ACC is a rare endocrine cancer with limited therapeutic options and poor clinical outcomes. Studies have increasingly identified molecular diagnostic and prognostic signatures of various cancers by screening multiple databases via high-throughput technologies such as microarrays and next-generation sequencing. Transcription factors (TFs) are often aberrantly expressed in tumors, and correlated with cancer prognosis 25,26. Recent studies have identified specific TFs that are independent prognostic factors in various cancers 15,27,28. The zinc-finger transcription factor Snail is associated with decreased survival of ACC patients and higher risk of distant metastasis 19. However, a TF-related prognostic signature has not yet been identified for ACC.
We analyzed the gene expression profiles of ACC patients deposited in GEO and TCGA databases, and constructed a prognostic signature of 13 TFs, including CREB3L3, NR0B1, CENPA, FOXM1, E2F2, MYBL2, HOXC11, ZIC2, ZNF282, DNMT1, TCF3, ELK4 and KLF6. NR0B1, also known as DAX1, is an atypical orphan nuclear receptor that plays a key role in several cancers 29. NR0B1 silencing decreased the in vitro invasiveness of the lung cancer cell line A549 and inhibited xenograft growth without affecting cell proliferation 30. In addition, NR0B1 is overexpressed in cervical cancer and promotes cancer cell proliferation via the Wnt/β-catenin pathway 31. It is also overexpressed in adrenocortical tumors 32, ovarian cancer 33, breast cancer 34, endometrial cancer 35 and prostate cancer 36, although its potential role in ACC has not been investigated.
CEPNA is a histone-H3 variant that regulates cell division by establishing kinetochore assembly and ensuring proper centromere segregation, and is associated with cancer progression 37,38. CENPA expression level is a potential biomarker of poor prognosis in cancer patients 39. FOXM1 and E2F2 are the upstream regulators of CENPA and play critical roles in cell cycle progression and tumorigenesis 40,41. Both TFs can potentially bind to the CENPA promoter sequence indicating that they regulate CENPA transcription 42. Previous studies have correlated CENPA with poor prognosis in ACC patients and identified E2F2 as an ACC-related TF 43,44. Although few studies have associated CREB3L3, MYBL2, HOXC11, ZIC2, ZNF282, DNMT1, TCF2, FLK4 and KLF6 with ACC progression 45,46, there is no evidence linking FOXM1 to ACC. We found that high levels of CREB3L3 and NR0B1 were correlated with good prognosis, while that of other TFs were correlated with poor prognosis in the ACC patients. Tumor stage was correlated with OS of patients in the training set but not in the validation set. Furthermore, the 13-TF signature was an independent prognostic factor in both TCGA and GEO datasets.
The GSEA results showed that G2M-CHECK POINT and E2F-TARGET were significantly enriched in the high-risk group. The G2/M checkpoint is frequently impaired in cancer cells, which promotes genomic instability and tumorigenesis 47. Since the E2F transcription factors regulate DNA replication and are aberrantly expressed in almost all human cancers 48, targeting E2Fs could be a generic approach in anti-cancer treatment.