Oncogene addiction

Protein folding, cellular stress and cancer

Proteins are acknowledged as the phenotypical manifestation of the genotype, because protein-coding genes carry the information for the strings of amino acids that constitute the proteins. It is widely accepted that protein function depends on the corresponding "native" structure or folding achieved within the cell, and that native protein folding corresponds to the lowest free energy minimum for a given protein. However, protein folding within the cell is a non-deterministic dissipative process that from the same input may produce different outcomes, thus conformational heterogeneity of folded proteins is the rule and not the exception. Local changes in the intracellular environment promote variation in protein folding. Hence protein folding requires "supervision" by a host of chaperones and co-chaperones that help their client proteins to achieve the folding that is most stable according to the local environment. Such environmental influence on protein folding is continuously transduced with the help of the cellular stress responses (CSRs) and this may lead to changes in the rules of engagement between proteins, so that the corresponding protein interactome could be modified by the environment leading to an alternative cellular phenotype. This allows for a phenotypic plasticity useful for adapting to sudden and/or transient environmental changes at the cellular level. Starting from this perspective, hereunder we develop the argument that the presence of sustained cellular stress coupled to efficient CSRs may lead to the selection of an aberrant phenotype as the resulting adaptation of the cellular proteome (and the corresponding interactome) to such stressful conditions, and this can be a common epigenetic pathway to cancer.

E2F1-Associated Purine Synthesis Pathway Is a Major Component of the MET-DNA Damage Response Network

Various lines of investigation support a signaling interphase shared by receptor tyrosine kinases and the DNA damage response. However, the underlying network nodes and their contribution to the maintenance of DNA integrity remain unknown. We explored MET-related metabolic pathways in which interruption compromises proper resolution of DNA damage. Discovery metabolomics combined with transcriptomics identified changes in pathways relevant to DNA repair following MET inhibition (METi). METi by tepotinib was associated with the formation of γH2AX foci and with significant alterations in major metabolic circuits such as glycolysis, gluconeogenesis, and purine, pyrimidine, amino acid, and lipid metabolism. 5'-Phosphoribosyl-N-formylglycinamide, a de novo purine synthesis pathway metabolite, was consistently decreased in in vitro and in vivo MET-dependent models, and METi-related depletion of dNTPs was observed. METi instigated the downregulation of critical purine synthesis enzymes including phosphoribosylglycinamide formyltransferase, which catalyzes 5'-phosphoribosyl-N-formylglycinamide synthesis. Genes encoding these enzymes are regulated through E2F1, whose levels decrease upon METi in MET-driven cells and xenografts. Transient E2F1 overexpression prevented dNTP depletion and the concomitant METi-associated DNA damage in MET-driven cells. We conclude that DNA damage following METi results from dNTP reduction via downregulation of E2F1 and a consequent decline of de novo purine synthesis.

SIGNIFICANCE

Maintenance of genome stability prevents disease and affiliates with growth factor receptor tyrosine kinases. We identified de novo purine synthesis as a pathway in which key enzymatic players are regulated through MET receptor and whose depletion via MET targeting explains MET inhibition-associated formation of DNA double-strand breaks. The mechanistic importance of MET inhibition-dependent E2F1 downregulation for interference with DNA integrity has translational implications for MET-targeting-based treatment of malignancies.

Systematic identification of a synthetic lethal interaction in brain-metastatic lung adenocarcinoma

Metastatic lung adenocarcinoma (LuAC) presents a significant clinical challenge due to the short latency and the lack of efficient treatment options. Therefore, identification of molecular vulnerabilities in metastatic LuAC holds great importance in the development of therapeutic drugs against this disease. In this study, we performed a genome-wide siRNA screening using poorly and highly brain-metastatic LuAC cell lines. Using this approach, we discovered that compared to poorly metastatic LuAC (LuAC-Par) cells, brain-metastatic LuAC (LuAC-BrM) cells exhibited a significantly higher vulnerability to c-FLIP (an inhibitor of caspase-8)-depletion-induced apoptosis. Furthermore, in vivo studies demonstrated that c-FLIP knockdown specifically inhibited growth of LuAC-BrM, but not the LuAC-Par, tumors, suggesting the addiction of LuAC-BrM to the function of c-FLIP for their survival. Our in vitro and in vivo analyses also demonstrated that LuAC-BrM is more sensitive to c-FLIP-depletion due to ER stress-induced activation of the c-JUN and subsequent induction of stress genes including ATF4 and DDIT3. Finally, we found that c-JUN not only sensitized LuAC-BrM to c-FLIP-depletion-induced cell death but also promoted brain metastasis in vivo, providing strong evidence for c-JUN's function as a double-edged sword in LuAC-BrM. Collectively, our findings not only reveal a novel link between c-JUN, brain metastasis, and c-FLIP addiction in LuAC-BrM but also present an opportunity for potential therapeutic intervention.

Structurally Specific Z-DNA Proteolysis Targeting Chimera Enables Targeted Degradation of Adenosine Deaminase Acting on RNA 1

Given the prevalent advancements in DNA- and RNA-based PROTACs, there remains a significant need for the exploration and expansion of more specific DNA-based tools, thus broadening the scope and repertoire of DNA-based PROTACs. Unlike conventional A- or B-form DNA, Z-form DNA is a configuration that exclusively manifests itself under specific stress conditions and with specific target sequences, which can be recognized by specific reader proteins, such as ADAR1 or ZBP1, to exert downstream biological functions. The core of our innovation lies in the strategic engagement of Z-form DNA with ADAR1 and its degradation is achieved by leveraging a VHL ligand conjugated to Z-form DNA to recruit the E3 ligase. This ingenious construct engendered a series of Z-PROTACs, which we utilized to selectively degrade the Z-DNA-binding protein ADAR1, a molecule that is frequently overexpressed in cancer cells. This meticulously orchestrated approach triggers a cascade of PANoptotic events, notably encompassing apoptosis and necroptosis, by mitigating the blocking effect of ADAR1 on ZBP1, particularly in cancer cells compared with normal cells. Moreover, the Z-PROTAC design exhibits a pronounced predilection for ADAR1, as opposed to other Z-DNA readers, such as ZBP1. As such, Z-PROTAC likely elicits a positive immunological response, subsequently leading to a synergistic augmentation of cancer cell death. In summary, the Z-DNA-based PROTAC (Z-PROTAC) approach introduces a modality generated by the conformational change from B- to Z-form DNA, which harnesses the structural specificity intrinsic to potentiate a selective degradation strategy. This methodology is an inspiring conduit for the advancement of PROTAC-based therapeutic modalities, underscoring its potential for selectivity within the therapeutic landscape of PROTACs to target undruggable proteins.

Methylated Nucleotide-Based Proteolysis-Targeting Chimera Enables Targeted Degradation of Methyl-CpG-Binding Protein 2

Methyl-CpG-binding protein 2 (MeCP2), a reader of DNA methylation, has been extensively investigated for its function in neurological and neurodevelopmental disorders. Emerging evidence indicates that MeCP2 exerts an oncogenic function in cancer; however, the endeavor to develop a MeCP2-targeted therapy remains a challenge. This work attempts to address it by introducing a methylated nucleotide-based targeting chimera termed methyl-proteolysis-targeting chimera (methyl-PROTAC). The methyl-PROTAC incorporates a methylated cytosine into an oligodeoxynucleotide moiety to recruit MeCP2 for targeted degradation in a von Hippel-Lindau- and proteasome-dependent manner, thus displaying antiproliferative effects in cancer cells reliant on MeCP2 overexpression. This selective cytotoxicity endows methyl-PROTAC with the capacity to selectively eliminate cancer cells that are addicted to the overexpression of the MeCP2 oncoprotein. Furthermore, methyl-PROTAC-mediated MeCP2 degradation induces apoptosis in cancer cells. These findings underscore the therapeutic potential of methyl-PROTAC to degrade undruggable epigenetic regulatory proteins. In summary, the development of methyl-PROTAC introduces an innovative strategy by designing a modified nucleotide-based degradation approach for manipulating epigenetic factors, thereby representing a promising avenue for the advancement of PROTAC-based therapeutics.

Tumor-associated macrophage (TAM)-derived CCL22 induces FAK addiction in esophageal squamous cell carcinoma (ESCC)

Tumor cell dependence on activated oncogenes is considered a therapeutic target, but protumorigenic microenvironment-mediated cellular addiction to specific oncogenic signaling molecules remains to be further defined. Here, we showed that tumor-associated macrophages (TAMs) produced an abundance of C-C motif chemokine 22 (CCL22), whose expression in the tumor stroma was positively associated with the level of intratumoral phospho-focal adhesion kinase (pFAK Tyr³⁹⁷), tumor metastasis and reduced patient survival. Functionally, CCL22-stimulated hyperactivation of FAK was correlated with increased malignant progression of cancer cells. CCL22-induced addiction to FAK was demonstrated by the persistent suppression of tumor progression upon FAK-specific inhibition. Mechanistically, we identified that diacylglycerol kinase α (DGKα) acted as a signaling adaptor to link the CCL22 receptor C-C motif chemokine receptor 4 (CCR4) and FAK and promoted CCL22-induced activation of the FAK/AKT pathway. CCL22/CCR4 signaling activated the intracellular Ca²⁺/phospholipase C-γ1 (PLC-γ1) axis to stimulate the phosphorylation of DGKα at a tyrosine residue (Tyr³³⁵) and promoted the translocation of DGKα to the plasma membrane to assemble the DGKα/FAK signalosome, which critically contributed to regulating sensitivity to FAK inhibitors in cancer cells. The identification of TAM-driven intratumoral FAK addiction provides opportunities for utilizing the tumor-promoting microenvironment to achieve striking anticancer effects.

Targeting drug-resistant mutations in ALK

Therapy resistance limits the clinical success of tyrosine kinase inhibitors (TKIs) in ALK-positive non-small cell lung cancer. A study now proposes a framework to identify compound resistance mutations to the lorlatinib TKI and provides structure-based drug design approaches to overcome resistance mediated by ALK(G1202R) or ALK(I1171N/S/T).

Functional genomics approaches to improve pre-clinical drug screening and biomarker discovery

Advances in sequencing technology have enabled the genomic and transcriptomic characterization of human malignancies with unprecedented detail. However, this wealth of information has been slow to translate into clinically meaningful outcomes. Different models to study human cancers have been established and extensively characterized. Using these models, functional genomic screens and pre-clinical drug screening platforms have identified genetic dependencies that can be exploited with drug therapy. These genetic dependencies can also be used as biomarkers to predict response to treatment. For many cancers, the identification of such biomarkers remains elusive. In this review, we discuss the development and characterization of models used to study human cancers, RNA interference and CRISPR screens to identify genetic dependencies, large-scale pharmacogenomics studies and drug screening approaches to improve pre-clinical drug screening and biomarker discovery.

Differential but Concerted Expression of HSD17B2, HSD17B3, SHBG and SRD5A1 Testosterone Tetrad Modulate Therapy Response and Susceptibility to Disease Relapse in Patients with Prostate Cancer

Simple Summary

Over the last two decades, our improved understanding of the pathobiology of androgen-addicted prostate cancer (PCa), and documented therapeutic advances/breakthroughs have not translated into any substantial or sustained curative benefit for patients treated with traditional ADT or novel immune checkpoint blockade therapeutics. This is invariably connected with the peculiar biology and intratumoral heterogeneity of PCa. Castration-resistant PCa, constituting ~30% of all PCa, remains a clinically enigmatic and therapeutically challenging disease sub-type, that is therapy-refractory and characterized by high risk for recurrence after initial response. Our findings highlight the role and exploitability of testosterone metabolic reprogramming in prostate TME for patient stratification and personalized/precision medicine based on the differential but concerted expression of molecular components of the proposed testosterone tetrad in patients with therapy-refractory, locally advanced, or recurrent PCa. The therapeutic exploitability and clinical feasibility of our proposed approach is suggested by our preclinical findings.

Abstract

Background: Testosterone plays a critical role in prostate development and pathology. However, the impact of the molecular interplay between testosterone-associated genes on therapy response and susceptibility to disease relapse in PCa patients remains underexplored. Objective: This study investigated the role of dysregulated or aberrantly expressed testosterone-associated genes in the enhanced dissemination, phenoconversion, and therapy response of treatment-resistant advanced or recurrent PCa. Methods: Employing a combination of multi-omics big data analyses, in vitro, ex vivo, and in vivo assays, we assessed the probable roles of HSD17B2, HSD17B3, SHBG, and SRD5A1-mediated testosterone metabolism in the progression, therapy response, and prognosis of advanced or castration-resistant PCa (CRPC). Results: Our bioinformatics-aided gene expression profiling and immunohistochemical staining showed that the aberrant expression of the HSD17B2, HSD17B3, SHBG, and SRD5A1 testosterone metabolic tetrad characterize androgen-driven PCa and is associated with disease progression. Reanalysis of the TCGA PRAD cohort (n = 497) showed that patients with SRD5A1-dominant high expression of the tetrad exhibited worse mid-term to long-term (≥5 years) overall survival, with a profoundly shorter time to recurrence, compared to those with low expression. More so, we observed a strong association between enhanced HSD17B2/SRD5A1 signaling and metastasis to distant lymph nodes (M1a) and bones (M1b), while upregulated HSD17B3/SHBG signaling correlated more with negative metastasis (M0) status. Interestingly, increased SHBG/SRD5A1 ratio was associated with metastasis to distant organs (M1c), while elevated SRD5A1/SHBG ratio was associated with positive biochemical recurrence (BCR) status, and shorter time to BCR. Molecular enrichment and protein–protein connectivity network analyses showed that the androgenic tetrad regulates testosterone metabolism and cross-talks with modulators of drug response, effectors of cell cycle progression, proliferation or cell motility, and activators/mediators of cancer stemness. Moreover, of clinical relevance, SHBG ectopic expression (SHBG_OE) or SRD5A1 knockout (sgSRD5A1) induced the acquisition of spindle fibroblastoid morphology by the round/polygonal metastatic PC-3 and LNCaP cells, attenuated their migration and invasion capability, and significantly suppressed their ability to form primary or secondary tumorspheres, with concomitant downregulation of stemness KLF4, OCT3/4, and drug resistance ABCC1, ABCB1 proteins expression levels. We also showed that metronomic dutasteride synergistically enhanced the anticancer effect of low-dose docetaxel, in vitro, and in vivo. Conclusion: These data provide proof of concept that re-reprogramming of testosterone metabolism through “SRD5A1 withdrawal” or “SHBG induction” is a workable therapeutic strategy for shutting down androgen-driven oncogenic signals, reversing treatment resistance, and repressing the metastatic/recurrent phenotypes of patients with PCa.

KRAS drives immune evasion in a genetic model of pancreatic cancer

Immune evasion is a hallmark of KRAS-driven cancers, but the underlying causes remain unresolved. Here, we use a mouse model of pancreatic ductal adenocarcinoma to inactivate KRAS by CRISPR-mediated genome editing. We demonstrate that at an advanced tumor stage, dependence on KRAS for tumor growth is reduced and is manifested in the suppression of antitumor immunity. KRAS-deficient cells retain the ability to form tumors in immunodeficient mice. However, they fail to evade the host immune system in syngeneic wild-type mice, triggering strong antitumor response. We uncover changes both in tumor cells and host immune cells attributable to oncogenic KRAS expression. We identify BRAF and MYC as key mediators of KRAS-driven tumor immune suppression and show that loss of BRAF effectively blocks tumor growth in mice. Applying our results to human PDAC we show that lowering KRAS activity is likewise associated with a more vigorous immune environment.

MYC and Twist1 cooperate to drive metastasis by eliciting crosstalk between cancer and innate immunity

Metastasis is a major cause of cancer mortality. We generated an autochthonous transgenic mouse model whereby conditional expression of MYC and Twist1 enables hepatocellular carcinoma (HCC) to metastasize in >90% of mice. MYC and Twist1 cooperate and their sustained expression is required to elicit a transcriptional program associated with the activation of innate immunity, through secretion of a cytokinome that elicits recruitment and polarization of tumor associated macrophages (TAMs). Systemic treatment with Ccl2 and Il13 induced MYC-HCCs to metastasize; whereas, blockade of Ccl2 and Il13 abrogated MYC/Twist1-HCC metastasis. Further, in 33 human cancers (n = 9502) MYC and TWIST1 predict poor survival (p=4.3×10⁻¹⁰), CCL2/IL13 expression (p<10⁻¹⁰⁹) and TAM infiltration (p<10⁻⁹⁶). Finally, in the plasma of patients with HCC (n = 25) but not cirrhosis (n = 10), CCL2 and IL13 were increased and IL13 predicted invasive tumors. Therefore, MYC and TWIST1 generally appear to cooperate in human cancer to elicit a cytokinome that enables metastasis through crosstalk between cancer and immune microenvironment.

Cancer develops when cells in the body gain mutations that allow them to grow and divide rapidly and uncontrollably. As the disease progresses these cancer cells develop the ability to spread around the body. This process of spreading, called metastasis, is responsible for most cancer-related deaths in humans, but no current treatments target it.

Mutations that increase the levels of two proteins known as MYC and TWIST1 in cells cause many human cancers. In healthy adult cells, normal levels of MYC and TWIST1 act as key regulators that switch thousands of genes on or off. TWIST1 is known to control the movement and spread of cells in the embryo. However, it is not known how MYC and TWIST1 work together to promote the metastasis of cancer cells.

To address this question, Dhanasekaran, Baylot et al. used mice to investigate the roles of MYC and TWIST1 in the metastasis of cancer cells. The experiments showed that these two proteins work together to reprogram mouse cancer cells to release signal molecules known as cytokines. These molecules convert immune cells known as macrophages to a tumor-friendly state that allows cancers cells to spread around the body. Inhibiting two cytokines known as CCL2 and IL13 prevented the cancer cells from moving.

Further experiments analyzed tumor samples from around 10,000 human patients with 33 different cancers. This revealed that patients that had higher levels of MYC and TWIST1 proteins in their tumors also had increased levels of CCL2 and IL13, more activated macrophages and were less likely to recover from their cancer.

The findings of Dhanasekaran, Baylot et al. suggest that MYC and TWIST1 may instigate metastasis in many human cancers, and therapies targeting specific cytokines may prevent these cancers from spreading around the body. Furthermore, screening blood for the levels of cytokines may help to identify the cancer patients who would benefit from such therapies.

Melanoma Therapeutic Strategies that Select against Resistance by Exploiting MYC-Driven Evolutionary Convergence

Diverse pathways drive resistance to BRAF/MEK inhibitors in BRAF-mutant melanoma, suggesting that durable control of resistance will be a challenge. By combining statistical modeling of genomic data from matched pre-treatment and post-relapse patient tumors with functional interrogation of >20 in vitro and in vivo resistance models, we discovered that major pathways of resistance converge to activate the transcription factor, c-MYC (MYC). MYC expression and pathway gene signatures were suppressed following drug treatment, and then rebounded during progression. Critically, MYC activation was necessary and sufficient for resistance, and suppression of MYC activity using genetic approaches or BET bromodomain inhibition was sufficient to resensitize cells and delay BRAFi resistance. Finally, MYC-driven, BRAFi-resistant cells are hypersensitive to the inhibition of MYC synthetic lethal partners, including SRC family and c-KIT tyrosine kinases, as well as glucose, glutamine, and serine metabolic pathways. These insights enable the design of combination therapies that select against resistance evolution.

An in vitro model demonstrates the potential of neoplastic human germ cells to influence the tumour microenvironment

Testicular germ cell tumours (TGCT) typically contain high numbers of infiltrating immune cells, yet the functional nature and consequences of interactions between GCNIS (germ cell neoplasia in situ) or seminoma cells and immune cells remain unknown. A co-culture model using the seminoma-derived TCam-2 cell line and peripheral blood mononuclear cells (PBMC, n = 7 healthy donors) was established to investigate how tumour and immune cells each contribute to the cytokine microenvironment associated with TGCT. Three different co-culture approaches were employed: direct contact during culture to simulate in situ cellular interactions occurring within seminomas (n = 9); indirect contact using well inserts to mimic GCNIS, in which a basement membrane separates the neoplastic germ cells and immune cells (n = 3); and PBMC stimulation prior to direct contact during culture to overcome the potential lack of immune cell activation (n = 3). Transcript levels for key cytokines in PBMC and TCam-2 cell fractions were determined using RT-qPCR. TCam-2 cell fractions showed an immediate increase (within 24 h) in several cytokine mRNAs after direct contact with PBMC, whereas immune cell fractions did not. The high levels of interleukin-6 (IL6) mRNA and protein associated with TCam-2 cells implicate this cytokine as important to seminoma physiology. Use of PBMCs from different donors revealed a robust, repeatable pattern of changes in TCam-2 and PBMC cytokine mRNAs, independent of potential inter-donor variation in immune cell responsiveness. This in vitro model recapitulated previous data from clinical TGCT biopsies, revealing similar cytokine expression profiles and indicating its suitability for exploring the in vivo circumstances of TGCT. Despite the limitations of using a cell line to mimic in vivo events, these results indicate how neoplastic germ cells can directly shape the surrounding tumour microenvironment, including by influencing local immune responses. IL6 production by seminoma cells may be a practical target for early diagnosis and/or treatment of TGCT.

ErbB Family Signalling: A Paradigm for Oncogene Addiction and Personalized Oncology

ErbB family members represent important biomarkers and drug targets for modern precision therapy. They have gained considerable importance as paradigms for oncoprotein addiction and personalized medicine. This review summarizes the current understanding of ErbB proteins in cell signalling and cancer and describes the molecular rationale of prominent cases of ErbB oncoprotein addiction in different cancer types. In addition, we have highlighted experimental technologies for the development of innovative cancer cell models that accurately predicted clinical ErbB drug efficacies. In the future, such cancer models might facilitate the identification and validation of physiologically relevant novel forms of oncoprotein and non-oncoprotein addiction or synthetic lethality. The identification of genotype-drug response relationships will further advance personalized oncology and improve drug efficacy in the clinic. Finally, we review the most important drugs targeting ErbB family members that are under investigation in clinical trials or that made their way already into clinical routine. Taken together, the functional characterization of ErbB oncoproteins have significantly increased our knowledge on predictive biomarkers, oncoprotein addiction and patient stratification and treatment.

The hallmarks of cancer: relevance to the pathogenesis of polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is a progressive inherited disorder in which renal tissue is gradually replaced with fluid-filled cysts, giving rise to chronic kidney disease (CKD) and progressive loss of renal function. ADPKD is also associated with liver ductal cysts, hypertension, chronic pain and extra-renal problems such as cerebral aneurysms. Intriguingly, improved understanding of the signalling and pathological derangements characteristic of ADPKD has revealed marked similarities to those of solid tumours, even though the gross presentation of tumours and the greater morbidity and mortality associated with tumour invasion and metastasis would initially suggest entirely different disease processes. The commonalities between ADPKD and cancer are provocative, particularly in the context of recent preclinical and clinical studies of ADPKD that have shown promise with drugs that were originally developed for cancer. The potential therapeutic benefit of such repurposing has led us to review in detail the pathological features of ADPKD through the lens of the defined, classic hallmarks of cancer. In addition, we have evaluated features typical of ADPKD, and determined whether evidence supports the presence of such features in cancer cells. This analysis, which places pathological processes in the context of defined signalling pathways and approved signalling inhibitors, highlights potential avenues for further research and therapeutic exploitation in both diseases.

Cancer nanoimmunotherapy using advanced pharmaceutical nanotechnology

Immunotherapy is a promising option for cancer treatment that might cure cancer with fewer side effects by primarily activating the host's immune system. However, the effect of traditional immunotherapy is modest, frequently due to tumor escape and resistance of multiple mechanisms. Pharmaceutical nanotechnology, which is also called cancer nanotechnology or nanomedicine, has provided a practical solution to solve the limitations of traditional immunotherapy. This article reviews the latest developments in immunotherapy and nanomedicine, and illustrates how nanocarriers (including micelles, liposomes, polymer-drug conjugates, solid lipid nanoparticles and biodegradable nanoparticles) could be used for the cellular transfer of immune effectors for active and passive nanoimmunotherapy. The fine engineering of nanocarriers based on the unique features of the tumor microenvironment and extra-/intra-cellular conditions of tumor cells can greatly tip the triangle immunobalance among host, tumor and nanoparticulates in favor of antitumor responses, which shows a promising prospect for nanoimmunotherapy.

Adaptive Resistance to Immunotherapy Directed Against p53 Can be Overcome by Global Expression of Tumor-Antigens in Dendritic Cells

Immunotherapy of cancer utilizes dendritic cells (DCs) for antigen presentation and the induction of tumor-specific immune responses. However, the therapeutic induction of anti-tumor immunity is limited by tumor escape mechanisms. In this study, immortalized dendritic D2SC/1 cells were transduced with a mutated version of the p53 tumor suppressor gene, p53M234I, or p53C132F/E168G, which are overexpressed in MethA fibrosarcoma tumor cells. In addition, D2SC/1 cells were fused with MethA tumor cells to generate a vaccine that potentially expresses a large repertoire of tumor-antigens. Cellular vaccines were transplanted onto Balb/c mice and MethA tumor growth and anti-tumor immune responses were examined in vaccinated animals. D2SC/1–p53M234I and D2SC/1–p53C132F/E168G cells induced strong therapeutic and protective MethA tumor immunity upon transplantation in Balb/c mice. However, in a fraction of immunized mice MethA tumor growth resumed after an extended latency period. Analysis of these tumors indicated loss of p53 expression. Mice, pre-treated with fusion hybrids generated from D2SC/1 and MethA tumor cells, suppressed MethA tumor growth and averted adaptive immune escape. Polyclonal B-cell responses directed against various MethA tumor proteins could be detected in the sera of D2SC/1–MethA inoculated mice. Athymic nude mice and Balb/c mice depleted of CD4⁺ or CD8⁺ T-cells were not protected against MethA tumor cell growth after immunization with D2SC/1–MethA hybrids. Our results highlight a potential drawback of cancer immunotherapy by demonstrating that the induction of a specific anti-tumor response favors the acquisition of tumor phenotypes promoting immune evasion. In contrast, the application of DC/tumor cell fusion hybrids prevents adaptive immune escape by a T-cell dependent mechanism and provides a simple strategy for personalized anti-cancer treatment without the need of selectively priming the host immune system.

Ribonucleoprotein HNRNPA2B1 interacts with and regulates oncogenic KRAS in pancreatic ductal adenocarcinoma cells

BACKGROUND & AIMS

Development of pancreatic ductal adenocarcinoma (PDAC) involves activation of c-Ki-ras2 Kirsten rat sarcoma oncogene homolog (KRAS) signaling, but little is known about the roles of proteins that regulate the activity of oncogenic KRAS. We investigated the activities of proteins that interact with KRAS in PDAC cells.

METHODS

We used mass spectrometry to demonstrate that heterogeneous nuclear ribonucleoproteins (HNRNP) A2 and B1 (encoded by the gene HNRNPA2B1) interact with KRAS G12V. We used co-immunoprecipitation analyses to study interactions between HNRNPA2B1 and KRAS in KRAS-dependent and KRAS-independent PDAC cell lines. We knocked down HNRNPA2B1 using small hairpin RNAs and measured viability, anchorage-independent proliferation, and growth of xenograft tumors in mice. We studied KRAS phosphorylation using the Phos-tag system.

RESULTS

We found that interactions between HRNPA2B1 and KRAS correlated with KRAS-dependency of some human PDAC cell lines. Knock down of HNRNPA2B1 significantly reduced viability, anchorage-independent proliferation, and formation of xenograft tumors by KRAS-dependent PDAC cells. HNRNPA2B1 knock down also increased apoptosis of KRAS-dependent PDAC cells, inactivated c-akt murine thymoma oncogene homolog 1 signaling via mammalian target of rapamycin, and reduced interaction between KRAS and phosphatidylinositide 3-kinase. Interaction between HNRNPA2B1 and KRAS required KRAS phosphorylation at serine 181.

CONCLUSIONS

In KRAS-dependent PDAC cell lines, HNRNPA2B1 interacts with and regulates the activity of KRAS G12V and G12D. HNRNPA2B1 is required for KRAS activation of c-akt murine thymoma oncogene homolog 1-mammalian target of rapamycin signaling, interaction with phosphatidylinositide 3-kinase, and PDAC cell survival and tumor formation in mice. HNRNPA2B1 might be a target for treatment of pancreatic cancer.

Epiregulin: roles in normal physiology and cancer

Epiregulin is a 46-amino acid protein that belongs to the epidermal growth factor (EGF) family of peptide hormones. Epiregulin binds to the EGF receptor (EGFR/ErbB1) and ErbB4 (HER4) and can stimulate signaling of ErbB2 (HER2/Neu) and ErbB3 (HER3) through ligand-induced heterodimerization with a cognate receptor. Epiregulin possesses a range of functions in both normal physiologic states as well as in pathologic conditions. Epiregulin contributes to inflammation, wound healing, tissue repair, and oocyte maturation by regulating angiogenesis and vascular remodeling and by stimulating cell proliferation. Deregulated epiregulin activity appears to contribute to the progression of a number of different malignancies, including cancers of the bladder, stomach, colon, breast, lung, head and neck, and liver. Therefore, epiregulin and the elements of the EGF/ErbB signaling network that lie downstream of epiregulin appear to be good targets for therapeutic intervention.

eIF4E-Overexpression imparts perillyl alcohol and rapamycin-mediated regulation of telomerase reverse transcriptase

Translation is mediated partly by regulation of free eukaryotic initiation factor 4E (eIF4E) levels through PI3K-Akt-mTOR signaling. Cancer cells treated with the plant-derived perillyl alcohol (POH) or the mechanistic target of rapamycin (mTOR) inhibitor rapamycin dephosphorylate eIF4E-binding protein (4E-BP1) and attenuate cap-dependent translation. We previously showed in cancer cell lines with elevated eIF4E that POH and rapamycin regulate telomerase activity through this pathway. Here, immortalized Chinese hamster ovary (CHO) control cells and CHO cells with forced eIF4E expression (rb4E) were used to elucidate eIF4E's role in telomerase regulation by POH and rapamycin. Despite 5-fold higher eIF4E amounts in rb4E, telomerase activity, telomerase reverse transcriptase (TERT) mRNA, and TERT protein were nearly equivalent in control and rb4E cells. In control cells, telomerase activity, TERT mRNA and protein levels were unaffected by either compound. In contrast, telomerase activity and TERT protein were both attenuated by either agent in rb4E cells, but without corresponding TERT mRNA decreases indicating a translational/post-translational process. S6K, Akt, and 4E-BP1 were modulated by mTOR mediators only in the presence of increased eIF4E. Thus, eIF4E-overexpression in rb4E cells enables inhibitory effects of POH and rapamycin on telomerase and TERT protein. Importantly, eIF4E-overexpression modifies cellular protein synthetic processes and gene regulation.

The molecular basis of targeting protein kinases in cancer therapeutics

In this paper, we provide an overview of targeted anticancer therapies with small molecule kinase inhibitors. First, we discuss why a single constitutively active kinase emanating from a variety of aberrant genetic alterations is capable of transforming a normal cell, leading it to acquire the hallmarks of a cancer cell. To draw attention to the fact that kinase inhibition in targeted cancer therapeutics differs from conventional cytotoxic chemotherapy, we exploit a conceptual framework explaining why suppressed kinase activity will selectively kill only the so-called oncogene 'addicted' cancer cell, while sparing the healthy cell. Second, we introduce the protein kinase superfamily in light of its common active conformation with precisely positioned structural elements, and the diversified auto-inhibitory conformations among the kinase families. Understanding the detailed activation mechanism of individual kinases is essential to relate the observed oncogenic alterations to the elevated constitutively active state, to identify the mechanism of consequent drug resistance, and to guide the development of the next-generation inhibitors. To clarify the vital importance of structural guidelines in studies of oncogenesis, we explain how somatic mutations in EGFR result in kinase constitutive activation. Third, in addition to the common theme of secondary (acquired) mutations that prevent drug binding from blocking a signaling pathway which is hijacked by the aberrant activated kinase, we discuss scenarios of drug resistance and relapse by compensating lesions that bypass the inactivated pathway in a vertical or horizontal fashion. Collectively, these suggest that the future challenge of cancer therapy with small molecule kinase inhibitors will rely on the discovery of distinct combinations of optimized drugs to target individual subtypes of different cancers.

Tyrosine kinase inhibitors: views of selectivity, sensitivity, and clinical performance

With the manufacture of imatinib, researchers introduced tyrosine kinase inhibitors (TKIs) into the clinical setting in 2000 to treat cancers; approximately fifteen other TKIs soon followed. Imatinib remains the most successful agent, whereas all the others have had modest effects on the cancers that they target. The current challenge is to identify the agents that need to be combined with TKIs to maximize their efficacy. One of the most promising approaches is to combine immune therapy with TKI treatment. In this review, the therapeutic potential of TKIs for treatment is discussed.

Quantitative and Sensitive Detection of Cancer Genome Amplifications from Formalin Fixed Paraffin Embedded Tumors with Droplet Digital PCR

For the analysis of cancer, there is great interest in rapid and accurate detection of cancer genome amplifications containing oncogenes that are potential therapeutic targets. The vast majority of cancer tissue samples are formalin fixed and paraffin embedded (FFPE) which enables histopathological examination and long term archiving. However, FFPE cancer genomic DNA is oftentimes degraded and generally a poor substrate for many molecular biology assays. To overcome the issues of poor DNA quality from FFPE samples and detect oncogenic copy number amplifications with high accuracy and sensitivity, we developed a novel approach. Our assay requires nanogram amounts of genomic DNA, thus facilitating study of small amounts of clinical samples. Using droplet digital PCR (ddPCR), we can determine the relative copy number of specific genomic loci even in the presence of intermingled normal tissue. We used a control dilution series to determine the limits of detection for the ddPCR assay and report its improved sensitivity on minimal amounts of DNA compared to standard real-time PCR. To develop this approach, we designed an assay for the fibroblast growth factor receptor 2 gene (FGFR2) that is amplified in a gastric and breast cancers as well as others. We successfully utilized ddPCR to ascertain FGFR2 amplifications from FFPE-preserved gastrointestinal adenocarcinomas.