Down-regulating GRP78 reverses pirarubicin resistance of triple negative breast cancer by miR-495-3p mimics and involves the p-AKT/mTOR pathway.

Due to the lack of known therapeutic targets for triple-negative breast cancer (TNBC), chemotherapy is the only available pharmacological treatment. Pirarubicin (tetrahydropyranyl Adriamycin, THP) is the most commonly used anthracycline chemotherapy agent. However, TNBC has a high recurrence rate after chemotherapy, and the mechanisms of chemoresistance and recurrence are not entirely understood. To study the chemoresistance mechanisms, we first screened compounds on a pirarubicin-resistant cell line (MDA-MB-231R) derived from MDA-MB-231. The drug resistance index of MDA-MB-231R cells was approximately five times higher than that of MDA-MB-231 cells. MDA-MB-231R cells have higher GRP78 and lower miR-495-3p expression levels than MDA-MB-231 cells. Transfecting MDA-MB-231R cells with a siGRP78 plasmid reduced GRP78 expression, which restored pirarubicin sensitivity. Besides, transfecting MDA-MB-231R cells with miR-495-3p mimics increased miR-495-3p expression, which also reversed pirarubicin chemoresistance. Cell counting kit-8 (CCK-8), EdU, wound healing, and Transwell assays showed that the miR-495-3p mimics also inhibited cell proliferation and migration. Based on our results, miR-495-3p mimics could down-regulate GRP78 expression via the p-AKT/mTOR signaling pathway in TNBC cells. Remarkably, chemo-resistant and chemo-sensitive TNBC tissues had opposite trends in GRP78 and miR-495-3p expressions. The lower the GRP78 and the higher the miR-495-3p expression, the better prognosis in TNBC patients. Therefore, the mechanism of pirarubicin resistance might involve the miR-495-3p/GRP78/Akt axis, which would provide a possible strategy for treating TNBC.

Liu M ，Yang J ，Lv W ，Wang S ，Du T ，Zhang K ，Wu Y ，Feng X ... -  《-》

Protective effect of hsa-miR-570-3p targeting CD274 on triple negative breast cancer by blocking PI3K/AKT/mTOR signaling pathway.

To find out the role of hsa-miR-570-3p targeting CD274 in triple negative breast cancer (TNBC) via PI3K/AKT/mTOR signaling pathway. Hsa-miR-570-3p and CD274 expressions in 175 TNBC patients were detected by qRT-PCR and immunohistochemistry respectively. The human TNBC cell lines (MDA-MB-468 and MDA-MB-231) were used to verify the targeting relationship between hsa-miR-570-3p and CD274 via dual-luciferase reporter gene assay. Then, MDA-MB-468 and MDA-MB-231 cells were divided into Blank, miR-NC, miR-570-3p mimics, NC siRNA, CD274 siRNA, and miR-570-3p inhibitors + CD274 siRNA groups. Next, the biological activities of cells were detected by MTT, Cell-Light EdU, Annexin-V-FITC/PI, wound healing and Transwell invasion assays. Western blotting was conducted to detect protein expressions.MiR-570-3p expression was lower in tumor tissues than that in adjacent normal tissues, which was more obvious in CD274-positive TNBC patients, which targeted CD274 in TNBC cell lines. MiR-570-3p inhibited cell proliferation, invasion and migration, but induced cell apoptosis accompanying the upregulation of apoptotic proteins and downregulation of anti-apoptotic protein. CD274 siRNA had the similar results of miR-570-3p mimics, which could be reversed by miR-570-3p inhibitors. Besides, both miR-570-3p mimics and CD274 siRNA blocked PI3K/AKT/mTOR signaling pathway in TNBC cell lines. Hsa-miR-570-3p was downregulated and CD274 was upregulated in TNBC patients. Besides, hsa-miR-570-3p targeted CD274 to inhibit cell proliferation, invasion, migration, and induce cell apoptosis, which may be related to the suppression of PI3K/AKT/mTOR pathway.

Wang LL ，Huang WW ，Huang J ，Huang RF ，Li NN ，Hong Y ，Chen ML ，Wu F ，Liu J ... -  《-》

Hsa_circ_0000199 facilitates chemo-tolerance of triple-negative breast cancer by interfering with miR-206/613-led PI3K/Akt/mTOR signaling.

Li H ，Xu W ，Xia Z ，Liu W ，Pan G ，Ding J ，Li J ，Wang J ，Xie X ，Jiang D ... -  《Aging-US》

Curcumol enhances the sensitivity of doxorubicin in triple-negative breast cancer via regulating the miR-181b-2-3p-ABCC3 axis.

Chemoresistance is a major cause of recurrence and poor prognosis in triple-negative breast cancer (TNBC) patients. The essential oil of Rhizoma Curcumae has been recently reported to enhance the chemosensitivity of cancer cells. However, few reports have systematically illuminated the mechanism. Curcumol is the major component of the essential oil of Rhizoma Curcumae. Therefore, we wondered whether curcumol combined with chemotherapy could increase the anticancer effects. In the present study, we evaluated the anticancer effects of doxorubicin and curcumol alone or in combination by a series of growth proliferation and apoptosis assays in TNBC cells. Our results showed that curcumol enhanced the sensitivity of MDA-MB-231 cells to doxorubicin in vitro and in vivo. Through miRNA-seq, we found that miR-181b-2-3p was involved in the curcumol-mediated promotion of doxorubicin-sensitivity in both parental and doxorubicin-resistant MDA-MB-231 (MDA-MB-231/ADR) cells. Further study showed that miR-181b-2-3p suppressed ABCC3 expression by targeting its 3'UTR. More importantly, we identified that overexpression of miR-181b-2-3p sensitized MDA-MB-231/ADR cells to doxorubicin by inhibiting the drug efflux transporter ABCC3. Furthermore, we found that NFAT1 could be activated by curcumol. In addition, ChIP assay results revealed that NFAT1 could directly bind to the promoter region of miR-181b-2-3p. Finally, using PDX models, we identified that curcumol could enhance sensitivity to doxorubicin to suppress tumor growth by the miR-181b-2-3p-ABCC3 axis in vivo. Taken together, our study provides novel mechanistic evidence for curcumol-mediated sensitization to doxorubicin in TNBC, and it highlights the potential therapeutic usefulness of curcumol as an adjunct drug in TNBC patients with doxorubicin-resistance.

Zeng C ，Fan D ，Xu Y ，Li X ，Yuan J ，Yang Q ，Zhou X ，Lu J ，Zhang C ，Han J ，Gu J ，Gao Y ，Sun L ，Wang S ... -  《-》

ROR2 promotes invasion and chemoresistance of triple-negative breast cancer cells by activating PI3K/AKT/mTOR signaling.

This study aimed to investigate the role of receptor tyrosine kinase-like orphan receptor 2 (ROR2) in triple-negative breast cancer (TNBC). ROR2 expression in primary TNBC and metastatic TNBC tissues was analyzed by immunohistochemical staining and PCR. ROR2 expression in TNBC cell lines was detected by PCR and Western blot analysis. The migration, invasion and chemosensitivity of TNBC cells with overexpression or knockdown of ROR2 were examined. ROR2 expression was high in metastatic TNBC tissues. ROR2 knockdown suppressed the migration, invasion and chemoresistance of TNBC cells. ROR2 overexpression in MDA-MB-435 cells promoted the migration, invasion, and chemoresistance. Moreover, ROR2 knockdown in HC1599 and MDA-MB-435 adriamycin-resistant cells enhanced chemosensitivity to adriamycin. ROR2 could activate PI3K/AKT/mTOR signaling in TNBC cells. ROR2 is upregulated and promotes metastatic phenotypes of TNBC by activating PI3K/AKT/mTOR signaling.

DA X ，Ge H ，Shi J ，Zhu C ，Wang G ，Fang Y ，Xu J ... -  《-》