Metaplastic breast cancer (MBC) is a rare special histologic type of triple-negative breast cancer, characterized by the presence of neoplastic cells showing differentiation towards squamous ...epithelium and/or mesenchymal elements. Here we sought to define whether histologically distinct subgroups of MBCs would be underpinned by distinct genomic and/or transcriptomic alterations. Microarray-based copy number profiling identified limited but significant differences between the distinct MBC subtypes studied here, despite the limited sample size (
= 17). In particular, we found that, compared to MBCs with chondroid or squamous cell metaplasia, MBCs with spindle cell differentiation less frequently harbored gain of 7q11.22-23 encompassing
and
, consistent with their lower expression of claudins and their association with the claudin-low molecular classification. Microarray-based and RNA-sequencing-based gene expression profiling revealed that MBCs with spindle cell differentiation differ from MBCs with chondroid or squamous cell metaplasia on the expression of epithelial-to-mesenchymal transition-related genes, including down-regulation of
and
. In addition, RNA-sequencing revealed that the histologic patterns observed in MBCs are unlikely to be underpinned by a highly recurrent expressed fusion gene or a pathognomonic expressed mutation in cancer genes. Loss of PTEN expression or mutations affecting
or
observed in 8/17 MBCs support the contention that PI3K pathway activation plays a role in the development of MBCs. Our data demonstrate that despite harboring largely similar patterns of gene copy number alterations, MBCs with spindle cell, chondroid and squamous differentiation are distinct at the transcriptomic level but are unlikely to be defined by specific pathognomonic genetic alterations.
The 19q12 locus is amplified in a subgroup of oestrogen receptor (ER)-negative grade III breast cancers. This amplicon comprises nine genes, including cyclin E1 (CCNE1), which has been proposed as ...its 'driver'. The aim of this study was to identify the genes within the 19q12 amplicon whose expression is required for the survival of cancer cells harbouring their amplification.
We investigated the presence of 19q12 amplification in a series of 313 frozen primary breast cancers and 56 breast cancer cell lines using microarray comparative genomic hybridisation (aCGH). The nine genes mapping to the smallest region of amplification on 19q12 were silenced using RNA interference in phenotypically matched breast cancer cell lines with (MDA-MB-157 and HCC1569) and without (Hs578T, MCF7, MDA-MB-231, ZR75.1, JIMT1 and BT474) amplification of this locus. Genes whose silencing was selectively lethal in amplified cells were taken forward for further validation. The effects of cyclin-dependent kinase 2 (CDK2) silencing and chemical inhibition were tested in cancer cells with and without CCNE1 amplification.
19q12 amplification was identified in 7.8% of ER-negative grade III breast cancer. Of the nine genes mapping to this amplicon, UQCRFS1, POP4, PLEKHF1, C19ORF12, CCNE1 and C19ORF2 were significantly over-expressed when amplified in primary breast cancers and/or breast cancer cell lines. Silencing of POP4, PLEKHF1, CCNE1 and TSZH3 selectively reduced cell viability in cancer cells harbouring their amplification. Cancer cells with CCNE1 amplification were shown to be dependent on CDK2 expression and kinase activity for their survival.
The 19q12 amplicon may harbour more than a single 'driver', given that expression of POP4, PLEKHF1, CCNE1 and TSZH3 is required for the survival of cancer cells displaying their amplification. The observation that cancer cells harbouring CCNE1 gene amplification are sensitive to CDK2 inhibitors provides a rationale for the testing of these chemical inhibitors in a subgroup of patients with ER-negative grade III breast cancers.
The small G-protein NRAS is mutated in 22% of human melanomas, whereas the related proteins KRAS and HRAS are mutated in only 2% and 1% of melanomas, respectively. We have developed a mouse model of ...melanoma in which Cre recombinase/LoxP technology is used to drive inducible expression of (G12V)KRAS in the melanocytic lineage. The mice develop skin hyperpigmentation, nevi, and tumors that bear many of the cardinal histopathology features and molecular characteristics of human melanoma. These tumors invade and destroy the underlying muscles and cells derived from them can grow as subcutaneous tumors and colonize the lungs of nude mice. These data establish that oncogenic KRAS can be a founder event in melanomagenesis.
Wnt signalling pathway is known to have a critical role in carcinogenesis and in epithelial-to-mesenchymal transition. Upon Wnt activation, β-catenin is translocated from the membrane to the ...cytoplasm and nucleus, where it interacts with transcriptional activators. It has been suggested that various spindle cell lesions of the breast may harbour Wnt pathway activation. Given that β-catenin nuclear localization constitutes a good surrogate marker of Wnt canonical pathway activation, we have investigated the distribution of β-catenin in spindle cell lesions of the breast and whether it could be employed in the differential diagnosis of these lesions. A total of 52 metaplastic breast carcinomas, eight fibromatoses and 23 phyllodes tumours were retrieved from our institutions' archives. We performed immunohistochemistry using two anti-β-catenin antibodies. In all, three fibromatoses and 21 metaplastic breast carcinomas were subjected to CTNNB1 (β-catenin encoding gene) mutation analysis by direct gene sequencing. A good correlation between the two antibodies was observed (Spearman's r>0.82, P<0.001). All fibromatoses and 23% of metaplastic breast carcinomas expressed nuclear β-catenin. In fibromatosis, β-catenin was more often diffusely expressed, whereas in metaplastic breast carcinomas, expression was more frequently focal. Membranous β-catenin expression was significantly lower in spindle cell carcinomas than in other subtypes of metaplastic breast carcinomas. In phyllodes tumours, stromal cells of benign and malignant subtypes displayed nuclear β-catenin expression in 94 and 57% of cases, respectively. No CTNNB1 mutation was identified in any of the 21 metaplastic carcinomas analysed, whereas the mutations 45S>S/P and 41T>T/A were found in samples of fibromatosis. In conclusion, β-catenin nuclear expression is a common feature in fibromatoses and in the stromal component of phyllodes tumours, but may also be observed in metaplastic breast carcinomas. β-catenin nuclear expression should not be used as a single marker to differentiate fibromatosis from other spindle cell tumours of the breast.
Aims
Breast myxoid fibroadenomas (MFAs) are characterized by a distinctive hypocellular myxoid stroma, and occur sporadically or in the context of Carney complex, an inheritable condition caused by ...PRKAR1A‐inactivating germline mutations. Conventional fibroadenomas (FAs) are underpinned by recurrent MED12 mutations in the stromal components of the lesions. The aim of this study was to investigate the genomic landscape of MFAs and compare it with that of conventional FAs.
Methods and results
Eleven MFAs from patients without clinical and/or genetic evidence of Carney complex were retrieved. DNA samples of tumour and matching normal tissue were subjected to massively parallel sequencing using the Memorial Sloan Kettering‐Integrated Mutation Profiling of Actionable Cancer Targets (MSK‐IMPACT) assay, an assay targeting 410 cancer genes. Genetic alterations detected by MSK‐IMPACT were tested in samples in which the stromal and epithelial components were separately laser capture‐microdissected. Sequencing revealed no germline PRKAR1A mutations and non‐synonymous mutations in six MFAs. Interestingly, in three of the MFAs in which the stromal and epithelial components were separately microdissected, the mutations were found to be restricted to the epithelial rather than the stromal component. The sole exception was a lesion harbouring a somatic truncating PRKAR1A mutation. Upon histological re‐review, this case was reclassified as a breast myxoma, consistent with the spectrum of tumous observed in Carney complex patients. In this case, the PRKAR1A somatic mutation was restricted to the stromal component.
Conclusion
MFAs lack MED12 mutations, and their stromal components seem not to harbour mutations in the 410 cancer genes tested. Whole‐exome and/or whole‐genome analyses of MFAs are required to elucidate their genetic drivers.
The cell surface glycoprotein P-cadherin is highly expressed in a number of malignancies, including those arising in the epithelium of the bladder, breast, esophagus, lung, and upper aerodigestive ...system. PCA062 is a P-cadherin specific antibody-drug conjugate that utilizes the clinically validated SMCC-DM1 linker payload to mediate potent cytotoxicity in cell lines expressing high levels of P-cadherin
, while displaying no specific activity in P-cadherin-negative cell lines. High cell surface P-cadherin is necessary, but not sufficient, to mediate PCA062 cytotoxicity.
, PCA062 demonstrated high serum stability and a potent ability to induce mitotic arrest. In addition, PCA062 was efficacious in clinically relevant models of P-cadherin-expressing cancers, including breast, esophageal, and head and neck. Preclinical non-human primate toxicology studies demonstrated a favorable safety profile that supports clinical development. Genome-wide CRISPR screens reveal that expression of the multidrug-resistant gene ABCC1 and the lysosomal transporter SLC46A3 differentially impact tumor cell sensitivity to PCA062. The preclinical data presented here suggest that PCA062 may have clinical value for treating patients with multiple cancer types including basal-like breast cancer.
Aims
Infiltrating epitheliosis is a rare complex sclerosing lesion (CSL) of the breast, characterized by infiltrating ducts immersed in a scleroelastotic stroma and filled with cells having ...architectural and cytological patterns reminiscent of those of usual ductal hyperplasia. In this study we sought to define the molecular characteristics of infiltrating epitheliosis.
Methods and results
Eight infiltrating epitheliosis, adjacent breast lesions (one usual ductal hyperplasia, one papilloma, one micropapillary ductal carcinoma in situ and one low‐grade adenosquamous carcinoma), and corresponding normal breast tissue from each case were microdissected and subjected to massively parallel sequencing analysis targeting all coding regions of 254 genes mutated recurrently in breast cancer and/or related to DNA repair. Mutations in components of the PI3K pathway were found in all infiltrating epitheliosis samples, seven of which harboured PIK3CA hotspot mutations, while the remaining case displayed a PIK3R1 somatic mutation.
Conclusions
Somatic mutations affecting PI3K pathway genes were found to be highly prevalent in infiltrating epitheliosis, suggesting that these lesions may be neoplastic rather than hyperplastic. The landscape of somatic genetic alterations found in infiltrating epitheliosis is similar to that of radial scars/CSLs, suggesting that infiltrating epitheliosis may represent one end of this spectrum of lesions.
A patient received a diagnosis of adenocarcinoma of the ampulla of Vater at 34 years of age. Two decades later, adenomatous polyps were found, followed by multiple primary invasive adenocarcinomas of ...both the colon and the stomach. Premature chromatid separation and mosaic variegated aneuploidy, combined with structural chromosomal abnormalities, were detected in his cells. We identified a germline homozygous intronic mutation, c.2386-11A→G, in the spindle-assembly checkpoint gene BUB1B, which creates a de novo splice site that is favored over the authentic (i.e., preferentially used) site. Our findings expand the phenotype associated with BUB1B mutations and the mosaic variegated aneuploidy syndrome to include common adult-onset cancers and provide evidence for the interdependency of the APC protein (encoded by the adenomatous polyposis coli gene) and the BUBR1 protein (encoded by BUB1B) in humans. (Funded by the Turner Family Cancer Research Fund and others.).
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