MALAT-1: Immunomodulatory lncRNA hampering the innate and the adaptive immune arms in triple negative breast cancer
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Date
2023-03
Journal Title
Journal ISSN
Volume Title
Type
Article
Publisher
Neoplasia Press
Series Info
Translational Oncology;31 (2023) 101653
Scientific Journal Rankings
Abstract
Background: Triple negative breast cancer (TNBC) is known as hot immunogenic tumor. Yet, it is one of the most
aggressive BC subtypes. TNBC evolve several tactics to evade the immune surveillance phenomena, one of which
is shedding of natural killer (NK) cells activating immune ligands such as MICA/B and/or by inducing the
expression of the immune checkpoints such as PD-L1 and B7-H4. MALAT-1 is an oncogenic lncRNA. MALAT-1
immunogenic profile is not well investigated.
Aim: The study aims at exploring the immunogenic role of MALAT-1 in TNBC patients and cell lines and to
identify its molecular mechanism in altering both innate and adaptive immune cells present at the tumor
microenvironment of TNBC
Methods: BC patients (n = 35) were recruited. Primary NK cells and cytotoxic T lymphocytes were isolated from
normal individuals using the negative selection method. MDA-MB-231 cells were cultured and transfected by
several oligonucleotides by lipofection technique. Screening of ncRNAs was performed using q-RT-PCR.
Immunological functional analysis experiments were performed upon co-culturing primary natural killer cells
and cytotoxic T lymphocytes using LDH assay. Bioinformatics analysis was performed to identify potential
microRNAs targeted by MALAT-1.
Results: MALAT-1 expression was significantly upregulated in BC patinets with a profound expression in TNBC
patients compared to their normal counterparts. Correlation analysis revealed a positive correlation between
MALAT-1, tumor size and lymph node metastasis. Knocking down of MALAT-1 in MDA-MB-231 cells resulted in a
significant induction of MICA/B, repression of PD-L1 and B7-H4 expression levels. Enhancement of cytotoxic
activity of co-cultured NK and CD8+ cells with MALAT-1 siRNAs transfected MDA-MB-231 cells. In silico analysis
revealed that miR-34a and miR-17–5p are potential targets to MALAT-1; accordingly, they were found to be
downregulated in BC patients. Forcing the expression of miR-34a in MDA-MB-231 cells resulted in a significant
induction in MICA/B levels. Ectopic expression of miR-17–5p in MDA-MB-231 cells significantly repressed the
expression of PD-L1 and B7-H4 checkpoints. Validations of MALAT-1/miR-34a" and "MALAT-1/miR-17–5p axes
were performed by a series of co-transfections and functional assessment of cytotoxic profile of primary immune
cells.
Conclusion: This study proposes a novel epigenetic alteration exerted by TNBC cells mainly by inducing the
expression of MALAT-1 lncRNA. MALAT-1 mediates innate and adaptive immune suppression events partially via
targeting miR-34a/MICA/B and miR-175p/PD-L1/B7-H4 axes in TNBC patients and cell lines.
Description
Keywords
MALAT-1, Natural killer cells, Cytotoxic t lymphocytes, Breast cancer, PD-L1, B7-H4, MICA/B, miR-34a, miR-17–5p