PHLPP Sensitizes Multiple Myeloma Cells to Bortezomib Through Regulating LAMP2

Modulation of gene expression by thymoquinone conjugated Zinc Oxide nanoparticles arrested cell cycle, DNA damage and increased apoptosis in triple negative breast cancer cell line MDA-MB-231

Nanomedicines include the area of science that combines the drugs or diagnostic molecules using nanotechnology approach to improve its ability to target specific cells or tissues. Zinc Oxide (ZnO) nanoparticles are known for its non-toxicity, biocompatibility and biosafety. Thymoquinone (TQ) is used in the present study from the seeds of Nigella sativa (Black cumin seed). ZnO nanoparticles and TQ-ZnO (TQ coated ZnO) nanoparticles were synthesized and its characterization were analyzed using spectrophotometeric analysis and dose of the treatment groups (ZnO, TQ and TQ-ZnO nanoparticles) were optimized in our previous studies. Triple Negative Breast Cancer (TNBC) cells, MDA-MB-231 were exposed to 30 µg/ml dose of TQ coated ZnO nanoparticles which were synthesized and characterized. Their anticancer properties were validated by testing their ability to induce DNA damage, to inhibit cell proliferation, to induce apoptosis and to arrest cell cycle. Modulation of gene expression and their intensities of the fluorogen reflecting the extent of gene expression were quantified using RT-PCR. Furthermore, the Human Breast Cancer PCR array profiles the expression of 84 genes and11 different biological pathways. The results revealed that the TQ-ZnO nanoparticles inhibited the proliferation of cells at synthesis phase and increased DNA damage, which further resulted in apoptosis. PCR array results showed that the combined effect have extensive applications in therapeutics. TQ-ZnO nanoparticles modulated the expression pattern of breast cancer associated genes in TNBC cells.

Reduced PHLPP Expression Leads to EGFR-TKI Resistance in Lung Cancer by Activating PI3K-AKT and MAPK-ERK Dual Signaling

Background

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) are effective in advanced EGFR-mutation non-small cell lung cancer (NSCLC) but the magnitude of tumor regression varies, and drug resistance is unavoidable. The pleckstrin homology domain leucine-rich repeat protein phosphatase (PHLPP) levels are reduced or lost and acts as a tumor suppressor in many cancers. Here, we hypothesized that PHLPP is a key regulator of EGFR-TKI sensitivity and a potential treatment target for overcoming resistance to EGFR-TKI in lung cancer.

Methods

Cell proliferation and growth inhibition were measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and colony formation assay. PHLPP- knockdown stable cell lines were generated by lentivirus-mediated delivery of PHLPP shRNAs. The expression of PHLPP mRNA and protein levels was detected by real-time quantitative polymerase chain reaction (qPCR) and Western blotting. Immunohistochemical (IHC) staining was performed to detect the PHLPP expression in clinical patient tissue samples. A transcriptomic assay of genome-wide RNA expressions of PHLPP in NSCLC cell lines according to gefitinib sensitivity was obtained from Gene Expression Omnibus (GEO) database. Murine xenograft model was established to verify the function of PHLPP in gefitinib resistance in vivo.

Results

PHLPP highly expressed in gefitinib-sensitive NSCLC cell lines than gefitinib-resistant NSCLC cell lines. In gefitinib-acquired resistance cell line HCC827-GR, PHLPP expression even dramatically reduced. Knockdown of PHLPP in NSCLC cells decreased cell death induced by the EGFR-TKI, while overexpression PHLPP in gefitinib-resistance NSCLC cells can enhance or restore EGFR-TKIs sensitivity. Mechanism study indicated that PHLPP downregulation attenuates the effect of EGFR-TKI on the both AKT and ERK pathway, thereby decreasing the cell death sensitivity to EGFR inhibitors. In xenograft mice, knockdown of PHLPP decreased tumor response to gefitinib and advanced tumor cells re-growth after gefitinib treatment. In clinical, PHLPP expression were reduced in the post-relapse tumor compared to that of pre-treatment, and lower pre-treatment PHLPP levels were significantly correlated with shorter progression-free survival (PFS) in patients with EGFR-mutant lung adenocarcinoma whom treated with EGFR-TKI.

Conclusions

Our data strongly demonstrated that loss of PHLPP function was a key factor of EGFR-TKI resistance in NSCLC. Downregulated PHLPP expression activated PI3K-AKT and MAPK-ERK pathway which strengthened cell survival to EGFR-TKI. Therefore, PHLPP expression level was not only a potential biomarker to predict EGFR-TKIs sensitivity but also as a therapeutic target in EGFR-TKIs therapy, enhancing PHLPP expression may be a valuable strategy for delaying or overcoming EGFR-TKIs drug resistance.