TRAIL-targeting Therapies Still Hold Promise in Cholangiocarcinoma
FROM CELLULAR AND MOLECULAR GASTROENTEROLOGY AND HEPATOLOGY
primarily due to the adaptive resistance and unexpected immune modulation, according to investigators.
Those prior studies evaluated a combination of immunotherapy and TRAIL agonism, but selective TRAIL antagonism shows greater potential via dual ligand/receptor (TRAIL/TRAIL-R) targeting to block immunosuppression, reported lead author Emilien J. Loeuillard, PhD, of Mayo Clinic, Rochester, Minnesota, and colleagues.
“The TRAIL/TRAIL-R system has garnered considerable interest in cancer biology, especially as a potential anticancer therapy,” the investigators wrote in Cellular and Molecular Gastroenterology and Hepatology. “However, TRAIL-R agonists have had very limited anticancer activity in human beings, challenging this concept of TRAIL as an anticancer agent.”
This may be because they were working in the wrong direction, Dr. Loeuillard and colleagues suggested, citing recent work linking TRAIL with tumor proliferation and invasion, possibly via modification of the tumor immune microenvironment.
Exact mechanisms of modification, however, remain unclear. While TRAIL has been associated with tumor-promoting effects like induction of a promyeloid secretome in adenocarcinoma, it has also been linked with anticancer effects like activation of natural killer cells and cytotoxic T lymphocytes.
“Thus, the potency and hierarchy of TRAIL anticancer vs procancer processes in cancer biology has yet to be defined,” the investigators wrote.
While TRAIL ligation of cognate receptors has been previously investigated and shown to trigger proapoptotic signaling pathways, noncanonical TRAIL-mediated signaling remains largely unexplored, particularly in CCA.
The present study evaluated TRAIL biology in CCA using immunocompetent mouse models.
These experiments showed that noncanonical TRAIL signaling immunosuppresses the tumor microenvironment by increasing quantity and activity of myeloid-derived suppressor cells (MDSCs). Blocking noncanonical TRAIL signaling by selective deletion of TRAIL-R in immune cells had significantly reduced tumor volumes alongside fewer MDSCs, driven by FLICE inhibitory protein (cFLIP)-dependent nuclear factor kappa-B activation (NF-kappa-B) in MDSCs, which has antiapoptotic activity. While MDSCs present one possible target in this chain of immunosuppression, “therapeutic strategies for targeting MDSCs are limited,” the investigators wrote, noting that available myeloid modulators have fallen short in clinical trials.
Instead, cFLIP may be a convincing option, they suggested, as targeting cFLIP can sensitize cancer cells to proapoptotic TRAIL signaling. What’s more, cFLIP appears to protect MDSCs from TRAIL-mediated apoptosis, so taking out this barrier could render MDSCs susceptible to therapy.
“Our studies suggest that switching prosurvival/proliferation TRAIL signaling to canonical proapoptotic TRAIL signaling will promote MDSC apoptosis, which in turn has therapeutic implications for CCA suppression,” the investigators wrote.
Hope therefore remains for targeting TRAIL in patients with CCA, but with selective antagonism instead of agonism, as previously attempted.
“In summary, our findings support the role of selective therapeutic targeting of TRAIL-positive cancer cells in an effort to block TRAIL/TRAIL-R–mediated tumor immunosuppression,” Dr. Loeuillard and colleagues concluded.
This study was funded by the Cholangiocarcinoma Foundation and the Mayo Clinic Eagles 5th District Cancer Telethon Funds for Research Fellowship Program, the CTSA/National Center for Advancing Translational Science, the National Institutes of Health/National Cancer Institute, and others. The investigators disclosed no conflicts of interest.