SUMMARY
There is a higher incidence and mortality of colorectal cancer (CRC) in individuals self-identifying as Black
race compared to all other races and ethnicities in the US. Previous studies comparing self-identified Black vs
self-identified White CRC frozen samples have detected significant differences in gene expression and indicate
that self-identified race is significantly associated with differences in CRC biology. However, the list of DEGs
generated independently from each individual study shows limited overlap. This is likely because of the small
sample sizes for each dataset, with the largest set being the TCGA data set with ~60 self-identified Black
samples. Complex environmental and germline genomic factors contribute to the DEGs and other biological
results. However, a major barrier to disentangling these factors is accessing large numbers of CRC tissues
annotated for potentially confounding co-variables linked to self-identified racial categories. To conduct such a
study we propose to demonstrate the feasibility of assembling a multi-disciplinary research team to analyze a
large (>1000) self-identified Black/ African Ancestry (AA) vs. White/European Ancestry (EA) formalin fixed
paraffin embedded (FFPE) tissue samples archived at Stony Brook University Hospital (SBUH), Kings County
Hospital Center (KCHC/NYCH+H) and Henry Ford Hospital (HFH). CXCL10 will be the initial DEG target since
this is one of the few DEGs identified by more than one RNA-sequence dataset. CXCL10 is an interferon gamma
inducible protein that is a T-cell attractant and has been positively associated with T-cell infiltration in CRC and
with post-operative progress free survival. The reduced expression of CXCL10 in self-identified Black CRC vs.
White CRC could therefore potentially link self-identified racial differences in CRC immunologic transcriptional
profiles and CRC outcomes. Data from the Broad single cell (sc) RNA sequence (seq) data portal revealed that
myeloid cells and particularly macrophage cell subtypes are a major source of CXCL10 expression in CRC
tumors. However, no information on racial categories was made available for this scRNA dataset. A recent
analysis of the TCGA data revealed that macrophage signature transcripts are also reduced in self-identified
Black vs. White CRC (10) but it remains to be demonstrated whether macrophage signature transcripts are
colocalized with the CXCL10 transcripts in the same cell. In Aim 1, spatial profiling of CXCL10 expression in
CRC FFPE sections using RNAScopeTM in situ hybridization will be piloted to evaluate the hypothesis that
CXCL10 expressing macrophages are reduced in self-identified Black vs. White CRC. In Aim 2, annotation of
CRC FFPE tissues with respect to potentially confounding co-variables, (including estimates of ancestry
admixture and mismatch repair- immunohistochemistry results) will be harmonized, with the overarching goal of
conducting multivariable analyses of racial effects on CRC cancer biology.