Adaptor SH3BGRL drives autophagy-mediated chemoresistance through promoting PIK3C3 translation and ATG12 stability in breast cancers.

Acquired chemotherapy resistance is one of the main culprits in the relapse of breast cancer. But the underlying mechanism of chemotherapy resistance remains elusive. Here, we demonstrate that a small adaptor protein, SH3BGRL, is not only elevated in the majority of breast cancer patients but also has relevance with the relapse and poor prognosis of breast cancer patients. Functionally, SH3BGRL upregulation enhances the chemoresistance of breast cancer cells to the first-line doxorubicin treatment through macroautophagic/autophagic protection. Mechanistically, SH3BGRL can unexpectedly bind to ribosomal subunits to enhance PIK3C3 translation efficiency and sustain ATG12 stability. Therefore, inhibition of autophagy or silence of PIK3C3 or ATG12 can effectively block the driving effect of SH3BGRL on doxorubicin resistance of breast cancer cells in vitro and in vivo. We also validate that SH3BGRL expression is positively correlated with that of PIK3C3 or ATG12, as well as the constitutive occurrence of autophagy in clinical breast cancer tissues. Taken together, our data reveal that SH3BGRL upregulation would be a key driver to the acquired chemotherapy resistance through autophagy enhancement in breast cancer while targeting SH3BGRL could be a potential therapeutic strategy against breast cancer.Abbreviations: ABCs: ATP-binding cassette transporters; Act D: actinomycin D; ACTB/ß-actin: actin beta; ATG: autophagy-related; Baf A1: bafilomycin A1; CASP3: caspase 3; CHX: cycloheximide; CQ: chloroquine; Dox: doxorubicin; FBS: fetal bovine serum; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GEO: gene expression omnibus; GFP: green fluorescent protein; G6PD: glucose-6-phosphate dehydrogenase; GSEA: gene set enrichment analysis; IHC: immunochemistry; KEGG: Kyoto Encyclopedia of Genes and Genomes; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; 3-MA: 3-methyladenine; mRNA: messenger RNA; PIK3C3: phosphatidylinositol 3-kinase catalytic subunit type 3; SH3BGRL: SH3 domain binding glutamate-rich protein-like; SQSTM1/p62: sequestosome 1; ULK1: unc-51 like autophagy activating kinase 1.

Reconstitution of polyunsaturated fatty acid synthesis enzymes in mammalian cells to convert LA to DHA / 生物工程学报

DHA (22:6n-3) is a Ω-3 polyunsaturated fatty acid with 22 carbon atoms and 6 double bonds, which has important biological functions in human body. Human and other mammals synthesize only limited amounts of DHA, more requirements must be satisfied from food resources. However, the natural resources of DHA (Mainly deep-sea fish and other marine products) are prone to depletion. New resources development is still insufficient to satisfy the growing market demand. Previous studies have revealed that the mammals can increase the synthesis of DHA and other long-chain polyunsaturated fatty acids after transgenic procedures. In this study, mammalian cells were transfected with Δ6, Δ5 desaturase, Δ6, Δ5 elongase, Δ15 desaturase (Isolated from nematode Caenorhabditis elegans) and Δ4 desaturase (Isolated from Euglena gracilis), simultaneously. Results show that the expression or overexpression of these 6 enzymes is capable of conversion of the o-6 linoleic acid (LA, 18:2n-6) in DHA (22:6n-3). DHA content has increased from 16.74% in the control group to 25.3% in the experimental group. The strategy and related technology in our research provided important data for future production the valuable DHA (22:6n-3) by using genetically modified animals.

Overexpression of four fatty acid synthase genes elevated the efficiency of long-chain polyunsaturated fatty acids biosynthesis in mammalian cells / 生物工程学报

Three long-chain polyunsaturated fatty acids, docosahexaenoic acid (DHA, 22:6n-3), eicosapentaenoic acid (EPA, 20:5n-3) and arachidonic acid (ARA, 20:4n-6), are the most biologically active polyunsaturated fatty acids in the body. They are important in developing and maintaining the brain function, and in preventing and treating many diseases such as cardiovascular disease, inflammation and cancer. Although mammals can biosynthesize these long-chain polyunsaturated fatty acids, the efficiency is very low and dietary intake is needed to meet the requirement. In this study, a multiple-genes expression vector carrying mammalian A6/A5 fatty acid desaturases and multiple-genes expression vector carrying mammalian Δ6/Δ5 fatty acid desaturases and Δ6/Δ5 fatty acid elongases coding genes was used to transfect HEK293T cells, then the overexpression of the target genes was detected. GC-MS analysis shows that the biosynthesis efficiency and level of DHA, EPA and ARA were significantly increased in cells transfected with the multiple-genes expression vector. Particularly, DHA level in these cells was 2.5 times higher than in the control cells. This study indicates mammal possess a certain mechanism for suppression of high level of biosynthesis of long chain polyunsaturated fatty acids, and the overexpression of Δ6/Δ5 fatty acid desaturases and Δ6/Δ5 fatty acid elongases broke this suppression mechanism so that the level of DHA, EPA and ARA was significantly increased. This study also provides a basis for potential applications of this gene construct in transgenic animal to produce high level of these long-chain polyunsaturated fatty acid.