ADM is an early recognizable morphological event in the pancreas in response to inflammation or oncogene activation and is regarded as a key event during the development of PDAC (Sun 2020). Studies have revealed that acinar cells under ADM transform into a more duct-like structure (Huang 2018). Despite great efforts to understand the etiology and pathogenesis of PDAC, the underlying molecular mechanisms of PDAC development remain unclear. The current therapy for PDAC is unsatisfactory, and novel therapeutic targets and drugs would be very valuable.
Chronic stress has been proposed as a risk factor for the development of cancer (Huang 2018). Usually, the expression of NE and epinephrine increases significantly when the body is in an acute or chronic stress state (Le 2016). NE released under chronic stress can promote the invasion and metastasis of cancer cells (Liu 2022). In the present study, NE contributed to the process of ADM in primary acinar cells. Amylase is a specific marker for acinar cell carcinoma, and CK-19 is a specific duct cell marker. The trans-differentiation of acinar cells to duct-like cells may lead to ADM, which is commonly observed in PDAC (Taherian 2022). ADM has been regarded as a necessary step for Kras-dependent pancreatic carcinogenesis, and acinar cells under ADM exhibit an increased tendency for malignant transition (Alonso-Curbelo 2021). In our study, we found that NE treatment significantly promoted the expression levels of CK-19 and inhibited the expression levels of amylase. Increased proliferative, migratory, and invasive abilities are hallmarks of pancreatic cancer cells. Thus, the effects of NE on cell proliferation, migration and invasion were investigated. We found that NE enhanced the proliferation, migration, and invasion of 266-6 and MiaPaCa-2 cells. Hence, PDAC growth promoted by NE may increase the death rate among patients with PDAC.
The Notch pathway plays a critical role in pancreatic cancer (Thomas 2014). We found that DAPT (Notch selective inhibitor) was able to partially reverse the function of NE in cell proliferation and invasion. It has been revealed that the Notch signaling pathway is involved in the cancer-promoting effects induced by NE. The vital components of the Notch signaling pathway are thought to be Notch1 proteins (Zhou 2022), which are crucial to the occurrence and progression of PDAC (Yang 2021). The results of our study demonstrate that Notch1 is activated following treatment with NE in 266-6, MiaPaCa-2 and primary acinar cells. However, this effect of NE was reversed by DAPT. Notch1 has also been shown to regulate the expression and activation of MMP9 through NF-κB in pancreatic cancer cells (Fazio 2016). In particular, MMP9 drives metastasis and tumor progression (Li 2020). We observed that NE can induce MMP9 and PCNA expression, and MMP9 and PCNA expression levels were downregulated in MiaPaCa-2 cells after treatment with DAPT. PCNA is widely used as a marker of cell proliferation in various tumors, including pancreatic cancers (Bai 2011). Additionally, we observed that NE treatment significantly promoted the expression levels of CK-19 and inhibited the expression levels of amylase. However, the expression levels of CK-19 were downregulated, and amylase expression levels were upregulated after DAPT treatment in 266-6 cells. These results indicate that the Notch signaling pathway is involved in the cancer-promoting effects induced by NE.
Resveratrol possesses a wide variety of health-promoting properties, including anticancer, anti-inflammatory, antimicrobial, cardioprotective and antioxidant activities (Cui 2016). Previous studies have shown that resveratrol can inhibit the proliferation of breast cancer cells, and studies in vivo have demonstrated that it can inhibit the growth of tumors (Qin 2020). Our research group previously verified that resveratrol could inhibit pancreatic cancer through the downregulation of NAF-1 (Qin 2020). In pancreatic cancer models, resveratrol has been considered to be a protective or therapeutic drug and has been shown to have synergistic antitumor effects in combination with gemcitabine (Liou 2015). However, the contribution of resveratrol to the tumor-promoting effect of chronic stress is unknown. Functional experiments found that NE promoted cell colony formation and migratory and invasive abilities, whereas resveratrol was able to nullify the cancer-promoting effects of NE. Mechanistic research showed that resveratrol inhibited the expression of Notch1, MMP-9, PCNA, and CK-19 and promoted the expression of amylase in 266-6 and MiaPaCa-2 cells. In general, resveratrol regulates ADM through Notch1, which may contribute to its anticancer effect.
Our present study demonstrates that the chronic stress hormone NE significantly increases cell proliferation, migration and invasion in pancreatic cancer. This regulation is most likely achieved through Notch signaling. Resveratrol is able to target Notch signaling to exert anticancer effects in NE-induced pancreatic cancer. Our findings provide a basis for future studies and novel ideas and strategies for the prevention and treatment of pancreatic cancer. However, there are limitations to the current study; this experiment was only performed in vitro. Whether such a mechanism develops in chronically stressed animals is not known and requires further study.