Involvement Of MYC Research Articles

Abstract 6274: Integrated multi-omics revealed the involvement of MYC and mTOR pathways in radiation resistance of adrenocortical cancer

Abstract The morbidity and mortality of patients with adrenocortical cancer (ACC) are commonly due to locoregional postoperative recurrence and progressive systemic metastasis. Surgical resection remains the only curative treatment option, but even with complete resection, locoregional recurrence rates remain high. Adjuvant radiation therapy (RT) has been shown to reduce recurrence rates and may improve overall survival in selected patients. However, half of the patients receiving postoperative RT still develop locoregional recurrence, clearly demonstrating the heterogeneous nature of ACC. Minimal investigation into the mechanisms underlying radiation response and resistance in ACC has been performed, but elucidating this information is critical to improving outcomes. To address this knowledge gap, NCI-H295R cells were treated with fractionated radiation at 1 Gray (Gy) per day for 5 consecutive days for two consecutive weeks, cumulating in a total radiation dose of 10 Gy. Treated and control ACC cells were harvested on days 7 and 14 for bulk RNA-sequencing (RNA-Seq) and total proteomics by liquid chromatography and tandem mass spectrometry. Significantly differentially expressed genes (DEGs) and proteomes (adj. p. value <0.05) that overlapped between day 7 and day 14 were selected for further analysis and comparison with publicly available gene expression data sets in ACC (The Cancer Genome Atlas (TCGA); Gene Expression Omnibus: GSE12368, GSE33371, GSE75415, GSE90713). There were 3993 DEGs and 423 proteomes identified, respectively. Of these, there were 139 overlapping DEGs with respective proteomes found, 72 of which were differentially expressed in the 4 GEO data sets comparing normal adrenal cortex to ACC. RNA-Seq pathway analysis demonstrated enrichment of E2F targets, G2M checkpoint, mTORC1 signaling, and MYC targets v1, while total proteomics pathway analysis revealed enrichment of cell cycle, transcriptional regulation, cellular stress and injury, alterations of RNA metabolism, and metabolism proteomes. Given that MYC and mTOR are both involved in transcriptional regulation and cell cycle regulation, and mTORC1 in particular is associated with cellular metabolism, the RNA-Seq and proteomics pathway analyses show general consistency with each other. TCGA gene expression analysis showed that overexpression of MYC or mTOR was correlated with shorter overall survival (OS) and disease-free survival (DFS) in the entire ACC cohort (p<0.05). Together, the combination of in vitro pathway analysis and TCGA analysis suggests a potential involvement of the MYC and mTOR pathways in radiation resistance in ACC. Further in vitro and in vivo studies are warranted to identify specific molecular compounds that target MYC and mTOR pathways and improve radiation response in ACC. Citation Format: Bhavishya Ramamoorthy, Prachi Mishra, Myriem Boufraqech, Nicholas Michael, Margaret Cam, Richard Finney, Thomas Meyer, Ronald Holewinski, Thorkell Andresson, Madeline Wong, Steven Shema, Desiree Tillo, Naris Nilubol. Integrated multi-omics revealed the involvement of MYC and mTOR pathways in radiation resistance of adrenocortical cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6274.

Removal of evolutionarily conserved functional MYC domains in a tilapia cell line using a vector-based CRISPR/Cas9 system

MYC transcription factors have critical roles in facilitating a variety of cellular functions that have been highly conserved among species during evolution. However, despite circumstantial evidence for an involvement of MYC in animal osmoregulation, mechanistic links between MYC function and osmoregulation are missing. Mozambique tilapia (Oreochromis mossambicus) represents an excellent model system to study these links because it is highly euryhaline and highly tolerant to osmotic (salinity) stress at both the whole organism and cellular levels of biological organization. Here, we utilize an O. mossambicus brain cell line and an optimized vector-based CRISPR/Cas9 system to functionally disrupt MYC in the tilapia genome and to establish causal links between MYC and cell functions, including cellular osmoregulation. A cell isolation and dilution strategy yielded polyclonal myca (a gene encoding MYC) knockout (ko) cell pools with low genetic variability and high gene editing efficiencies (as high as 98.2%). Subsequent isolation and dilution of cells from these pools produced a myca ko cell line harboring a 1-bp deletion that caused a frameshift mutation. This frameshift functionally inactivated the transcriptional regulatory and DNA-binding domains predicted by bioinformatics and structural analyses. Both the polyclonal and monoclonal myca ko cell lines were viable, propagated well in standard medium, and differed from wild-type cells in morphology. As such, they represent a new tool for causally linking myca to cellular osmoregulation and other cell functions.

Abstract 6713: Myc-regulated miR17, 20a modulate RANK expression in osteosarcoma

Abstract Osteosarcoma (OS) is the most common primary bone tumor in children and adolescents. Approximately 25-30% of these tumors carry amplification of chromosome 8q24, which harbors the oncogene c-Myc, and correlates with a poor prognosis in patients with OS. To understand the mechanisms that underlie the ability of Myc to alter both the tumor and its surrounding tumor immune microenvironment (TiME), we generated and molecularly characterized an osteoblast-specific Cre-Lox-Stop-Lox;(LSL)-c-MycT58A;p53f/+ knockin genetically engineered mouse model (GEMM). Phenotypically, the Myc knockin-GEMM had rapid tumor development with a high incidence of metastasis. Myc-dependent gene signature in our murine model demonstrated significant homology to the human Myc-amplified OS.Interestingly, we noticed a significant reduction in the osteoclast (OCL) cell population in the Myc knockin OS tumor compared to the p53-driven. We found the expression of RANK was significantly downregulated in the Myc knockin tumor compared to the Non-knockin p53 heterozygous tumors. The RANK/RANKL pathway is vital in OCL maturation and bone modeling/remodeling. To understand the involvement of Myc in RANK regulation, we used murine-derived OS cell lines and transiently knocked down of Myc expression using siRNA. We observed a significant upregulation in RANK expression after Myc knockdown. To decipher the molecular mechanism behind the Myc-dependent regulation of RANK expression in OS, we looked into the Myc-mediated microRNAs. Myc regulates the expression of several microRNAs, including the polycistronic miR-17-92 cluster. The expression of miR17-5p and Mir20a-5p was significantly higher in the GEMM tumor tissue samples isolated from the Myc knockin compared to the p53-driven. Further, we validated the Myc-dependent regulation of miR-17-5p/20a-5p expression using transient knockdown of Myc in mouse Myc knockin-derived cell lines. To examine the role of miR17-5p/20a-5p on the RANK regulation, we performed both gain and loss-of-function studies using microRNA-17/20a mimics and inhibitors. After the treatment with miR-17-5p/20a-5p inhibitors, the expression of RANK was significantly upregulated whereas in the case of miR17/20a mimics reversed these effects and led to a downregulation of RANK expression. We established that miR-17-5p/20a-5p is causally responsible for at least part of the mechanism by which Myc regulates the RANK expression in OS.We concluded that the Myc-regulated miR17/20a modulates the RANK expression that is involved in the OCL cell population regulation and function in the OS. Citation Format: Bikesh Kumar Nirala, Lyazat Kurenbekova, Tajhal Patel, Ryan Lane Shuck, Atreyi Dasgupta, Nino Carlo Rainusso, Jason T. Yustein. Myc-regulated miR17, 20a modulate RANK expression in osteosarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6713.

When Just One Phosphate Is One Too Many: The Multifaceted Interplay between Myc and Kinases.

Myc transcription factors are key regulators of many cellular processes, with Myc target genes crucially implicated in the management of cell proliferation and stem pluripotency, energy metabolism, protein synthesis, angiogenesis, DNA damage response, and apoptosis. Given the wide involvement of Myc in cellular dynamics, it is not surprising that its overexpression is frequently associated with cancer. Noteworthy, in cancer cells where high Myc levels are maintained, the overexpression of Myc-associated kinases is often observed and required to foster tumour cells' proliferation. A mutual interplay exists between Myc and kinases: the latter, which are Myc transcriptional targets, phosphorylate Myc, allowing its transcriptional activity, highlighting a clear regulatory loop. At the protein level, Myc activity and turnover is also tightly regulated by kinases, with a finely tuned balance between translation and rapid protein degradation. In this perspective, we focus on the cross-regulation of Myc and its associated protein kinases underlying similar and redundant mechanisms of regulation at different levels, from transcriptional to post-translational events. Furthermore, a review of the indirect effects of known kinase inhibitors on Myc provides an opportunity to identify alternative and combined therapeutic approaches for cancer treatment.

ATIC facilitates cell growth and migration by upregulating Myc expression in lung adenocarcinoma.

5-Aminoimidazole-4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase (ATIC), a catalysing enzyme in the de novo purine biosynthetic pathway, has been previously reported to be upregulated and to participate in myeloma and hepatocellular carcinoma progression. In the present study, by using bioinformatics technology, a higher ATIC expression was identified in lung adenocarcinoma (LUAD) tissues than in normal tissues, and ATIC expression was found to be positively associated with Myc expression in LUAD tissues. In addition, the role of ATIC in modulating the growth and migration of LUAD cells was explored and the involvement of Myc was revealed. ATIC expression in 56 paired LUAD and tumour adjacent non-cancerous tissues was assessed using reverse transcription-quantitative PCR and western blot analysis. Pearson's correlation analysis was applied to evaluate the correlation between ATIC and Myc expression levels in LUAD tissues. A rescue experiment was performed to explore the role of ATIC/Myc in regulating the growth, migration and invasion of HCC827 and NCI-H1435 cells. It was demonstrated that ATIC was overexpressed in LUAD tissues, particularly in advanced-stage LUAD, and was predicted to be associated with an advanced TNM stage, a higher lymph node metastasis rate, poor tissue differentiation and a lower overall survival rate. ATIC overexpression promoted cell growth, migratory and invasive capacities, whereas this effect was abrogated by Myc knockdown in the HCC827 and NCI-H1435 cells. On the whole, the present study demonstrates that ATIC promotes LUAD cell growth and migration by increasing Myc expression.

Obscure Involvement of MYC in Neurodegenerative Diseases and Neuronal Repair.

MYC is well known as a potent oncogene involved in regulating cell cycle and metabolism. Augmented MYC expression leads to cell cycle dysregulation, intense cell proliferation, and carcinogenesis. Surprisingly, its increased expression in neurons does not induce their proliferation, but leads to neuronal cell death and consequent development of a neurodegenerative phenotype. Interestingly, while cancer and neurodegenerative diseases such as Alzheimer's disease are placed at the opposite sides of cell division spectrum, both start with cell cycle dysregulation and stimulation of proliferation. It seems that MYC action directed toward neuron cell proliferation and neural tissue repair collides with evolutional loss of regenerative capacity of CNS neurons in order to strengthen synaptic structure, to protect our cognitive abilities and therefore character. Accordingly, there are abundant mechanisms that block its expression and action specifically in the brain. Moreover, while MYC expression in brain neurons during neurodegenerative processes is related to their death, there are obvious evidences that MYC action after physical injury is beneficial in case of peripheral nerve recovery. MYC might be a useful tool to repair brain cells upon development of neurodegenerative disease or CNS trauma, including stroke and traumatic brain and spinal cord injury, as even imperfect axonal growth and regeneration strategies will likely be of profound benefit. Understanding complex control of MYC action in the brain might have important therapeutic significance, but also it may contribute to the comprehension of development of neurodegenerative diseases.

Dracocephalumpalmatum Stephan extract induces caspase‑ and mitochondria‑dependent apoptosis via Myc inhibition in diffuse large Bcell lymphoma.

Dracocephalumpalmatum Stephan (DPS), a medicinal plant used by Russian nomads, has been known to exhibit antioxidant properties. However, to the best of our knowledge, its anticancer effect has not been elucidated. The present study aimed to evaluate the tumor‑suppressive effect of DPS extract (DPSE) in diffuse large Bcell lymphoma (DLBCL) and the underlying mechanism. MTS assays and AnnexinV staining were performed to assess the anti‑proliferative and apoptotic effects of DPSE, respectively. To reveal the underlying mechanisms, the levels of pro‑ and anti‑apoptotic Bcl‑2 members were analyzed by western blotting. Rescue experiments were performed to investigate the potential involvement of Myc in DPSE‑induced tumor‑inhibitory effects. Additionally, high‑performance liquid chromatography analysis was performed to analyze the components with anticancer effects. Exposure of multiple DLBCL cell lines to DPSE significantly decreased cell viability and increased apoptosis, whereas it had no effect on the survival of normal cells invitro and invivo. This indicates that its cytotoxic effect may be specific to cancer cells. Mechanistically, cell death induced by DPSE was dependent on the activation of caspase‑3/7 and the disruption of mitochondrial membrane potential. Treatment with the extract ameliorated the expression of anti‑apoptotic Bcl‑2 members Bcl‑xL and Mcl‑1, and upregulated that of pro‑apoptotic Bcl‑2 members Bax and Bak. These modulations led to the disruption of mitochondrial membrane potential, which culminated in the activation of executioner caspases‑3 and‑7. Notably, overexpression of Myc inhibited DPSE‑induced cell killing, indicating the involvement of Myc in this process. Given that dysregulation of Myc is strongly associated with the pathobiology of DLBCL, the present study highlights the potential therapeutic efficacy of DPSE in patients with DLBCL with aberrant Myc expression. Furthermore, fractionation of DPSE by thin layer chromatography and liquid chromatography/mass spectrometry‑based investigation of the fraction with bioactive compounds demonstrated that flavonoids may be responsible for most, if not all, of the anti‑lymphoma effect. Efforts to identify the bioactive flavonoids is currently underway.

Abstract PR09: Targeting the MYC-WDR5 nexus in colorectal cancer

Abstract The overexpression of c-MYC is one of the most prominent alterations in colorectal cancer (CRC), featuring in roughly 70% of colorectal adenocarcinomas. Induction of MYC is a critical event in the development and progression of CRC, as it causes a variety of biological responses, including cell cycle progression, cellular growth, and differentiation. The contribution of the MYC oncoprotein to the pathogenesis of CRC is evidenced by its widespread overexpression and its correlation with poor patient survival, and by observations that deletion of c-Myc—or mutation of the β-catenin/TCF/LEF enhancer upstream of c-Myc—dramatically reduces intestinal tumor burden in ApcMin mice. Despite the pervasive involvement of MYC in CRC, and a wealth of studies in other systems demonstrating that genetic inhibition of MYC promotes frank tumor regression, MYC is generally considered undruggable—as of yet, no drug-like molecules have been discovered that are capable of blocking MYC function in cancer cells. Recently, however, we devised a novel approach to target MYC, based on our observations that binding of MYC to its target genes in the context of chromatin is dependent on interaction with the chromatin-scaffolding protein WDR5. We have proposed that target gene recognition by MYC is an avidity-based mechanism that involves two critical sets of interactions: one between MYC/MAX heterodimers and DNA, and another between MYC and chromatin-bound WDR5. We showed that interaction with WDR5 is necessary for the ability of MYC to function as a transcription factor and oncoprotein. Importantly, structural analysis revealed that MYC directly binds WDR5 by engaging a shallow, hydrophobic, cleft on the surface of WDR5 that is well-suited for drug discovery. The tractability of the MYC–WDR5 interface as a vehicle for drug discovery should make it possible to identify drug-like molecules that disrupt interaction of MYC with chromatin and diminish its tumorigenic potential. Fueled by the potential of this discovery, the Fesik and Tansey laboratories collaborate to identify, refine, and validate drug-like molecules that disrupt the MYC–WDR5 interaction, and propose to explore their efficacy as anti-cancer agents. Since the overexpression of MYC is featured in the majority of colorectal adenomas, we will investigate the requirement of the MYC–WDR5 interaction in colorectal carcinoma cell lines and in mice. During the small-molecule discovery phase, an inducible mutant version of MYC will be utilized to determine the effects of loss of the MYC–WDR5 interaction in CRC cell lines and in mice with adenomatous polyps, both further elucidating the biological basis of this interaction, as well as establishing a baseline for effects we should see from on-target small-molecule inhibitors. Through cellular, molecular, and genomic comparison of the effects of genetic versus chemical disruption of the MYC–WDR5 interaction, we will validate on-target action of probe compounds, providing critical information needed to select candidate molecules that will be refined for drug-like properties. Successful completion of this work will generate novel insights into MYC biology, its role in CRC, as well as first-in-class MYC–WDR5 inhibitors validated for their efficacy in CRC. This abstract is also being presented as Poster B18. Citation Format: Audra M. Foshage, Lance R. Thomas, Shaun R. Stauffer, Stephen W. Fesik, William P. Tansey. Targeting the MYC-WDR5 nexus in colorectal cancer. [abstract]. In: Proceedings of the AACR Special Conference on Colorectal Cancer: From Initiation to Outcomes; 2016 Sep 17-20; Tampa, FL. Philadelphia (PA): AACR; Cancer Res 2017;77(3 Suppl):Abstract nr PR09.

Intense Cytarabine-Based Chemo-Immunotherapy, Central Nervous System (CNS) Prophylaxis and Early High-Dose Chemotherapy and Autologous Stem Cell Support (HDC-ASCS) in First Remission Are Associated with an Improved Clinical Outcome in Double-Hit (DHL)/Triple-Hit (THL) Diffuse Large B-Cell Lymphoma (DLBCL)

Based on molecular studies, DLBCL is now further divided in three subtypes with distinct pathogenesis and clinical outcomes. Fluorescence in situ hybridization (FISH) studies identified a subgroup of DLBCL with a poor clinical outcome harboring concurrent gene rearrangements of the MYC, BCL2 and/or BCL6 proto-oncogenes leading to the over-expression of c-Myc, Bcl-2 and Bcl-6, inferior response rates to rituximab-based chemotherapy, and a shorter progression-free survival (PFS)/overall survival (OS). This group of patients is now categorized as double-hit (DHL) or triple-hit (THL) DLBCL. Immunohistochemistry (IHC) studies suggested that DLBCL patients with over-expression of Bcl-2 and c-Myc proteins exhibit a similar clinical course than those patients with DHL/THL. Alternative transcriptional (i.e. gene amplification or chromosomal gain) or post-translational regulatory mechanisms (yet to be defined) may be responsible for the over-expression of c-Myc, Bcl-2, or Bcl-6 in some patients with DHL/THL phenotype. The appropriate therapy for DHL/THL remains to be defined, but retrospective studies had demonstrated that at standard doses of R+CHOP are suboptimal. In order to study the impact of more aggressive therapeutic approaches in the management of DHL/THL, we retrospectively evaluated our single institution outcome experience over the last 14 years. Using the lymphoma translational database that includes 611 DLBCL patients, we identified 24 patients (M=13/F=11) (4%) with FISH-confirmed DHL/THL DLBCL. Demographic characteristics, clinical data, treatment history in the front line (including the use of CNS prophylaxis, high-dose chemotherapy and autologous stem cell support [HDC-ASCS] or allogeneic bone marrow transplant [allo-BMT]) were collected. In addition, response rate, PFS and OS were calculated. Since the first case-reports were published, we observed a steady increase in the number of DHL/THL patients at our Institution (7 vs. 18 cases before or after 2011) which represents an increasing medical awareness of this new clinical entity. The mean age at diagnosis was 62 years (25 to 85 years), most of them Caucasians (N=22). The median Ki67 proliferation index was 90%. Using the Han’s algorithm, 11 of the DHL/THL were categorized as germinal center B-cell like (GCB), 6 patients as non-GCB, and 7 patients could not be classified. By FISH studies, 58% were DHL (involvement of MYC and BCL2 [N=22] or BCL6 [N=10]) and 42% THL (involvement of MYC, BCL2 and BCL6, N=10). Gene rearrangements involving MYC, BCL2, or BCL6 were observed in 18 patients and MYC, BCL2 or BCL6 gain in 6. Clinically, 95% of the patients presented with stage III/IV, 67% with High-intermediate/High IPI score, and 79% of the patients had extranodal disease. Front-line chemo-immunotherapy included 1) standard doxorubicin-containing regimens: R+CHOP (N=10) or R-EPOCH (N=7), or 2) intensified regimens: R-DHAC (N=2) and R+HyperCVAD/R+HDMTXCytarabine (N=4). Prophylaxis IT chemotherapy was administered to 16 (67%) patients. The complete remission (CR) rate was 62.5% and 29% of the patients underwent HDC-ASCS (N=4)/allo-BMT (N=2) in first (N=2) or second-remission (N=4). In this group of patients, the use of intensified regimens was associated with a non-statistically significant improvement is OS when compared to R+CHOP/R+DA-EPOCH (OS at 3 years of 85.7% vs. 58%). Similarly, an improvement in OS was observed among patients receiving HDC-ASCT/allo-BMT as consolidation (71% vs. 60%, P=0.27). Of interest, CNS prophylaxis was associated with an improvement in OS at 3 years (81% vs. 37%, P=0.032). No differences in clinical outcomes were observed between DHL/THL harboring gene-rearrangements vs. gene gain. In summary, our single institution experience suggests that DHL/THL are increasingly being recognized as more aggressive sub-types of DLBCL with a dismal outcome with conventional therapeutic approaches. A high-index of suspicion should be raised and testing for DHL/THL in those DLBCL presenting with advance stage, multiple extra-nodal site of disease, and an elevated Ki67 index should be done. The accurate identification of DHL/THL patients is necessary, as they appear to benefit from rituximab-based intensified cytarabine-containing regimens, CNS prophylaxis and HDC-ASCT/allo-BMT consolidation. DisclosuresNo relevant conflicts of interest to declare.

Abstract 2604: Characterization of the activity and the mechanism of action of the new retinoid derivative ST5589 in pre-clinical models of lymphomas: involvement of MYC and cell cycle genes

Abstract Innovative and effective treatments are necessary for lymphomas that are common and still deadly cancers for many patients. Atypical retinoids show cytotoxic activity in different pre-clinical tumor models even though their mechanism of action is still largely unclear. Here, we report activity and mechanistic data with ST5589 (adarotene derivative), an active representative of this new class of agents (1), in pre-clinical lymphoma models. Methods. Cell lines from diffuse large B-cell lymphoma (DLBCL, n=17), mantle cell lymphoma (MCL, n=4), splenic marginal zone lymphoma (SMZL, n=3) underwent 72 hr exposure to increasing doses of ST5589 (Sigma Tau, Pomezia, IT) to assess anti-proliferative activity by MTT assay. Apoptosis was assessed by Annexin-V/7-AAD staining. Gene expression profiling (GEP) was done with Illumina HumanHT-12 Expression BeadChips at baseline on all cell lines and, in triplicate, on 1 ABC- (TMD8) and 1 GCB-DLBCL (DOHH2) cell line treated with 300 nM ST5589 or DMSO for 8 hrs. Cell lines with IC50 < than the median were defined as sensitive. GEP/IC50 correlation was assessed by Pearson correlation. Differential expression analysis was performed with LIMMA, GSEA, Metacore. Results. Median IC50 was 235 nM (91-2652) for all the cell lines without significant differences among histological subtypes or between GCB- and ABC-DLBCL: DLBCL, 269 (97-2652); GCB-DLBCL 250, (97-1684); ABC-DLBCL, 531 (181-2625); MCL, 237 (91-401); SMZL, 144 (135-203). ST5589 induced apoptosis in 4/5 DLBCL cell lines (DOHH2, TMD8, SU-DHL-2, VAL). GEP in two DLBCL treated with ST5589 or DMSO was performed, and ST5589 significantly affected transcripts involved in multiple cell cycle-related gene-sets. Aurora kinase A coding gene was one of the most down-regulated. MYC translocation was associated with lower IC50 (P 0.045) and higher number of responders (P 0.021). Transcripts associated with resistance to ST5589 were significantly enriched of genes involved in MYD88/TLR/STAT3 signaling and MAPK pathway, while transcripts associated with sensitivity were enriched of MYC target genes, genes high in Burkitt lymphoma, and involved in cellular respiration, and proteoglycan biosynthesis. Conclusions. ST5589 showed anti-proliferative and cytotoxic preclinical activity in lymphoma, affecting cell-cycle regulation. While MYD88, TLR, STAT3 and MAPK pathways activation correlated with reduced drug activity, MYC deregulation was associated with sensitivity to ST5589. Our data, together with direct cytotoxicity and immune-system mediated activity reported for the parent compound adarotene ST1926 (2), make ST5589 worth of further studies in MYC-driven lymphomas as a representative of the innovative therapeutic class of atypical retinoids. References 1 Giannini et al. Bioorganic and Med Chemistry 2012, 20: 2405-15 2 Pisano et al. Proceedings AACR 2004 Abstract #2075 Citation Format: Elena Bernasconi, Ivo Kwee, Andrea Rinaldi, Luciano Cascione, Maurilio Ponzoni, Loredana Vesci, Giuseppe Giannini, Anastasios Stathis, Emanuele Zucca, Eugenio Gaudio, Francesco Bertoni. Characterization of the activity and the mechanism of action of the new retinoid derivative ST5589 in pre-clinical models of lymphomas: involvement of MYC and cell cycle genes. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2604. doi:10.1158/1538-7445.AM2014-2604

Array CGH analysis identifies two distinct subgroups of primary angiosarcoma of bone.

Molecular genetic studies on vascular tumors are rare. Recently, possible involvement of MYC and KDR has been documented in a subset of angiosarcomas of soft tissue. We performed a cytogenetic analysis of primary angiosarcomas of bone (n = 13) and soft tissue (n = 5) using high density array-comparative genomic hybridization (array-CGH). Regions of interest were validated by fluorescence in situ hybridization (FISH). Antibodies for candidate genes (SKI, MYC, KDR, and MAPK9) were selected and immunohistochemistry was performed. Six angiosarcomas of bone and four angiosarcomas of soft tissue showed chromosomal losses, gains, and high level amplifications. Cluster analysis identified two groups: a group with a complex genetic profile and a group with only few genetic aberrations. Five regions of interest were selected, which were located at chromosome bands 1p36.23, 2q32-34, 5q35, 8q24, and 17q21.32-24.2. Interphase FISH confirmed the high-level amplifications. Immunohistochemical analysis showed high expression of MYC (16/60), MAPK9 (63/69), and SKI (52/62). There were no differences between the two groups with regards to location, immunohistochemical expression nor survival. In summary, we identified two subgroups of angiosarcoma: those with few or no gross aberrations and those which show numerous genetic aberrations consisting of chromosomal losses, gains and high level amplifications or complex aberrations. The most common finding was amplification of 2q and 17q in both angiosarcoma of bone and soft tissue, suggesting overlap in tumorigenesis irrespective of their location. We show MYC amplification in primary angiosarcoma indicating this is not entirely specific for radiation-induced angiosarcoma.

Complex IGH rearrangements in multiple myeloma: Frequent detection discrepancies among three different probe sets

Primary IGH translocations involving seven recurrent partner loci and oncogenes are present in about 40% of multiple myeloma tumors. Secondary IGH rearrangements, which occur in a smaller fraction of tumors, usually are complex structures, including insertions or translocations that can involve three chromosomes, and often with involvement of MYC. The main approach to detect IGH rearrangements is interphase-but sometimes metaphase-FISH strategies that use a telomeric variable region probe and a centromeric constant region/ Eα enhancer or 3' flanking probe to detect a separation of these two probes, or a fusion of these probes with probes located at nonrandom partner sites in the genome. We analyzed 18 myeloma cell lines for detection discrepancies among Vysis, Cytocell, and in-house IGH probe sets that hybridize with differing sequences in the IGH locus. There were no detection discrepancies for the three telomeric IGH probes, or for unrearranged IGH loci or primary IGH translocations using the centromeric IGH probes. However, the majority of complex IGH rearrangements had detection discrepancies among the three centromeric IGH probes.

Role of Myc in hepatocellular proliferation and hepatocarcinogenesis

Myc is involved in cell growth, proliferation, apoptosis, energy metabolism, and differentiation. Whether it is essential for hepatocellular proliferation and carcinogenesis is unclear due to a lack of an efficient hepatocyte-specific Myc disruption model. This study used a novel genetic model to investigate the involvement of Myc in hepatocellular proliferation and hepatocarcinogenesis in mice. Temporal hepatocyte-specific Myc disruption was achieved by use of the tamoxifen-inducible Cre-ER(T2) recombinase system under control of the serum albumin promoter. Hepatocyte proliferation was assessed by administering peroxisome proliferator-activated receptor α (PPARα) agonist Wy-14,643. A diethylnitrosamine-induced liver cancer model was used to evaluate the role of Myc in hepatocarcinogenesis. Tamoxifen administration induced recombination of Myc specifically in hepatocytes of Myc(fl/fl,ERT2-Cre) mice. When treated with a known hepatocellular proliferative stimulus Wy-14,643, Myc(fl/fl,ERT2-Cre) mice showed a lower liver/body weight ratio and suppressed hepatocyte proliferation as compared to Myc(fl/fl) mice. Hepatic expression of cell cycle control genes, DNA repair genes, and Myc target gene miRNAs were upregulated in Wy-14,643-treated Myc(fl/fl) mouse livers, but not in Wy-14,643-treated Myc(fl/fl,ERT2-Cre) livers. However, no differences were observed in the lipid-lowering effect of Wy-14,643 between Myc(fl/fl,ERT2-Cre) and Myc(fl/fl) mice, consistent with no differences in the expression of several PPARα target genes involved in fatty acid β-oxidation. Moreover, when subjected to the diethylnitrosamine liver cancer bioassay, Myc(fl/fl,ERT2-Cre) mice exhibited a markedly lower incidence of tumor formation compared with Myc(fl/fl) mice. Myc plays an essential role in hepatocellular proliferation and liver tumorigenesis.

MYC oncogene in myeloid neoplasias

MYC is a transcription factor that regulates many critical genes for cell proliferation, differentiation, and biomass accumulation. MYC is one of the most prevalent oncogenes found to be altered in human cancer, being deregulated in about 50 % of tumors. Although MYC deregulation has been more frequently associated to lymphoma and lymphoblastic leukemia than to myeloid malignancies, a body of evidence has been gathered showing that MYC plays a relevant role in malignancies derived from the myeloid compartment. The myeloid leukemogenic activity of MYC has been demonstrated in different murine models. Not surprisingly, MYC has been found to be amplified or/and deregulated in the three major types of myeloid neoplasms: acute myeloid leukemia, myelodysplastic syndromes, and myeloproliferative neoplasms, including chronic myeloid leukemia. Here, we review the recent literature describing the involvement of MYC in myeloid tumors.

Highlights from Recent Cancer Literature

Highlights from Recent Cancer Literature

Potential Involvement of MYC- and p53-Related Pathways in Tumorigenesis in Human Oral Squamous Cell Carcinoma Revealed by Proteomic Analysis

Oral squamous cellular carcinoma is a malignant tumor with poor prognosis. Discovery of early markers to discriminate between malignant and normal cells is of high importance in clinical diagnosis. Subcellular fractions from 10 oral squamous cell carcinoma and corresponding control samples, enriched in mitochondrial and cytosolic proteins, as well as blood from the tumor were analyzed by proteomics, two-dimensional gel electrophoresis, followed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Three-hundred and fifty different gene products were identified. Twenty proteins showed deranged levels in oral squamous cell carcinoma in comparison with the control samples and are potentially involved in tumor growth and metastasis. Of these, 16 proteins were upregulated. By applying pathway analysis, we found 8 of the upregulated gene products to be linked to three main locus genes, p53, MYC, and MYCN, and could be candidate biomarkers for OSCC. The findings of this pilot study show that OSCC gene ontology combined with proteomic analysis is a powerful tool in systems biology for the elucidation of the complexity of expression profiles in cellular processes. Application of such pathway analysis has the potential to generate new insights into complex molecular mechanisms underlying disease related processes and could therefore significantly contribute to the efficient performance of the entire discovery process.

Molecular mechanisms of the antiangiogenic and antitumor effects of mycophenolic acid

The relative risk for the development of malignancies following solid organ transplantation seems to be decreased in patients treated with the immunosuppressive agent mycophenolic acid (MPA). However, the molecular mechanisms of the antineoplastic effects of MPA are not completely understood. Here, we report that human endothelial cells and fibroblasts are highly sensitive to MPA treatment. We found that U87 glioblastoma cells were resistant to MPA treatment in vitro. However, U87 tumor growth was markedly inhibited in vivo in BALB/c nude mice, suggesting that MPA exerted its antitumor effects via modulation of the tumor microenvironment. Accordingly, microvascular density and pericyte coverage were markedly reduced in MPA-treated tumors in vivo. Using functional in vitro assays, we showed that MPA potently inhibited endothelial cell and fibroblast proliferation, invasion/migration, and endothelial cell tube formation. To identify the genetic participants governing the antiangiogenic and antifibrotic effects of MPA, we performed genome-wide transcriptional analysis in U87, endothelial and fibroblast cells at 6 and 12 h after MPA treatment. Network analysis revealed a critical role for MYC signaling in endothelial cells treated with MPA. Moreover, we found that the antiangiogenic effects of MPA were organized by coordinated communications between MYC and NDRG1, YYI, HIF1A, HDAC2, CDC2, GSK3B, and PRKACB signaling. The regulation of these "hub nodes" was confirmed by real-time quantitative reverse transcription-PCR and protein analysis. The critical involvement of MYC in the antiangiogenic signaling of MPA was further shown by gene knockdown experiments. Together, these data provide a molecular basis for the antiangiogenic and antifibrotic effects of MPA, which warrants further clinical investigations.

Insights into Disease Evolution of Transformed Follicular Lymphoma Derived from Cytogenetics.

Background: Follicular lymphoma (FL) is an indolent lymphoma with a median survival of 8 years. Transformation to diffuse large B cell lymphoma (DLBCL) is a major cause of mortality. The critical events leading to transformation are still unknown. Studies looking at the clonal cytogenetic evolution of FL have implicated −6q, +7, +12, −17p, +der(18), +X and abnormalities in chromosomes 1 or 8 as poor prognostic factors.Methods: We investigated the effect of these abnormalities and the number of alterations per tumor (NAPT) on the risk of developing transformed lymphoma (TLy) in a cohort of FL patients treated at the British Columbia Cancer Agency (BCCA) from 1983 to 2005. Karyotypes were determined on all samples by classic G banding technique. NAPT and the presence of the previously mentioned abnormalities were determined. TLy was defined as a DLBCL or Burkitt-like or composite histology (focal DLBCL with residual FL) on repeat biopsy or the presence of one of the following clinical features: rapid discordant nodal growth, sudden rise in LDH (≥2x baseline), unusual extranodal involvement or hypercalcemia. 279 FL biopsies had available karyotypes and clinical information required for this analysis.Results: With a median follow up time of 9.5 years, 54 patients (19%) developed TLy. The mean NAPT in the initial biopsy specimen was similar whether or not TLy developed (5.3 vs 5.0). The mean NAPT in patients who developed TLy early (≤2 years) was not greater than in those who developed TLy late (> 2 years) (4.8 vs 5.2). The incidence of specific cytogenetic changes was comparable to what is reported in the literature: +X (24%), 6q- (22%), +7 (15%), +12 (10%), −17p (9%), der (18) (24%) and abnormalities in chromosomes 1 (35%) or 8 (5%). These changes did not appear to influence the risk of developing TLy nor were they more prevalent in those who developed TLy. In 12 cases where the initial and TLy karyotypes could be compared, two patterns of cytogenetic evolution emerged. In 4 cases, the initial karyotype was clearly present in the TLy karyotype, including additional secondary cytogenetic abnormalities. In the remaining 8 cases, karyotypes of the TLy lacked many of the cytogenetic abnormalities that were present in the initial biopsy, except the t(14;18) or variant. Three out of the 8 cases had a lower NAPT in the TLy. Overall, there was no correlation between the NAPT of the initial and TLy biopsies (r= −0.38 p=0.3). Amongst the 12 paired specimens, the incidence of MYC breakpoints (8q24) and P53 deletions (17p13) were greater in the TLy karyotype (25% vs 0% and 16% vs 0%, respectively).Conclusions: The karyotype in FL at diagnosis does not influence the risk of transformation and cannot be used to predict which patients will transform early. Furthermore, there is no correlation between the NAPT in the karyotypes of the paired specimens (FL→DLBCL) even though the involvement of MYC and P53 is more prevalent in the TLy karyotypes. We hypothesize that transformation is a random event that can occur in FL cells that are less clonally evolved than those represented in the initial biopsy, analogous to a “FL stem cell”. Alternatively, the initial biopsy may not have captured the particular clone that eventually resulted in transformation, favoring subclone selection rather than clonal evolution. Newer technologies that study the genome and proteome in more detail, including the effect of the microenvironment may improve our understanding of the critical events leading to FL transformation.