Page 52 - Bio Engineering Approaches to Cancer Diagnosis and Treatment

50 CHAPTER 3 Immune assay assisted cancer diagnostic

There are several methods for identification of TAA and autoantibody including
SEREX, phage display, protein microarray, SERPA, and Mapping.
Serological analysis of tumor antigens by recombinant cDNA expression cloning
(SEREX):
In 1995, Serological analysis of tumor antigens by recombinant cDNA expres-
sion cloning (SEREX) was developed. SEREX involves the recognition of TAAs
by screening patient’s sera against a cDNA expression library acquired from the
autologous tumor tissues. Afterward, a large number of TAAs associated with many
cancer types have been detected using this technique. The usage of SEREX has facil-
itated the detection of TAAs as potential cancer biomarkers. This method in various
types of cancers, including lung, liver, breast, prostate, ovarian, renal, head and neck,
esophageal, leukemia, and melanoma have been used. There are, however, some
restrictions to the SEREX approach. First, TAAs detected by SEREX are mostly
linear epitopes. Second, there is a bias toward antigens that are overexpressed in the
tumor tissues used to make cDNA libraries. Thus, overexpression of the antigens is
often causes by their immunogenicity identified by SEREX. However, TAAs that are
of low quantities are missed by SEREX. Third, SEREX is time-consuming, labor-
intensive and cannot be automated. Thus, this method is not useful for analyzing
a large number of patient serum samples. Finally, posttranslational modifications
(PTMs) cannot be recognized by SEREX.

3.2.1 Phage display

In the phage display technique, a cDNA phage display library is created using a
tumor tissue or cancer cell line. Peptides from the tumor or cell line are expressed
as fusions with phage proteins and are displayed on the host surface. This aspect
of the method allows inexpensive and labor-effective screening during biopanning.
This technique also eliminates proteins that cannot be displayed on the surface of the
phage species. Although this technique is effective for throughput than SEREX, it
still cannot detect antigens with PTMs (e.g., glycosylated cancer antigens).

3.2.2 Serological proteome analysis (SERPA)
Another method used in the detection of TAAs is the proteomics-based technique
termed SERPA or proteomics which uses a combination of 2D electrophoresis,
western blotting, and mass spectrometry (MS). Proteins from tumor tissues or cell
lines are obtained by 2D electrophoresis, and have transferred onto membranes by
electroblotting and analyzed with sera from healthy people or patients with cancer.
These include biases to abundant proteins and barriers in resolving certain types of
proteins and in complexity producing reproducible 2D gels. Because of the method
that western blots are prepared, only linear epitopes can be recognized [20]. SERPA
has been used in the study of many cancers, such as neuroblastoma, lung carcinoma,
breast carcinoma, renal cell carcinoma, HCC, and ovarian cancer. For example, the
use of SERPA has recognized calreticulin and DEAD-box protein 48 (DDX48) in
pancreatic cancer [21].