The circadian rhythm-related genes BHLHE40/DEC1 and BHLHE41/DEC2 have various functions under different cell and tissue conditions. BHLHE41/DEC2 has been reported to be both a cancer-suppressive and an oncogenic gene during cancer development. The effects of BHLHE41/DEC2 on differentiation have been examined using Bhlhe41/Dec2 knockout mice and/or in vitro differentiation models, and research has been conducted using genetic analysis of tumor cells, in vitro analysis of cancer cell lines, and immunohistochemical studies of the clinical samples. We summarize some of these studies, detail several problems, and consider possible reasons for contradictory results and the needs for further research.

Lung cancer constitutes a threat to human health. BHLHE41 plays important roles in circadian rhythm and cell differentiation as a negative regulatory transcription factor. This study investigates the role of BHLHE41 in lung cancer progression. We analyzed BHLHE41 function via in silico and immunohistochemical studies of 177 surgically resected non-small cell lung cancer (NSCLC) samples and 18 early lung squamous cell carcinoma (LUSC) cases. We also examined doxycycline (DOX)-inducible BHLHE41-expressing A549 and H2030 adenocarcinoma cells. BHLHE41 expression was higher in normal lung than in lung adenocarcinoma (LUAD) tissues and was associated with better prognosis for the overall survival (OS) of patients. In total, 15 of 132 LUAD tissues expressed BHLHE41 in normal lung epithelial cells. Staining was mainly observed in adenocarcinoma in situ and the lepidic growth part of invasive cancer tissue. BHLHE41 expression constituted a favorable prognostic factor for OS (p = 0.049) and cause-specific survival (p = 0.042) in patients with LUAD. During early LUSC, 7 of 18 cases expressed BHLHE41, and this expression was inversely correlated with the depth of invasion. DOX suppressed cell proliferation and increased the autophagy protein LC3, while chloroquine enhanced LC3 accumulation and suppressed cell death. In a xenograft model, DOX suppressed tumor growth. Our results indicate that BHLHE41 expression prevents early lung tumor malignant progression by inducing autophagic cell death in NSCLC.

Background/Aim: Pancreatic cancer (PC) has a poor prognosis and limited treatment options. The development of resistance to anticancer agents poses a significant challenge in the treatment of PC. Our previous study indicated that basic helix-loop-helix family member e41 (BHLHE41) is associated with the prognosis of lung cancer. Additionally, BHLHE41 affects the prognosis and response to anticancer drugs in several cancers. However, the functional role of BHLHE41 in cancer remains unclear. In PC, its expression has been reported to influence tumor malignancy; however, its impact on chemosensitivity has not yet been elucidated. Therefore, this study aimed to investigate the effects of BHLHE41 on PC chemosensitivity. Materials and Methods: Genetic modification and MTT assays were performed to evaluate the effect of BHLHE41 on anticancer agents. RNA sequencing (RNA-seq) was conducted to analyze the downstream pathways of BHLHE41. Furthermore, anticancer agent sensitivity tests were performed for the candidate genes identified through RNA-seq. Results: BHLHE41 enhanced the sensitivity of PC cells to gemcitabine (GEM) while suppressing the expression of insulin-like growth factor binding protein 4 (IGFBP4). Additionally, IGFBP4 affected sensitivity to GEM independently of BHLHE41, suggesting that IGFBP4 contributes to resistance to this agent in PC cells. Conclusion: These findings provide novel insights that may help identify potential targets for patients with PC undergoing chemotherapy and open new avenues for research and therapeutic strategies.