Page 53 - Bio Engineering Approaches to Cancer Diagnosis and Treatment

3.2 Monoclonal antibody-based immune assays 51

3.2.3 Multiple affinity protein profiling (mapping)
Mapping involves 2D immunoaffinity chromatography, digestion of the isolated
proteins by enzyme, and identification of TAAs by consecutive nano liquid chro-
matography-mass spectrometry (nano LC-MS /MS), may enable the identification
of these unknown antibodies of patient. In the first step of the chromatography, non-
specific TAAs in a cancer cell line or tumor tissue lysate such as colon cancer cells
bind to IgG gotten from healthy controls in the immunoaffinity column and then are
deleted from the lysate. The “flow-through fraction” of the lysate is then put to the
2D immunoaffinity column that comprises IgG from patients with cancer. TAAs that
bind simultaneously are likely to be cancer-specific and are removed for enzymatic
digestion and detection by consecutive MS [20].
Finally, antibodies are biochemically well-known molecules, and many avail-
able reagents and techniques are available for their detection, simplifying assay
development.

3.2.4 Proteomic microarray
One of the necessities needed to improve the survival rate of patients with cancer is
early diagnosis. Gene expression is a key to cellular processes, like stem cell main-
tenance, cell cycle, and cellular differentiation, as well as response to environmental
changes. Any epigenetic alteration in control of gene expression could lead to the
many different diseases such as the formation of tumors. DNA methylation was the
first epigenetic mark known to be a crucial cause of cancer. The difference between
tumor cell and normal cells is because of aberrant changes in the methylation pat-
tern or chromatin modification which is occurred in cells. Therefore, by comparing
malignant cells with normal cells, early detection of cancer would be feasible before
any symptoms have appeared. The latest advances in research have shown that PTMs
of histones (such as phosphorylation, acetylation, or methylation) were also found
to be involved in tumorigenesis [22,23]. Interestingly, more than 200 different PTMs
are identified in proteins. The PTM of the proteome is a dynamic process that adjusts
the cell signaling process. PTM has the inherent characteristics that have the abil-
ity to produce changes in macromolecules that potentially affect cancer activation,
progression, and therapeutic response. This feature of PTM has been used in cancer
diagnosis.
Detection of PTM and biomarkers is an important method for cancer diagnosis
and in this way proteomic technology has played an important role in biomarker
discovery and early detection. Clinical samples of proteins can be analyzed through
procedures, such as MS, two-dimensional polyacrylamide gel electrophoresis (2D
PAGE), and protein arrays in order to help compare the protein variability between
samples. Table 3.4 describes the advantages and disadvantages of proteomic technol-
ogy which has been investigated for cancer diagnosis [24,25].
Each proteomic technique has its own advantages or disadvantages and based
on researcher's requirement or its own feature are used in different fields. Another
important feature of a useful proteomic techniques is its noninvasive feature, which