according to the authors of new research.
These findings support the previously reported link between fatty liver and colorectal cancer (CRC) liver metastasis, and suggest that CRC patients with nonalcoholic fatty liver disease (NAFLD) may respond differently to treatment than CRC patients without NAFLD, wrote lead author Zhijun Wang, MD, PhD, of Cedars-Sinai Medical Center, Los Angeles, and colleagues, in their paper.
“Obesity and NAFLD are the significant risk factors for CRC,” the investigators explained, in Cell Metabolism. “A growing body of epidemiological evidence indicates that fatty liver increases the occurrence of CRC liver metastasis and the local recurrence after resection of CRC liver metastases, thereby worsening prognosis ... There is an urgent need to understand the molecular mechanisms of metastasis in patients with fatty liver to manage those patients effectively.”
To this end, Dr. Wang and colleagues conducted a series of experiments involving mice, cell cultures, and human sera. They found that fatty liver increases risk of CRC liver metastasis via extracellular vesicles (EVs) that contain procarcinogenic miRNAs. As these EVs transfer microRNAs from fatty liver hepatocytes to metastatic cancer cells, YAP activity increases, which, in turn, suppresses immune activity within the tumor microenvironment, promoting growth of CRC metastasis.
Beyond the increased risk of liver metastasis presented by fatty liver, the investigators suggested that NAFLD may cause “more complex” metastatic tumor microenvironments, potentially explaining “diverse responses” to cancer therapies among patients with CRC and liver metastases.
“In summary, our study demonstrates that the pre- and prometastatic liver environment of fatty liver is induced by procarcinogenic EVs and results in an immunosuppressive tumor microenvironemnt, in which YAP plays an important role,” the investigators concluded. “Our study provides new insight into [the] distinct liver tumor microenvironment in patients with fatty liver and without fatty liver, which may contribute to the aggressiveness of metastatic tumors and weak responses to anticancer therapy in patients with fatty liver. Additional studies are warranted to develop precision medicine for treating patients with CRC and liver metastasis.”
One of the study authors disclosed relationships with Altimmune, Cytodyn, Novo Nordisk, and others. The other investigators had no relevant financial disclosures.