From the AGA Journals

Unique T cell populations pinpointed in hepatocellular carcinoma tissue

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Checkpoint inhibitor therapy may work but for which cell clusters?

Immunotherapy with checkpoint inhibitors has been suggested for the treatment of hepatocellular carcinoma (HCC) and finding relevant predictors of response to immunotherapy remains one of the most challenging tasks for solid gastrointestinal cancers such as HCC where efficiency of immune therapy suggests only a moderate response so far. Recently, two randomized phase 3 trials on checkpoint inhibitors in HCC, both first-line against sorafenib (Checkmate 459) as well as second-line against placebo (KEYNOTE-240), have failed to show an overall survival benefit despite clinical benefit in some patients and a manageable side effects profile. The study by Di Blasi et al. therefore provides important insights into the immune cell composition of tumor-infiltrating lymphocytes (TILs) in HCC. In this study it was possible to identify certain cell populations within TILs that resembled recently activated tumor-specific T cells that were in an exhausted state. It was possible to reinvigorate these exhausted cell clusters and to activate IFN-delta–producing T cells with the help of checkpoint inhibitor therapy in these patients. These data suggest that the enumeration of certain immune cell infiltrates may identify patients responding to checkpoint inhibitor therapy. Another important observation from this study was that not all immune-inflamed tumors identified by immunohistochemistry (or so-called “hot tumors”) responded to checkpoint inhibitor therapy and that more sophisticated analysis of the immune infiltrates with, e.g., flow cytometry or mass cytometry seems to be necessary to understand which patients respond. Different immune cell clusters have been suggested by other research groups and further research is needed to confirm this theory and to understand which of the proposed immune cell clusters and phenotypic profiles will prove most valuable in terms of prognosis for checkpoint inhibitor therapy in HCC.

Nico Buettner, MD, and Robert Thimme, MD, are professors in the department of medicine II, Medical Center University of Freiburg, Germany. They have no conflicts of interest.


 

FROM CELLULAR AND MOLECULAR GASTROENTEROLOGY AND HEPATOLOGY

Hepatocellular carcinoma (HCC) tissue contains several unique populations of tumor infiltrating cells, including some exhausted effector T cells that regain normal function when treated with the immunotherapy drug nivolumab, according to researchers.

The unique populations of recently activated CD4+, CD8+, and CD4-CD8 double-negative cells identified in the tumors expressed specific activation markers and inhibitor receptors, according to investigators, who have published the results of their immune profiling analyses in Cellular and Molecular Gastroenterology and Hepatology.

“Importantly, these cells expressed markers of activation and tissue residence, possibly suggesting activation within the tumor,” said Daniela Di Blasi, PhD, and the others researchers, of the University of Basel in Switzerland.

A further look at tumor histology revealed an accumulation of those activated T cells in immune-inflamed HCC, according to the investigators, who added that enumeration of specific tumor-infiltrating lymphocytes could represent “a prognostic indicator of therapy responsiveness.”

However, they advised caution in interpreting the results to date: “We are aware that the analysis described here is based on a small number of patients and that validation of its prognostic value requires ad hoc prospective studies that include more patients,” they said in their report.

The researcher’s findings were based on analysis of HCC biopsies before and after treatment with the immune checkpoint inhibitor nivolumab, nontumor liver tissue biopsies, and peripheral blood samples from 36 patients, most of whom were male, and about half of whom had cirrhosis. Investigators used multiparametric flow cytometry to characterize expression of activation markers including CD137, CD150, and ICOS, among others, as well as expression of inhibitory receptors including TIGIT and PD1.

Compared with nonneoplastic liver tissue, tumor tissue was enriched with T cells expressing the activation marker CD137 and the inhibitory receptor ICOS, indicating that HCC tumor-infiltrating lymphocytes “are different from liver-resident T cells and might have immunologic relevance,” Dr. Di Blasi and coauthors said in their report.

Further analysis revealed several cell populations unique to HCC samples, the authors said, including CD4+ T cells coexpressing ICOS and TIGIT, which tended to accumulate in tumor tissue, compared with nontumor tissue and peripheral blood mononuclear cells. Those CD4+ tumor-infiltrating T cells were functionally impaired, they added, as shown by a lack of cytokine production.

Activated CD8+ T cells likewise preferentially accumulated in tumor tissue, and most of those tumor-infiltrating cells expressed CD38 and PD1. The presence of these proliferating and functional cells may contribute to local inflammation and antitumor response, according to the investigators, who also identified two unique populations of double-negative T cells, including some that expressed CD137, which they said was a marker of recent T-cell activation.

The investigators also looked at the presence of tumor-infiltrating lymphocytes correlated to the presence of mononuclear cell infiltrate in tumor tissue. They found that immune-inflamed tumors had significantly increased proliferation of unique CD4+, CD8+, and double-negative T cell populations.

Nivolumab treatment appeared to substantially reduce the proportion of impaired CD4+ T cells, while increasing the percentage of interferon gamma–producing CD38+ CD4+ T cells and also promoting enrichment of interferon gamma–producing CD38+ CD8+ cells. Those increases in release of interferon gamma may have a positive influence on antitumor immunity via modulation of immune and tumor cell functions, according to the investigators.

Not all immune-inflamed tumors responded to nivolumab treatment, suggesting that an immune-inflamed profile is “necessary but not sufficient” for clinical response to an anti-PD1 agent, noted Dr. Di Blasi and colleagues.

Taken together, the researchers said their investigations suggest the presence of unique populations of T cells that might be providing effective anti-tumor immunity.

“These studies set the point for the identification of the tumor antigens stimulating these T cells and their possible exploitation as immunotherapeutic targets in HCC,” they concluded in the report.

The study was supported by grants from the European Research Council and the Swiss Initiative in Systems Biology, among others. Dr. Di Blasi and coauthors disclosed no conflicts of interest.

SOURCE: Di Blasi D et al. Cell Mol Gastroenterol Hepatol. 2019 Aug 22. doi: 10.1016/j.jcmgh.2019.08.004.

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