The molecular changes that are involved in the pathogenesis of ACC are poorly understood. TNM classification remains the most commonly used parameter for guiding therapy and prognosis. However, there is a need for new prognostic and therapeutic markers, particularly with the development of new molecular-targeted therapies, including anti-EGFR molecules. In this study, we have investigated EGFR protein expression, EGFR mutations, and EGFR gene copy number variations in adrenocortical neoplasms, specifically in 22 conventional ACC cases and 22 conventional ACA cases.
EGFR is a member of the EGF-related family of tyrosine kinase receptors. Upon the binding of EGFR ligands, downstream signaling pathways are activated, which results in strong stimulatory effects on cell proliferation, differentiation, survival, angiogenesis and migration [7, 8]. The expression of EGFR in ACC has been described in previous studies [12–15]. However, some of these studies have not differentiated between cytoplasmic and membranous staining, and only the latter type is currently considered to represent specific staining. In our previous study, we have found that EGFR protein expression was more frequent in myxoid ACC than in myxoid ACA . In the current study, our results also demonstrated that EGFR immunoreactivity was significantly more frequent among conventional ACC than conventional ACA cases. The relative abundance of EGFR in ACC suggests that anti-EGFR agents may be beneficial for patients with ACC.
Cetuximab, gefitinib, and erlotinib, chemotherapeutic agents that target the EGFR gene, have been administered to patients with cancer (e.g., non-small-cell lung cancer) . In addition, EGFR gene mutations have been reported in patients with non-small-cell lung cancer, and the status of these mutations has been correlated with the clinical response to tyrosine kinase inhibitors such as gefitinib . Kotoula et al. detected four tumor specimens that harbored TK domain mutations from a panel of 35 ACC (11.4%), suggesting that ACC that harbor an EGFR mutation exhibit increased phosphorylation of EGFR compared with wild-type carcinomas . In contrast, our previous and current study did not detect any mutations in samples of ACC and ACA . It is possible that the method used in this study was only able to detect 29 of the most common mutations.
EGFR gene amplification and structural genetic alterations have been reported in several types of adenocarcinoma, including non-small-cell lung cancer, glioblastoma, pancreatic cancer, and squamous cell carcinoma of the head and neck.
In our previous study of 10 myxoid adrenocortical neoplasms, only 1 ACA showed high polysomy on chromosome 7 . In current study, we examined the EGFR gene copy number in conventional ACC and ACA. Moreover, our study analyzed the relationship between EGFR copy number and the clinicopathological features of patients with ACC. In our series of cases, 50% of the ACC cases showed FISH positivity, and all ACA cases demonstrated FISH negativity based on the criteria of Capuzzo et al. . We discovered that there was a statistically significant difference between benign and malignant tumors regarding their alterations in the EGFR gene copy number. This result could potentially be used for the differential diagnosis of ACA and ACC. In addition, all of the positive cases showed high polysomy on chromosome 7, and none of the ACC cases demonstrated EGFR amplification, suggesting that EGFR amplification may be rare in ACC. However, according to the statistical analysis, EGFR FISH positivity was not associated with gender, age, tumor size, tumor weight, hormonal function, recurrence, metastasis or tumor stage. Therefore, our study does not provide evidence that high polysomy is related to the aggressive nature of these tumors. The survival curves demonstrated that there were no significant associations between EGFR protein expression, high polysomy on chromosome 7 and the overall survival of patients with ACC. This result may be related to certain cases that were lost track of during follow-up, but it would be necessary to increase the number of cases and the rate of follow-up for future studies.
In our study, EGFR protein expression and high polysomy were more frequently seen in conventional ACC than in conventional ACA, and EGFR immunohistochemical staining were more intensive in ACC cases than in ACA cases, whether this can be used as differential diagnosis still need to be demonstrated by large sample size. Furthermore, no association was found between EGFR protein expression and alterations in the EGFR gene copy number, this suggested that EGFR protein expression may not be due to increased copy number, other mechanisms, possibly transcriptional, post-transcriptional or epigenetic, may be associated with EGFR protein expression.
In summary, EGFR expression and high polysomy on chromosome 7 are frequent abnormalities in ACC than in ACA, suggesting that these abnormalities could potentially be used in the differential diagnosis of ACA and ACC. Furthermore, an investigation of the EGFR gene status may provide further information regarding potential therapeutic targets in patients with ACC.