Hyperactive mTOR and MNK1 phosphorylation of eIF4E confer tamoxifen resistance and estrogen independence through selective mRNA translation reprogramming.

The majority of breast cancers expresses the estrogen receptor (ER+) and is treated with anti-estrogen therapies, particularly tamoxifen in premenopausal women. However, tamoxifen resistance is responsible for a large proportion of breast cancer deaths. Using small molecule inhibitors, phospho-mimetic proteins, tamoxifen-sensitive and tamoxifen-resistant breast cancer cells, a tamoxifen-resistant patient-derived xenograft model, patient tumor tissues, and genome-wide transcription and translation studies, we show that tamoxifen resistance involves selective mRNA translational reprogramming to an anti-estrogen state by Runx2 and other mRNAs. Tamoxifen-resistant translational reprogramming is shown to be mediated by increased expression of eIF4E and its increased availability by hyperactive mTOR and to require phosphorylation of eIF4E at Ser209 by increased MNK activity. Resensitization to tamoxifen is restored only by reducing eIF4E expression or mTOR activity and also blocking MNK1 phosphorylation of eIF4E. mRNAs specifically translationally up-regulated with tamoxifen resistance include Runx2, which inhibits ER signaling and estrogen responses and promotes breast cancer metastasis. Silencing Runx2 significantly restores tamoxifen sensitivity. Tamoxifen-resistant but not tamoxifen-sensitive patient ER+ breast cancer specimens also demonstrate strongly increased MNK phosphorylation of eIF4E. eIF4E levels, availability, and phosphorylation therefore promote tamoxifen resistance in ER+ breast cancer through selective mRNA translational reprogramming.

Resistance to abemaciclib is associated with increased metastatic potential and lysosomal protein deregulation in breast cancer cells.

Cyclin dependent kinase 4 and 6 inhibitors such as abemaciclib are routinely used to treat metastatic estrogen receptor positive (ER+) breast cancer. However, adaptive mechanisms inhibit their effectiveness and allow for disease progression. Using ER+ breast cancer cell models, we show that acquired resistance to abemaciclib is accompanied by increase in metastatic potential. Mass spectrometry-based proteomics from abemaciclib sensitive and resistant cells showed that lysosomal proteins including CTSD (cathepsin D), cathepsin A and CD68 were significantly increased in resistant cells. Combination of abemaciclib and a lysosomal destabilizer, such as hydroxychloroquine (HCQ) or bafilomycin A1, resensitized resistant cells to abemaciclib. Also, combination of abemaciclib and HCQ decreased migration and invasive potential and increased lysosomal membrane permeability in resistant cells. Prosurvival B cell lymphoma 2 (BCL2) protein levels were elevated in resistant cells, and a triple treatment with abemaciclib, HCQ, and BCL2 inhibitor, venetoclax, significantly inhibited cell growth compared to treatment with abemaciclib and HCQ. Furthermore, resistant cells showed increased levels of Transcription Factor EB (TFEB), a master regulator of lysosomal-autophagy genes, and siRNA mediated knockdown of TFEB decreased invasion in resistant cells. TFEB was found to be mutated in a subset of invasive human breast cancer samples, and overall survival analysis in ER+, lymph node-positive breast cancer showed that increased TFEB expression correlated with decreased survival. Collectively, we show that acquired resistance to abemaciclib leads to increased metastatic potential and increased levels of protumorigenic lysosomal proteins. Therefore, the lysosomal pathway could be a therapeutic target in advanced ER+ breast cancer.

Estrogen receptor blockade and radiation therapy cooperate to enhance the response of immunologically cold ER+ breast cancer to immunotherapy.

BACKGROUND: Most patients with estrogen receptor positive (ER+) breast cancer do not respond to immune checkpoint inhibition (ICI); the tumor microenvironment (TME) of these cancers is generally immunosuppressive and contains few tumor-infiltrating lymphocytes. Radiation therapy (RT) can increase tumor inflammation and infiltration by lymphocytes but does not improve responses to ICIs in these patients. This may result, in part, from additional effects of RT that suppress anti-tumor immunity, including increased tumor infiltration by myeloid-derived suppressor cells and regulatory T cells. We hypothesized that anti-estrogens, which are a standard of care for ER+ breast cancer, may ameliorate these detrimental effects of RT by reducing the recruitment/ activation of suppressive immune populations in the radiated TME, increasing anti-tumor immunity and responsiveness to ICIs. METHODS: To interrogate the effect of the selective estrogen receptor downregulator, fulvestrant, on the irradiated TME in the absence of confounding growth inhibition by fulvestrant on tumor cells, we used the TC11 murine model of anti-estrogen resistant ER+ breast cancer. Tumors were orthotopically transplanted into immunocompetent syngeneic mice. Once tumors were established, we initiated treatment with fulvestrant or vehicle, followed by external beam RT one week later. We examined the number and activity of tumor infiltrating immune cells using flow cytometry, microscopy, transcript levels, and cytokine profiles. We tested whether fulvestrant improved tumor response and animal survival when added to the combination of RT and ICI. RESULTS: Despite resistance of TC11 tumors to anti-estrogen therapy alone, fulvestrant slowed tumor regrowth following RT, and significantly altered multiple immune populations in the irradiated TME. Fulvestrant reduced the influx of Ly6C+Ly6G+ cells, increased markers of pro-inflammatory myeloid cells and activated T cells, and augmented the ratio of CD8+: FOXP3+ T cells. In contrast to the minimal effects of ICIs when co-treated with either fulvestrant or RT alone, combinatorial treatment with fulvestrant, RT and ICIs significantly reduced tumor growth and prolonged survival. CONCLUSIONS: A combination of RT and fulvestrant can overcome the immunosuppressive TME in a preclinical model of ER+ breast cancer, enhancing the anti-tumor response and increasing the response to ICIs, even when growth of tumor cells is no longer estrogen sensitive.

Specific Forms of Graphene Quantum Dots Induce Apoptosis and Cell Cycle Arrest in Breast Cancer Cells.

Graphene quantum dots (GQDs), nanomaterials derived from graphene and carbon dots, are highly stable, soluble, and have exceptional optical properties. Further, they have low toxicity and are excellent vehicles for carrying drugs or fluorescein dyes. Specific forms of GQDs can induce apoptosis and could be used to treat cancers. In this study, three forms of GQDs (GQD (nitrogen:carbon = 1:3), ortho-GQD, and meta-GQD) were screened and tested for their potential to inhibit breast cancer cell (MCF-7, BT-474, MDA-MB-231, and T-47D) growth. All three GQDs decreased cell viability after 72 h of treatment and specifically affected breast cancer cell proliferation. An assay for the expression of apoptotic proteins revealed that p21 and p27 were up-regulated (1.41-fold and 4.75-fold) after treatment. In particular, ortho-GQD-treated cells showed G2/M phase arrest. The GQDs specifically induced apoptosis in estrogen receptor-positive breast cancer cell lines. These results indicate that these GQDs induce apoptosis and G2/M cell cycle arrest in specific breast cancer subtypes and could potentially be used for treating breast cancers.

Metastatic ER+ Breast Cancer: Mechanisms of Resistance and Future Therapeutic Approaches.

Endocrine therapy is the main treatment for hormone receptor-positive (HR+) breast cancer. However, advanced tumors develop resistance to endocrine therapy, rendering it ineffective as the disease progresses. There are several molecular mechanisms of primary and secondary endocrine resistance. Resistance can develop due to either alteration of the estrogen receptor pathway (e.g., ESR1 mutations) or upstream growth factors signaling pathways (e.g., PI3K/Akt/mTOR pathway). Despite progress in the development of molecularly targeted anticancer therapies, the emergence of resistance remains a major limitation and an area of unmet need. In this article, we review the mechanisms of acquired endocrine resistance in HR+ advanced breast cancer and discuss current and future investigational therapeutic approaches.

Examining the prevalence of homologous recombination repair defects in ER+ breast cancers.

PURPOSE: Homologous recombination deficiency (HRD) is well characterized in triple-negative breast cancer (TNBC), but its prevalence in the hormone-receptor-positive breast cancer subtypes is not as clearly defined. It is estimated that around 50-60% of TNBC cases are deficient in HR. We sought to identify HRD cases in ER+/Her2- patients using various mutational HRD signatures. METHODS: We abstracted published HRD genomic signatures from the Pan-Cancer Analysis of Whole Genomes (PCAWG) database and compared the prevalence of HRD in ER+/Her2- breast cancer, comparing this to the control of set of triple-negative breast cancers. RESULTS: In 78 patients with ER+/Her2- breast cancer, 13 patients have over a 70% probability of being HRD as measured by HRDetect, while 18 qualify as HRD based on HRD score, with an approximate prevalence of HRD ranging between 14 and 20% of cases. CONCLUSION: Our analyses suggest that 14% of ER+/Her2- patients may be HRD and therefore potentially eligible for treatments with HRD-directed therapies such as platinum agents and PARP inhibitors. As the ER+/Her2- subtype is the most common breast cancer subtype, this group of HRD patients is likely more sizable than that of HRD TNBC patients.

18F-fluorodeoxyglucose (FDG) PET or 18F-fluorothymidine (FLT) PET to assess early response to aromatase inhibitors (AI) in women with ER+ operable breast cancer in a window-of-opportunity study.

PURPOSE: This study evaluated the ability of 18F-Fluorodeoxyglucose (FDG) and 18F-Fluorothymidine (FLT) imaging with positron emission tomography (PET) to measure early response to endocrine therapy from baseline to just prior to surgical resection in estrogen receptor positive (ER+) breast tumors. METHODS: In two separate studies, women with early stage ER+ breast cancer underwent either paired FDG-PET (n = 22) or FLT-PET (n = 27) scans prior to endocrine therapy and again in the pre-operative setting. Tissue samples for Ki-67 were taken for all patients both prior to treatment and at the time of surgery. RESULTS: FDG maximum standardized uptake value (SUVmax) declined in 19 of 22 lesions (mean 17% (range -45 to 28%)). FLT SUVmax declined in 24 of 27 lesions (mean 26% (range -77 to 7%)). The Ki-67 index declined in both studies, from pre-therapy (mean 23% (range 1 to 73%)) to surgery [mean 8% (range < 1 to 41%)]. Pre- and post-therapy PET measures showed strong rank-order agreement with Ki-67 percentages for both tracers; however, the percent change in FDG or FLT SUVmax did not demonstrate a strong correlation with Ki-67 index change or Ki-67 at time of surgery. CONCLUSIONS: A window-of-opportunity approach using PET imaging to assess early response of breast cancer therapy is feasible. FDG and FLT-PET imaging following a short course of neoadjuvant endocrine therapy demonstrated measurable changes in SUVmax in early stage ER+ positive breast cancers. The percentage change in FDG and FLT-PET uptake did not correlate with changes in Ki-67; post-therapy SUVmax for both tracers was significantly associated with post-therapy Ki-67, an established predictor of endocrine therapy response.

Synthesis and preliminary evaluation of a PET-FI bimodal imaging agent targeting estrogen receptor.

Estrogen receptor is an attractive target for the diagnosis and treatment of breast cancer. This article reports for the first time a dual-modality imaging agent targeting estrogen receptor that can use PET imaging to diagnose breast cancer and utilize fluorescence imaging to achieve intraoperative navigation. Fluorescence experiments show that [natGa] 1 has typical aggregate induced emission characteristics. Above the critical concentration, [natGa] 1 can form biocompatible nanomicelles. [natGa] 1 can quickly light up estrogen receptor positive MCF-7 cells. Cell uptake experiments show that [68Ga] 1 is mediated by estrogen receptor. Therefore, [nat/68Ga] 1 shows the characteristics of highly sensitive diagnosis and visualization of breast cancer, and can be used as a lead compound for the development of a novel PET-FI bimodal imaging agent targeting the estrogen receptor.

Resistance to CDK4/6 Inhibitors in Estrogen Receptor-Positive Breast Cancer.

Estrogen receptor-positive (ER+) breast cancer is the most common form of breast cancer. Antiestrogens were the first therapy aimed at treating this subtype, but resistance to these warranted the development of a new treatment option. CDK4/6 inhibitors address this problem by halting cell cycle progression in ER+ cells, and have proven to be successful in the clinic. Unfortunately, both intrinsic and acquired resistance to CDK4/6 inhibitors are common. Numerous mechanisms of how resistance occurs have been identified to date, including the activation of prominent growth signaling pathways, the loss of tumor-suppressive genes, and noncanonical cell cycle function. Many of these have been successfully targeted and demonstrate the ability to overcome resistance to CDK4/6 inhibitors in preclinical and clinical trials. Future studies should focus on the development of biomarkers so that patients likely to be resistant to CDK4/6 inhibition can initially be given alternative methods of treatment.

Antitumor activity of Z-endoxifen in aromatase inhibitor-sensitive and aromatase inhibitor-resistant estrogen receptor-positive breast cancer.

BACKGROUND: The tamoxifen metabolite, Z-endoxifen, demonstrated promising antitumor activity in endocrine-resistant estrogen receptor-positive (ER+) breast cancer. We compared the antitumor activity of Z-endoxifen with tamoxifen and letrozole in the letrozole-sensitive MCF7 aromatase expressing model (MCF7AC1), as well as with tamoxifen, fulvestrant, exemestane, and exemestane plus everolimus in a letrozole-resistant MCF7 model (MCF7LR). METHODS: MCF7AC1 tumor-bearing mice were randomized to control (no drug), letrozole (10 µg/day), tamoxifen (500 µg/day), or Z-endoxifen (25 and 75 mg/kg). Treatment in the letrozole arm was continued until resistance developed. MCF7LR tumor-bearing mice were then randomized to Z-endoxifen (50 mg/kg) or tamoxifen for 4 weeks and tumors harvested for microarray and immunohistochemistry analysis. The antitumor activity of Z-endoxifen in the MCF7LR tumors was further compared in a second in vivo study with exemestane, exemestane plus everolimus, and fulvestrant. RESULTS: In the MCF7AC1 tumors, both Z-endoxifen doses were significantly superior to control and tamoxifen in reducing tumor volumes at 4 weeks. Additionally, the 75 mg/kg Z-endoxifen dose was additionally superior to letrozole. Prolonged letrozole exposure resulted in resistance at 25 weeks. In MCF7LR tumor-bearing mice, Z-endoxifen significantly reduced tumor volumes compared to tamoxifen, letrozole, and exemestane, with no significant differences compared to exemestane plus everolimus and fulvestrant. Additionally, compared to tamoxifen, Z-endoxifen markedly inhibited ERα target genes, Ki67 and Akt expression in vivo. CONCLUSION: In endocrine-sensitive and letrozole-resistant breast tumors, Z-endoxifen results in robust antitumor and antiestrogenic activity compared to tamoxifen and aromatase inhibitor monotherapy. These data support the ongoing development of Z-endoxifen.

Sequencing Endocrine Therapy for Metastatic Breast Cancer: What Do We Do After Disease Progression on a CDK4/6 Inhibitor?

PURPOSE OF REVIEW: Cyclin-dependent kinases 4 and 6 (CDK4/6) inhibitors have revolutionized the treatment landscape for patients with hormone receptor-positive (HR+) and HER2-negative (HER2-) metastatic breast cancer (MBC). However, optimal therapy after CDK4/6 inhibitors is unknown. This review provides an update on recent understanding of potential resistance mechanisms to CDK4/6 inhibitors and therapeutic strategies. RECENT FINDINGS: CDK4/6 inhibitors are broadly effective for HR+/HER2- MBC. However, intrinsic and acquired resistance is inevitable. Although there are no established clinical predictors of response aside from ER positivity, several cell cycle-specific and non-specific mechanisms have emerged as potential resistance biomarkers and therapeutic targets in recent studies. Examples include loss of function mutations in RB1 or FAT1, overexpression or amplification of CDK6 and CCNE1, alterations of FGFR, and PI3K/mTOR-mediated CDK2 activation. Biomarker studies and clinical trials targeting CDK4/6 inhibitor resistance are critical to improve treatments for HR+/HER2- MBC.

Vitamin D supplementation decreases serum 27-hydroxycholesterol in a pilot breast cancer trial.

PURPOSE: 27-hydroxycholesterol (27HC), an endogenous selective estrogen receptor modulator (SERM), drives the growth of estrogen receptor-positive (ER+) breast cancer. 1,25-dihydroxyvitamin D (1,25(OH)2D), the active metabolite of vitamin D, is known to inhibit expression of CYP27B1, which is very similar in structure and function to CYP27A1, the synthesizing enzyme of 27HC. Therefore, we hypothesized that 1,25(OH)2D may also inhibit expression of CYP27A1, thereby reducing 27HC concentrations in the blood and tissues that express CYP27A1, including breast cancer tissue. METHODS: 27HC, 25-hydroxyvitamin D (25OHD), and 1,25(OH)2D were measured in sera from 29 breast cancer patients before and after supplementation with low-dose (400 IU/day) or high-dose (10,000 IU/day) vitamin D in the interval between biopsy and surgery. RESULTS: A significant increase (p = 4.3E-5) in 25OHD and a decrease (p = 1.7E-1) in 27HC was observed in high-dose versus low-dose vitamin D subjects. Excluding two statistical outliers, 25OHD and 27HC levels were inversely correlated (p = 7.0E-3). CONCLUSIONS: Vitamin D supplementation can decrease circulating 27HC of breast cancer patients, likely by CYP27A1 inhibition. This suggests a new and additional modality by which vitamin D can inhibit ER+ breast cancer growth, though a larger study is needed for verification.

microRNA Regulation in Estrogen Receptor-Positive Breast Cancer and Endocrine Therapy.

As de novo and acquired resistance to standard first line endocrine therapies is a growing clinical challenge for estrogen receptor-positive (ER+) breast cancer patients, understanding the mechanisms of resistance is critical to develop novel therapeutic strategies to prevent therapeutic resistance and improve patient outcomes. The widespread post-transcriptional regulatory role that microRNAs (miRNAs) can have on various oncogenic pathways has been well-documented. In particular, several miRNAs are reported to suppress ERα expression via direct binding with the 3' UTR of ESR1 mRNA, which can confer resistance to estrogen/ERα-targeted therapies. In turn, estrogen/ERα activation can modulate miRNA expression, which may contribute to ER+ breast carcinogenesis. Given the reported oncogenic and tumor suppressor functions of miRNAs in ER+ breast cancer, the targeted regulation of specific miRNAs is emerging as a promising strategy to treat ER+ breast cancer and significantly improve patient responsiveness to endocrine therapies. In this review, we highlight the major miRNA-ER regulatory mechanisms in context with ER+ breast carcinogenesis, as well as the critical miRNAs that contribute to endocrine therapy resistance or sensitivity. Collectively, this comprehensive review of the current literature sheds light on the clinical applications and challenges associated with miRNA regulatory mechanisms and novel miRNA targets that may have translational value as potential therapeutics for the treatment of ER+ breast cancer.

Targeting cancer metabolism at the plasma membrane by limiting amino acid access through SLC6A14.

Rapidly proliferating cancer cells increase flux through anabolic pathways to build the mass necessary to support cell division. Imported amino acids and glucose lie at the apex of the anabolic pyramid. Consistent with this, elevated expression of nutrient transporter proteins is characteristic of aggressive and highly malignant cancers. Because tumour cells are more dependent than their normal neighbours on accelerated nutrient import, these up-regulated transporters could be excellent targets for selective anti-cancer therapies. A study by Babu et al. in a recent issue of the Biochemical Journal definitively shows that SLC6A14 (where SLC is solute carrier) is one such cancer-specific amino acid transporter. Although mice completely lacking SLC6A14 are viable and exhibit normal mammary gland development, these animals are highly resistant to mammary tumour initiation and progression driven by potent oncogenes. Because SLC6A14 is essential for tumour growth yet dispensable for normal development and tissue maintenance, small molecules that block amino acid import through this transporter could be effective and selective anti-cancer agents, particularly as components of rational drug combinations.

TRIM33 Is a Co-Regulator of Estrogen Receptor Alpha.

Estrogen receptor alpha (ER)-positive breast cancer is responsible for over 60% of breast cancer cases in the U.S. Among patients diagnosed with early-stage ER+ disease, 1/3 will experience recurrence despite treatment with adjuvant endocrine therapy. ER is a nuclear hormone receptor responsible for estrogen-driven tumor growth. ER transcriptional activity is modulated by interactions with coregulators. Dysregulation of the levels of these coregulators is involved in the development of endocrine resistance. To identify ER interactors that modulate transcriptional activity in breast cancer, we utilized biotin ligase proximity profiling of ER interactomes. Mass spectrometry analysis revealed tripartite motif containing 33 (TRIM33) as an estrogen-dependent interactor of ER. shRNA knockdown showed that TRIM33 promoted ER transcriptional activity and estrogen-induced cell growth. Despite its known role as an E3 ubiquitin ligase, TRIM33 increased the stability of endogenous ER in breast cancer cells. TRIM33 offers a novel target for inhibiting estrogen-induced cancer cell growth, particularly in cases of endocrine resistance driven by ER (ESR1) gene amplification or overexpression.

EGFR and HER2 hyper-activation mediates resistance to endocrine therapy and CDK4/6 inhibitors in ER+ breast cancer.

In patients with ER + metastatic breast cancer (mBC), the first-line treatment involves the combination of endocrine therapy (ET) and CDK4/6 inhibitors (CDK4/6i). However, a significant group of patients experiences disease progression, emphasizing the urgent clinical need to identify novel anti-tumor therapies. We previously generated breast cancer cells resistant to the combination of fulvestrant (ER downregulator) and abemaciclib (CDK4/6 inhibitor) from MCF7 and T47D (MCF7-FAR and T47D-FAR). RNA-seq-based Gene Set Enrichment Analysis (GSEA) revealed hyper-activation of EGFR, HER2, and AKT signaling in both MCF7-FAR and T47D-FAR. Modulating EGFR or ERBB2 expression through loss- and gain-of-function experiments altered tumor sensitivity to fulvestrant and abemaciclib in parental and FAR spheroids, affecting ERK and AKT/S6 pathways. Cetuximab treatment overcame tumor resistance to fulvestrant and abemaciclib in FAR and EGFR-overexpressing breast cancer spheroids and xenografts. Likewise, patient-derived organoids (PDOs) from individuals with ER + mBC, progressing on palbociclib, exhibited up-regulation of EGFR and HER2 pathways. In conclusion, our findings suggest that inhibiting EGFR and HER2 pathways might overcome resistance to ET + CDK4/6i in selected patients with ER + mBC.

Genomic analysis uncovers that cold-inducible RNA binding protein is associated with estrogen receptor in breast cancer.

BACKGROUND: RNA-binding proteins (RBPs) perform various biological functions in humans and are associated with several diseases, including cancer. Therefore, RBPs have emerged as novel therapeutic targets. Although recent investigations have shown that RBPs have crucial functions in breast cancer (BC), detailed research is underway to determine the RBPs that are closely related to cancers. OBJECTIVE: To provide an insight into estrogen receptor (ER) regulation by cold-inducible RNA binding protein (CIRBP) as a novel therapeutic target. RESULTS: By analyzing the genomic data, we identified a potential RBP in BC. We found that CIRBP is highly correlated with ER function and influences clinical outcomes, such as patient survival and endocrine therapy responsiveness. In addition, CIRBP influences the proliferation of BC cells by directly binding to ER-RNA. CONCLUSION: Our results suggest that CIRBP is a novel upstream regulator of ER and that the interplay between CIRBP and ER may be associated with the clinical relevance of BC.

Does Sentinel Lymph Node Biopsy Influence Subsequent Management Decisions in Women With Breast Cancer ≥ 70 Years Old?

BACKGROUND: There have been ongoing attempts to de-escalate surgical intervention in older breast cancer patients in recent years. However, there remains ongoing hesitancy amongst surgeons to de-implement axillary staging in this cohort. The supporting argument for performing a sentinel lymph node biopsy (SLNB) is that it may guide subsequent management. METHODS: A retrospective review was performed of 356 SLNBs, in 342 women ≥ 70 years of age with invasive breast cancer, between 2014 and 2022 in a single institution. Data were collected on patient and tumor characteristics and subsequent management for all patients and for patients with ER+/HER2-, early-stage disease. RESULTS: Positive SLNB significantly increased likelihood of receiving adjuvant chemotherapy (CTh) in patients aged 70-75 in all clinical subtypes (OR 4.0, 95% CI, 1.6-10; P = .0035). Positive SLNB did not significantly increase likelihood of receiving adjuvant CTh in patients aged 75-80, however, an Oncotype Dx score of ≥ 26 did (OR 34.50, 95% CI, 3.00-455.2; P = .0103). Positive SLNB was significantly associated with receiving adjuvant radiotherapy (RTh) in all patients aged 70-75 (OR 4.5, 95% CI, 2.0-11; P = .0004) and 75-80 (OR 9.7, 95% CI, 2.7-46; P = .0015). In patients aged ≥ 80 years, positive SLNB did not have a significant influence on subsequent treatments. CONCLUSION: In this study, SLNB did not significantly influence subsequent management decisions in patients over 80 and should rarely be performed in this cohort. However, SLNB still had a role in patients aged 70-80 and should be used selectively in this cohort.

Targeting estrogen mediated CYP4F2/CYP4F11-20-HETE metabolic disorder decelerates tumorigenesis in ER+ breast cancer.

Purpose: As the most common subset of breast cancer (BC), estrogen receptor positive (ER+) BC accounting for 80% of cases, has become a global public health concern. The female hormone estrogen (E2) unequivocally drives ER + breast malignancies. The reasons that estrogen affects BC development has long been considered, yet further study remains to be conducted of the molecular events in the E2-estrogen receptor α (ERα) signaling pathway in ER + BC progression, especially lipid metabolism, so providing more options for tailored and individualized therapy. Our aim is to find out new targets and clinical biomarkers for ER + breast cancer treatment from the perspective of lipid metabolism. Methods: Lipid metabolomics profiling was used to examine the membrane phospholipid stimulated by E2. Clinical BC samples were used to assess the association of CYP4F2, CYP4F11 expression with clinicopathological characteristics and patient outcomes. Some inhibitors of main enzymes in AA metabolism were used combined with E2 to assess roles of CYP4F2/CYP4F11 in the progression of ER + BC. CYP4F2, CYP4F11 overexpression and knockdown BC cell lines were employed to examine the effects of CYP4F2, CYP4F11 on cellular proliferation, apoptosis and tumor growth. Western blotting, qPCR, Immunohistochemical staining and flow cytometry were also conducted to determine the underlying mechanisms related to CYP4F2, CYP4F11 function. Results: The activation of the CYP450 signaling pathway in arachidonic acid metabolism contributed to ER + BC tumorigenesis. In ER + BC, CYP4F2 and CYP4F11 overexpression induced by E2 could promote cancer cell proliferation and resistance to apoptosis by producing the metabolite 20-HETE and activating the antiapoptotic protein Bcl-2. CYP4F2 and CYP4F11 elevation correlates with poorer overall survival and disease-free survival in ER + BC patients. Conclusion: CYP4F2, CYP4F11 and their metabolite 20-HETE could serve as effective prognostic markers and attractive therapeutic targets for novel anticancer drug development about ER + BC.