Systematic screening for potential therapeutic targets in osteosarcoma through a kinome-wide CRISPR-Cas9 library

Atypical inflammatory kinase IKBKE phosphorylates and inactivates FoxA1 to promote liver tumorigenesis

Physiologically, FoxA1 plays a key role in liver differentiation and development, and pathologically exhibits an oncogenic role in prostate and breast cancers. However, its role and upstream regulation in liver tumorigenesis remain unclear. Here, we demonstrate that FoxA1 acts as a tumor suppressor in liver cancer. Using a CRISPR-based kinome screening approach, noncanonical inflammatory kinase IKBKE has been identified to inhibit FoxA1 transcriptional activity. Notably, IKBKE directly binds to and phosphorylates FoxA1 to reduce its complex formation and DNA interaction, leading to elevated hepatocellular malignancies. Nonphosphorylated mimic Foxa1 knock-in mice markedly delay liver tumorigenesis in hydrodynamic transfection murine models, while phospho-mimic Foxa1 knock-in phenocopy Foxa1 knockout mice to exhibit developmental defects and liver inflammation. Notably, Ikbke knockout delays diethylnitrosamine (DEN)-induced mouse liver tumor development. Together, our findings not only reveal FoxA1 as a bona fide substrate and negative nuclear effector of IKBKE in hepatocellular carcinioma (HCC) but also provide a promising strategy to target IKBEK for HCC therapy.

CRISPR screen identifies GATAD1 as a synthetic lethal target with CDK4/6 inhibitors in estrogen receptor-positive breast cancer

Estrogen receptor-positive (ER+) breast cancer represents approximately two-thirds of all breast cancers and has a sustained risk of late disease recurrence. Combining cyclin-dependent kinase 4/6 (CDK4/6) inhibitors with anti-estrogen therapies significantly improves ER+ advanced breast cancer clinical outcomes. Despite promising clinical outcomes, intrinsic or acquired resistance to CDK4/6 inhibitors has limited their success. We used CRISPR to screen MCF-7 cells to explore the targets whose inhibition is synthetic lethal with CDK4/6 inhibitors in ER+ breast cancer cells. We found that GATA zinc finger domain containing 1 (GATAD1) is a new synthetic lethal target with CDK4/6 inhibitors in ER+ breast cancer cells. Mechanistically, GATAD1 promotes cell proliferation by transcriptionally inhibiting p21 in ER+ breast cancer cells. GATAD1 depletion decreased the phosphorylation of CDK2/4 and RB transcriptional corepressor 1 (RB1), inducing cell cycle arrest. P21 overexpression abolished the enhanced proliferation induced by GATAD1 overexpression. Our results identify GATAD1 as a therapeutic target in ER+ breast cancer, which is beneficial to provide a novel treatment strategy.

Kinome-wide CRISPR-Cas9 knockout screens revealed PLK1 as a therapeutic target for osteosarcoma

Osteosarcoma is the most common malignant bone tumor, tending to be aggressive and recurrent. The therapeutic development for treating osteosarcoma has been largely hampered by the lack of effective and specific targets. Using kinome-wide CRISPR-Cas9 knockout screens, we systematically revealed a cohort of kinases essential for the survival and growth of human osteosarcoma cells, in which Polo-like kinase 1 (PLK1) appeared as a specific prominent hit. PLK1 knockout substantially inhibited proliferation of osteosarcoma cells in vitro and the tumor growth of osteosarcoma xenograft in vivo. Volasertib, a potent experimental PLK1 inhibitor, can effectively inhibit the growth of the osteosarcoma cell lines in vitro. It can also disrupt the development of tumors in the patient-derived xenograft (PDX) models in vivo. Furthermore, we confirmed that the mode of action (MoA) of volasertib is primarily mediated by the cell-cycle arrest and apoptosis triggered by DNA damage. As PLK1 inhibitors are entering phase III clinical trials, our findings provide important insights into the efficacy and MoA of the relevant therapeutic approach for combating osteosarcoma.

Idarubicin combats abiraterone and enzalutamide resistance in prostate cells via targeting XPA protein

Although second-generation therapies like abiraterone (ABI) and enzalutamide (ENZ) benefit patients with castration-resistant prostate cancer (CRPC), drug resistance frequently occurs, eventually resulting in therapy failure. In this study, we used two libraries, FDA-approved drug library and CRISP/Cas9 knockout (GeCKO) library to screen for drugs that overcome treatment resistance and to identify the potential drug-resistant genes involved in treatment resistance. Our screening results showed that the DNA-damaging agent idarubicin (IDA) overcame abiraterone and enzalutamide resistance in prostate cancer cells. IDA treatment inhibited the DNA repair protein XPA expression in a transcription-independent manner. Consistently, XPA knockout sensitized prostate cancer cells to abiraterone and enzalutamide treatment. In conclusion, IDA combats abiraterone and enzalutamide resistance by reducing XPA protein level in prostate cancer.

c-Myb-mediated inhibition of miR-601 in facilitating malignance of osteosarcoma via augmentation of PKMYT1

The crosstalk between osteosarcoma (OS) development and abnormally expressed microRNA (miR)-601 is not explored explicitly. Here, we identified the downregulated miR-601 in osteosarcoma (OS) through a comprehensive bioinformatics analysis of GEO Datasets. The results indicated that miR-601 was downregulated in both OS cells and tissues. The OS patients with reduced expression of miR-601 displayed worse prognosis. The results of in vitro and in vivo assay revealed that elevated miR-601 inhibited the proliferative, migratory and invasive capacities in OS cells. Mechanically, miR-601 exerted its function via targeting oncogene protein kinase membrane associated tyrosine/threonine 1 (PKMYT1) at post-transcriptional level. Moreover, miR-601 was attenuated by c-Myb at transcriptional level. Taken together, our studies reveal that miR-601 is a suppressive gene negatively correlated with malignancy of OS.

Targeting GRP78 enhances the sensitivity of HOS osteosarcoma cells to pyropheophorbide-α methyl ester-mediated photodynamic therapy via the Wnt/β-catenin signaling pathway

Photodynamic therapy (PDT), which is a new method for treating tumors, has been used in the treatment of cancer. In-depth research has shown that PDT cannot completely kill tumor cells, indicating that tumor cells are resistant to PDT. Glucose regulatory protein 78 (GRP78), which is a key regulator of endoplasmic reticulum stress, has been confirmed to be related to tumor resistance and recurrence, but there are relatively few studies on the further mechanism of GRP78 in PDT. Our experiment aimed to observe the role of GRP78 in HOS human osteosarcoma cells treated with pyropheophorbide-α methyl ester-mediated photodynamic therapy (MPPα-PDT) and to explore the possible mechanism by which the silencing of GRP78 expression enhances the sensitivity of HOS osteosarcoma cells to MPPα-PDT. HOS osteosarcoma cells were transfected with siRNA-GRP78. Apoptosis and reactive oxygen species (ROS) levels were detected by Hoechst staining and flow cytometry, cell viability was detected by Cell Counting Kit-8 assay, GRP78 protein fluorescence intensity was detected by immunofluorescence, and apoptosis-related proteins, cell proliferation-related proteins, and Wnt pathway-related proteins were detected by western blot. The results showed that MPPα-PDT can induce HOS cell apoptosis and increase GRP78 expression. After successful siRNA-GRP78 transfection, HOS cell proliferation was decreased, and apoptosis-related proteins expressions was increased, Wnt/β-catenin-related proteins expressions was decreased, and ROS levels was increased. In summary, siRNA-GRP78 enhances the sensitivity of HOS cells to MPPα-PDT, the mechanism may be related to inhibiting Wnt pathway activation and increasing ROS levels.

Genome-editing approaches and applications: a brief review on CRISPR technology and its role in cancer

The development of genome-editing technologies in 1970s has discerned a new beginning in the field of science. Out of different genome-editing approaches such as Zing-finger nucleases, TALENs, and meganucleases, clustered regularly interspaced short palindromic repeats-CRISPR-associated protein 9 (CRISPR/Cas9) is a recent and versatile technology that has the ability of making changes to the genome of different organisms with high specificity. Cancer is a complex process that is characterized by multiple genetic and epigenetic changes resulting in abnormal cell growth and proliferation. As cancer is one of the leading causes of deaths worldwide, a large number of studies are done to understand the molecular mechanisms underlying the development of cancer. Because of its high efficiency and specificity, CRISPR/Cas9 has emerged as a novel and powerful tool in the field of cancer research. CRISPR/Cas9 has the potential to accelerate cancer research by dissecting tumorigenesis process, generating animal and cellular models, and identify drug targets for chemotherapeutic approaches. However, despite having tremendous potential, there are certain challenges associated with CRISPR/Cas9 such as safe delivery to the target, potential off-target effects and its efficacy which needs to be addressed prior to its clinical application. In this review, we give a gist of different genome-editing technologies with a special focus on CRISPR/Cas9 development, its mechanism of action and its applications, especially in different type of cancers. We also highlight the importance of CRISPR/Cas9 in generating animal models of different cancers. Finally, we present an overview of the clinical trials and discuss the challenges associated with translating CRISPR/Cas9 in clinical use.