Variability in Platelet-Derived Growth Factor Receptor Alpha Antibody Specificity May Impact Clinical Utility of Immunohistochemistry Assays

Abstract

Aberrant regulation of the receptor tyrosine kinase platelet-derived growth factor alpha (PDGFRα) is implicated in several types of cancer. Inhibition of the PDGFRα pathway may be a beneficial therapy, and detection of PDGFRα in tumor biopsies may lead to insights about which patients respond to therapy. Exploratory or clinical biomarker use of PDGFRα IHC has been frequently reported, often with polyclonal antibody sc-338. An sc-338-based assay was systematically compared with anti-PDGFRα rabbit monoclonal antibody D13C6 using immunoblot profiling and IHC in formalin-fixed and paraffin-embedded human tumor cell lines. Application of sc-338 to blots of whole cell lysates showed multiple bands including some of unknown origin, whereas application of D13C6 resulted in a prominent band at the expected molecular mass of PDGFRα. The IHC assay using D13C6 showed appropriate staining in cell lines, whereas the assay using sc-338 suggested nonspecific detection of proteins. An optimized IHC assay using D13C6 showed a range of staining in the tumor stromal compartment in lung and ovarian carcinomas. These observations suggest that use of clone sc-338 produced unreliable results and should not be used for an IHC research grade assay. In addition, this precludes its use as a potential antibody for a clinical diagnostic tool.

Olaratumab Exerts Antitumor Activity in Preclinical Models of Pediatric Bone and Soft Tissue Tumors through Inhibition of Platelet-Derived Growth Factor Receptor α

“…These data are suggestive of potential alterations in the tumor transcriptome when cultured or propagated outside of its native environment and are reminiscent of a previous report describing changes in the epigenome and transcriptome of mammalian cells isolated from primary tissues upon exposure to cell culture (43). Furthermore, a recent study demonstrated that an anti-PDGFRa polyclonal antibody frequently used in previous IHC analyses cross-reacts with PDGFRb, further confounding previous reports regarding the prevalence of PDGFRa expression in pediatric bone and soft tissue tumor patient samples (44). In light of this discordance in receptor expression between available preclinical bioresources and clinical specimens, it is difficult to investigate the full range of olaratumab activity in pediatric sarcoma in a preclinical setting and to identify potential predictive biomarkers.…”

The expression of Platelet-derived Growth factor receptors (PDGFRs) and their correlation with overall survival of patients with ovarian cancer

“…Additionally, there is significant variability in the specificity of various sets of anti-PDGFR-alpha antibodies. Thus, the different antibodies used in each of the studies may have influenced the differences between the studies' results [33].…”

Critical Review: What Cell Types Are the Lung Telocytes?

“…Therefore, the expression of PDGFR in TCs or TC‐like cells in a stromal niche could simply indicate that they are spindle‐shaped MSCs that were not yet reverted toward endothelial progenitors. Moreover, aberrations in PDGFR‐α activation caused by overexpression, amplification, translocation, or point mutations of the PDGFRA gene play roles in cellular transformation (Holzer et al, ). Therefore, PDGFR‐α should be used with caution to detect specific cell lines.…”

“…PDGFR‐α IHC is notoriously problematic, as heterogeneous results in terms of staining specificity are obtained depending on the antibodies and methods that are used. Although IHC using monoclonal antibodies shows appropriate staining in cell lines, the use of polyclonal antibodies to detect PDGFR‐α expression might lead to nonspecific detection of proteins (Holzer et al, ). Moreover, the information about antibodies targeting the same antigen varies significantly depending on the manufacturer, and the responsibility for proof of specificity lies with the purchaser (Bordeaux et al, ).…”