, in bulk quantities as a High Purity grade or Standard Grade, typically used for supporting the development of in vitro diagnostics.

CS070                    Native Human Alpha-Fetoprotein, High Purity

CS071                    Native Human Carcinoembryonic Antigen, High Purity

CS072                    Native Human Growth Hormone, High Purity

CS073                    Native Human Chorionic Gonadotropin Alpha Subunit, High Purity

CS074                    Native Human Prostate Specific Antigen, High Purity

CS075                    Native Human Prostate Specific Antigen, Standard Grade

CS076                    Native Human Chorionic Gonadotropin, Standard Grade

CS077                    Native Human Chorionic Gonadotropin, High Purity

CS078                    Native Human Thyroid Stimulating Hormone, High Purity

CS079                    Native Human Prolactin, High Purity

CS080                    Native Human Thyroid Stimulating Hormone Beta Subunit, Standard Grade

CS084                    Native Human Luteinizing Hormone, High Purity

CSI13970              Native Human Chorionic Gonadotropin Beta Subunit, High Purity