Understanding the Tumor Microenvironment of Cholangiocarcinoma

Investigators at Johns Hopkins University have published what they call the first “atlas” of the tumor microenvironment of cholangiocarcinoma, mapping out what they say is not 1 disease but 3, each with distinct immune signatures. The authors say their work will not only inform future clinical trials of immunotherapy for this type of cancer, but that it also shows why future studies must account for how drugs behave in each subgroup: intrahepatic (ICC), hilar (HC), and distal (DCC).

For this analysis, the investigators began with 104 surgically resected cholangiocarcinomas, which had not been treated. Of these, 44 were ICC, 20 were HC, and 40 were DCC. They performed multiplex immunohistochemistry with a pair of 15-marker immune panels and Nanostring assays, for an analysis that they wrote, “created a broad atlas of tumor-infiltrating immune cells,” which is now “the largest resource of its kind for the research community of cholangiocarcinoma.”

The research involved evaluating the prognostic value of the major immune subtypes, and examining their association with overall survival (OS). Across all 3 types of cholangiocarcinoma, higher densities of CD8+ T cells are associated with better survival—but long-term survival is not uniform. Among patients with ICC whose tumors had higher densities of CD8+ T cells, 75% had survival of more than 3 years following resection, while patients with DCC with higher densities of CD8+ T cells had a long-term survival rate of just 40%.

The analysis of the effect of density of CD4+ T cells revealed differences by subtype of cholangiocarcinoma. In ICC, there was “no significant difference” between tumors with higher and lower densities of these cells, but in DCC, higher density of CD4+ T cells was linked to significantly poorer OS; there was a trend toward poor OS that did not reach significance in HC.

The role of PD-1. Investigators were interested in the prognostic value of programmed cell death-1 (PD-1) and programmed cell death ligand-1 (PD-L1), of course. Across the 3 cholangiocarcinoma subtypes, OS of more than 3 years was associated with lower percentages of PD-1+ cells among the CD8+ T cells than those with OS of less than 3 years. “This confirmed that PD-1 is a factor for poor prognosis in ICC and DCC,” the authors wrote. But it wasn’t so simple.

When CD8+ T cells are divided into groups, PD-1+EOMES+ and PD-1+EOMES−, the researchers found that neither of these subtypes was associated with OS in any type of cholangiocarcinoma. Only when they looked at higher-density CD8+ T cells with PD-1−EOMES+ did they find a significant association with better OS in DCC, “likely because CD8+ T cells in general are associated with better OS in DCC.”

“Therefore, PD-1 and EOMES represent 2 independent exhaustion pathways in all 3 types of cholangiocarcinoma,” they wrote.

As for PD-L1, it is largely expressed in myeloid cells in the tumor microenvironment in the 3 cholangiocarcinoma types; among myeloid cells, PD-L1+ neutrophils are most abundant—but only a small share of neutrophils are PD-L1+. Among the myeloid subtypes examined, TAMs appear to have the highest percentages of cells expressing PD-L1, but neither TAM nor PD-L1 are sufficient markers. The investigators examined the prognostic value of macrophases, M1 and M2, and found these are associated with good prognosis in DCC and some groups of ICC.

Returning to the multiplex immunohistochemistry method, they looked at the prognostic value of various macrophage, TAM, and PD-L1 combinations. Their work, they wrote, “demonstrates the superiority and necessity of using multiple biomarkers to distinguish cholangiocarcinoma patients with different prognoses."

Finally, the authors found that the relationship between immunosuppressive cells and effector T cells in HC and DCC has important implications for treatment, in that the tumor microenvironment would likely need to be primed, perhaps with vaccine therapy, for a treatment strategy to be effective. They pointed to the example of a current clinical trial involving durvalumab with a CSF-1R inhibitor following chemotherapy or radioembolization for patients with ICC.

“This study suggests the importance of targeting immunosuppressive cells in all types of cholangiocarcinoma and priming the [tumor microenvironment] with effector T cells as a combination immunotherapy strategy for distal cholangiocarcinoma and hilar cholangiocarcinoma,” they concluded.

Reference

Xia T, Li K, Niu N, et al. Immune cell atlas of cholangiocarcinomas reveals distinct tumor microenvironments and associated prognoses. J Hematol Oncol. Oublished online March 28, 2022. doi:10.1186/s13045-022-01253-z