placebo) in patients with stage-II/III TNBC, which demonstrated an ORR of 60 and 20%, respectively (152)

placebo) in patients with stage-II/III TNBC, which demonstrated an ORR of 60 and 20%, respectively (152). TNBC, targeted therapy for early and advanced TNBC, and advances in non-coding RNA in therapy are the key highlights in this review. (42) performed gene expression profiling of 2,188 genes from 587 patients with TNBC and classified TNBC into six new groups, namely, basal-like 1 (BL1), basal-like 2 (BL2), immunomodulatory (IM), luminal androgen receptor (LAR), mesenchymal stem cell-like (MSL) and mesenchymal (M). The rest was classified as an unstable type (UNS/UNC). Each subtype had its characteristic feature. Basal-like was the most common type of TNBC (BL1, 22%; BL2, 12%) and was characterized by high Ki67 and DNA damage response levels. The IM subtype (18%) had basal-like characteristics with activation l-Atabrine dihydrochloride l-Atabrine dihydrochloride of IFN and IFN signaling and high RYBP cytotoxic T-lymphocyte associated protein 4 gene expression. Mesenchymal subtypes (M, 21%; MSL, 10%), along with cell differentiation pathways, showed deregulation of EGFR, calcium signaling, MAPK, and PI3K signaling. In the LAR subtype (9%), an ~10-fold increase in androgen receptor (AR) expression was seen, compared with other subtypes. Activation of various pathways, such as steroid synthesis and FOXA1 and ERBB signaling, were observed in this subtype (Table I) (42,43). Burstein (43) used a non-negative matrix factorization method to derive a panel consisting of 80 core genes that divided TNBC into four subtypes, luminal-AR (LAR), mesenchymal (MES), basal-like immune-suppressed (BLIS), and basal-like immune-activated (BLIA). BLIA has the best disease-free survival outcome compared to other subtypes (44). Based on DNA copy number, these subtypes can be placed into two groups, LAR or others l-Atabrine dihydrochloride (Table I) (31). Liu (45) performed mRNA and long non-coding RNA (lncRNA) expression analysis in 165 TNBC tumor samples at Fudan University Shanghai Cancer Centre. The tumor samples were categorized into four subtypes (IM, LAR, MES, and BLIS subtypes), consistent with the classification by Burstein (43). The IM subtype comprised of genes related to immune functions such as CCR2, CXCL13, CXCL11, CD1C, CXCL10, and CCL5, along with ENST00000443397 long ncRNA. In contrast, the LAR subtype had enrichment of hormone regulation signaling and ENST00000447908 lncRNA (45). The MES subtype expressed lncRNA “type”:”entrez-nucleotide”,”attrs”:”text”:”NR_003221″,”term_id”:”115392024″,”term_text”:”NR_003221″NR_003221 together with genes and pathways that promoted epithelial-to-mesenchymal (EMT) transition. Pathways and molecules such as DNA repair, replication, and mitosis, lncRNA TCONS_00000027 were enriched in the BLIS subtype (45,46). Genomic/transcriptomic data from a set of 997 primary tumors were extracted, and an integrated analysis was performed by Curtis (47). A set of 995 tumors from the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) cohort was used as a validation set that divided TNBC into ten groups, named Integrated Clusters (IntClust) 1C10 (47). Basal-like breast cancer mostly fell in IntClust 4 and 10 (~80%). IntClust 4 is known to have l-Atabrine dihydrochloride greater TIL counts, while IntClust 10 subtype can display genomic instability and chromosomal aberrations (Table I) (47C49). 4.?Molecular aberrations in TNBC Through whole-exome and whole-genome data, it is evident that most of the genetic alterations in TNBC are copy number alterations and somatic mutations (40). The BRCA1 and BRCA2 tumor suppressor genes are required for the maintenance of genomic stability. These genes play a role in DNA repair and replication error control (50,51). A total of 10% of patients with TNBC are known to harbor germline mutations in BRCA1 or BRCA2 (12,26,27). The lifetime risk of breast cancer becomes 60C70% in the presence of such mutations (52). Gene alterations leading to homologous recombination (HR) defects other than germline BRCA mutations are termed BRCAness (53). Moreover, ~35% of TNBC tumors show abnormalities in the HR pathway, making them sensitive to poly (ADP-ribose) polymerase (PARP) inhibitors and DNA-damaging l-Atabrine dihydrochloride agents (54). Other common mutations observed in TNBC patients include those in TP53 (50C60%) and PIK3CA (~10%) (18,42). An analysis from the Catalogue of Somatic Mutations in Cancer (COSMIC) database revealed that the top genes mutated in TNBC, apart from BRCA1/2, TP53, and PIK3CA, were RB1, PTEN, NOTCH1 and BRAF (Fig. 2A). Among the point mutations observed, 34% of them were nonsense substitutions (where a base change leads to a stop codon in the DNA.