D-G23

CRISPR-Cas9 HDR knock-in uses a guide RNA to direct Cas9 to a genomic target adjacent to a PAM, where Cas9 creates a double-strand break; if a donor DNA template with homology to the cut region is present, cellular HDR can copy the donor sequence into the genome, producing a precise substitution, tag, reporter, or insertion rather than an indel. The readout is the fraction of alleles or cells carrying the intended donor-derived edit, measured by junction PCR, restriction-fragment analysis, Sanger sequencing, amplicon deep sequencing, flow cytometry for reporter knock-in, or clone genotyping; NHEJ indels and partial or non-HDR insertions are measured in parallel because they compete with or confound precise HDR outcomes.

Breast cancer is a heterogeneous cancer, and it has been distinguished into four subtypes: luminal A, luminal B, HER2-positive and basal-like. Molecular mutations, epigenetic alterations, hormone exposure and immune microenvironment are related to the progression of breast cancer.