Background: Transmembrane protein 27 (TMEM27/collectrin), a glycoprotein and homolog of angiotensin-converting enzyme 2 (ACE2), is a regulator of renal amino acid uptake in the proximal tubule and may have a protective role in hypertension. Two previous reports have shown that the absence of TMEM27 expression in clear cell renal cell carcinoma (ccRCC) correlates with poorer cancer-related survival. We report our findings of TMEM27 expression in ccRCC and clinical outcomes in an independent third cohort.
Material and methods: We conducted a retrospective analysis to identify all 321 cases of ccRCC diagnosed between 2010 and 2015 at the University of Rochester Medical Center. The intensity of TMEM27 immunostaining on tumor tissue was semi-quantitatively graded on a scale of 0, 0.5, 1, 1.5, 2, 2.5, and 3 by a single pathologist, and correlated with tumor characteristics and survival.
Results: There was evidence of metastasis at time of nephrectomy in 36 (11.2%) cases, and at the latest follow-up in 70 (21.8%) cases. As of Spring 2021, 82 (25.5%) had died. TMEM27 staining intensity correlated inversely with various tumor characteristics. Kaplan-Meier survival analysis showed worse overall all-cause mortality (p = 0.02) and disease-free survival (p = 0.028) for tumors without any TMEM27 staining (0) compared to 0.5 or higher by log-rank test.
Conclusion: The absence of TMEM27 expression is associated with more aggressive tumor characteristics and poorer all-cause mortality and disease-free survival in ccRCC. TMEM27 may be a useful biomarker to assess cancer prognosis. Further studies are needed to better assess if TMEM27 is protective in RCC, and its potential role in active surveillance and prediction of response to target therapy.
Keywords: Transmembrane protein 27 (TMEM27); clear cell renal cell carcinoma; collectrin.