Identification of novel pancreatic adenocarcinoma cell-surface targets by gene expression profiling and tissue microarray

Abstract

Pancreatic cancer has a high mortality rate, which is generally related to the initial diagnosis coming at late stage disease combined with a lack of effective treatment options. Novel agents that selectively detect pancreatic cancer have potential for use in the molecular imaging of cancer, allowing for non-invasive determination of tumor therapeutic response and molecular characterization of the disease. Such agents may also be used for the targeted delivery of therapy to tumor cells while decreasing systemic effects. Using complementary assays of mRNA expression profiling to determine elevated expression in pancreatic cancer tissues relative to normal pancreas tissues, and validation of protein expression by immunohistochemistry on tissue microarray, we have identified cell-surface targets with potential for imaging and therapeutic agent development. Expression profiles of 2177 cell-surface genes for 28 pancreatic tumor specimens and 4 normal pancreas tissue samples were evaluated. Expression in normal tissues was evaluated using array data from 103 samples representing 28 organ sites as well as mining published data. One-hundred seventy unique targets were highly expressed in 2 or more of the pancreatic tumor specimens and were not expressed in the normal pancreas samples. Two targets (TLR2 and ABCC3) were further validated for protein expression by tissue microarray (TMA) based immunohistochemistry. These validated targets have potential for the development of diagnostic imaging and therapeutic agents for pancreatic cancer.

Figure 1

Representative immunostaining results of ABCC3 (TOP) and TLR2 (BOTTOM) in pancreatic adenocarcinoma (LEFT) and normal pancreas (RIGHT).

Figure 2

Representative immunostaining results of TLR2 staining in normal pancreas samples from the normal tissue microarray (CHTN2002N1). Panel A, arrows indicate subset of positive staining cells. Panel B, arrow indicates positive cell with possible “fried egg” stem cell morphology. Panel C, arrow indicates single positive cell in duct.

Figure 3

Representative immunostaining results of ABCC3 and TLR2 in normal adrenal tissue from the corresponding region of adjacent sections from the normal tissue microarray (CHTN2002N1).

Figure 4

Expression signal distribution analysis of ABCC3 (A) and TLR2 (B) in normal and tumor tissues from public databases: Normal tissue group of 212 samples from 70 tissue types (solid line); and tumor tissue group of 1781 samples (dotted line) from a variety of histological tumor classes from several tissue sites.