Colorectal/GI
CME
Muhammad bilal Mirza, MD
Post-doctoral research fellow
Department of surgery
nashville, Tennessee, United States
Disclosure(s): No financial relationships to disclose
Muhammad bilal Mirza, MD
Post-doctoral research fellow
Department of surgery
nashville, Tennessee, United States
Disclosure(s): No financial relationships to disclose
David Hanna, MD
Resident Physician
Vanderbilt University Medical Center
Nashville, Tennessee, United States
Disclosure information not submitted.
Chandrasekhar Padmanabhan, MD
Assistant Professor of Surgery
Vanderbilt University Medical Center, United States
Disclosure information not submitted.
Deepa Magge, MD, FACS
Assistant Professor of Surgery
Vanderbilt University Medical Center
Nashville, Tennessee, United States
Disclosure information not submitted.
.jpg "Christina E. Bailey, MD, MSCI photo")
Christina E. Bailey, MD, MSCI
Associate Professor of Surgery, General Surgery Program Director
Vanderbilt University Medical Center
Nashville, Tennessee, United States
Disclosure information not submitted.
Robert D. Beauchamp, MD
J.C. Foshee Distinguished Professor of Surgery, Professor of Cell and Developmental Biology Co-Leade
VUMC, United States
Disclosure information not submitted.
Mustafa Raoof, MD, FACS
Assistant Professor
Department of Surgery, Cancer Genetics and Epigenetics
Duarte, California, United States
Disclosure information not submitted.
Andrea Califano, PhD
Clyde and Helen Wu Professor of Chemical and Systems Biology Chair, Department of Systems Biology
Colombia, United States
Disclosure information not submitted.
Kamran Idrees, MD, MSCI, MMHC
Chief, Division of Surgical Oncology and Endocrine Surgery
Vanderbilt University Medical Center
Nashville, Tennessee, United States
Disclosure information not submitted.
Little is known about the role of the Tumor-associated Macrophages (TAMs) in progression of metastatic Colorectal Cancer (mCRC). Here in, we performed an in-depth analysis of mCRC using single cell RNA sequencing (scRNAseq), to evaluate the functional heterogeneity and phenotypic diversity of TAMs.
Methods:
We performed scRNAseq on 19 samples from 13 patients with mCRC and bulk RNA sequencing (bulk RNAseq) on 72 samples from 17 patients with mCRC. We used the Louvain algorithm in the Seurat pipeline to identify distinct TAMs sub-clusters in the scRNAseq cohort. Cell populations were validated using gene set enrichment analysis (GSEA) on the bulk RNAseq cohort. Kaplan-Meier survival analysis was used to estimate overall survival using The Cancer Genome Atlas (TCGA) Colon Cancer dataset.
Results:
All CRC samples were categorized into four groups: Primary tumors, hematogenous metastasis (HM), colorectal peritoneal metastasis (CPM), and malignant ascites (MA). By scRNAseq analysis, we identified 10 different cell populations across all CRC samples, consisting of cancer cells, immune cells (TAMs, T cells, B cells), and stromal cells. We discovered nine unique sub-clusters of TAMs which corresponded to five functional subsets in mCRC. TAMs were differentially distributed based on the tumor sites sites (primary vs. HM vs. CPM vs. MA; figure1a). Primary tumors were predominantly enriched in NLRP3 and IL-1b TAMs, involved in the inflammasome signalling. By contrast, HMs were enriched in C1QC TAMs, which play a role in complement activation and antigen presentation. CPMs, on the other hand, were significantly enriched in SPP1 TAMs, which are known to be involved in epithelial to mesenchymal transition. PLTP TAMs, associated with multiple immunosuppressive pathways, were identified in MA. Enrichment of each unique TAM sub-clusters was further validated on our independent bulk RNAseq dataset of mCRC metastasis, including HM and CPM. Survival analysis using CRC TCGA dataset, when comparing TAMs enriched in CPM (SPP1) versus HM (C1QC), revealed that SPP1highC1QClow TAMs as opposed to SPP1lowC1QChigh TAMs were associated with significantly poor overall survival (p < 0.05; figure 1b).
Conclusions:
Deconvolution of CRC metastasis at a single-cell resolution deepens our understanding of functional heterogeneity of TAMs and their variable expression patterns in hematogenous and peritoneal metastases. Our findings may partially explain the differences in the tumor biology, treatment response, and clinical outcomes between CPM and HM.