Abstract 1779P
Background
In Tumor microenvironment, the anti-inflammatory Tumor associated macrophages (TAMs) promot angiogenesis, tumor growth, invasion, and metastasis. MALAT1 and HOTAIR are promising oncogenic lncRNAs. CD80 and Mesothelin (MSLN) are over expressed in breast cancer (BC). Our previous data showed MSLN overexpression upon silencing MALAT1 in BC. This study investigate the immunomodulatory role of HOTAIR and MALAT1 in TAMs of BC patients.
Methods
55 blood samples BC patients were collected. CD14+ monocytes were isolated from PBMCs then differentiated to TAMs (7 days/IL10, IL4, MCSF and Tumor conditioned media). TAMs were transfected with HOTAIR and MALAT1 siRNAs. Relative expression of target mRNA was anaylzed (RealTime PCR).
Results
In hormonal, HER2+ and TNBC (all BC subtypes), MALAT1 was downregulated by siHOTAIR (p=0.0024, 0.0026, <0.0001) that was more significant than by siMALAT1 itself (p=0.0024, 0.0272, <0.0001). While siMALAT1 upregulated HOTAIR as a compensatory mechanism for the downregulation of MALAT1 (p=0.0174, 0.0819, 0.0003). CD80 and MSLN were inversely correlated with MALAT1 in TAMs. In HER2+ BC TAMs, their expression was upregulated by siMALAT1 (p=<0.0001, 0.1649), while their upregulation was more dramatic by siHOTAIR (p=0.0401, 0.0401). siMALAT1/siHOTAIR cotransfection upregulated CD80 and MSLN (p=0.0002,0.0183). In TNBC TAMs, CD80 and MSLN were overexpressed by siMALAT1 (p=<0.0001, p=<0.0001). They were upregulated more significantly by siHOTAIR (p=<0.0001, p=<0.0001). siMALAT1/siHOTAIR cotransfection upregulated CD80 and MSLN (p=0.0230, <0.0001). In hormonal BC TAMs, CD80 and MSLN were downregulated by siMALAT1 (p=0.2180, p=0.9987), this downregulation is proposed to be due to the overexpression of estrogen since estrogen is known to downregulate CD80 and MSLN. CD80 and MSLN expression was abolished upon siHOTAIR (p=<0.0001, 0.0003) due to the significant downregulation of MALAT1 and the dominancy of estrogen on both CD80 and MSLN. Co-transfection of siMALAT1/siHOTAIR downregulated CD80 and MSLN (p=0.0033,0.0016).
Conclusions
These findings shed the light on the pivotal dual immunoregulatory role HOTAIR and MALAT1 in BC.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
Molecular Pharmacology Research Group, Department of Pharmacology and Toxicology, Faculty of Pharmacy and Biotechnology, German University in Cairo, Egypt.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.