The Engineered Drug 3'UTRMYC1-18 Degrades the c-MYC-STAT5A/B-PD-L1 Complex In Vivo to Inhibit Metastatic Triple-Negative Breast Cancer.

c-MYC is overexpressed in 70% of human cancers, including triple-negative breast cancer (TNBC), yet there is no clinically approved drug that directly targets it. Here, we engineered the mRNA-stabilizing poly U sequences within the 3'UTR of c-MYC to specifically destabilize and promote the degradation of c-MYC transcripts. Interestingly, the engineered derivative outcompetes the endogenous overexpressed c-MYC mRNA, leading to reduced c-MYC mRNA and protein levels. The iron oxide nanocages (IO-nanocages) complexed with MYC-destabilizing constructs inhibited primary and metastatic tumors in mice bearing TNBC and significantly prolonged survival by degrading the c-MYC-STAT5A/B-PD-L1 complexes that drive c-MYC-positive TNBC. Taken together, we have described a novel therapy for c-MYC-driven TNBC and uncovered c-MYC-STAT5A/B-PD-L1 interaction as the target.

Nanocage-incorporated engineered destabilized 3'UTR ARE of ERBB2 inhibits tumor growth and liver and lung metastasis in EGFR T790M osimertinib- and trastuzumab-resistant and ERBB2-expressing NSCLC via the reduction of ERBB2.

Non-small cell lung cancer (NSCLC) caused more deaths in 2017 than breast cancer, prostate, and brain cancers combined. This is primarily due to their aggressive metastatic nature, leading to more fatal rates of cancer patients. Despite this condition, there are no clinically approved drugs that can target metastasis. The NSCLC with EGFR T790M-overexpressing HER2 shows the resistance to osimertinib and trastuzumab starting 10-18 months after the therapy, and thus prospects are grim to these patients. To target the recalcitrant ERBB2 driver oncogene, we developed two engineered destabilizing 3'UTR ERBB2 constructs that degrade the endogenous ERBB2 transcript and proteins by overwriting the encoded endogenous ERBB2 mRNA with the destabilizing message. When iron oxide nanocages (IO nanocages) were used as vehicles to deliver them to tumors and whole tissues in mice bearing tumors, it was well tolerated and safe and caused no genome rearrangement whereas they were integrated into genome deserts (non-coding regions). We achieved significant reduction of the primary tumor volume with desARE3'UTRERBB2-30, achieving 50% complete tumor lysis and inhibiting 60%-80% of liver metastasis, hepatomegaly, and 90% of lung metastasis, through ERBB2 downregulation. These constructs were distributed robustly into tumors, livers, lungs, kidneys, and spleen and mildly in the brain and not in the heart. They caused no abnormality in both short- and long-term administrations as well as in healthy mice. In summary, we accomplished significant breakthrough for the therapeutics of intractable lung cancer patients whose cancers become resistant and metastasize.

Destabilized 3'UTR elements therapeutically degrade ERBB2 mRNA in drug-resistant ERBB2+ cancer models.

Breast, lung, and colorectal cancer resistance to molecular targeted therapy is a major challenge that unfavorably impacts clinical outcomes leading to hundreds of thousands of deaths annually. In ERBB2+ cancers regardless of the tissue of origin, many ERBB2+ cancers are resistant to ERBB2-targeted therapy. We discovered that ERBB2+ cancer cells are enriched with poly U sequences on their 3'UTR which are mRNA-stabilizing sequences. We developed a novel technology, in which we engineered these ERBB2 mRNA-stabilizing sequences to unstable forms that successfully overwrote and outcompeted the endogenous ERBB2 mRNA-encoded message and degraded ERBB2 transcripts which led to the loss of the protein across multiple cancer cell types both in the wildtype and drug-resistance settings in vitro and in vivo, offering a unique safe novel modality to control ERBB2 mRNA and other pervasive oncogenic signals where current targeted therapies fail.

Genome scale CRISPR Cas9a knockout screen reveals genes that control glioblastoma susceptibility to the alkylating agent temozolomide.

Glioblastoma is the most fatal of all primary human brain tumors with 14 months median survival. The mainstay therapy for this tumor involves temozolomide, surgery, radiotherapy and tumor treating electric field. Cancer resistance to commonly available chemotherapeutics remains a major challenge in glioblastoma patients receiving treatment and unfavorably impact their overall survival and outcome. However, the lack of progress in this area could be attributed to lack of tools to probe unbiasedly at the genome wide level the coding and non-coding elements contribution on a large scale for factors that control resistance to chemotherapeutics. Understanding the mechanisms of resistance to chemotherapeutics will enable precision medicine in the treatment of cancer patients. CRISPR Cas9a has emerged as a functional genomics tool to study at genome level the factors that control cancer resistance to drugs. Recently, we used genome wide CRISPR-Cas9a screen to identify genes responsible for glioblastoma susceptibility to etoposide. We extended our inquiry to understand genes that control glioblastoma response to temozolomide by using genome scale CRISPR. This study shows that the unbiased genome-wide loss of function approach can be applied to discover genes that influence tumor resistance to chemotherapeutics and contribute to chemoresistance in glioblastoma.

Therapeutic Targeting of Exportin-1 in Childhood Cancer.

Overexpression of Exportin-1 (XPO1), a key regulator of nuclear-to-cytoplasmic transport, is associated with inferior patient outcomes across a range of adult malignancies. Targeting XPO1 with selinexor has demonstrated promising results in clinical trials, leading to FDA approval of its use for multiple relapsed/refractory cancers. However, XPO1 biology and selinexor sensitivity in childhood cancer is only recently being explored. In this review, we will focus on the differential biology of childhood and adult cancers as it relates to XPO1 and key cargo proteins. We will further explore the current state of pre-clinical and clinical development of XPO1 inhibitors in childhood cancers. Finally, we will outline potentially promising future therapeutic strategies for, as well as potential challenges to, integrating XPO1 inhibition to improve outcomes for children with cancer.

NSUN6, an RNA methyltransferase of 5-mC controls glioblastoma response to temozolomide (TMZ) via NELFB and RPS6KB2 interaction.

Nop2/Sun RNA methyltransferase (NSUN6) is an RNA 5-methyl cytosine (5mC) transferase with little information known of its function in cancer and response to cancer therapy. Here, we show that NSUN6 methylates both large and small RNA in glioblastoma and controls glioblastoma response to temozolomide with or without influence of the MGMT promoter status, with high NSUN6 expression conferring survival benefit to glioblastoma patients and in other cancers. Mechanistically, our results show that NSUN6 controls response to TMZ therapy via 5mC-mediated regulation of NELFB and RPS6BK2. Taken together, we present evidence that show that NSUN6-mediated 5mC deposition regulates transcriptional pause by accumulation of NELFB and the general transcription factor complexes (POLR2A, TBP, TFIIA, and TFIIE) on the preinitiation complex at the TATA binding site to control translation machinery in glioblastoma response to alkylating agents. Our findings open a new frontier into controlling of transcriptional regulation by RNA methyltransferase and 5mC.

Ribosomal protein S11 influences glioma response to TOP2 poisons.

Topoisomerase II poisons are one of the most common class of chemotherapeutics used in cancer. We and others had shown that a subset of glioblastomas, the most malignant of all primary brain tumors in adults, is responsive to TOP2 poisons. To identify genes that confer susceptibility to this drug in gliomas, we performed a genome-scale CRISPR knockout screen with etoposide. Genes involved in protein synthesis and DNA damage were implicated in etoposide susceptibility. To define potential biomarkers for TOP2 poisons, CRISPR hits were overlapped with genes whose expression correlates with susceptibility to this drug across glioma cell lines, revealing ribosomal protein subunit RPS11, 16, and 18 as putative biomarkers for response to TOP2 poisons. Loss of RPS11 led to resistance to etoposide and doxorubicin and impaired the induction of proapoptotic gene APAF1 following treatment. The expression of these ribosomal subunits was also associated with susceptibility to TOP2 poisons across cell lines from gliomas and multiple other cancers.

Topoisomerase II Poisons for Glioblastoma; Existing Challenges and Opportunities to Personalize Therapy.

Despite advances in surgery, radiotherapy, and chemotherapy, glioblastoma (GBM) remains a malignancy with poor prognosis. The molecular profile of GBM is diverse across patients, and individual responses to therapy are highly variable. Yet, patients diagnosed with GBM are treated with a rather uniform paradigm. Exploiting these molecular differences and inter-individual responses to therapy may present an opportunity to improve the otherwise bleak prognosis of patients with GBM. This review aims to examine one group of chemotherapeutics: Topoisomerase 2 (TOP2) poisons, a class of drugs that enables TOP2 to induce DNA damage, but interferes with its ability to repair it. These potent chemotherapeutic agents are currently used for a number of malignancies and have shown promise in the treatment of GBM. Despite their robust efficacy in vitro, some of these agents have fallen short of achieving similar results in clinical trials for this tumor. In this review, we explore reasons for this discrepancy, focusing on drug delivery and individual susceptibility differences as challenges for effective TOP2-targeting for GBM. We critically review the evidence implicating genes in susceptibility to TOP2 poisons and categorize this evidence as experimental, correlative or both. This is important as mere experimental evidence does not necessarily lead to identification of genes that serve as good biomarkers of susceptibility for personalizing the use of these drugs.

Mechanism of allele specific assembly and disruption of master regulator transcription factor complexes of NF-KBp50, NF-KBp65 and HIF1a on a non-coding FAS SNP.

A challenging question in genetics is to understand the molecular function of non-coding variants of the genome. By using differential EMSA, ChIP and functional genome analysis, we have found that changes in transcription factors (TF) apparent binding affinity and dissociation rates are responsible for allele specific assembly or disruption of master TFs: we observed that NF-KBp50, NF-KBp65 and HIF1a bind with an affinity of up to 10 fold better to the C-allele than to the T-allele of rs7901656 both in vivo and in vitro. Furthermore, we showed that NF-KBp50, p65 and HIF1a form higher order heteromultimeric complexes overlapping rs7901656, implying synergism of action among TFs governing cellular response to infection and hypoxia. With rs7901656 on the FAS gene as a paradigm, we show how allele specific transcription factor complex assembly and disruption by a causal variant contributes to disease and phenotypic diversity. This finding provides the highly needed mechanistic insight into how the molecular etiology of regulatory SNPs can be understood in functional terms.

Promiscuous partnering and independent activity of MexB, the multidrug transporter protein from Pseudomonas aeruginosa.

The MexAB-OprM drug efflux pump is central to multidrug resistance of Pseudomonas aeruginosa. The ability of the tripartite protein to confer drug resistance on the pathogen is crucially dependent on the presence of all three proteins of the complex. However, the role of each protein in the formation of the intact functional complex is not well understood. One of the key questions relates to the (in)ability of MexB to act independently of its cognitive partners, MexA and OprM. In the present study, we have demonstrated that, in the absence of MexA and OprM, MexB can: (i) recruit AcrA and TolC from Escherichia coli to form a functional drug-efflux complex; (ii) transport the toxic compound ethidium bromide in a Gram-positive organism where the periplasmic space and outer membrane are absent; and (iii) catalyse transmembrane chemical proton gradient (DeltapH)-dependent drug transport when purified and reconstituted into proteoliposomes. Our results represent the first evidence of drug transport by an isolated RND (resistance-nodulation-cell division)-type multidrug transporter, and provide a basis for further studies into the energetics of RND-type transporters and their assembly into multiprotein complexes.