Methylation of histone H3 lysine 36 is a barrier for therapeutic interventions of head and neck squamous cell carcinoma.

Approximately 20% of head and neck squamous cell carcinomas (HNSCCs) exhibit reduced methylation on lysine 36 of histone H3 (H3K36me) due to mutations in histone methylase NSD1 or a lysine-to-methionine mutation in histone H3 (H3K36M). Whether such alterations of H3K36me can be exploited for therapeutic interventions is still unknown. Here, we show that HNSCC models expressing H3K36M can be divided into two groups: those that display aberrant accumulation of H3K27me3 and those that maintain steady levels of H3K27me3. The former group exhibits reduced proliferation, genome instability, and heightened sensitivity to genotoxic agents like PARP1/2 inhibitors. Conversely, H3K36M HNSCC models with constant H3K27me3 levels lack these characteristics unless H3K27me3 is elevated by DNA hypomethylating agents or inhibiting H3K27me3 demethylases KDM6A/B. Mechanistically, H3K36M reduces H3K36me by directly impeding the activities of the histone methyltransferase NSD3 and the histone demethylase LSD2. Notably, aberrant H3K27me3 levels induced by H3K36M expression are not a bona fide epigenetic mark because they require continuous expression of H3K36M to be inherited. Moreover, increased sensitivity to PARP1/2 inhibitors in H3K36M HNSCC models depends solely on elevated H3K27me3 levels and diminishing BRCA1- and FANCD2-dependent DNA repair. Finally, a PARP1/2 inhibitor alone reduces tumor burden in a H3K36M HNSCC xenograft model with elevated H3K27me3, whereas in a model with consistent H3K27me3, a combination of PARP1/2 inhibitors and agents that up-regulate H3K27me3 proves to be successful. These findings underscore the crucial balance between H3K36 and H3K27 methylation in maintaining genome instability, offering new therapeutic options for patients with H3K36me-deficient tumors.

Smoothened (SMO) regulates insulin-like growth factor 1 receptor (IGF1R) levels and protein kinase B (AKT) localization and signaling.

The oncoprotein Smoothened (SMO), a Frizzled-class-G-protein-coupled receptor, is the central transducer of hedgehog (Hh) signaling. While canonical SMO signaling is best understood in the context of cilia, evidence suggests that SMO has other functions in cancer biology that are unrelated to canonical Hh signaling. Herein, we provided evidence that elevated levels of human SMO show a strong correlation with elevated levels of insulin-like growth factor 1 receptor (IGF1R) and reduced survival in diffuse large B-cell lymphoma (DLBCL). As an integral component of raft microdomains, SMO plays a fundamental role in maintaining the levels of IGF1R in lymphoma and breast cancer cells as well IGF1R-associated activation of protein kinase B (AKT). Silencing of SMO increases lysosomal degradation and favors a localization of IGF1R to late endosomal compartments instead of early endosomal compartments from which much of the receptor would normally recycle. In addition, loss of SMO interferes with the lipid raft localization and retention of the remaining IGF1R and AKT, thereby disrupting the primary signaling context for IGF1R/AKT. This activity of SMO is independent of its canonical signaling and represents a novel and clinically relevant contribution to signaling by the highly oncogenic IGF1R/AKT signaling axis.

Genetic targeting of chemical indicators in vivo.

Fluorescent protein reporters have become the mainstay for tracing cellular circuitry in vivo but are limited in their versatility. Here we generated Cre-dependent reporter mice expressing the Snap-tag to target synthetic indicators to cells. Snap-tag labeling worked efficiently and selectively in vivo, allowing for both the manipulation of behavior and monitoring of cellular fluorescence from the same reporter.

A subpopulation of itch-sensing neurons marked by Ret and somatostatin expression.

Itch, the unpleasant sensation that elicits a desire to scratch, is mediated by specific subtypes of cutaneous sensory neuron. Here, we identify a subpopulation of itch-sensing neurons based on their expression of the receptor tyrosine kinase Ret. We apply flow cytometry to isolate Ret-positive neurons from dorsal root ganglia and detected a distinct population marked by low levels of Ret and absence of isolectin B4 binding. We determine the transcriptional profile of these neurons and demonstrate that they express neuropeptides such as somatostatin (Sst), the NGF receptor TrkA, and multiple transcripts associated with itch. We validate the selective expression of Sst using an Sst-Cre driver line and ablated these neurons by generating mice in which the diphtheria toxin receptor is conditionally expressed from the sensory neuron-specific Avil locus. Sst-Cre::Avil(iDTR) mice display normal nociceptive responses to thermal and mechanical stimuli. However, scratching behavior evoked by interleukin-31 (IL-31) or agonist at the 5HT1F receptor is significantly reduced. Our data provide a molecular signature for a subpopulation of neurons activated by multiple pruritogens.

Two types of BCR interactions are positively selected during leukemia development in the Eµ-TCL1 transgenic mouse model of CLL.

Chronic lymphocytic leukemia (CLL) is a common B-cell malignancy characterized by a highly variable course and outcome. The disease is believed to be driven by B-cell receptor (BCR) signals generated by external antigens and/or cell-autonomous BCR interactions, but direct in vivo evidence for this is still lacking. To further define the role of the BCR pathway in the development and progression of CLL, we evaluated the capacity of different types of antigen/BCR interactions to induce leukemia in the Eµ-TCL1 transgenic mouse model. We show that cell autonomous signaling capacity is a uniform characteristic of the leukemia-derived BCRs and represents a prerequisite for CLL development. Low-affinity BCR interactions with autoantigens generated during apoptosis are also positively selected, suggesting that they contribute to the pathogenesis of the disease. In contrast, high-affinity BCR interactions are not selected, regardless of antigen form or presentation. We also show that the capacity of the leukemic cells to respond to cognate antigen correlates inversely with time to leukemia development, suggesting that signals induced by external antigen increase the aggressiveness of the disease. Collectively, these findings provide in vivo evidence that the BCR pathway drives the development and can influence the clinical course of CLL.

FOG-1 and GATA-1 act sequentially to specify definitive megakaryocytic and erythroid progenitors.

The transcription factors that control lineage specification of haematopoietic stem cells (HSCs) have been well described for the myeloid and lymphoid lineages, whereas transcriptional control of erythroid (E) and megakaryocytic (Mk) fate is less understood. We here use conditional removal of the GATA-1 and FOG-1 transcription factors to identify FOG-1 as required for the formation of all committed Mk- and E-lineage progenitors, whereas GATA-1 was observed to be specifically required for E-lineage commitment. FOG-1-deficient HSCs and preMegEs, the latter normally bipotent for the Mk and E lineages, underwent myeloid transcriptional reprogramming, and formed myeloid, but not erythroid and megakaryocytic cells in vitro. These results identify FOG-1 and GATA-1 as required for formation of bipotent Mk/E progenitors and their E-lineage commitment, respectively, and show that FOG-1 mediates transcriptional Mk/E programming of HSCs as well as their subsequent Mk/E-lineage commitment. Finally, C/EBPs and FOG-1 exhibited transcriptional cross-regulation in early myelo-erythroid progenitors making their functional antagonism a potential mechanism for separation of the myeloid and Mk/E lineages.

Monocyte/Macrophage-derived IGF-1 Orchestrates Murine Skeletal Muscle Regeneration and Modulates Autocrine Polarization.

Insulin-like growth factor 1 (IGF-1) is a potent enhancer of tissue regeneration, and its overexpression in muscle injury leads to hastened resolution of the inflammatory phase. Here, we show that monocytes/macrophages constitute an important initial source of IGF-1 in muscle injury, as conditional deletion of the IGF-1 gene specifically in mouse myeloid cells (ϕIGF-1 CKO) blocked the normal surge of local IGF-1 in damaged muscle and significantly compromised regeneration. In injured muscle, Ly6C+ monocytes/macrophages and CD206+ macrophages expressed equivalent IGF-1 levels, which were transiently upregulated during transition from the inflammation to repair. In injured ϕIGF-1 CKO mouse muscle, accumulation of CD206+ macrophages was impaired, while an increase in Ly6C+ monocytes/macrophages was favored. Transcriptional profiling uncovered inflammatory skewing in ϕIGF-1 CKO macrophages, which failed to fully induce a reparative gene program in vitro or in vivo, revealing a novel autocrine role for IGF-1 in modulating murine macrophage phenotypes. These data establish local macrophage-derived IGF-1 as a key factor in inflammation resolution and macrophage polarization during muscle regeneration.

Tyrosine phosphorylation of CARM1 promotes its enzymatic activity and alters its target specificity.

An important epigenetic component of tyrosine kinase signaling is the phosphorylation of histones, and epigenetic readers, writers, and erasers. Phosphorylation of protein arginine methyltransferases (PRMTs), have been shown to enhance and impair their enzymatic activity. In this study, we show that the hyperactivation of Janus kinase 2 (JAK2) by the V617F mutation phosphorylates tyrosine residues (Y149 and Y334) in coactivator-associated arginine methyltransferase 1 (CARM1), an important target in hematologic malignancies, increasing its methyltransferase activity and altering its target specificity. While non-phosphorylatable CARM1 methylates some established substrates (e.g. BAF155 and PABP1), only phospho-CARM1 methylates the RUNX1 transcription factor, on R223 and R319. Furthermore, cells expressing non-phosphorylatable CARM1 have impaired cell-cycle progression and increased apoptosis, compared to cells expressing phosphorylatable, wild-type CARM1, with reduced expression of genes associated with G2/M cell cycle progression and anti-apoptosis. The presence of the JAK2-V617F mutant kinase renders acute myeloid leukemia (AML) cells less sensitive to CARM1 inhibition, and we show that the dual targeting of JAK2 and CARM1 is more effective than monotherapy in AML cells expressing phospho-CARM1. Thus, the phosphorylation of CARM1 by hyperactivated JAK2 regulates its methyltransferase activity, helps select its substrates, and is required for the maximal proliferation of malignant myeloid cells.

Targeted Bioluminescent Imaging of Pancreatic Ductal Adenocarcinoma Using Nanocarrier-Complexed EGFR-Binding Affibody-Gaussia Luciferase Fusion Protein.

In vivo imaging has enabled impressive advances in biological research, both preclinical and clinical, and researchers have an arsenal of imaging methods available. Bioluminescence imaging is an advantageous method for in vivo studies that allows for the simple acquisition of images with low background signals. Researchers have increasingly been looking for ways to improve bioluminescent imaging for in vivo applications, which we sought to achieve by developing a bioluminescent probe that could specifically target cells of interest. We chose pancreatic ductal adenocarcinoma (PDAC) as the disease model because it is the most common type of pancreatic cancer and has an extremely low survival rate. We targeted the epidermal growth factor receptor (EGFR), which is frequently overexpressed in pancreatic cancer cells, using an EGFR-specific affibody to selectively identify PDAC cells and delivered a Gaussia luciferase (GLuc) bioluminescent protein for imaging by engineering a fusion protein with both the affibody and the bioluminescent protein. This fusion protein was then complexed with a G5-PAMAM dendrimer nanocarrier. The dendrimer was used to improve the protein stability in vivo and increase signal strength. Our targeted bioluminescent complex had an enhanced uptake into PDAC cells in vitro and localized to PDAC tumors in vivo in pancreatic cancer xenograft mice. The bioluminescent complexes could delineate the tumor shape, identify multiple masses, and locate metastases. Through this work, an EGFR-targeted bioluminescent-dendrimer complex enabled the straightforward identification and imaging of pancreatic cancer cells in vivo in preclinical models. This argues for the targeted nanocarrier-mediated delivery of bioluminescent proteins as a way to improve in vivo bioluminescent imaging.

Smoking induces WEE1 expression to promote docetaxel resistance in esophageal adenocarcinoma.

Esophageal adenocarcinoma (EAC) patients have poor clinical outcomes, with an overall 5-year survival rate of 20%. Smoking is a significant risk factor for EAC. The role of WEE1, a nuclear kinase that negatively regulates the cell cycle in normal conditions, in EAC tumorigenesis and drug resistance is not fully understood. Immunohistochemistry staining shows significant WEE1 overexpression in human EAC tissues. Nicotine, nicotine-derived nitrosamine ketone, or 2% cigarette smoke extract treatment induces WEE1 protein expression in EAC, detected by western blot and immunofluorescence staining. qRT-PCR and reporter assay indicates that smoking induces WEE1 expression through miR-195-5p downregulation in EAC. ATP-Glo cell viability and clonogenic assay confirmed that WEE1 inhibition sensitizes EAC cells to docetaxel treatment in vitro. A TE-10 smoking machine with EAC patient-derived xenograft mouse model demonstrated that smoking induces WEE1 protein expression and resistance to docetaxel in vivo. MK-1775 and docetaxel combined treatment improves EAC patient-derived xenograft mouse survival in vivo. Our findings demonstrate, for the first time, that smoking-induced WEE1 overexpression through miRNA dysregulation in EAC plays an essential role in EAC drug resistance. WEE1 inhibition is a promising therapeutic method to overcome drug resistance and target treatment refractory cancer cells.

The SWI/SNF chromatin-remodeling subunit DPF2 facilitates NRF2-dependent antiinflammatory and antioxidant gene expression.

During emergency hematopoiesis, hematopoietic stem cells (HSCs) rapidly proliferate to produce myeloid and lymphoid effector cells, a response that is critical against infection or tissue injury. If unresolved, this process leads to sustained inflammation, which can cause life-threatening diseases and cancer. Here, we identify a role of double PHD fingers 2 (DPF2) in modulating inflammation. DPF2 is a defining subunit of the hematopoiesis-specific BAF (SWI/SNF) chromatin-remodeling complex, and it is mutated in multiple cancers and neurological disorders. We uncovered that hematopoiesis-specific Dpf2-KO mice developed leukopenia, severe anemia, and lethal systemic inflammation characterized by histiocytic and fibrotic tissue infiltration resembling a clinical hyperinflammatory state. Dpf2 loss impaired the polarization of macrophages responsible for tissue repair, induced the unrestrained activation of Th cells, and generated an emergency-like state of HSC hyperproliferation and myeloid cell-biased differentiation. Mechanistically, Dpf2 deficiency resulted in the loss of the BAF catalytic subunit BRG1 from nuclear factor erythroid 2-like 2-controlled (NRF2-controlled) enhancers, impairing the antioxidant and antiinflammatory transcriptional response needed to modulate inflammation. Finally, pharmacological reactivation of NRF2 suppressed the inflammation-mediated phenotypes and lethality of Dpf2Δ/Δ mice. Our work establishes an essential role of the DPF2-BAF complex in licensing NRF2-dependent gene expression in HSCs and immune effector cells to prevent chronic inflammation.

Methylation of histone H3 lysine 36 is a barrier for therapeutic interventions of head and neck squamous cell carcinoma.

Approximately 20% of head and neck squamous cell carcinomas (HNSCC) exhibit reduced methylation on lysine 36 of histone H3 (H3K36me) due to mutations in histone methylase NSD1 or a lysine-to-methionine mutation in histone H3 (H3K36M). Whether such alterations of H3K36me can be exploited for therapeutic interventions is still unknown. Here, we show that HNSCC models expressing H3K36M can be divided into two groups: those that display aberrant accumulation of H3K27me3 and those that maintain steady levels of H3K27me3. The first group shows decreased proliferation, genome instability, and increased sensitivity to genotoxic agents, such as PARP1/2 inhibitors. In contrast, the H3K36M HNSCC models with steady H3K27me3 levels do not exhibit these characteristics unless H3K27me3 levels are elevated, either by DNA hypomethylating agents or by inhibiting the H3K27me3 demethylases KDM6A/B. Mechanistically, we found that H3K36M reduces H3K36me by directly impeding the activities of the histone methyltransferase NSD3 and the histone demethylase LSD2. Notably, we found that aberrant H3K27me3 levels induced by H3K36M expression is not a bona fide epigenetic mark in HNSCC since it requires continuous expression of H3K36M to be inherited. Moreover, increased sensitivity of H3K36M HNSCC models to PARP1/2 inhibitors solely depends on the increased H3K27me3 levels. Indeed, aberrantly high H3K27me3 levels decrease BRCA1 and FANCD2-dependent DNA repair, resulting in higher sensitivity to DNA breaks and replication stress. Finally, in support of our in vitro findings, a PARP1/2 inhibitor alone reduce tumor burden in a H3K36M HNSCC xenograft model with elevated H3K27me3, whereas in a H3K36M HNSCC xenograft model with consistent H3K27me3 levels, a combination of PARP1/2 inhibitors and agents that upregulate H3K27me3 proves to be successful. In conclusion, our findings underscore a delicate balance between H3K36 and H3K27 methylation, essential for maintaining genome stability. This equilibrium presents promising therapeutic opportunities for patients with H3K36me-deficient tumors.

Oxidized mC modulates synthetic lethality to PARP inhibitors for the treatment of leukemia.

TET2 haploinsufficiency is a driving event in myeloid cancers and is associated with a worse prognosis in patients with acute myeloid leukemia (AML). Enhancing residual TET2 activity using vitamin C increases oxidized 5-methylcytosine (mC) formation and promotes active DNA demethylation via base excision repair (BER), which slows leukemia progression. We utilize genetic and compound library screening approaches to identify rational combination treatment strategies to improve use of vitamin C as an adjuvant therapy for AML. In addition to increasing the efficacy of several US Food and Drug Administration (FDA)-approved drugs, vitamin C treatment with poly-ADP-ribosyl polymerase inhibitors (PARPis) elicits a strong synergistic effect to block AML self-renewal in murine and human AML models. Vitamin-C-mediated TET activation combined with PARPis causes enrichment of chromatin-bound PARP1 at oxidized mCs and γH2AX accumulation during mid-S phase, leading to cell cycle stalling and differentiation. Given that most AML subtypes maintain residual TET2 expression, vitamin C could elicit broad efficacy as a PARPi therapeutic adjuvant.

Statins enhance the chemosensitivity of R-CHOP in diffuse large B-cell lymphoma.

The beneficial effect of statins on the anti-lymphoma activity of the rituximab-based chemotherapy regimen is controversial. Here, we retrospectively reviewed patients with naïve-treated advanced diffuse large B-cell lymphoma (DLBCL) receiving frontline R-CHOP, and for whom data regarding differential statins use was available at the time of initiation of treatment. We observe that patients treated with statins and R-CHOP experienced a significantly higher CR rate as compared to those who received R-CHOP only. We further show that patients receiving medium or high intensity statins and R-CHOP experienced a significantly higher CR as compared to those treated with R-CHOP. Six-year progression free survival was higher for patients who received medium or higher intensity statins as compared to low or no statins. The potential contribution of cholesterol pathway in doxorubicin sensitivity was supported by in vitro/in vivo studies. Our study suggests that targeting cholesterol-using lovastatin could be a therapeutic strategy to enhance responses to R-CHOP in DLBCL patients.

Aminopyridine analogs selectively target metastatic pancreatic cancer.

Metastatic outgrowth is supported by metabolic adaptations that may differ from the primary tumor of origin. However, it is unknown if such adaptations are therapeutically actionable. Here we report a novel aminopyridine compound that targets a unique Phosphogluconate Dehydrogenase (PGD)-dependent metabolic adaptation in distant metastases from pancreatic cancer patients. Compared to structurally similar analogs, 6-aminopicolamine (6AP) potently and selectively reversed PGD-dependent metastatic properties, including intrinsic tumorigenic capacity, excess glucose consumption, and global histone hyperacetylation. 6AP acted as a water-soluble prodrug that was converted into intracellular bioactive metabolites that inhibited PGD in vitro, and 6AP monotherapy demonstrated anti-metastatic efficacy with minimal toxicity in vivo. Collectively, these studies identify 6AP and possibly other 6-aminopyridines as well-tolerated prodrugs with selectivity for metastatic pancreatic cancers. If unique metabolic adaptations are a common feature of metastatic or otherwise aggressive human malignancies, then such dependencies could provide a largely untapped pool of druggable targets for patients with advanced cancers.

Endocrine resistance and breast cancer plasticity are controlled by CoREST.

Resistance to cancer treatment remains a major clinical hurdle. Here, we demonstrate that the CoREST complex is a key determinant of endocrine resistance and ER+ breast cancer plasticity. In endocrine-sensitive cells, CoREST is recruited to regulatory regions co-bound to ERα and FOXA1 to regulate the estrogen pathway. In contrast, during temporal reprogramming towards a resistant state, CoREST is recruited to AP-1 sites. In reprogrammed cells, CoREST favors chromatin opening, cJUN binding to chromatin, and gene activation by controlling SWI/SNF recruitment independently of the demethylase activity of the CoREST subunit LSD1. Genetic and pharmacological CoREST inhibition reduces tumorigenesis and metastasis of endocrine-sensitive and endocrine-resistant xenograft models. Consistently, CoREST controls a gene signature involved in invasiveness in clinical breast tumors resistant to endocrine therapies. Our studies reveal CoREST functions that are co-opted to drive cellular plasticity and resistance to endocrine therapies and tumorigenesis, thus establishing CoREST as a potential therapeutic target for the treatment of advanced breast cancer.

Combination venetoclax and selinexor effective in relapsed refractory multiple myeloma with translocation t(11;14).

Patients with multiple myeloma-bearing translocation t(11;14) have recently been shown to benefit from the apoptosis-inducing drug venetoclax; however, the drug lacks FDA approval in multiple myeloma thus far due to a potential safety signal in the overall patient population. Selinexor is an inhibitor of nuclear export that is FDA-approved for patients with multiple myeloma refractory to multiple lines of therapy. Here, we report that in four patients with multiple myeloma with t(11;14), the concomitant administration of venetoclax and selinexor was safe and associated with disease response. Moreover, the combination was synergistic in t(11;14) multiple myeloma cell lines and caused decreased levels of Cyclin D1 (which is overexpressed due to the CCND1-IGH fusion) when given in combination as compared to single agents. These data suggest that the combination of venetoclax and selinexor is effective and t(11;14) may serve as a therapeutic marker for response and target for future clinical trials.

Increased cardiogenesis in P19-GFP teratocarcinoma cells expressing the propeptide IGF-1Ea.

The mechanism implicated in differentiation of endogenous cardiac stem cells into cardiomyocytes to regenerate the heart tissue upon an insult remains elusive, limiting the therapeutical goals to exogenous cell injection and/or gene therapy. We have shown previously that cardiac specific overexpression of the insulin-like growth factor 1 propeptide IGF-1Ea induces beneficial myocardial repair after infarct. Although the mechanism is still under investigation, the possibility that this propeptide may be involved in promoting stem cell differentiation into the cardiac lineage has yet to be explored. To investigate whether IGF-1Ea promote cardiogenesis, we initially modified P19 embryonal carcinoma cells to express IGF-1Ea. Taking advantage of their cardiomyogenic nature, we analyzed whether overexpression of this propeptide affected cardiac differentiation program. The data herein presented showed for the first time that constitutively overexpressed IGF-1Ea increased cardiogenic differentiation program in both undifferentiated and DMSO-differentiated cells. In details, IGF-1Ea overexpression promoted localization of alpha-actinin in finely organized sarcomeric structure compared to control cells and upregulated the cardiac mesodermal marker NKX-2.5 and the ventricular structural protein MLC2v. Furthermore, activated IGF-1 signaling promoted cardiac mesodermal induction in undifferentiated cells independently of cell proliferation. This analysis suggests that IGF-1Ea may be a good candidate to improve both in vitro production of cardiomyocytes from pluripotent stem cells and in vivo activation of the differentiation program of cardiac progenitor cells.

Vitamin C sensitizes triple negative breast cancer to PI3K inhibition therapy.

Rationale: The clinical use of PI3K inhibitors, such as buparlisib, has been plagued with toxicity at effective doses. The aim of this study is to determine if vitamin C, a potent epigenetic regulator, can improve the therapeutic outcome and reduce the dose of buparlisib in treating PIK3CA-mutated triple negative breast cancer (TNBC). Methods: The response of TNBC cells to buparlisib was assessed by EC50 measurements, apoptosis assay, clonogenic assay, and xenograft assay in mice. Molecular approaches including Western blot, immunofluorescence, RNA sequencing, and gene silencing were utilized as experimental tools. Results: Treatment with buparlisib at lower doses, along with vitamin C, induced apoptosis and inhibited the growth of TNBC cells in vitro. Vitamin C via oral delivery rendered a sub-therapeutic dose of buparlisib able to inhibit TNBC xenograft growth and to markedly block metastasis in mice. We discovered that buparlisib and vitamin C coordinately reduced histone H3K4 methylation by enhancing the nuclear translocation of demethylase, KDM5, and by serving as a cofactor to promote KDM5-mediated H3K4 demethylation. The expression of genes in the PI3K pathway, such as AKT2 and mTOR, was suppressed by vitamin C in a KDM5-dependent manner. Vitamin C and buparlisib cooperatively blocked AKT phosphorylation. Inhibition of KDM5 largely abolished the effect of vitamin C on the response of TNBC cells to buparlisib. Additionally, vitamin C and buparlisib co-treatment changed the expression of genes, including PCNA and FILIP1L, which are critical to cancer growth and metastasis. Conclusion: Vitamin C can be used to reduce the dosage of buparlisib needed to produce a therapeutic effect, which could potentially ease the dose-dependent side effects in patients.

Proteomics reveal cap-dependent translation inhibitors remodel the translation machinery and translatome.

Tactical disruption of protein synthesis is an attractive therapeutic strategy, with the first-in-class eIF4A-targeting compound zotatifin in clinical evaluation for cancer and COVID-19. The full cellular impact and mechanisms of these potent molecules are undefined at a proteomic level. Here, we report mass spectrometry analysis of translational reprogramming by rocaglates, cap-dependent initiation disruptors that include zotatifin. We find effects to be far more complex than simple "translational inhibition" as currently defined. Translatome analysis by TMT-pSILAC (tandem mass tag-pulse stable isotope labeling with amino acids in cell culture mass spectrometry) reveals myriad upregulated proteins that drive hitherto unrecognized cytotoxic mechanisms, including GEF-H1-mediated anti-survival RHOA/JNK activation. Surprisingly, these responses are not replicated by eIF4A silencing, indicating a broader translational adaptation than currently understood. Translation machinery analysis by MATRIX (mass spectrometry analysis of active translation factors using ribosome density fractionation and isotopic labeling experiments) identifies rocaglate-specific dependence on specific translation factors including eEF1ε1 that drive translatome remodeling. Our proteome-level interrogation reveals that the complete cellular response to these historical "translation inhibitors" is mediated by comprehensive translational landscape remodeling.