Utility of alpha-methylacyl coenzyme A racemase (p504s antibody) as a diagnostic immunohistochemical marker for cancer.

Alpha-methylacyl-coenzyme A racemase (AMACR; P504S) is a mitochondrial and peroxisomal enzyme involved in the metabolism of branched-chain fatty acid and bile acid intermediates. Recently, AMACR has been demonstrated to be overexpressed in localized and metastatic prostate cancer and in high-grade prostatic intraepithelial neoplasia but not in normal prostatic glands, suggesting that it may be an important tumor marker. This study examines AMACR expression in a variety of human cancers to assess its viability as a tumor marker in the clinical setting. Two hundred sixty-three cancers from different sites were examined in three multitumor tissue micro arrays, which included two or three tissue cores (1.0 mm in diameter) from each neoplastic and normal tissue specimen. Cancers studied included breast (94 cases), prostate (38), lung (28), endometrium (27), colon (29), ovary (26), and melanoma (21). Normal tissues in the microarray were prostate (15), lung (6), endometrium (5), colon (4), ovary (2), and skin (3). Sections were immunostained, after prior pressure cooker antigen retrieval, using rabbit monoclonal AMACR antibody (1:40) (Zeta Corp, Sierra Madre, CA) and horseradish peroxidase-labeled polymer conjugated secondary antibody (Envision, Dako, Carpinteria, CA). A section of prostate cancer and prostatic intraepithelial neoplasia was used as positive control. Protein expression was scored as negative, weak (faint cytoplasmic or granular apical staining), moderate (diffuse granular cytoplasmic stain), and strong (diffuse intense cytoplasmic stain). Only moderate and strong staining was considered as positive staining, based on prior work. AMACR protein overexpression was found in several cancers, including prostate (34/38 [89.5%]), colon (13/29 [44.8%]), lung (4/28 [14.3%]), melanoma (2/21 [9.5%]), endometrium (2/27 [7.4%]), and breast (3/94 [3.2%]). None of the ovarian cancers (26 cases) demonstrated AMACR overexpression. AMACR expression was not present in any of the normal tissues nor in benign prostatic tissue associated with prostate carcinomas. This study suggests that AMACR is potentially an important tumor marker, particularly for prostate and colon cancer. It may be a useful adjunct to an immunohistochemical panel employed in the differential diagnosis of colon versus ovarian and breast carcinoma; the latter two infrequently express AMACR.

Mitogen-actived protein kinase activation is an early event in melanoma progression.

PURPOSE: Melanoma is the most common cause of death from cutaneous malignancy, and is the cancer that is most rapidly rising in incidence. Because current therapeutic methods for metastatic melanoma are poorly efficacious, enhanced understanding of signal transduction in melanoma progression is warranted. Prior experimental studies in murine models and human tissues have shown a correlation among activation of mitogen activated protein kinase (MAPK) signaling, angiogenesis, and tumorigenesis. Because of these findings, we wanted to assess the role of MAPK signaling in melanoma progression and angiogenesis. EXPERIMENTAL DESIGN: We studied expression of phosphorylated (active) MAPK and two target genes known to be induced by MAPK signaling, tissue factor and vascular endothelial growth factor, in 131 melanocytic lesions, ranging from atypical nevi to metastatic melanoma. RESULTS: We observed little staining for activated (phosphorylated) MAPK and low amounts of angiogenesis in atypical nevi, but angiogenesis and MAPK activation were activated in radial growth melanoma and in later stage lesions. CONCLUSIONS: Our findings implicate MAPK activation as an early event in melanoma progression, and MAPK may be a potential target for pharmacologic intervention.