The expression and clinical effects of alpha-methylacyl-CoA racemase (AMACR/ P504S) as an immunohistochemical marker in malign pleural mesothelioma

Our plain-English summary of The expression and clinical effects of alpha-methylacyl-CoA racemase (AMACR/ P504S) as an immunohistochemical marker in malign pleural mesothelioma, by S.Ş. Duyar, A. Yilmaz, F. Demirag, et al (Turkish Journal of Medical Sciences, 2015).

The study

• Authors: S.Ş. Duyar, A. Yilmaz, F. Demirag, Y. Erdoğan, Ü. Yazici, J. Karakaya
• Journal: Turkish Journal of Medical Sciences
• Published: 2015;45(3):607-14
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background/aim: Alpha-methylacyl-CoA racemase (AMACR), an intracellular enzyme involved in lipid metabolism, has emerged as an immunohistochemical marker for many types of cancer. Recent studies about the role of lipid metabolism in pathogenesis of mesothelioma have brought up some positive results. This study was conducted to investigate AMACR expression in the diagnosis of malignant pleural mesothelioma (MPM) and the correlation of this marker with clinical characteristics and survival.

Materials And Methods: The clinicopathologic characteristics and resection materials of 71 patients were reviewed retrospectively. AMACR expression was evaluated immunohistochemically. The correlations among AMACR expression, clinicopathologic factors, and survival were investigated.

Results: AMACR expression was detected in 42.3% of the study group. The specificity and sensitivity of AMACR immunostaining in detecting mesothelioma were 41.1% and 42.3%, respectively. AMACR-positive and negative groups were similar for age, sex, smoking history, tumor diameter, lymph node involvement, differentiation, T-N factor, and stage. Overall survival was not significantly different between the groups, either.

Conclusion: The sensitivity of immunostaining was not high enough to use AMACR as a diagnostic tool in MPM. AMACR expression did not have a prognostic value in MPM, either.

In plain English

This retrospective study from a chest diseases hospital in Ankara, Turkey, tested whether a protein called AMACR, detected by staining tissue samples, helps diagnose malignant pleural mesothelioma or predict survival. The study did not measure asbestos exposure. The authors reviewed tissue and records of 71 patients who had surgery between June 2000 and June 2009. Staining was positive in 42.3% of patients: 42% of 50 epithelioid and 52.9% of 17 biphasic tumors. All 4 sarcomatoid and desmoplastic tumors were negative. Positivity was not statistically significantly linked to age, sex, smoking, T or N status, or stage. Among 53 patients analyzed for survival, median survival was 16 months for AMACR-positive and 13 months for AMACR-negative patients. This difference was not statistically significant (P = 0.190). The article reports sensitivity and specificity as 41.1% and 42.3% but assigns the two figures inconsistently. The authors concluded that AMACR alone cannot be used as a diagnostic tool. They suggested that their small, varied patient group may explain the non-significant survival results.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Retrospective study of patient records and tissue samples, with immunohistochemical staining for AMACR
• Who was studied: 71 patients with malignant pleural mesothelioma who had surgery between June 2000 and June 2009 at Atatürk Chest Diseases and Chest Surgery Education and Research Hospital, Ankara, Turkey. The group was 45 men and 26 women; 50 epithelioid, 17 biphasic, 2 sarcomatoid and 2 desmoplastic tumors. 53 patients were included in the survival analysis.
• Exposure: No asbestos or fiber exposure was studied. The factor examined was expression of the enzyme AMACR (P504S) in tumor tissue, detected with a rabbit monoclonal antibody. Weak staining was counted as positive.
• Main results:
  • AMACR staining was positive in 30 of 71 patients (42.3%)
  • 42% of 50 epithelioid and 52.9% of 17 biphasic mesotheliomas were AMACR-positive; the 2 pure sarcomatoid and 2 desmoplastic cases were AMACR-negative
  • AMACR expression showed no statistically significant correlation with age, sex, smoking history, pathologic T–N status, or stage (P > 0.05)
  • AMACR positivity was more frequent in a lung adenocarcinoma group (73 cases) from the authors' earlier study than in this mesothelioma group (P = 0.046)
  • Sensitivity and specificity of AMACR staining for detecting mesothelioma were given as 41.1% and 42.3%. The body text and the abstract assign these two figures in opposite order.
  • Among 53 patients analyzed, median survival was 13 ± 3.65 months in the AMACR-negative group and 16 ± 5.96 months in the AMACR-positive group. The difference was not statistically significant (P = 0.190, log-rank).
  • In Cox regression, lymph node (N) status had a statistically significant effect on overall survival: N2–N3 versus N0, HR 6.585 (95% CI 2.117 to 20.483), P = 0.001. AMACR status did not: negative versus positive, HR 2.141 (95% CI 0.91 to 5.039), P = 0.081.
• The authors' conclusion: The authors concluded that AMACR alone cannot be used as a diagnostic tool in the differential diagnosis of malignant pleural mesothelioma. They recommended larger studies with a more uniform patient group to examine AMACR's effect on survival and response to chemotherapy.
• Limitations the authors state:
  • The authors stated that the relatively small number of patients and the group's heterogeneity in performance status and other prognostic factors might explain the non-significant survival results

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Mesothelioma, Overall Survival.

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