R9-caPep

The EdU incorporation assay measures DNA synthesis by adding the thymidine analog 5-ethynyl-2′-deoxyuridine to cells or tissues, where it is incorporated into newly synthesized DNA during S phase. Incorporated EdU is detected by copper-catalyzed azide-alkyne cycloaddition, in which a fluorescent azide covalently reacts with the ethynyl group on EdU, allowing S-phase cells to be detected by fluorescence microscopy, flow cytometry, or high-content imaging. EdU detection does not require DNA denaturation or anti-BrdU antibody access, which preserves sample structure and improves compatibility with immunostaining and multiparameter cytometry compared with BrdU-based detection. EdU can be cytotoxic in a cell-type- and exposure-dependent manner, so pulse duration, concentration, and continuous-labeling designs should be validated for each cell type.

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.

Apoptosis, also called programmed cell death, is generally characterized by distinct morphological characteristics.

TUNEL staining detects DNA strand breaks by using terminal deoxynucleotidyl transferase to add labeled nucleotides to exposed 3′-OH DNA termini, generating either microscopic staining in fixed cells or tissue sections, or fluorescence/cytometric signal in cell suspensions. TUNEL positivity reflects DNA fragmentation but should not be interpreted alone as definitive apoptosis, because TUNEL can also label necrotic, autolytic, mechanically damaged, or DNA-repair-associated DNA breaks.

PCNA immunodetection measures proliferative activity by detecting proliferating cell nuclear antigen, a nuclear protein associated with DNA polymerase δ function and DNA replication. The assay readout is the proportion of PCNA-positive nuclei among total counted cells, but PCNA labeling is not identical to BrdU labeling because PCNA can mark late G1/early S-associated replication competence and may persist beyond active DNA synthesis depending on fixation and extraction conditions.

Annexin V-based apoptosis assays rely on the detection of phosphatidylserine (PS) externalization from the inner leaflet of the plasma membrane to the outer leaflet, an early biochemical hallmark of apoptosis. Fluorescently labeled Annexin V binds PS in a calcium-dependent manner, enabling identification of early apoptotic cells by flow cytometry or fluorescence microscopy. When combined with a membrane-impermeant DNA-binding dye (e. g. , propidium iodide), this approach allows discrimination between viable (Annexin V−/dye−), early apoptotic (Annexin V+/dye−), and late apoptotic or necrotic (Annexin V+/dye+) cell populations by assessing membrane integrity and PS exposure.

Bromodeoxyuridine (BrdU) incorporation assay is based on the principle that BrdU, a thymidine analog, is incorporated into newly synthesized DNA during the S phase of the cell cycle, thereby serving as a marker of DNA replication and cellular proliferation. Incorporated BrdU can be detected using anti-BrdU antibodies following DNA denaturation, enabling visualization or quantification of proliferating cells through immunochemical detection methods such as immunofluorescence or immunohistochemistry.

Apoptosis is a regulated, generally non-lytic cell-death pathway that removes unwanted, damaged, infected, or abnormal cells through coordinated morphological changes, caspase activation, DNA fragmentation, and membrane remodeling. The intrinsic apoptosis pathway is controlled mainly by mitochondrial outer membrane permeabilization, BCL-2 family proteins, cytochrome c release, apoptosome formation, caspase-9 activation, and downstream executioner caspase-3/7 activation. The extrinsic apoptosis pathway is initiated by death receptors such as Fas, TNFR, and TRAIL receptors, which recruit adaptor proteins and activate caspase-8 before engaging executioner caspases or mitochondrial amplification through BID cleavage. Apoptosis is linked to many phenotypes, including cancer cell killing, tissue homeostasis, immune regulation, neurodegeneration, infection response, and treatment-induced cytotoxicity; unresolved questions include how apoptosis interacts with necroptosis, pyroptosis, ferroptos

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.

The bacterial reverse mutation assay detects point mutations that restore amino-acid prototrophy in auxotrophic Salmonella typhimurium or Escherichia coli tester strains; after exposure to a test article, mutagenic activity is read out as an increased number of revertant colonies on minimal agar compared with the vehicle control. The assay uses tester strains with different mutation targets so that base-substitution and frameshift mutagens can be detected, and testing is performed with and without exogenous mammalian metabolic activation because some chemicals require biotransformation to become mutagenic.