Breast cancer prevention is daunting, yet not an unsurmountable goal. Mammary stem and progenitors have been proposed as the cells‐of‐origin in breast cancer. Here, we present the concept of limiting ...these breast cancer precursors as a risk reduction approach in high‐risk women. A wealth of information now exists for phenotypic and functional characterization of mammary stem and progenitor cells in mouse and human. Recent work has also revealed the hormonal regulation of stem/progenitor dynamics as well as intrinsic lineage distinctions between mammary epithelial populations. Leveraging these insights, molecular marker‐guided chemoprevention is an achievable reality.
In our mini‐series on breast cancer, Khokha and colleagues review the revised perspectives on chemoprevention for high‐risk patients based on the current state of mammary gland molecular biology, and discuss its promises and challenges.
Patient-derived tumor organoids (PDOs) are a highly promising preclinical model that recapitulates the histology, gene expression, and drug response of the donor patient tumor. Currently, PDO culture ...relies on basement-membrane extract (BME), which suffers from batch-to-batch variability, the presence of xenogeneic compounds and residual growth factors, and poor control of mechanical properties. Additionally, for the development of new organoid lines from patient-derived xenografts, contamination of murine host cells poses a problem. We propose a nanofibrillar hydrogel (EKGel) for the initiation and growth of breast cancer PDOs. PDOs grown in EKGel have histopathologic features, gene expression, and drug response that are similar to those of their parental tumors and PDOs in BME. In addition, EKGel offers reduced batch-to-batch variability, a range of mechanical properties, and suppressed contamination from murine cells. These results show that EKGel is an improved alternative to BME matrices for the initiation, growth, and maintenance of breast cancer PDOs.
Expression of the Notch ligand Jagged 1 (JAG1) and Notch activation promote poor-prognosis in breast cancer. We used high throughput screens to identify elements responsible for Notch activation in ...this context. Chemical kinase inhibitor and kinase-specific small interfering RNA libraries were screened in a breast cancer cell line engineered to report Notch. Pathway analyses revealed MAPK-ERK signaling to be the predominant JAG1/Notch regulator and this was supported by gene set enrichment analyses in 51 breast cancer cell lines. In accordance with the chemical screen, kinome small interfering RNA high throughput screens identified Tribbles homolog 3 (TRB3), a known regulator of MAPK-ERK, among the most significant hits. We demonstrate that TRB3 is a master regulator of Notch through the MAPK-ERK and TGFβ pathways. Complementary in vitro and in vivo studies underscore the importance of TRB3 for tumor growth. These data demonstrate a dominant role for TRB3 and MAPK-ERK/TGFβ pathways as Notch regulators in breast cancer, establishing TRB3 as a potential therapeutic target.
Oxidative stress plays an important role in cancer development and treatment. Recent data implicate the tumor suppressor BRCA1 in regulating oxidative stress, but the molecular mechanism and the ...impact in BRCA1-associated tumorigenesis remain unclear. Here, we show that BRCA1 regulates Nrf2-dependent antioxidant signaling by physically interacting with Nrf2 and promoting its stability and activation. BRCA1-deficient mouse primary mammary epithelial cells show low expression of Nrf2-regulated antioxidant enzymes and accumulate reactive oxygen species (ROS) that impair survival in vivo. Increased Nrf2 activation rescues survival and ROS levels in BRCA1-null cells. Interestingly, 53BP1 inactivation, which has been shown to alleviate several defects associated with BRCA1 loss, rescues survival of BRCA1-null cells without restoring ROS levels. We demonstrate that estrogen treatment partially restores Nrf2 levels in the absence of BRCA1. Our data suggest that Nrf2-regulated antioxidant response plays a crucial role in controlling survival downstream of BRCA1 loss. The ability of estrogen to induce Nrf2 posits an involvement of an estrogen-Nrf2 connection in BRCA1 tumor suppression. Lastly, BRCA1-mutated tumors retain a defective antioxidant response that increases the sensitivity to oxidative stress. In conclusion, the role of BRCA1 in regulating Nrf2 activity suggests important implications for both the etiology and treatment of BRCA1-related cancers.
Antitumor T cells are subject to multiple mechanisms of negative regulation. Recent findings that innate lymphoid cells (ILCs) regulate adaptive T cell responses led us to examine the regulatory ...potential of ILCs in the context of cancer. We identified a unique ILC population that inhibits tumor-infiltrating lymphocytes (TILs) from high-grade serous tumors, defined their suppressive capacity in vitro, and performed a comprehensive analysis of their phenotype. Notably, the presence of this CD56
CD3
population in TIL cultures was associated with reduced T cell numbers, and further functional studies demonstrated that this population suppressed TIL expansion and altered TIL cytokine production. Transcriptome analysis and phenotypic characterization determined that regulatory CD56
CD3
cells exhibit low cytotoxic activity, produce IL-22, and have an expression profile that overlaps with those of natural killer (NK) cells and other ILCs. NKp46 was highly expressed by these cells, and addition of anti-NKp46 antibodies to TIL cultures abrogated the ability of these regulatory ILCs to suppress T cell expansion. Notably, the presence of these regulatory ILCs in TIL cultures corresponded with a striking reduction in the time to disease recurrence. These studies demonstrate that a previously uncharacterized ILC population regulates the activity and expansion of tumor-associated T cells.
Notch activation, which is associated with basal-like breast cancer (BLBC), normally directs tissue patterning, suggesting that it may shape the tumor microenvironment. Here, we show that Notch in ...tumor cells regulates the expression of two powerful proinflammatory cytokines, IL1β and CCL2, and the recruitment of tumor-associated macrophages (TAM). Notch also regulates TGFβ-mediated activation of tumor cells by TAMs, closing a Notch-dependent paracrine signaling loop between these two cell types. We use a mouse model in which Notch can be regulated in spontaneous mammary carcinoma to confirm that IL1β and CCL2 production, and macrophage recruitment are Notch-dependent. In human disease, expression array analyses demonstrate a striking association between Notch activation, IL1β and CCL2 production, macrophage infiltration, and BLBC. These findings place Notch at the nexus of a vicious cycle of macrophage infiltration and amplified cytokine secretion and provide immunotherapeutic opportunities in BLBC.
BLBC is aggressive and has an unmet need for effective targeted treatment. Our data highlight immunotherapeutic opportunities in Notch-activated BLBC. Effective IL1β and CCL2 antagonists are currently in clinical review to treat benign inflammatory disease, and their transition to the cancer clinic could have a rapid impact.
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Rapid molecular profiling of biological tissues with picosecond infrared laser mass spectrometry (PIRL-MS) has enabled the detection of clinically important histologic types and molecular subtypes of ...human cancers in as little as 10 s of data collection and analysis time. Utilizing an engineered cell line model of actionable BRAF-V600E mutation, we observed statistically significant differences in 10 s PIRL-MS molecular profiles between BRAF-V600E and BRAF-wt cells. Multivariate statistical analyses revealed a list of mass-to-charge (m/z) values most significantly responsible for the identification of BRAF-V600E mutation status in this engineered cell line that provided a highly controlled testbed for this observation. These metabolites predicted BRAF-V600E expression in human melanoma cell lines with greater than 98% accuracy. Through chromatography and tandem mass spectrometry analysis of cell line extracts, a 30-member “metabolite array” was characterized for determination of BRAF-V600E expression levels in subcutaneous melanoma xenografts with an average sensitivity and specificity of 95.6% with 10 s PIRL-MS analysis. This proof-of-principle work warrants a future large-scale study to identify a metabolite array for 10 s determination of actionable BRAF-V600E mutation in human tissue to guide patient care.
Background Studies have failed to identify characteristics of women who have been diagnosed with ductal carcinoma in situ (DCIS) and have a high or low risk of subsequent invasive cancer. Methods We ...conducted a nested case–control study in a population-based cohort of 1162 women who were diagnosed with DCIS and treated by lumpectomy alone from 1983 to 1994. We collected clinical characteristics and information on subsequent tumors, defined as invasive breast cancer or DCIS diagnosed in the ipsilateral breast containing the initial DCIS lesion or at a regional or distant site greater than 6 months after initial treatment of DCIS (N = 324). We also conducted standardized pathology reviews and immunohistochemical staining for the estrogen receptor (ER), progesterone receptor, Ki67 antigen, p53, p16, epidermal growth factor receptor-2 (ERBB2, HER2/neu oncoprotein), and cyclooxygenase-2 (COX-2) on the initial paraffin-embedded DCIS tissue. Competing risk models were used to determine factors associated with risk of subsequent invasive cancer vs DCIS, and cumulative incidence survival functions were used to estimate 8-year risk. Results Factors associated with subsequent invasive cancer differed from those associated with subsequent DCIS. Eight-year risk of subsequent invasive cancer was statistically significantly (P = .018) higher for women with initial DCIS lesions that were detected by palpation or that were p16, COX-2, and Ki67 triple positive (p16+COX-2+Ki67+) (19.6%, 95% confidence interval CI = 18.0% to 21.3%) than for women with initial lesions that were detected by mammography and were p16, COX-2, and Ki67 triple negative (p16−COX-2−Ki67−) (4.1%, 95% CI = 3.4% to 5.0%). In a multivariable model, DCIS lesions that were p16+COX-2+Ki67+ or those detected by palpation were statistically significantly associated with subsequent invasive cancer, but nuclear grade was not. Eight-year risk of subsequent DCIS was highest for women with DCIS lesions that had disease-free margins of 1 mm or greater combined with either ER−ERBB2+Ki67+ or p16+COX-2−Ki67+ status (23.6%, 95% CI = 18.1% to 34.0%). Conclusion Biomarkers can identify which women who were initially diagnosed with DCIS are at high or low risk of subsequent invasive cancer, whereas histopathology information cannot.
Breast cancer is the most common female cancer, affecting approximately one in eight women during their life- time. Besides environmental triggers and hormones, inherited mutations in the breast ...cancer 1 （BRCA1） or BRCA2 genes markedly increase the risk for the development of breast cancer. Here, using two different mouse models, we show that genetic inactivation of the key osteoclast differentiation factor RANK in the mammary epithelium markedly delayed onset, reduced incidence, and attenuated progression of Brcal;p53 mutation-driven mammary cancer. Long-term pharmacological inhibition of the RANK ligand RANKL in mice abolished the occurrence of Brcal mutation-driven pre-neoplastic lesions. Mechanistically, genetic inactivation of Rank or RANKL/RANK blockade impaired proliferation and expansion of both murine Brcal;p53 mutant mammary stem cells and mammary progenitors from human BRCA1 mutation carriers. In addition, genome variations within the RANK locus were significantly associated with risk of developing breast cancer in women with BRCA1 mutations. Thus, RANKL/ RANK control progenitor cell expansion and tumorigenesis in inherited breast cancer. These results present a viable stratesy for the uossible prevention of breast cancer in BRCA1 mutant i~atients.
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