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Breast cancer is the most common malignancy in women. Metastatic breast cancer is incurable and is a major cause of shortened patient survival. The different molecular types of breast cancer make targeted therapy difficult and a complex challenge. Aryl hydrocarbon receptor (AhR) is an evolutionarily conserved transcription factor that has been implicated in the metabolism of xenobiotic ligands. AhR is activated by numerous exogenous and endogenous ligands and participates in multiple physiological processes, including proliferation, migration, invasion and apoptosis. AhR expression is upregulated in certain breast cancer subtypes, including estrogen receptor-positive breast cancer, and has been implicated in the development and progression of breast cancer. Over the last two decades, AhR and its ligands have emerged as novel biological targets for the treatment of breast cancer. Both AhR agonists and antagonists may be effective in inhibiting critical activities of breast cancer. The present review evaluates the role and underlying mechanisms of AhR and its ligands in breast cancer and demonstrates the potential of exploiting AhR as a novel target for breast cancer therapy. [ABSTRACT FROM AUTHOR]

In several recent studies on metastatic breast cancer (MBC), ligand binding domain mutations of the estrogen receptor, which is coded by the ESR1 gene, were induced by long-term endocrine therapy and resulted in acquired endocrine therapy resistance and poor outcomes. Knowledge of the association between the development of ESR1 mutation and the clinicopathologic features may guide the decision-making process of metastatic breast cancer treatment, including endocrine therapy. The aim of the present study was to evaluate the association between the development of ESR1 mutation and the clinicopathologic characteristics of patients with MBC. To evaluate the association between the development of ESR1 mutation and clinicopathologic features, a cohort of 22 patients with MBC were retrospectively analyzed using next generation sequencing. In 14 of 22 patients, four mutations were detected on the metastatic site, including Tyr537Ser, Glu542Asp, Leu536Arg and Arg548Cys. Univariate analysis demonstrated that the duration of aromatase inhibitor and selective estrogen receptor modulator treatment, as well as the age of treatment initiation for early-stage breast cancer, were significantly associated with the development of ESR1 mutation. ESR1 mutation was identified in all five patients who received selective estrogen receptor modulators in the adjuvant setting followed by aromatase inhibitors in the metastatic setting, as well as in two of the three patients who received no selective estrogen receptor modulators in adjuvant setting followed by aromatase inhibitors in the metastatic setting. In conclusion, the results of the present study suggested that administrating adjuvant selective estrogen receptor modulator followed by aromatase inhibitor for metastasis may increase the frequency of ESR1 mutation. [ABSTRACT FROM AUTHOR]

The tumor immune environment not only modulates the effects of immunotherapy, but also the effects of other anticancer drugs and treatment outcomes. These immune responses may be evaluated by measuring tumor-infiltrating lymphocytes (TILs), which has been frequently verified clinically. In the present study, the prediction of the therapeutic effect of endocrine therapy by TILs on stage IV breast cancer was clinically analyzed. Data from 40 patients who underwent endocrine therapy as the initial drug therapy for stage IV breast cancer were used. The correlation between TILs, evaluated according to standard methods, and prognosis, including the efficacy of endocrine therapy, was investigated retrospectively. Patients with ≥50% lymphocytic infiltration were considered to have lymphocyte-predominant breast cancer (LPBC). An analysis of outcomes revealed no difference in progression-free survival (PFS; P=0.171), time to treatment failure (TTF; P=0.054), or overall survival (OS; P=0.641) between the high TIL (>10%) and low TIL (≤10%) groups. Patients with LPBC (≥50%) exhibited a significant prolongation of PFS (P=0.005, log-rank), TTF (P=0.001) and OS (P=0.027) compared with non-LPBC patients. On receiver operating characteristics (ROC) curve analysis, better results were obtained with LPBCs [area under the curve (AUC)=0.700] than with TILs (AUC=0.606). The present findings suggest that a high level of lymphocytic infiltration in the tumor stroma may serve as a predictor of the therapeutic efficacy of endocrine therapy in patients with stage IV estrogen receptor-positive breast cancer. [ABSTRACT FROM AUTHOR]

Palbociclib is a potent cyclin-dependent kinase (CDK)4/6 inhibitor that disrupts cell cycle progression and has been recently approved in combination with an aromatase inhibitor or fulvestrant as first- and second-line treatment in hormone receptor (HR)+, human epidermal growth factor receptor (HER)2- metastatic breast cancer. There is evidence that palbociclib may reverse endocrine therapy resistance and that it may also be added to ongoing endocrine therapy beyond progression to obtain clinical benefit. The aim of the present study was to explore this possibility in 5 patients who received palbociclib + fulvestrant following disease progression while under treatment with fulvestrant alone. The median progression-free survival was not reached during a median follow-up of 25 months, and the most frequent best response was stable disease. Three patients remained under treatment on the last re-evaluation. All patients had highly endocrine-sensitive disease and had previously received fulvestrant for ≥12 months. The hypothesis that a selected subpopulation of patients with HR+/HER2- metastatic breast cancer may benefit from the addition of palbociclib to ongoing endocrine therapy beyond disease progression merits further investigation. [ABSTRACT FROM AUTHOR]

Trastuzumab has markedly improved the treatment and long-term prognosis of patients with HER2-positive breast cancer. A frequent clinical challenge in patients with relapsing and/or metastatic disease is de novo or acquired trastuzumab resistance, and to date no predictive biomarkers for palliative trastuzumab have been established. In the present study, the prognostic values of factors involved in the HER2-associated PI3K/Akt signalling pathway were explored. The first 46 consecutive patients treated at the Department of Oncology, Linköping University Hospital between 2000 and 2007 with trastuzumab for HER2-positive metastatic breast cancer were retrospectively included. The gene copy number variation and protein expression of several components of the PI3K/Akt pathway were assessed in the tumour tissue and biopsy samples using droplet digital polymerase chain reaction and immunohistochemistry. Patients with tumours displaying a high-grade ERBB2 (HER2) amplification level of ≥6 copies had a significantly improved overall survival hazard ratio [(HR)=0.4; 95%, confidence interval (CI): 0.2–0.9] and progression-free survival (HR=0.3; 95% CI: 0.1–0.7) compared with patients with tumours harbouring fewer ERBB2 copies. High-grade ERBB2 amplification was significantly associated with the development of central nervous system metastases during palliative treatment. Copy gain (≥3 copies) of the gene encoding the tyrosine phosphatase PTPN2 was associated with a shorter overall survival (HR=2.0; 95% CI: 1.0–4.0) and shorter progression-free survival (HR=2.1; 95% CI: 1.0–4.1). In conclusion, high ERBB2 amplification level is a potential positive prognostic factor in trastuzumab-treated HER2-positive metastatic breast cancer, whereas PTPN2 gain is a potential negative prognostic factor. Further studies are warranted on the role of PTPN2 in HER2 signalling. [ABSTRACT FROM AUTHOR]

Exemestane (Exe) in combination with Everolimus (Eve) represents an important treatment option for patients diagnosed with hormone receptor positive (HR+), human epidermal growth factor receptor 2 negative (HER2-) metastatic breast cancer (MBC), which was previously treated with non-steroidal aromatase inhibitors (NSAI). Data from unselected populations may be useful for defining the optimal therapeutic algorithm within a clinical setting. Data from 264 HR+, HER2- MBC patients who received Exe-Eve treatment in combination, following the failure of NSAIs was retrospectively analyzed. Different lines of endocrine treatment (ET) were investigated to evaluate the efficacy and toxicity of the treatment within the 'everyday clinical practice' population. The disease control rate (DCR) was 73.1%, with no statistically significant difference among the different settings. At a median follow-up of 42 months, the median progression free survival (PFS) was 11.6, 9.7 and 7.5 months for patients treated with Exe-Eve as first, second or third line therapy, respectively. There was a statistically significant correlation with younger age, no previous adjuvant chemotherapy (CT), no previous adjuvant endocrine therapy (ET), HT duration =36 months, involvement of liver and/or lung, no prior CT for metastatic disease and PS=0 at the start of treatment. The median overall survival (OS) was 33.0 months; at a median follow-up of 67 months, the median OS was 43.1, 31.7 and 27.9 months in patients treated with Exe-Eve in first, second or third line therapy, respectively. On multivariate analysis, diabetes and previous CT for metastatic disease were revealed to correlate with a worse outcome. Conversely, the presence of mucositis was significantly associated with long-term survival. Overall, Exe-Eve was typically well tolerated and the majority toxicities were G1 or 2, while treatment discontinuation due to unacceptable toxicity was only required in 5.7% of patients. Despite the limitations due to the observational nature of this study, the findings suggest that treatment with Exe-Eve is an active and safe therapeutic option for endocrine-sensitive MBC patients in a real-world clinical setting, regardless of treatment lines. [ABSTRACT FROM AUTHOR]

The present case report describes a postmenopausal patient with hormone receptor (HR)+/human epidermal growth factor receptor 2 (HER2)+ metastatic breast cancer, who experienced progression of disease in bilateral lungs, lymph nodes and the liver under previous endocrine therapy and trastuzumab. Following the failure of two lines of endocrine-based treatment, the patient was administered the combined treatment of everolimus, trastuzumab and exemestane following surgical resection of the liver metastasis. A durable partial remission was achieved, which has continued for >27 months. This prominent clinical outcome in this patient demonstrates that the combined administration of endocrine therapy, trastuzumab and everolimus is clinically effective, and may induce long-term remission in patients with HR+/HER2+ metastatic breast cancer. [ABSTRACT FROM AUTHOR]

Although human epidermal growth factor receptor 2 (HER2)-targeted therapy significantly improves the prognosis of patients with HER2-positive breast cancer, most patients with advanced breast cancer eventually progress due to drug resistance. At present, there is no standard treatment after patients become resistant to HER2-targeted therapy. Previous studies have indicated that anti-angiogenesis drugs have potential efficacy in the treatment of advanced breast cancer. The present study reported on a case of a pretreated patient with HER2-positive advanced breast cancer with brain metastases who developed resistance to multiple lines of HER2-targeted treatment. The patient was treated with apatinib combined with trastuzumab and albumin-bound paclitaxel. The patient achieved partial response to the third-line treatment with a progression-free survival of 9 months. After combination treatment, the symptoms of headache and vomiting were relieved and all the brain metastases were significantly reduced. The present case indicated that apatinib may have anti-tumor activity in patients with HER2-positive breast cancer with HER2-targeted drug resistance. The present case provides valuable information and may offer a new possibility for the treatment of patients with breast cancer with brain metastases who progressed after clinical treatment with small-molecule anti-HER2 tyrosine kinase inhibitor drugs. [ABSTRACT FROM AUTHOR]

Breast cancer (BC) with overexpression of human epidermal growth factor receptor 2 (HER2) is closely associated with an elevated risk of multiple distant metastases and unfavorable prognosis. Disitamab Vedotin (RC48) is a newly developed antibody-drug conjugate targeting HER2, which is comprised of hertuzumab coupled to monomethyl auristatin E via a cleavable linker. Pre-clinical studies indicated its strong anti-tumor activity in HER2-positive and low HER2 expression models of BC. The present study reported on the case of a 60-year-old postmenopausal female who suffered from fatigue and was diagnosed with a right-sided BC tumor. The diagnosis was stage IV (cT4N3M1) hormone receptor (HR)-positive and HER2-positive invasive ductal carcinoma with systemic metastases (brain included). The patient initially responded well to 26 cycles of the first-line anti-HER2 targeted therapy plus chemotherapy (trastuzumab+pertuzumab+nab-paclitaxel) combined with whole-brain radiotherapy. However, both extracranial and intracranial lesions achieved progressive disease (PD), which eventually occurred during 5 sequential cycles of maintenance therapy. Subsequently, 4 cycles of second-line treatment (trastuzumab + pyrotinib + capecitabin) were continued until the levels of blood tumor markers CEA, CA15-3 and CA125 were elevated, and systemic PD was able to be attained (the brain metastases were rated as stable disease). Finally, the patient received RC48 as the third-line therapy and achieved a durable and effective clinical response. To date, the patient has benefited from 12 cycles of RC48 without any severe adverse effects. The overall survival was >3 years. The present study showcased that RC48 was effective and tolerable for a patient with HR- and HER2-positive BMBC. [ABSTRACT FROM AUTHOR]

Currently, endocrine therapy is the standard treatment for hormone receptor-positive advanced breast cancer (ABC). Despite the high sensitivity of anti-estrogen therapy, many breast cancer patients still experience disease progression, relapse, and reduced overall survival (OS) because of endocrine resistance. Several underlying mechanisms of this phenomenon include a change in hormone receptor expression, mutations in ESR1 and modification of important signaling pathways, but thus far none of these can be defined as the complete explanation. Additionally, it has been shown that in some breast cancers, expression of the estrogen receptor (ER) can be repressed by epigenetic modifications such as DNA methylation and histone deacetylation, and this could be a mechanism for endocrine resistance. Interestingly, although the efficacy of the combination of histone deacetylase (HADC) inhibitors and exemestane in hormone receptor-positive ABC that progressed on prior endocrine therapy has been investigated in several studies, whether pharmacologic blocking of HDAC activity acts as a therapeutic strategy remains highly controversial. Herein, we conducted a meta-analysis to evaluate the efficacy and safety of an HDAC inhibitor plus exemestane vs. exemestane alone in this setting. Our meta-analysis demonstrated that the combination group exhibited significantly prolonged progression-free survival (PFS) [hazard ratio (HR)=0.776, 95% confidence interval (CI)=0.675-0.892, P=0.000] and an improved objective response rate (ORR) (RR=1.612, 95% CI=1.085-2.396, P=0.018) compared to those treated with exemestane alone. Additionally, in terms of OS, the combination group failed to achieve a significant clinical OS benefit (HR=0.811, 95% CI=0.596-1.104, P=0.183). Although grade 3/4 toxicities were more common in the combination group, those toxicities were mostly asymptomatic and manageable. In conclusion, the addition of an HDAC inhibitor to exemestane significantly improves PFS over exemestane alone in hormone receptor-positive ABC patients who progressed on previous endocrine therapy. Identification of novel biomarkers to select patients who will benefit from this combination strategy is a high priority. [ABSTRACT FROM AUTHOR]

Immune checkpoint inhibitors have been critical in the treatment of advanced malignancies in recent years. Encephalitis caused by atezolizumab is an uncommon immune-related adverse event. The case of a 65-year-old female diagnosed with encephalitis closely associated with atezolizumab medication for metastatic advanced breast cancer is presented in the current study. Following a fourth atezolizumab dose 10 days previously, the patient fell into a deep coma. Initial brain magnetic resonance imaging revealed multiple patchy T2 hyperintensities in the bilateral cerebellar hemisphere, vermis of the cerebellum, bilateral frontal lobe, temporal lobe, parietal lobe and occipital cortex. Meanwhile, there were aberrant signs on diffusion-weighted imaging. The diagnosis of atezolizumab-induced encephalitis seemed probable after ruling out other possible causes of encephalitis. Subsequently, the condition of the patient worsened and there were indications of cardiac and respiratory arrest. Chest compressions were provided immediately, as well as a balloon mask for assisted ventilation, a medication boost, stimulated breathing and other symptomatic therapy. The patient's vital signs temporarily stabilised after this series of rescue measures. The patient refused further therapy and insisted on being discharged, and died a few days after being discharged from the hospital. In this case, the patient's encephalitis symptoms associated with atezolizumab were not as typical as previously documented. The patient's condition swiftly deteriorated to heartbeat apnea, and steroid pulse therapy was not received in a timely manner, resulting in an unfavourable outcome. [ABSTRACT FROM AUTHOR]

Cyclin-dependent-kinase 4–6 inhibitors (CDK4/6i) have improved the management of hormone receptor (HR)+/human epidermal growth factor receptor (HER)2− metastatic breast cancer (mBC). Currently, there are no valid prognostic factors for response to CDK4/6i. Baseline lymphopenia is reported as a prognostic factor in several types of cancer. The present retrospective study aimed to evaluate the effect of baseline absolute lymphocyte count (ALC) on response to palbociclib. Progression-free survival (PFS) was the primary endpoint. Secondary endpoints were overall survival (OS), best response and safety. A total of 114 patients treated for mBC between 2016 and 2019 were included. Median baseline ALC was 1.4 g/l (range, 0.2-4.3 g/l). A total of 65 (57%) and 49 (43%) patients had baseline ALC values of <1.5 and ≥1.5 g/l, respectively. Patients with baseline lymphopenia exhibited significantly shorter PFS (6 vs. 10 months; P=0.004) and OS (20 vs. 33 months; P=0.02). ALC <1.5 g/l independently predicted worse survival, as indicated by multivariate analysis (P=0.04; hazard ratio, 1.76; 95% confidence interval, 1.02-3.02). Patients with baseline ALC <1.5 g/l had significantly less partial response (14 vs. 22%; P=0.016) and more disease progression (46 vs. 20%; P=0.016) than those with ALC ≥1.5 g/l. ALC is a strong and easy-to-use dosage with prognostic factor for patients with HR+/HER2− mBC treated with palbociclib and endocrine therapy. Lymphopenia may also be a predictive factor of early progression. These data need to be verified in a larger prospective study. [ABSTRACT FROM AUTHOR]

Aromatase inhibitors (AIs), such as letrozole, are considered as first-line treatment for estrogen receptor-positive breast cancer in postmenopausal women. Despite the successful use of letrozole, resistance to therapy, tumor relapse and metastasis remain principal causes of patient mortality. Although there is no therapy currently available for AI-resistant breast cancer, previous reports have demonstrated that AI resistance is associated with hormone independence, increased growth factor signaling, enhanced cellular motility and epithelial to mesenchymal transition (EMT). This suggests a convergence of EMT and cancer stem cells (CSCs) in endocrine resistance. The present study evaluated the contribution of mammospheres in letrozole-resistant breast cancer by characterizing mammospheres and their potential impact on cellular motility. Ovariectomized immunocompromised female mice were inoculated in the mammary fat pad with either letrozole-resistant MCF-7 cells (LTLT-Ca) or letrozole-sensitive MCF-7 cells (AC-1). Subsequently, intratumoral CSC marker expression was assessed by immunohistochemistry. The results indicated that LTLT-Ca tumors were CD44+/CD24+, while AC-1 tumors presented low CD44/CD24 expression. Since mammosphere formation depends on CSCs, both cell lines were cultured either adherently (2D) or as mammospheres (3D) to assess the CD44/CD24 protein expression profile. When 3D culturing both cell lines, higher expression levels of CD44 and CD24 were observed when compared with their adherent counterparts, with the most robust change observed in the LTLT-Ca cell line. To quantitate the breast cancer stem cell activity, mammosphere formation assays were performed, and the LTLT-Ca cells formed mammospheres at a 3.4-fold higher index compared with AC-1 cells. Additionally, targeted gene expression arrays were conducted to compare the LTLT-Ca 3D and 2D cells, revealing that LTLT-Ca 3D cells displayed decreased expression levels of genes involved in cell adhesion and tumor suppression (e. g., E-cadherin, caveolin 1 and β-catenin). To validate this finding, wound healing assays were performed, and LTLT-Ca mammospheres exhibited a 70% wound closure, whereas AC-1 mammospheres exhibited a 39% wound closure. Collectively, the present findings demonstrated a strong association between AI-resistant mammospheres and an increased propensity for migration, which may be indicative of a poor prognosis. [ABSTRACT FROM AUTHOR]

Modulated electro-hyperthermia (mEHT) is a new treatment modality developed to overcome the problems associated with traditional hyperthermia; mEHT uses a precise impedance-matched system and modulated radiofrequency current flow to malignant tumors. It selects the malignant cells based on their biophysical differences, due to their high metabolic rate, individual (autonomic) behavior and membrane status. The aim of the present study was to report the outcomes of mEHT in the treatment of advanced breast cancer. mEHT was examined in 10 patients with advanced metastatic breast cancer and recurrent disease, who were considered incurable by standard therapy protocols. Of the 10 patients, partial response was achieved in 3, disease stability in 3, and progressive disease in 4; however, their quality of life was improved based on their subjective reports. No adverse effects were observed in any of the 10 patients. The present study demonstrated the feasibility of mEHT as a possible therapy for advanced breast cancer cases when standard therapies fail. Moreover, mEHT had no side effects and may be combined with various treatments for long-term therapy. [ABSTRACT FROM AUTHOR]

Human epidermal growth factor receptor 2 (HER2)-overexpressing breast cancer has been historically associated with an aggressive disease course with common distant metastasis and poor prognosis. HER2-targeting therapies have significantly changed treatment and drastically improved outcomes for this group of patients. However, primary or acquired resistance to anti-HER2 regimens leads almost universally to disease progression, often with difficult to treat central nervous system (CNS) metastases. The current review summarized the existing therapeutic options for HER2-positive metastatic disease in the first, second and further line setting. Furthermore, novel agents currently under development were presented, which have demonstrated encouraging results in heavily pretreated patients or specific subgroups, such as HR-positive/HER2-positive tumors and CNS disease. [ABSTRACT FROM AUTHOR]

Bone is the most common site of metastatic spread in patients with breast cancer. Patients with bone-only metastasis (BOM) are a unique group. The aim of the present study was to compare the clinicopathological characteristics, survival and prognostic factors of patients with BOM and non-BOM. The clinical data of 1,290 patients with metastatic breast cancer treated at the Tianjin Medical University Cancer Institute and Hospital (Tianjin, China) between January 2008 and December 2017 were reviewed. The clinical data were divided into a BOM group (n=208 cases) and a non-BOM group (n=1,082 cases). Patients with BOM had longer disease-free survival, progression-free survival (PFS) and overall survival (OS) compared with patients in the non-BOM group. The hormone receptor (HR) status and number of metastases were significant influencing factors of PFS in the BOM group. Furthermore, the HR status, location of bone metastasis and number of bone metastases were significantly associated with OS of patients in the BOM group. Age at diagnosis of metastasis, HR status and tumor stage were significantly associated with OS in the non-BOM group. In the BOM group, patients with HR+/human epidermal growth factor receptor 2 (HER2)− tumors had the most favorable prognosis. In the non-BOM group, patients with HR+/HER2− and HER2+ tumors had improved prognosis. In the BOM with HR+/HER2− subgroup, the PFS and OS of patients receiving endocrine therapy or sequential therapy (chemotherapy followed by endocrine therapy) was significantly improved compared with those receiving chemotherapy alone (P<0.05). Skeletal-related events were significantly associated with the number of bone metastases (P<0.001). The most common secondary metastatic site in the BOM group was the liver. The prognosis of the patients in the BOM group was improved compared with that in the non-BOM patients. HR− and multiple bone metastases, as well as combined axial and appendicular bone metastases, were significantly associated with poor prognosis in the patients with BOM. For patients in the HR+/HER2− BOM subgroup, endocrine therapy alone resulted in satisfactory results. [ABSTRACT FROM AUTHOR]