While lung carcinoma and pleural mesothelioma are both malignancies, mesothelioma can grow and spread differently and may respond better to different types of treatment than lung carcinoma. Unfortunately, the two cancers can be difficult to differentiate from one another using current testing methods.
But researchers at the University of Hawaii, Honolulu’s Queen Medical Center and the NYU’s Langone Medical Center believe they have found a way to improve the diagnostic accuracy of immunohistochemical (IHC) staining for mesothelioma. The key is BRCA1-associated protein 1 (BAP1) protein.
BAP1 and Malignant Mesothelioma
BAP1 is a tumor suppressing protein encoded by the BAP1 gene. Scientists know that people with a mutation in the BAP1 tumor suppressor gene are more likely to develop certain kinds of cancer, including malignant mesothelioma.
On the other hand, the odds of surviving mesothelioma appear to be higher in patients who have this mutation.
A study published last year found that, in part because mesothelioma patients with BAP1 mutations tend to be younger (and healthier) at diagnosis than those without the mutation, they may live longer.
Improving Mesothelioma Diagnosis with BAP1
Malignant pleural mesothelioma and lung cancer can produce many of the same symptoms, including cough, chest pain, and fatigue. IHC can often help tell them apart by searching for biomarkers that are usually present in mesothelioma and less likely to be present in lung cancer.
But as the authors of the newly published report observe, in about 10 to 20 percent of cases, the IHC results “can be confusing and inconclusive”.
To see if adding a BAP1 test could help make it more accurate, Dr. Michele Carbone and his colleagues stained 45 non-small cell lung cancer samples and 35 malignant mesothelioma biopsies for BAP1.
“All 45 non-small cell lung cancer biopsies stained positive for nuclear BAP1, whereas 22/35 (63%) of malignant mesothelioma biopsies lacked nuclear BAP1 staining, consistent with previous data,” reports Dr. Carbone in the journal Oncotarget. “Our study indicated that absence of nuclear BAP1 stain helps differentiate malignant mesothelioma from lung carcinomas.”
The team suggests that BAP1 staining be added to the IHC panel currently used to distinguish between the two types of cancer.
Carbone, M, et al, “Positive nuclear BAP1 immunostaining helps differentiate non-small cell lung carcinomas from malignant mesothelioma”, July 18, 2016, Oncotarget, Epub ahead of print