Prognostic value of CD73 expression in resected colorectal cancer liver metastasis

Abstract

Immune checkpoint blockade has not yet been effective in patients with mismatch repair proficient metastatic colorectal cancer. Targeting immunosuppressive metabolic pathways is being explored as a new immunotherapeutic approach. We assessed whether CD73, the rate limiting enzyme that catalyzes the degradation of extracellular AMP into immunosuppressive adenosine, could be an immunological determinant of colorectal liver metastases (CRLMs). By immunofluorescence on tissue microarrays, intratumoral CD73 expression (tCD73) was analyzed in 391 CRLMs resected in 215 patients, and soluble CD73 (sCD73) was measured by ELISA in the pre-operative serum of 193 patients. High tCD73 was associated with worse pathological features, such as multiple and larger CRLMs, and poorer pathologic response to pre-operative chemotherapy. The median time to recurrence and disease-specific survival after CRLM resection was significantly shorter in patients with high tCD73 (11.0 and 46.4 months, respectively) compared with low tCD73 (19.0 and 61.5 months, respectively). tCD73 was strongly associated with patient outcomes independently of clinicopathological variables. sCD73 did not correlate with tCD73. Patients with high levels of sCD73 also had shorter disease-specific survival. Our results suggested that CD73 in CRLMs may be prognostically informative and may help select patients more likely to respond to adenosine pathway blocking agents.

Keywords: CD73-Adenosine pathway; biomarker; colorectal cancer; immune checkpoint; liver metastasis.

Figure 1.

CD73 expression in CRLM and soluble CD73 serum level. (a) Representative examples of CD73 detection by multiplex immunofluorescence, near absent (left) and high in the stroma and within lumens of cancer pseudoglands. By immunohistochemistry (IHC), detection of membrane-bound CD73 on the apical border of cancer pseudoglands (arrow) in conjunction with shed or immune-cell bound detection within pseudogland lumens (right). Hematoxylin and eosin staining are shown for morphological reference in upper left corners. Bars represent 50 μm. (b) Correlation between percent necrotic CRLM surface area and intratumoral CD73 detection (tCD73). (c) Correlation between soluble CD73 (sCD73) serum level and tCD73. (d) tCD73 levels according to pre-operative chemotherapy status (left) and histologic pathological response to chemotherapy, assessed by the Tumor Regression Grade (TRG) system, where 1 represent complete response and 5 absence of response. Correlations assessed with Spearman method. Means compared with Mann-Whitney test and One-Way ANOVA test. MFI, Mean Fluorescence Intensity; CK, Cytokeratins; DAPI, 4ʹ.6ʹ-Diamidino-2-Phenylindol.

Figure 2.

Prognostic value of CD73 in colorectal cancer liver metastasis. Time to recurrence (upper panels) and disease-specific survival (lower panels) of patients according to (a) high (yellow) versus low (black) intra-tumoral CD73 expression (tCD73), using the upper tertile as cutoff (MFI > 398.3), (b) histopathologic response (Tumor Regression Grade, TRG) (left) and the degree of necrosis (right) in patients who received pre-operative chemotherapy, and (c) high (blue) versus low (black) soluble CD73 serum level (sCD73), using a cutoff value of 7.2 ng/mL (minimal p-value approach). Median time to recurrence and disease-specific survival are annotated on graphs. Log-rank test.