Modulation of Immune Checkpoints by Chemotherapy in Human Colorectal Liver Metastases

Abstract

Summary Metastatic colorectal cancer (CRC) is a major cause of cancer-related death, and incidence is rising in younger populations (younger than 50 years). Current chemotherapies can achieve response rates above 50%, but immunotherapies have limited value for patients with microsatellite-stable (MSS) cancers. The present study investigates the impact of chemotherapy on the tumor immune microenvironment. We treat human liver metastases slices with 5-fluorouracil (5-FU) plus either irinotecan or oxaliplatin, then perform single-cell transcriptome analyses. Results from eight cases reveal two cellular subtypes with divergent responses to chemotherapy. Susceptible tumors are characterized by a stemness signature, an activated interferon pathway, and suppression of PD-1 ligands in response to 5-FU+irinotecan. Conversely, immune checkpoint TIM-3 ligands are maintained or upregulated by chemotherapy in CRC with an enterocyte-like signature, and combining chemotherapy with TIM-3 blockade leads to synergistic tumor killing. Our analyses highlight chemomodulation of the immune microenvironment and provide a framework for combined chemo-immunotherapies.

Liver Immune Microenvironment and Metastasis from Colorectal Cancer-Pathogenesis and Therapeutic Perspectives

“…Previous study showed that the expression of PD-L1 was increased in liver metastases compared to primary CRC, indicating different intrinsic microenvironment between primary and metastatic CRC [ 110 ], which may help CRC liver metastases escape from immune surveillance. In addition, it was reported that chemotherapy can modulate PD-L1 and TIM-3 expression in CRC liver metastases, suggesting the potential strategy of combined chemo-immunotherapies [ 111 ]. Preclinical study showed that dual CTLA4 and PD-1 blockade could significantly suppress colon cancer growth and liver metastasis by enhancing T cell responses and M1 macrophage polarization [ 112 ].…”

Protocol for tissue slice cultures from human solid tumors to study therapeutic response

“…The tumor slice culture method can be used to study tumor response to chemotherapies, immunotherapies, or combined chemo-immunotherapies. In previously published work ( Jabbari et al., 2020 ) the response of human colorectal liver metastases (CRLM) treated with chemotherapy and immunotherapy combinations was evaluated utilizing tissue slice cultures. Here we show an example of a case of CRLM treated with two different chemotherapy combinations with endpoints for tumor response including viability (based on percent change in MTS absorbance), histology including immunohistochemistry, and single-cell RNA sequencing.…”

“… (B) Another set of treated slices were used to perform single-cell RNA sequencing. Figure reprinted with permission from Jabbari et al, 2020 . Note how slices are dispersed over the treatment and endpoint assay.…”

“…See Figures 5 A and 5B for example of slice dispersion. Note: If slices are treated with immunotherapies or combined chemo-immunotherapies ( Jabbari et al., 2020 ) use appropriate IgG antibody for negative control. Slices are incubated at 37°C and 5% CO 2 with chemotherapy or immunotherapy for desired treatment period.…”

“…For complete details on the use and execution of this protocol, please refer to Kenerson et al. (2020) , Jabbari et al. (2020) , Brempelis et al.…”