**3.2 Cancer antigen 19-9**

*Advances in the Molecular Understanding of Colorectal Cancer*

**144**

**Protein** S100A8

Histological: 6 CRC

2DGE. In gel digestion,

protein spots excised for MS

and 6 healthy controls

Plasma: 77 CRC, 11

adenoma, 21 healthy

controls

S100A9

**Sample type**

**Workflow**

**MS platform**

AB 4700

Proteomics

Analyzer

LC-MS/MS

**Proteins identified**

34 increased and 17 decreased

proteins on gel spots, 4 selected

for RT-PCR and IMMUNOBLOT

analysis: Nm23-H1, S100A8, S100A9,

Adenosylhomocysteinase.

**Validation set** Semi-quantitative PCR and

[36]

IMMUNOBLOT analysis.

IMMUNOBLOT analysis

preformed for plasma samples.

S100A8 and S100A9 were

significantly increased in the

plasma of CRC and colorectal

adenoma patients compared to

controls.

*Synopsis of biomarker identification including sample type, pre-analytic workflow and MS technique (where applicable).*

**Table 2.**

*Summary of CRC biomarker identification methods.*

**References**

Cancer (or Carbohydrate) antigen 19-9 (CA 19-9) is a clinical biomarker used in various diseases. Elevation can occur in benign conditions such as biliary and pancreatic disease, pulmonary disease, renal failure and autoimmune disease as well as malignant conditions of the pancreas, colon, rectum, liver, ovary and lung. CA 19-9 is therefore considered a non-specific biomarker of CRC [66] and is a classical marker for late stage disease and metastasis. For this reason it is not appropriate for use as a screening, or diagnostic, marker of carcinoma [67]. CA 19-9 can be used in tandem with CEA for post-operative monitoring to detect recurrence, or as a prognostic indicator as pre-operative elevation without correspond elevation of CEA is associated with a poorer 5-year survival [68]. When the combination of preoperative elevation of both CEA and CA19-9 occurs, this is predictive of increased cancer mortality compared to non-elevated pre-operative levels [69].
