Alterations in sphingolipid metabolism have been shown to contribute to the development of endocrine resistance and breast cancer tumor survival. Sphingosine kinase (SK), in particular, is overexpressed in breast cancer and is a promising target for breast cancer drug development. In this study, we used the novel SK inhibitor ABC294640 as a tool to explore the relationship between SK and estrogen (E2) receptor (ER) signaling in breast cancer cells. Treatment with ABC294640 decreased E2-stimulated ERE-luciferase activity in both MCF-7 and ER-transfected HEK293 cells. Furthermore, the inhibitor reduced E2-mediated transcription of the ER-regulated genes progesterone receptor and SDF-1. Competitive receptor-binding assays revealed that ABC294640 binds in the antagonist ligand-binding domain of the ER, acting as a partial antagonist similar to tamoxifen. Finally, treatment with ABC294640 inhibited ER-positive breast cancer tumor formation in vivo. After 15 d of treatment with ABC294640, tumor volume was reduced by 68.4% (P < 0.05; n = 5) compared with control tumors, with no marked weight loss or illness. Taken together, these results provide strong evidence that this novel SK inhibitor, which had not previously been known to interact with E2 signaling pathways, has therapeutic potential in treating ER-positive breast cancer via inhibition of both SK and ER signaling.
Adult human mesenchymal stem cells (hMSCs) have been shown to home to sites of breast cancer and integrate into the tumor stroma. We demonstrate here the effect of hMSCs on primary breast tumor growth and the progression of these tumors to hormone independence. Co-injection of bone marrow-derived hMSCs enhances primary tumor growth of the estrogen receptor-positive, hormone-dependent breast carcinoma cell line MCF-7 in the presence or absence of estrogen in SCID/beige mice. We also show hormone-independent growth of MCF-7 cells when co-injected with hMSCs. These effects were found in conjunction with increased immunohistochemical staining of the progesterone receptor in the MCF-7/hMSC tumors as compared to MCF-7 control tumors. This increase in PgR expression indicates a link between MCF-7 cells and MSCs through ER-mediated signaling. Taken together, our data reveal the relationship between tumor microenvironment and tumor growth and the progression to hormone independence. This tumor stroma-cell interaction may provide a novel target for the treatment of estrogen receptor-positive, hormone-independent, and endocrine-resistant breast carcinoma.
BackgroundAdult human mesenchymal stem cells (hMSC) have been shown to home to sites of carcinoma and affect biological processes, including tumour growth and metastasis. Previous findings have been conflicting and a clear understanding of the effects of hMSCs on cancer remains to be established. Therefore, we set out to investigate the impact of hMSCs on the oestrogen receptor positive, hormone-dependent breast carcinoma cell line MCF-7.ResultsIn this study, we show the effects of hMSCs on cancer cells are mediated through a secreted factor(s) which are enhanced by cancer cell-hMSC contact/communication. In addition to enhanced proliferation when in co-culture with hMSCs, MCF-7 cells were found to have increased migration potential in vitro. Inhibition of ER signalling by the pure anti-oestrogen ICI 182,780 decreased the effect of hMSCs on MCF-7 cell proliferation and migration supporting a role for ER signalling in the hMSC/MCF-7 cell interaction. Additionally, hMSCs have been shown to secrete a wide variety of growth factors and chemokines including stromal cell-derived factor-1 (SDF-1). This coupled with the knowledge that SDF-1 is an ER-mediated gene linked with hormone-independence and metastasis led to the investigation of the SDF-1/CXCR4 signalling axis in hMSC-MCF-7 cell interaction. Experiments revealed an increase in SDF-1 gene expression both in vivo and in vitro when MCF-7 cells were cultured with hMSCs. SDF-1 treatment of MCF-7 cells alone increased proliferation to just below that seen with hMSC co-culture. Additionally, blocking SDF-1 signalling using a CXCR4-specific inhibitor decreased hMSC induced proliferation and migration of MCF-7. However, the combined treatment of ICI and AMD3100 reduced MCF-7 cell proliferation and migration below control levels, indicating targeting both the ER and CXCR4 pathways is effective in decreasing the hMSCs induction of MCF-7 cell proliferation and migration.ConclusionsThe sum of these data reveals the relationship between tumour microenvironment and tumour growth and progression. Better understanding of the mechanisms involved in this tumour stroma cell interaction may provide novel targets for the development of treatment strategies for oestrogen receptor positive, hormone-independent, and endocrine-resistant breast carcinoma.
BACKGROUND: Little is known about the clinical factors associated with COVID-19 disease severity in children and adolescents. METHODS: We conducted a retrospective cohort study across 45 US children’s hospitals between April 2020 to September 2020 of pediatric patients discharged with a primary diagnosis of COVID-19. We assessed factors associated with hospitalization and factors associated with clinical severity (eg, admission to inpatient floor, admission to intensive care unit [ICU], admission to ICU with mechanical ventilation, shock, death) among those hospitalized. RESULTS: Among 19,976 COVID-19 encounters, 15,913 (79.7%) patients were discharged from the emergency department (ED) and 4063 (20.3%) were hospitalized. The clinical severity distribution among those hospitalized was moderate (3222, 79.3%), severe (431, 11.3%), and very severe (380, 9.4%). Factors associated with hospitalization vs discharge from the ED included private payor insurance (adjusted odds ratio [aOR],1.16; 95% CI, 1.1-1.3), obesity/type 2 diabetes mellitus (type 2 DM) (aOR, 10.4; 95% CI, 8.9-13.3), asthma (aOR, 1.4; 95% CI, 1.3-1.6), cardiovascular disease, (aOR, 5.0; 95% CI, 4.3-5.8), immunocompromised condition (aOR, 5.9; 95% CI, 5.0-6.7), pulmonary disease (aOR, 5.3; 95% CI, 3.4-8.2), and neurologic disease (aOR, 3.2; 95% CI, 2.7-5.8). Among children and adolescents hospitalized with COVID-19, greater disease severity was associated with Black or other non-White race; age greater than 4 years; and obesity/type 2 DM, cardiovascular, neuromuscular, and pulmonary conditions. CONCLUSIONS: Among children and adolescents presenting to US children’s hospital EDs with COVID-19, 20% were hospitalized; of these, 21% received care in the ICU. Older children and adolescents had a lower risk for hospitalization but more severe illness when hospitalized. There were differences in disease severity by race and ethnicity and the presence of selected comorbidities. These factors should be taken into consideration when prioritizing mitigation and vaccination strategies.
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