RESUMO
Research in toxicology relies on in vitro models such as cell lines. These living models are prone to change and may be described in publications with insufficient information or quality control testing. This article sets out recommendations to improve the reliability of cell-based research.
Assuntos
Técnicas de Cultura de Células/normas , Linhagem Celular , Modelos Biológicos , Animais , Autenticação de Linhagem Celular , Humanos , Controle de Qualidade , Reprodutibilidade dos Testes , Toxicologia/métodos , Toxicologia/normasRESUMO
The bromodomain and extra-terminal (BET) family of proteins, consisting of the bromodomains containing protein 2 (BRD2), BRD3, BRD4, and the testis-specific BRDT, are key epigenetic regulators of gene transcription and has emerged as an attractive target for anticancer therapy. Herein, we describe the discovery of a novel potent BET bromodomain inhibitor, using a systematic structure-based approach focused on improving potency, metabolic stability, and permeability. The optimized dimethylisoxazole aryl-benzimidazole inhibitor exhibited high potency towards BRD4 and related BET proteins in biochemical and cell-based assays and inhibited tumor growth in two proof-of-concept preclinical animal models.
Assuntos
Benzimidazóis/farmacologia , Descoberta de Drogas , Isoxazóis/farmacologia , Mieloma Múltiplo/tratamento farmacológico , Fatores de Transcrição/antagonistas & inibidores , Administração Oral , Animais , Benzimidazóis/química , Benzimidazóis/metabolismo , Disponibilidade Biológica , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Relação Dose-Resposta a Droga , Humanos , Isoxazóis/administração & dosagem , Isoxazóis/química , Isoxazóis/metabolismo , Camundongos , Estrutura Molecular , Mieloma Múltiplo/metabolismo , Mieloma Múltiplo/patologia , Neoplasias Experimentais/tratamento farmacológico , Neoplasias Experimentais/metabolismo , Neoplasias Experimentais/patologia , Domínios Proteicos/efeitos dos fármacos , Relação Estrutura-Atividade , Fatores de Transcrição/metabolismoRESUMO
Targeting of histone methylation has therapeutic potential in oncology. Here, we provide proof-of-principle that pharmacological inhibition of KDM5 histone-demethylases is a new strategy for the personalized treatment of HER2+ breast cancer. The anti-proliferative effects of the prototype of a new class of selective KDM5-inhibitors (KDM5-inh1) are evaluated in 40 cell lines, recapitulating the heterogeneity of breast cancer. This analysis demonstrates that HER2+ cells are particularly sensitive to KDM5 inhibition. The results are confirmed in an appropriate in vivo model with a close structural analog (KDM5-inh1A). RNA-seq data obtained in HER2+ BT-474 cells exposed to KDM5-Inh1 indicate that the compound alters expression of numerous genes downstream of the ERBB2 gene-product, HER2. In selected HER2-positive breast-cancer cells, we demonstrate synergistic interactions between KDM5-inh1 and HER2-targeting agents (trastuzumab and lapatinib). In addition, HER2+ cell lines with innate and acquired resistance to trastuzumab show sensitivity to KDM5-inh1. The levels of KDM5A/B/C proteins, which are selectively targeted by the agent, have no significant association with KDM5-inh1 responsiveness across our panel of breast-cancer cell lines, suggesting the existence of other determinants of sensitivity. Using RNA-seq data of the breast-cancer cell lines we generate a gene-expression model that is a robust predictor of KDM5-inh1 sensitivity. In a test set of breast cancers, this model predicts sensitivity to the compound in a large fraction of HER2+ tumors. In conclusion, KDM5 inhibition has potential in the treatment of HER2+ breast cancer and our gene-expression model can be developed into a diagnostic tool for the selection of patients.
Assuntos
Neoplasias da Mama/genética , Regulação Neoplásica da Expressão Gênica/genética , Receptor ErbB-2/genética , Proteína 2 de Ligação ao Retinoblastoma/genética , Neoplasias da Mama/tratamento farmacológico , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Proliferação de Células/genética , Feminino , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Humanos , Trastuzumab/farmacologiaRESUMO
Targeting KRAS mutant tumors through inhibition of individual downstream pathways has had limited clinical success. Here we report that RAF inhibitors exhibit little efficacy in KRAS mutant tumors. In combination drug screens, MEK and PI3K inhibitors synergized with pan-RAF inhibitors through an RAS-GTP-dependent mechanism. Broad cell line profiling with RAF/MEK inhibitor combinations revealed synergistic efficacy in KRAS mutant and wild-type tumors, with KRASG13D mutants exhibiting greater synergy versus KRASG12 mutant tumors. Mechanistic studies demonstrate that MEK inhibition induced RAS-GTP levels, RAF dimerization and RAF kinase activity resulting in MEK phosphorylation in synergistic tumor lines regardless of KRAS status. Taken together, our studies uncover a strategy to rewire KRAS mutant tumors to confer sensitivity to RAF kinase inhibition.
Assuntos
Fosfatidilinositol 3-Quinases/efeitos dos fármacos , Inibidores de Proteínas Quinases/farmacologia , Proteínas Proto-Oncogênicas p21(ras)/efeitos dos fármacos , Linhagem Celular Tumoral , Guanosina Trifosfato/metabolismo , Humanos , Mutação/efeitos dos fármacos , Mutação/genética , Fosfatidilinositol 3-Quinases/genética , Proteínas Proto-Oncogênicas B-raf/efeitos dos fármacos , Proteínas Proto-Oncogênicas B-raf/genética , Proteínas Proto-Oncogênicas p21(ras)/genética , Proteínas ras/efeitos dos fármacos , Proteínas ras/genéticaRESUMO
A variety of analytical approaches have indicated that melanoma cell line UCLA-SO-M14 (M14) and breast carcinoma cell line MDA-MB-435 originate from a common donor. This indicates that at some point in the past, one of these cell lines became misidentified, meaning that it ceased to correspond to the reported donor and instead became falsely identified (through cross-contamination or other means) as a cell line from a different donor. Initial studies concluded that MDA-MB-435 was the misidentified cell line and M14 was the authentic cell line, although contradictory evidence has been published, resulting in further confusion. To address this question, we obtained early samples of the melanoma cell line (M14), a lymphoblastoid cell line from the same donor (ML14), and donor serum preserved at the originator's institution. M14 samples were cryopreserved in December 1975, before MDA-MB-435 cells were established in culture. Through a series of molecular characterizations, including short tandem repeat (STR) profiling and cytogenetic analysis, we demonstrated that later samples of M14 and MDA-MB-435 correspond to samples of M14 frozen in 1975, to the lymphoblastoid cell line ML14, and to the melanoma donor's STR profile, sex and blood type. This work demonstrates conclusively that M14 is the authentic cell line and MDA-MB-435 is misidentified. With clear provenance information and authentication testing of early samples, it is possible to resolve debates regarding the origins of problematic cell lines that are widely used in cancer research.
Assuntos
Neoplasias da Mama/patologia , Linhagem Celular Tumoral , Melanoma/patologia , Neoplasias da Mama/genética , DNA de Neoplasias/genética , Feminino , Humanos , Hibridização in Situ Fluorescente , Melanoma/genéticaRESUMO
Letrozole is a commonly used treatment option for metastatic hormone receptor-positive (HR+) breast cancer, but many patients ultimately relapse. Due to the importance of phosphoinositide-3 kinase (PI3K) in breast cancer, PI3K inhibitors such as taselisib are attractive for combination with endocrine therapies such as letrozole. Taselisib was evaluated as a single agent and in combination with letrozole in a breast cancer cell line engineered to express aromatase. The combination of taselisib and letrozole decreased cellular viability and increased apoptosis relative to either single agent. Signaling cross-talk between the PI3K and ER pathways was associated with efficacy for the combination. In a secreted factor screen, multiple soluble factors, including members of the epidermal and fibroblast growth factor families, rendered breast cancer cells non-responsive to letrozole. It was discovered that many of these factors signal through the PI3K pathway and cells remained sensitive to taselisib in the presence of the soluble factors. We also found that letrozole resistant lines have elevated PI3K pathway signaling due to an increased level of p110α, but are still sensitive to taselisib. These data provide rationale for clinical evaluation of PI3K inhibitors to overcome resistance to endocrine therapies in ER+ breast cancer.
RESUMO
Reproducibility and transparency in biomedical sciences have been called into question, and scientists have been found wanting as a result. Putting aside deliberate fraud, there is evidence that a major contributor to lack of reproducibility is insufficient quality assurance of reagents used in preclinical research. Cell lines are widely used in biomedical research to understand fundamental biological processes and disease states, yet most researchers do not perform a simple, affordable test to authenticate these key resources. Here, we provide a synopsis of the problems we face and how standards can contribute to an achievable solution.
Assuntos
Pesquisa Biomédica/métodos , Perfilação da Expressão Gênica/métodos , Técnicas de Genotipagem/métodos , Repetições de Microssatélites/genética , Polimorfismo de Nucleotídeo Único , Pesquisa Biomédica/normas , Linhagem Celular , Perfilação da Expressão Gênica/normas , Técnicas de Genotipagem/normas , Humanos , Publicações/normas , Padrões de Referência , Reprodutibilidade dos TestesRESUMO
The use of large-scale genomic and drug response screening of cancer cell lines depends crucially on the reproducibility of results. Here we consider two previously published screens, plus a later critique of these studies. Using independent data, we show that consistency is achievable, and provide a systematic description of the best laboratory and analysis practices for future studies.
Assuntos
Antineoplásicos/farmacologia , Ensaios de Seleção de Medicamentos Antitumorais/métodos , Ensaios de Seleção de Medicamentos Antitumorais/normas , Neoplasias/genética , Neoplasias/patologia , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Marcadores Genéticos/genética , Genoma Humano/genética , Humanos , Controle de Qualidade , Reprodutibilidade dos TestesRESUMO
Targeted cancer therapies are designed to deactivate signaling pathways used by cancer cells for survival. However, cancer cells are often able to adapt by activating alternative survival pathways, thereby acquiring drug resistance. An emerging theory is that autocrine or paracrine growth factor signaling in the cancer microenvironment represent an important mechanism of drug resistance. In the present study we wanted to examine whether paracrine interactions between groups of melanoma cells result in resistance to vemurafenib - an FDA approved drug targeting the BRAF mutation in metastatic melanoma. We used a vemurafenib-resistant melanoma model which secretes fibroblast growth factor (FGF)-2 to test our hypothesis that this is a key paracrine mediator of resistance to vemurafenib. Sensitive cells treated with media conditioned by resistant cells did not protect from the effects of vemurafenib. To query paracrine interactions further we fabricated a microfluidic co-culture device with two parallel compartments, separated by a 100 µm wide hydrogel barrier. The gel barrier prevented resorting/contact of cells while permitting paracrine cross-talk. In this microfluidic system, sensitive cells did become refractive to the effects of vemurafenib when cultured adjacent to resistant cells. Importantly, incorporation of FGF-2 capture probes into the gel barrier separating the two cell types prevented onset of resistance to vemurafenib. Microfluidic tools described here allow for more sensitive analysis of paracrine signals, may help better understand signaling in the cancer microenvironment and may enable development of more effective cancer therapies.
Assuntos
Técnicas de Cocultura/instrumentação , Resistencia a Medicamentos Antineoplásicos , Hidrogel de Polietilenoglicol-Dimetacrilato/química , Técnicas Analíticas Microfluídicas/instrumentação , Comunicação Parácrina/efeitos dos fármacos , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Desenho de Equipamento , Fator 2 de Crescimento de Fibroblastos/metabolismo , Humanos , Indóis/farmacologia , Melanoma/tratamento farmacológico , Melanoma/metabolismo , Sulfonamidas/farmacologia , VemurafenibRESUMO
FGF receptors (FGFR) are attractive candidate targets for cancer therapy because they are dysregulated in several human malignancies. FGFR2 and FGFR3 can be inhibited potentially without disrupting adult tissue homeostasis. In contrast, blocking the closely related FGFR1 and FGFR4, which regulate specific metabolic functions, carries a greater safety risk. An anti-FGFR3 antibody was redesigned here to create function-blocking antibodies that bind with dual specificity to FGFR3 and FGFR2 but spare FGFR1 and FGFR4. R3Mab, a previously developed monospecific anti-FGFR3 antibody, was modified via structure-guided phage display and acquired additional binding to FGFR2. The initial variant was trispecific, binding tightly to FGFR3 and FGFR2 and moderately to FGFR4, while sparing FGFR1. The X-ray crystallographic structure indicated that the antibody variant was bound to a similar epitope on FGFR2 as R3Mab on FGFR3. The antibody was further engineered to decrease FGFR4-binding affinity while retaining affinity for FGFR3 and FGFR2. The resulting dual-specific antibodies blocked FGF binding to FGFR3 and FGFR2 and inhibited downstream signaling. Moreover, they displayed efficacy in mice against human tumor xenografts overexpressing FGFR3 or FGFR2. Thus, a monospecific antibody can be exquisitely tailored to confer or remove binding to closely related targets to expand and refine therapeutic potential.
Assuntos
Anticorpos Monoclonais/farmacologia , Antineoplásicos/farmacologia , Receptor Tipo 2 de Fator de Crescimento de Fibroblastos/imunologia , Receptor Tipo 3 de Fator de Crescimento de Fibroblastos/imunologia , Animais , Anticorpos Monoclonais/química , Especificidade de Anticorpos , Antineoplásicos/química , Linhagem Celular Tumoral , Cristalografia por Raios X , Desenho de Fármacos , Feminino , Humanos , Camundongos Endogâmicos BALB C , Camundongos SCID , Simulação de Acoplamento Molecular , Ligação Proteica , Receptor Tipo 2 de Fator de Crescimento de Fibroblastos/antagonistas & inibidores , Receptor Tipo 2 de Fator de Crescimento de Fibroblastos/química , Receptor Tipo 3 de Fator de Crescimento de Fibroblastos/antagonistas & inibidores , Receptor Tipo 3 de Fator de Crescimento de Fibroblastos/química , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
Cell line misidentification, contamination and poor annotation affect scientific reproducibility. Here we outline simple measures to detect or avoid cross-contamination, present a framework for cell line annotation linked to short tandem repeat and single nucleotide polymorphism profiles, and provide a catalogue of synonymous cell lines. This resource will enable our community to eradicate the use of misidentified lines and generate credible cell-based data.
Assuntos
Linhagem Celular/classificação , Linhagem Celular/metabolismo , Curadoria de Dados , Guias como Assunto , Separação Celular , Genótipo , Repetições de Microssatélites/genética , Polimorfismo de Nucleotídeo Único/genética , Controle de Qualidade , Reprodutibilidade dos Testes , Especificidade da Espécie , Terminologia como AssuntoRESUMO
Cell lines are the foundation for much of the fundamental research into the mechanisms underlying normal biologic processes and disease mechanisms. It is estimated that 15%-35% of human cell lines are misidentified or contaminated, resulting in a huge waste of resources and publication of false or misleading data. Here we evaluate a panel of 96 single-nucleotide polymorphism (SNP) assays utilizing Fluidigm microfluidics technology for authentication and sex determination of human cell lines. The SNPtrace Panel was tested on 907 human cell lines. Pairwise comparison of these data show the SNPtrace Panel discriminated among identical, related and unrelated pairs of samples with a high degree of confidence, equivalent to short tandem repeat (STR) profiling. We also compared annotated sex calls with those determined by the SNPtrace Panel, STR and Illumina SNP arrays, revealing a high number of male samples are identified as female due to loss of the Y chromosome. Finally we assessed the sensitivity of the SNPtrace Panel to detect intra-human cross-contamination, resulting in detection of as little as 2% contaminating cell population. In conclusion, this study has generated a database of SNP fingerprints for 907 cell lines used in biomedical research and provides a reliable, fast, and economic alternative to STR profiling which can be applied to any human cell line or tissue sample.
Assuntos
Bancos de Espécimes Biológicos/normas , Linhagem Celular , Código de Barras de DNA Taxonômico/métodos , Código de Barras de DNA Taxonômico/normas , Polimorfismo de Nucleotídeo Único , Feminino , Genótipo , Humanos , Hibridização in Situ Fluorescente , Masculino , Repetições de Microssatélites , Análise para Determinação do Sexo , Cariotipagem EspectralRESUMO
Tumor-derived cell lines have served as vital models to advance our understanding of oncogene function and therapeutic responses. Although substantial effort has been made to define the genomic constitution of cancer cell line panels, the transcriptome remains understudied. Here we describe RNA sequencing and single-nucleotide polymorphism (SNP) array analysis of 675 human cancer cell lines. We report comprehensive analyses of transcriptome features including gene expression, mutations, gene fusions and expression of non-human sequences. Of the 2,200 gene fusions catalogued, 1,435 consist of genes not previously found in fusions, providing many leads for further investigation. We combine multiple genome and transcriptome features in a pathway-based approach to enhance prediction of response to targeted therapeutics. Our results provide a valuable resource for studies that use cancer cell lines.
Assuntos
Neoplasias/genética , Transcrição Gênica , Sequência de Bases , Linhagem Celular Tumoral , Análise por Conglomerados , Regulação Neoplásica da Expressão Gênica , Redes Reguladoras de Genes , Humanos , Mutação/genética , Fusão Oncogênica/genética , Especificidade de Órgãos/genética , Polimorfismo de Nucleotídeo Único/genéticaRESUMO
Molecularly targeted drug therapies have revolutionized cancer treatment; however, resistance remains a major limitation to their overall efficacy. Epithelial-to-mesenchymal transition (EMT) has been linked to acquired resistance to tyrosine kinase inhibitors (TKI), independent of mutational resistance mechanisms. AXL is a receptor tyrosine kinase associated with EMT that has been implicated in drug resistance and has emerged as a candidate therapeutic target. Across 643 human cancer cell lines that were analyzed, elevated AXL was strongly associated with a mesenchymal phenotype, particularly in triple-negative breast cancer and non-small cell lung cancer. In an unbiased screen of small-molecule inhibitors of cancer-relevant processes, we discovered that AXL inhibition was specifically synergistic with antimitotic agents in killing cancer cells that had undergone EMT and demonstrated associated TKI resistance. However, we did not find that AXL inhibition alone could overcome acquired resistance to EGFR TKIs in the EMT setting, as previously reported. These findings reveal a novel cotreatment strategy for tumors displaying mesenchymal features that otherwise render them treatment refractory.
Assuntos
Antineoplásicos/farmacologia , Cisplatino/farmacologia , Proteínas Proto-Oncogênicas/antagonistas & inibidores , Quinazolinas/farmacologia , Receptores Proteína Tirosina Quinases/antagonistas & inibidores , Animais , Proteína Quinase CDC2 , Quinases Ciclina-Dependentes/metabolismo , Docetaxel , Resistencia a Medicamentos Antineoplásicos , Sinergismo Farmacológico , Transição Epitelial-Mesenquimal , Cloridrato de Erlotinib , Células HeLa , Humanos , Mesoderma/patologia , Camundongos Nus , Mitose/efeitos dos fármacos , Proteínas Proto-Oncogênicas/metabolismo , Receptores Proteína Tirosina Quinases/metabolismo , Taxoides/farmacologia , Fator de Crescimento Transformador beta/fisiologia , Ensaios Antitumorais Modelo de Xenoenxerto , Receptor Tirosina Quinase AxlRESUMO
Pancreatic adenocarcinoma (PDAC) is a major unmet medical need and a deeper understanding of molecular drivers is needed to advance therapeutic options for patients. We report here that p21-activated kinase 1 (PAK1) is a central node in PDAC cells downstream of multiple growth factor signalling pathways, including hepatocyte growth factor (HGF) and MET receptor tyrosine kinase. PAK1 inhibition blocks signalling to cytoskeletal effectors and tumour cell motility driven by HGF/MET. MET antagonists, such as onartuzumab and crizotinib, are currently in clinical development. Given that even highly effective therapies have resistance mechanisms, we show that combination with PAK1 inhibition overcomes potential resistance mechanisms mediated either by activation of parallel growth factor pathways or by direct amplification of PAK1. Inhibition of PAK1 attenuated in vivo tumour growth and metastasis in a model of pancreatic adenocarcinoma. In human tissues, PAK1 is highly expressed in a proportion of PDACs (33% IHC score 2 or 3; n = 304) and its expression is significantly associated with MET positivity (p < 0.0001) and linked to a widespread metastatic pattern in patients (p = 0.067). Taken together, our results provide evidence for a functional role of MET/PAK1 signalling in pancreatic adenocarcinoma and support further characterization of therapeutic inhibitors in this indication.
Assuntos
Adenocarcinoma/metabolismo , Movimento Celular , Resistencia a Medicamentos Antineoplásicos/fisiologia , Neoplasias Pancreáticas/metabolismo , Proteínas Proto-Oncogênicas c-met/metabolismo , Quinases Ativadas por p21/metabolismo , Adenocarcinoma/patologia , Animais , Anticorpos Monoclonais/farmacologia , Protocolos de Quimioterapia Combinada Antineoplásica/farmacologia , Azetidinas/farmacologia , Movimento Celular/efeitos dos fármacos , Modelos Animais de Doenças , Humanos , Imuno-Histoquímica , Camundongos , Neoplasias Pancreáticas/patologia , Piperidinas/farmacologia , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/fisiologiaRESUMO
Phosphoinositide-3 kinase (PI3K) signaling pathway alterations occur broadly in cancer and PI3K is a promising therapeutic target. Here, we investigated acquired resistance to GDC-0941, a PI3K inhibitor in clinical trials. Colorectal cancer (CRC) cells made to be resistant to GDC-0941 were discovered to secrete amphiregulin, which resulted in increased EGFR/MAPK signaling. Moreover, prolonged PI3K pathway inhibition in cultured cells over a period of months led to a secondary loss of PTEN in 40% of the CRC lines with acquired resistance to PI3K inhibition. In the absence of PI3K inhibitor, these PTEN-null PI3K inhibitor-resistant clones had elevated PI3K pathway signaling and decreased sensitivity to MAPK pathway inhibitors. Importantly, PTEN loss was not able to induce resistance to PI3K inhibitors in the absence of amphiregulin, indicating a multimodal mechanism of acquired resistance. The combination of PI3K and MAPK pathway inhibitors overcame acquired resistance in vitro and in vivo.
RESUMO
Gastric cancer is the second leading cause of worldwide cancer mortality, yet the underlying genomic alterations remain poorly understood. Here we perform exome and transcriptome sequencing and SNP array assays to characterize 51 primary gastric tumours and 32 cell lines. Meta-analysis of exome data and previously published data sets reveals 24 significantly mutated genes in microsatellite stable (MSS) tumours and 16 in microsatellite instable (MSI) tumours. Over half the patients in our collection could potentially benefit from targeted therapies. We identify 55 splice site mutations accompanied by aberrant splicing products, in addition to mutation-independent differential isoform usage in tumours. ZAK kinase isoform TV1 is preferentially upregulated in gastric tumours and cell lines relative to normal samples. This pattern is also observed in colorectal, bladder and breast cancers. Overexpression of this particular isoform activates multiple cancer-related transcription factor reporters, while depletion of ZAK in gastric cell lines inhibits proliferation. These results reveal the spectrum of genomic and transcriptomic alterations in gastric cancer, and identify isoform-specific oncogenic properties of ZAK.
Assuntos
Isoformas de Proteínas/genética , Proteínas Quinases/genética , Neoplasias Gástricas/genética , Sequência de Bases , Linhagem Celular , Proliferação de Células/genética , Perfilação da Expressão Gênica , Sequenciamento de Nucleotídeos em Larga Escala , Humanos , MAP Quinase Quinase Quinases , Instabilidade de Microssatélites , Repetições de Microssatélites/genética , Análise de Sequência com Séries de Oligonucleotídeos , Polimorfismo de Nucleotídeo Único , Receptor ErbB-2/genética , Análise de Sequência de DNA , Transcriptoma/genéticaRESUMO
Cancer genomes maintain a complex array of somatic alterations required for maintenance and progression of the disease, posing a challenge to identify driver genes among this genetic disorder. Toward this end, we mapped regions of recurrent amplification in a large collection (n=392) of primary human cancers and selected 620 genes whose expression is elevated in tumors. An RNAi loss-of-function screen targeting these genes across a panel of 32 cancer cell lines identified potential driver genes. Subsequent functional assays identified SHMT2, a key enzyme in the serine/glycine synthesis pathway, as necessary for tumor cell survival but insufficient for transformation. The 26S proteasomal subunit, PSMB4, was identified as the first proteasomal subunit with oncogenic properties promoting cancer cell survival and tumor growth in vivo. Elevated expression of SHMT2 and PSMB4 was found to be associated with poor prognosis in human cancer, supporting the development of molecular therapies targeting these genes or components of their pathways.