Association of Tumor Budding With Immune Evasion Pathways in Primary Colorectal Cancer and Patient-Derived Xenografts

Abstract

Tumor budding has been found to be of prognostic significance for several cancers, including colorectal cancer (CRC). Additionally, the molecular classification of CRC has led to the identification of different immune microenvironments linked to distinct prognosis and therapeutic response. However, the association between tumor budding and the different molecular subtypes of CRC and distinct immune profiles have not been fully elucidated. This study focused, firstly, on the validation of derived xenograft models (PDXs) for the evaluation of tumor budding and their human counterparts and, secondly, on the association between tumor budding and the immune tumor microenvironment by the analysis of gene expression signatures of immune checkpoints, Toll-like receptors (TLRs), and chemokine families. Clinical CRC samples with different grades of tumor budding and their corresponding PDXs were included in this study. Tumor budding grade was reliably reproduced in early passages of PDXs, and high-grade tumor budding was intimately related with a poor-prognosis CMS4 mesenchymal subtype. In addition, an upregulation of negative regulatory immune checkpoints (PDL1, TIM-3, NOX2, and IDO1), TLRs (TLR1, TLR3, TLR4, and TLR6), and chemokine receptors and ligands (CXCR2, CXCR4, CXCL1, CXCL2, CXCL6, and CXCL9) was detected in high-grade tumor budding in both human samples and their corresponding xenografts. Our data support a close link between high-grade tumor budding in CRC and a distinctive immune-suppressive microenvironment promoting tumor invasion, which may have a determinant role in the poor prognosis of the CMS4 mesenchymal subtype. In addition, our study demonstrates that PDX models may constitute a robust preclinical platform for the development of novel therapies directed against tumor budding in CRC.

Tumor bud-derived CCL5 recruits fibroblasts and promotes colorectal cancer progression via CCR5-SLC25A24 signaling

“…Tumor budding in CRC is defined as a single tumor cell or a cell cluster of up to four tumor cells, assessed in one hotspot (in a field measuring 0.785 mm 2 ) at the invasive front [ 12 , 13 ]. Studies have indicated a close link between tumor budding and a distinctive immune-suppressing microenvironment that promotes tumor invasion in gastric adenocarcinoma [ 14 ], stage I lung adenocarcinoma [ 15 ], pancreatic cancer [ 16 ], and CRC [ 17 ]. Nevertheless, the crosstalk between fibroblasts and tumor buds, and the mechanism through which the crosstalk occurs remain unknown.…”

Tumor Budding Is an Independent Prognostic Factor in Pancreatic Adenocarcinoma and It Positively Correlates with PD-L1 Expression on Tumor Cells

“…This finding is supported by a recent study by Sadozai et al, which demonstrated that extensive tumor budding is accompanied by diminished anti-tumor immunity and higher B7-H3 (CD276) expression [ 33 ]. In colorectal cancer, high-grade tumor budding is associated with an up-regulation of negative regulatory immune checkpoints and immune evasion [ 34 ]. We and others identified tumor budding as the independent prognostic factor in pancreatic cancer [ 35 , 36 ].…”

Multiplexed 3D atlas of state transitions and immune interactions in colorectal cancer

“…In region IM-A, tumor cells having poorly differentiated morphology invade the underlying stroma and classical budding is observed. This is a consequence of reduced cell-cell cohesion and is associated with metastasis and poor prognosis (Guil-Luna et al, 2020). Tumor buds are classically defined ≤4 cells in a cluster surrounded by stroma (Lugli et al, 2017a), but 3D reconstruction shows that these represent the termini of extended fibrillary structures whose distal tips generate the bud morphology in cross-section (Bronsert et al, 2014).…”

“…In this case, however, PD-L1 + macrophages were the immune cells most frequently in contact with CD8 + PD1 + T cells; in contrast, PD-L1 expression on tumor cells was low and few Tregs were present. Thus, the established connection between tumor budding, metastasis and disease recurrence is likely to reflect the presence of tumor cells undergoing EMT (and developing the ability to disseminate) as well as a permissive and immunosuppressive environment(Guil-Luna et al, 2020).…”