Dysfunction of the TP53 tumor suppressor gene in lymphoid malignancies

Cross-talk between Myc and p53 in B-cell lymphomas

Myc and p53 proteins are closely associated with many physiological cellular functions, including immune response and lymphocyte survival, and are expressed in the lymphoid organs, which are sites for the development and activation of B-cell malignancies. Genetic alterations and other mechanisms resulting in constitutive activation, rearrangement, or mutation of MYC and TP53 contribute to the development of lymphomas, progression and therapy resistance by gene dysregulation, activation of downstream anti-apoptotic pathways, and unfavorable microenvironment interactions. The cross-talk between the Myc and p53 proteins contributes to the inferior prognosis in many types of B-cell lymphomas. In this review, we present the physiological roles of Myc and p53 proteins, and recent advances in understanding the pathological roles of Myc, p53, and their cross-talk in lymphoid neoplasms. In addition, we highlight clinical trials of novel agents that directly or indirectly inhibit Myc and/or p53 protein functions and their signaling pathways. Although, to date, these trials have failed to overcome drug resistance, the new results have highlighted the clinical efficiency of targeting diverse mechanisms of action with the goal of optimizing novel therapeutic opportunities to eradicate lymphoma cells.

Marine Carotenoid Fucoxanthin Possesses Anti-Metastasis Activity: Molecular Evidence

Fucoxanthin is commonly found in marine organisms; however, to date, it has been one of the scarcely explored natural compounds. We investigated its activities in human cancer cell culture-based viability, migration, and molecular assays, and found that it possesses strong anticancer and anti-metastatic activities that work irrespective of the p53 status of cancer cells. In our experiments, fucoxanthin caused the transcriptional suppression of mortalin. Cell phenotype-driven molecular analyses on control and treated cells demonstrated that fucoxanthin caused a decrease in hallmark proteins associated with cell proliferation, survival, and the metastatic spread of cancer cells at doses that were relatively safe to the normal cells. The data suggested that the cancer therapy regimen may benefit from the recruitment of fucoxanthin; hence, it warrants further attention for basic mechanistic studies as well as drug development.

Clinical aspects of TP53 gene inactivation in diffuse large B-cell lymphoma

Background

The knowledge about specific mechanisms generating TP53 dysfunction in diffuse large B-cell lymphoma is limited. The aim of the current study was to comprehensively explore TP53 gene variability resulting from somatic mutations, promoter methylation, and allelic imbalance in tumorous tissue of diffuse large B-cell lymphoma (DLBCL).

Methods

DNA samples from 74 patients with DLBCL were used. Genomic DNA was isolated from paraffin blocks of lymph nodes or from extranodal biopsies of tumors by the phenol–chloroform extraction method with guanidine. Analysis of coding sequences of the TP53 gene was based on Sanger’s direct sequencing method. The methylation status of the TP53 promoter was analyzed using by methylation-specific PCR on bisulfite-converted DNA. Assessment of the detected mutations was carried out in the IARC TP53 Database and the TP53 UMD mutation database of human cancer.

Results

The mutations in regions coding for the DNA-binding domain were prevalent (95%). In the analyzed sample of patients, codons 275, 155, 272, and 212 were hotspots of mutations in the TP53 gene. In addition, functionally significant intron mutations (IVS6-36G > C and IVS5 + 43G > T) were detected. Instances of TP53 promoter methylation were observed only in a few samples of diffuse large B-cell lymphoma tissue. Furthermore, loss of heterozygosity was revealed only in the subgroup of patients with altered status of the gene (mutations were detected in five patients and promoter methylation in one case).

Conclusions

Thus, the results suggest that there are two sequential events in the formation of diffuse large B-cell lymphoma in at least some cases. The first event is mutation or methylation of the TP53 promoter, leading to appearance of a cell with increased risk of malignant transformation. The second event is the loss of an intact allele of the gene; this change is necessary for tumorigenesis. We identified TP53 mutation patterns in a Russian cohort of patients with de novo DLBCL who were treated with R-CHOP and R-CHOP-like regimens and confirmed that TP53 mutation status is a valuable prognostic biomarker.

The effect of malondialdehyde is modified by simian virus 40 transformation in human lung fibroblast cells

The effects of malondialdehyde (MDA), a product of oxidative stress, on normal lung fibroblast cells (MRC5) and transformed cells (MRC5 SV2) showed differing responses between the two cell lines. MRC5 cells showed lower viability at low MDA concentrations (<250 μM) but had better viability at higher concentrations than the transformed cells. Both cell lines showed an increase in the number of micronuclei, nuclear size and a relocation of p53 to the nucleus with increasing MDA. The expression of p53 was higher in the MRC5 cells at 24 h; 2-8 fold induction vs 1-2.5 fold in the MRC5 SV2 cells, but reduced to almost zero at 48 h in the MRC5 cells. Mutation sequencing of the PCR products of a 689 bp region (residues 4640-5328) of the TP53 gene revealed MRC5 had more mutations than MRC5 SV2 cells (n = 21 and 11 respectively) and that they were predominantly insertions (MRC5 81%, MRC5 SV2 100%). A common mutation was observed in both cell lines; a G insertion at residue 4724 (n = 7) which could prove to be a mutational hotspot. These results indicate that the transformed cells are slower to respond to oxidative stress and/or mutagenic compounds. The mutation spectrum of predominantly frameshift mutations (insertions) suggests that oxidative stress plays a minimal role in smoking related lung cancer, but could be of greater importance to other lung diseases and cancer caused by exposures such as passive smokers, passive vapers and atmospheric pollutants.

How Recent Advances in Biology of Waldenström's Macroglobulinemia May Affect Therapy Strategy

PURPOSE OF REVIEW

Waldenström macroglobulinemia (WM) is a rare lymphoproliferative disorder. Up to now, therapeutic choice was not influenced by the biological characteristics of the disease. Here, we will review how recent advances in biology in WM may affect therapy strategy.

RECENT FINDINGS

Recently, WM has been described as a new oncogenic model. MyD88 mutation has been described as a key driver mutation and has functional consequences which could be targeted. Other mutations, such as CXCR4 or TP53, have been reported. These mutations are associated with different clinical presentation, prognosis, and treatment response. Mutational status may influence therapeutic choice in some patients but additional data are required. New targeted therapies are on development.

Chk1 Inhibition Restores Inotuzumab Ozogamicin Citotoxicity in CD22-Positive Cells Expressing Mutant p53

Inotuzumab ozogamicin (IO) is an anti-CD22 calicheamicin immunoconjugate that has been recently approved for the treatment of relapsed or refractory B-Acute Lymphoblastic Leukemia (r/r B-ALL). We employed both immortalized and primary cells derived from CD22-positive lymphoproliferative disorders to investigate the signaling pathways contributing to IO sensitivity or resistance. We found that the drug reduced the proliferation rate of CD22-positive cell lines expressing wild-type p53, but was remarkably less effective on cells exhibiting mutant p53. In addition, CD22-positive cells surviving IO were mostly blocked in the G2/M phase of the cell cycle because of Chk1 activation that, in the presence of a wild-type p53 background, led to p21 induction. When we combined IO with the Chk1 inhibitor UCN-01, we successfully abrogated IO-induced G2/M arrest regardless of the underlying p53 status, indicating that the DNA damage response triggered by IO is also modulated by p53-independent mechanisms. To establish a predictive value for p53 in determining IO responsiveness, we expressed mutant p53 in cell lines displaying the wild-type gene and observed an increase in IO IC₅₀ values. Likewise, overexpression of an inducible wild-type p53 in cells natively presenting a mutant protein decreased their IC₅₀ for IO. These results were also confirmed in primary CD22-positive cells derived from B-ALL patients at diagnosis and from patients with r/r B-ALL. Furthermore, co-treatment with IO and UCN-01 significantly increased cell death in primary cells expressing mutant p53. In summary, our findings suggest that p53 status may represent a biomarker predictive of IO efficacy in patients diagnosed with CD22-positive malignancies.

Understanding the evolutionary trend of intrinsically structural disorders in cancer relevant proteins as probed by Shannon entropy scoring and structure network analysis

BACKGROUND

Malignant diseases have become a threat for health care system. A panoply of biological processes is involved as the cause of these diseases. In order to unveil the mechanistic details of these diseased states, we analyzed protein families relevant to these diseases.

RESULTS

Our present study pivots around four apparently unrelated cancer types among which two are commonly occurring viz. Prostate Cancer, Breast Cancer and two relatively less frequent viz. Acute Lymphoblastic Leukemia and Lymphoma. Eight protein families were found to have implications for these cancer types. Our results strikingly reveal that some of the proteins with implications in the cancerous cellular states were showing the structural organization disparate from the signature of the family it constitutes. The sequences were further mapped onto respective structures and compared with the entropic profile. The structures reveal that entropic scores were able to reveal the inherent structural bias of these proteins with quantitative precision, otherwise unseen from other analysis. Subsequently, the betweenness centrality scoring of each residue from the structure network models was resorted to explore the changes in dependencies on residue owing to structural disorder.

CONCLUSION

These observations help to obtain the mechanistic changes resulting from the structural orchestration of protein structures. Finally, the hydropathy indexes were obtained to validate the sequence space observations using Shannon entropy and in-turn establishing the compatibility.

Mate pair sequencing improves detection of genomic abnormalities in acute myeloid leukemia

OBJECTIVE

Acute myeloid leukemia (AML) can be subtyped based on recurrent cytogenetic and molecular genetic abnormalities with diagnostic and prognostic significance. Although cytogenetic characterization classically involves conventional chromosome and/or fluorescence in situ hybridization (FISH) assays, limitations of these techniques include poor resolution and the inability to precisely identify breakpoints.

METHOD

We evaluated whether an NGS-based methodology that detects structural abnormalities and copy number changes using mate pair sequencing (MPseq) can enhance the diagnostic yield for patients with AML.

RESULTS

Using 68 known abnormal and 20 karyotypically normal AML samples, each recurrent primary AML-specific abnormality previously identified in the abnormal samples was confirmed using MPseq. Importantly, in eight cases with abnormalities that could not be resolved by conventional cytogenetic studies, MPseq was utilized to molecularly define eight recurrent AML-fusion events. In addition, MPseq uncovered two cryptic abnormalities that were missed by conventional cytogenetic studies. Thus, MPseq improved the diagnostic yield in the detection of AML-specific structural rearrangements in 10/88 (11%) of cases analyzed.

CONCLUSION

Utilization of MPseq represents a precise, molecular-based technique that can be used as an alternative to conventional cytogenetic studies for newly diagnosed AML patients with the potential to revolutionize the diagnosis of hematologic malignancies.

Wild-type p53-modulated autophagy and autophagic fibroblast apoptosis inhibit hypertrophic scar formation

Hypertrophic scarring is a serious fibrotic skin disease, and the abnormal activation of hypertrophic scar fibroblasts (HSFs) intensifies its pathogenesis. Our previous studies have demonstrated that the dysregulation of autophagy in HSFs is associated with fibrosis. However, knowledge regarding the regulation of HS fibrosis by p53-modulated autophagy is limited. Here, we investigated the effect of p53-modulated autophagy on HS fibrosis. The overexpression of wtp53 (Adp53) promoted autophagic capacity and inhibited collagen and α-SMA expression in HSFs. In contrast, LC3 (AdLC3) overexpression did not suppress Col 1, Col 3, or α-SMA expression, but LC3 (shLC3) knockdown downregulated collagen expression. Adp53-modulated autophagy altered Bcl-2 and Bcl-xL expression, but AdLC3 affected only Bcl-xL expression. Silencing Bcl-xL suppressed collagen expression, but autophagy was also inhibited. Flow cytometry showed that the silencing of Bcl-2 (sibcl-2), Bcl-xL (sibcl-xL), and Adp53 significantly increased apoptosis in the HSFs. Therefore, wtp53 inhibited fibrosis in the HSFs by modulating autophagic HSF apoptosis; moreover, the inhibition of autophagy by sibcl-xL had antifibrotic effects. In addition, treatment with Adp53, AdLC3, shLC3, sibcl-2, and sibcl-xL reduced scar formation in a rabbit ear scar model. These data confirm that wtp53-modulated autophagy and autophagic HSF apoptosis can serve as potential molecular targets for HS therapy.

Paeonol exhibits anti-tumor effects by apoptotic and anti-inflammatory activities in 7,12-dimethylbenz(a)anthracene induced oral carcinogenesis

We investigated the preventive potential of paeonol on 7,12-dimethylbenz(a)anthracene (DMBA) induced oral carcinogenesis. Oral tumors were developed in the buccal pouches of Syrian golden hamsters using topical application of 0.5% DMBA three times/week for 10 weeks. DMBA treated hamsters developed hyperplasia, dysplasia and well-differentiated squamous cell carcinoma. The animals also exhibited increased lipid oxidation, decreased antioxidant status and altered levels of detoxification agents. Paeonol treatment of DMBA treated hamsters for 14 weeks decreased tumor incidence, volume and burden Paeonol treatment also increased antioxidant activity and decreased lipid oxidation to near normal levels. Histomorphology and the expression patterns of mutant p53, cyclo-oxygenase (COX-2) and caspase-9 were investigated in the oral buccal mucosa. Paeonol exhibited protective effects against DMBA induced oral carcinogenesis owing to its antitumor, antioxidant, anti-inflammatory and apoptosis inducing properties.

TP53 rs1625895 is Related to Breast Cancer Incidence and Early Death in Iranian Population

Breast cancer as the second most common cancer worldwide tend to be experienced by Iranian women 10 years earlier with a peak incidence at the premenopausal stage. Genetic mutations of TP53 tumor suppressor gene has been shown to be related to early onset of breast cancer. It has been shown already that rs1625895 polymorphic site is related to glioma as well as lung cancer. In this study, we have investigated the role of rs1625895 polymorphism in breast cancer incidence in Iranian women. DNA extraction of 86 breast cancer patients and 96 control individuals have been used for allele-specific primer-PCR and genotyping of allele A and allele G of the TP53 rs1625895. Genotypes frequencies have been shown that GG homozygosis as the most frequent genotype is a significant association with increased risk of breast cancer development in Iranian women (odds ratio = 6, p = 0.002). On the other hand and in comparison to allele G, allele A could cause early death of breast cancer patients by threefolds significantly (p = 0.011). As a conclusion, we show that allele A is the minor allele in both breast cancer patients and also control individuals and major allele G, is related to the increased risk of breast cancer development in Iranian women.

Critically dysregulated signaling pathways and clinical utility of the pathway biomarkers in lymphoid malignancies

Accumulating evidence confirmed that many dysregulated signaling pathways and aberrant genetic alterations contribute to the oncogenesis and heterogeneity of lymphoid malignancies. Therapeutically targeting dysregulating signaling pathways and their hidden oncogenic biomarkers are becoming available, but did not show desired therapeutic effect in current clinical practice. It is meaningful to further understand the underlying mechanisms of the dysregulated signaling pathways and to address the potential utility of pathway-related biomarkers. To precisely identify the dysregulation of signaling pathways and the “driver” oncogenic biomarkers, as well as to develop reliable and reproducible risk-stratification based on biomarkers will be challenging. Nevertheless, pathway-based targeted therapy will raise the hope to improve the outcomes of the patients with lymphoid malignancies, especially with aggressive types, and the efficient utility of pathway-related biomarkers in diagnosis, prognosis, prediction of lymphoid malignancies may also be able to power precision medicine.

Mutations or copy number losses of CD58 and TP53 genes in diffuse large B cell lymphoma are independent unfavorable prognostic factors

The advent of next generation sequencing (NGS) technologies has expedited the discovery of novel genetic lesions in DLBCL. The prognostic significance of these identified gene mutations is largely unknown. In this study, we performed NGS for the 27 genes most frequently implicated in 196 patients. Interestingly, TP53 mutations were found to be significantly more common in DLBCL with MYC translocations (r = 0.446, P = 0.034). While no gene mutation was found to be more prevalent in patients with DLBCL with bone marrow involvement, MYD88 mutations were more common in primary DLBCL of the CNS or testis. To evaluate the prognostic significance of the abnormalities of these 27 genes, a total of 165 patients with newly diagnosed DLBCL, NOS were included in a multivariate survival analysis. Surprisingly, in addition to the TP53 mutation, CD58 mutation was found to predict poor clinical outcome. Furthermore, copy number loss of CD58 or TP53 was also identified to be an independent negative prognostic factor. Our results have uncovered the previously unknown critical impact of gene mutations on the prognosis of DLBCL and are fundamentally important for the future design of tailored therapy for improved clinical outcomes.

Diffuse large B-cell lymphoma

Diffuse large B cell lymphoma (DLBCL) is the most common type of non-Hodgkin lymphoma worldwide, representing approximately 30-40% of all cases in different geographic regions. Patients most often present with a rapidly growing tumour mass in single or multiple, nodal or extranodal sites. The most common type of DLBCL, designated as not otherwise specified, represents 80-85% of all cases and is the focus of this review. There are also rare types of lymphoma composed of large B-cells, in aggregate about 15-20% of all neoplasms that are sufficiently distinctive to recognise separately. DLBCL not otherwise specified (referred to henceforth as DLBCL) is a heterogeneous entity in terms of clinical presentation, genetic findings, response to therapy, and prognosis. A major advance was the application of gene expression profiling (GEP) to the study of DLBCL which further clarified this heterogeneity and provided a rationale for subdividing cases into groups. The most popular system divides cases of DLBCL according to cell-of-origin into germinal centre B-cell like (GCB) and activated B-cell like (ABC) subtypes, with about 10-15% of cases being unclassifiable. Patients with the GCB subtype usually have better prognosis than patients with the ABC subtype. Although cell-of-origin is useful for predicting outcome, the GCB and ABC subtypes remain heterogeneous, with better and worse prognostic subsets within each group. Next generation sequencing (NGS) analysis of DLBCL has facilitated global identification of numerous and diverse genetic abnormalities in these neoplasms and has shown that GCB and ABC tumours have different mutation profiles. Although the therapy of patients with DLBCL is an active area of research, the current 5-year overall survival rate is 60-70% using standard-of-care frontline therapy. A precision medicine approach for the design of new therapies based on molecular findings in DLBCL is likely the best path forward. As pathologists, our role has expanded beyond diagnosis. We must perform a complete work-up of DLBCL cases. In addition to our traditional role in establishing the diagnosis, we need to analyse markers that provide information regarding prognosis and potential therapeutic targets. We also must ensure that adequate tissue is triaged for molecular studies which are essential for designing therapy regimens, particularly in the setting of disease relapse.

Anticancer activities of ethanol extract from the Antarctic freshwater microalga, Botryidiopsidaceae sp

Background

Cancer is a leading cause of human death around the world and occurs through the highly complex coordination of multiple cellular pathways. Recent studies have revealed that microalgal extracts exhibit considerable pharmaceutical activities, including those against various cancer cells. Thus, microalgae are promising candidates as novel cancer therapeutic drugs. In this study, we evaluated the biological functions of the ethanolic extract of the Antarctic freshwater microalga, Botryidiopsidaceae sp., such as its antioxidant, anti-proliferative, apoptotic and anti-invasive properties.

Methods

To estimate antioxidant capacity of ethanol extract of Botryidiopsidaceae sp. (ETBO), free radical 2,2′-azino-bis (3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) assays were used. The anti-proliferative activity of ETBO was assessed in several cancer cell lines (A375, Hs578T and HeLa) and non-tumorigenic keratinocyte cells (HaCaT), using MTT assay. In addition, Annexin V binding was performed to detect ETBO-induced apoptotic cells, and the expression levels of apoptosis-regulating proteins, caspase-3, p53, and Bcl-2, were determined by western blot. Boyden chamber assays were used to determine anti-migratory and anti-invasive properties of ETBO.

Results

ETBO exhibited antioxidant activity and concentration-dependent anticancer activities, such as anti-proliferation and pro-apoptotic activities against cancer cells. Furthermore, the expression of the apoptosis-inducing proteins, p53 and caspase-3, significantly increased in response to ETBO, whereas the expression of the anti-apoptotic protein, Bcl-2, decreased. These data imply that ETBO induces apoptosis by caspase activation through the modulation of pro-apoptotic and anti-apoptotic gene, p53 and Bcl-2, respectively. In addition, ETBO significantly inhibited migration and invasion of cervical cancer cells in a concentration-dependent manner.

Conclusion

In this study, ETBO exhibited considerable anticancer activities, such as inhibition of proliferation, invasion, and migration, as well as induction of apoptosis. These data suggest that ETBO is a promising therapeutic agent in cancer therapy and drug discovery.

Apoptotic Effect of Nigella sativa on Human Lymphoma U937 Cells

Objective:

Nigella sativa is from botanical Ranunculaceae family and commonly known as black seed. Apoptotic effect of N. sativa and its apoptotic signaling pathways on U937 lymphoma cells are unknown.

Materials and Methods:

In this study, we investigated selective cytotoxic and apoptotic effects of N. sativa extract and its apoptotic mechanisms on U937 cells. In addition, we also studied selective cytotoxic activity of thymoquinone that is the most active essential oil of N. sativa.

Results:

Our results showed that N. sativa extract has selective cytotoxicity and apoptotic effects on U937 cells but not ECV304 control cells. However, thymoquinone had no significant cytotoxicity against on both cells. N. sativa extract increased significantly caspase-3, BAD, and p53 gene expressions in U937 cells.

Conclusions:

N. sativa may have anticancer drug potential and trigger p53-induced apoptosis in U937 lymphoma cells.

SUMMARY

This is the first study showing the apoptotic effect of Nigella sativa extract on U937 cells.

Abbreviations used: CI: Cytotoxicity index, DMEM: Dulbecco's Modified Eagle Medium, HL: Hodgkin's lymphoma, MTT: 3-(4,5-dimethy lthiazol-2yl)-2,5-diphenyl tetrazolium bromide, RPMI: Roswell Park Memorial Institute medium.

Clinical utility of recently identified diagnostic, prognostic, and predictive molecular biomarkers in mature B-cell neoplasms

Genomic profiling studies have provided new insights into the pathogenesis of mature B-cell neoplasms and have identified markers with prognostic impact. Recurrent mutations in tumor-suppressor genes (TP53, BIRC3, ATM), and common signaling pathways, such as the B-cell receptor (CD79A, CD79B, CARD11, TCF3, ID3), Toll-like receptor (MYD88), NOTCH (NOTCH1/2), nuclear factor-κB, and mitogen activated kinase signaling, have been identified in B-cell neoplasms. Chronic lymphocytic leukemia/small lymphocytic lymphoma, diffuse large B-cell lymphoma, follicular lymphoma, mantle cell lymphoma, Burkitt lymphoma, Waldenström macroglobulinemia, hairy cell leukemia, and marginal zone lymphomas of splenic, nodal, and extranodal types represent examples of B-cell neoplasms in which novel molecular biomarkers have been discovered in recent years. In addition, ongoing retrospective correlative and prospective outcome studies have resulted in an enhanced understanding of the clinical utility of novel biomarkers. This progress is reflected in the 2016 update of the World Health Organization classification of lymphoid neoplasms, which lists as many as 41 mature B-cell neoplasms (including provisional categories). Consequently, molecular genetic studies are increasingly being applied for the clinical workup of many of these neoplasms. In this review, we focus on the diagnostic, prognostic, and/or therapeutic utility of molecular biomarkers in mature B-cell neoplasms.

Chronic lymphocytic leukemia with isochromosome 17q: An aggressive subgroup associated with TP53 mutations and complex karyotypes

Although i(17q) [i(17q)] is frequently detected in hematological malignancies, few studies have assessed its clinical role in chronic lymphocytic leukemia (CLL). We recruited a cohort of 22 CLL patients with i(17q) and described their biological characteristics, mutational status of the genes TP53 and IGHV and genomic complexity. Furthermore, we analyzed the impact of the type of cytogenetic anomaly bearing the TP53 defect on the outcome of CLL patients and compared the progression-free survival (PFS) and overall survival (OS) of i(17q) cases with those of a group of 38 CLL patients harboring other 17p aberrations. We detected IGHV somatic hypermutation in all assessed patients, and TP53 mutations were observed in 71.4% of the cases. Patients with i(17q) were more commonly associated with complex karyotypes (CK) and tended to have a poorer OS than patients with other anomalies affecting 17p13 (median OS, 44 vs 120 months, P = 0.084). Regarding chromosomal alterations, significant differences in the median OS were found among groups (P = 0.044). In conclusion, our findings provide new insights regarding i(17q) in CLL and show a subgroup with adverse prognostic features.

Complex analysis of the TP53 tumor suppressor in mantle cell and diffuse large B-cell lymphomas

Mutations and deletions of the tumor suppressor TP53 gene are the most frequent genetic alterations detected in human tumors, though they are rather less frequent in lymphomas. However, acquisition of the TP53 mutation was demonstrated to be one of the characteristic markers in mantle cell lymphoma (MCL) and diffuse large B-cell lymphoma (DLBCL) and prognostic value of the TP53 status has been recognized for these diseases. We present the complex analysis of the TP53 aberrations in 57 cases of MCL and 131 cases of DLBCL. The TP53 status was determined by functional analyses in yeast (FASAY) followed by cDNA and gDNA sequencing. The level of the p53 protein was assessed by immunoblotting and loss of the TP53-specific locus 17p13.3 was detected by FISH. Altogether, we detected 13 TP53 mutations among MCL cases (22.8%) and 29 TP53 mutations in 26 from 131 DLBCL cases (19.8%). The ratio of missense TP53 mutations was 76.9% in MCL and 82.8% in DLBCL. The frequency of TP53 locus deletion was rather low in both diseases, reaching 9.3% in MCL and 15.3% in DLBCL. The presence of TP53 mutation was associated with shorter overall survival (OS) and progression-free survival (PFS) in MCL. Among DLBCL cases, the TP53 mutations shortened both OS and PFS of patients treated with R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone) and decreased both OS and PFS of patients with secondary DLBCL disease.

TP53 Mutation and Its Prognostic Significance in Waldenstrom's Macroglobulinemia

Purpose:TP53 is a tumor-suppressor gene that functions as a regulator influencing cellular responses to DNA damage, and TP53 alterations are associated with pejorative outcome in most B-lymphoid disorders. Little is known regarding TP53 alteration in Waldenstrom's macroglobulinemia (WM).Experimental Design: Here, we have explored the incidence of TP53 alteration using Sanger sequencing and ultradeep-targeted sequencing in 125 WM and 10 immunoglobulin M (IgM) monoclonal gammopathy of undetermined significance (MGUS), along with the clinical features and the associated genomic landscape using single-nucleotide polymorphism array and mutational landscape in an integrative study.Results: Overall, we have identified alteration of TP53 locus including mutation, deletion, and copy-neutral LOH in 11.2% of WM. TP53 mutation was acquired in 7.3% of patients with WM at diagnosis, being absent in IgM MGUS, and was highly correlated to deletion 17p. No correlation with CXCR4 mutations was observed. Patients with TP53 alteration had a greater number of genomic abnormalities. Importantly, WM with TP53 alteration had a significantly shorter overall survival, particularly in symptomatic WM, and independently of the international prognostic scoring system for Waldenstrom macroglobulinemia (IPSSWM) score. Specific treatment for WM with TP53 may have to be studied. Nutlin-3a-targeted p53 signaling induced cytotoxicity preclinically, along with new compounds such as ibrutinib, Prima^Met, or CP31398 that bypass p53 pathway in WM, paving the path for future treatment-tailored options.Conclusions: Our results highlight the clinical significance of detection of TP53 alteration in WM to determine the prognosis of WM and guide the treatment choice. Clin Cancer Res; 23(20); 6325-35. ©2017 AACR.

MDM2/X inhibitors under clinical evaluation: perspectives for the management of hematological malignancies and pediatric cancer

The two murine double minute (MDM) family members MDM2 and MDMX are at the center of an intense clinical assessment as molecular target for the management of cancer. Indeed, the two proteins act as regulators of P53, a well-known key controller of the cell cycle regulation and cell proliferation that, when altered, plays a direct role on cancer development and progression. Several evidence demonstrated that functional aberrations of P53 in tumors are in most cases the consequence of alterations on the MDM2 and MDMX regulatory proteins, in particular in patients with hematological malignancies where TP53 shows a relatively low frequency of mutation while MDM2 and MDMX are frequently found amplified/overexpressed. The pharmacological targeting of these two P53-regulators in order to restore or increase P53 expression and activity represents therefore a strategy for cancer therapy. From the discovery of the Nutlins in 2004, several compounds have been developed and reported with the ability of targeting the P53-MDM2/X axis by inhibiting MDM2 and/or MDMX. From natural compounds up to small molecules and stapled peptides, these MDM2/X pharmacological inhibitors have been extensively studied, revealing different biological features and different rate of efficacy when tested in in vitro and in vivo experimental tumor models. The data/evidence coming from the preclinical experimentation have allowed the identification of the most promising molecules and the setting of clinical studies for their evaluation as monotherapy or in therapeutic combination with conventional chemotherapy or with innovative therapeutic protocols in different tumor settings. Preliminary results have been recently published reporting data about safety, tolerability, potential side effects, and efficacy of such therapeutic approaches. In this light, the aim of this review is to give an updated overview about the state of the art of the clinical evaluation of MDM2/X inhibitor compounds with a special attention to hematological malignancies and to the potential for the management of pediatric cancers.

Antiangiogenic effects of oridonin

Background

Oridonin, the major terpene found in Rabdosia rubescens (Henmsl.) Hara, is widely used as a dietary supplement and therapeutic drug. Oridonin has been proven to possess good anti-tumour activity, but little is known about its effect on angiogenesis. The aim of this study was to investigate the antiangiogenic effects of oridonin in vivo and in vitro and prove that oridonin anti-tumour activity is based on suppressing angiogenesis.

Methods

In vitro, the antiangiogenesis effect was studied by proliferation, apoptosis, migration, invasion, and tube formation experiments on human umbilical vascular endothelial cells (HUVECs). In vivo, using the Tg (fli1: GFP) zebrafish model, the embryonic vasculogenesis and postnatal regeneration were evaluated. The vascular endothelial growth factor (VEGF) signalling pathway gene expressions were assessed by reverse transcription-polymerase chain reaction (RT-PCR). Furthermore, the inhibition effects on tumour growth and metastasis were observed using a xenograft zebrafish tumour model and xenograft nude mouse tumour model. Angiogenesis was assayed by immunostaining with cluster of differentiation 31. Importantly, the proteins were identified as being differentially expressed in an in vivo model by two-dimensional electrophoresis-mass spectrometry (2D–MS) and western blot (WB).

Results

The results indicated that oridonin inhibited HUVEC proliferation, migration, invasion, and tube formation and induced cell apoptosis. Oridonin inhibited zebrafish angiogenesis during embryonic development and tail fin regeneration. RT-PCR showed that oridonin decreased the VEGFA, VEGFR2, and VEGFR3 expressions in zebrafish, while the TP53 expression increased. Moreover, oridonin had strong effects on tumour growth and metastasis in vivo. 2D–MS identified a total of 50 proteins differentially expressed (17 up-expressed, 28 down-expressed). Lastly, WB showed that Claudin 1, Claudin 4, and Claudin 7 were closely related to tumour growth and metastasis.

Conclusion

This study demonstrated that oridonin could inhibit tumour growth and metastasis, which mainly based on oridonin antiangiogenic effects. Claudin 1, Claudin 4, and Claudin 7 were the main contributors to the mechanism.

TP53 mutation predicts the poor prognosis of non-Hodgkin lymphomas: Evidence from a meta-analysis

Non-Hodgkin lymphoma (NHL) is a group of malignant hematologic disorders with high heterogeneity. The diagnosis, clinical manifestations, classification, and prognosis of this condition differ among numerous NHL subgroups. The prognostic significance of the mutation of TP53, a tumor suppressor gene involved in cell cycle regulation, should be confirmed in NHL. In this study, our searching strategy and inclusion criteria were implemented, and the pooled hazard ratios (HRs) of the included studies were calculated directly or indirectly. A total of 1,851 patients were enrolled in 22 studies. A meta-analysis was then performed using STATA version 12.0 to confirm the correlation between the status of TP53 mutation and the survival time of patients with NHL. Statistical heterogeneity was assessed with a chi-square-based Q statistical test and Inconsistency index (I2) statistic. Sensitivity analysis and publication bias were also evaluated. A total of 22 studies were included in our meta-analysis. The pooled HR of the overall survival from 20 studies was 2.30 (95% CI: 1.92-2.76, p = 0.001) with heterogeneity (I2 30.2% p = 0.099). The pooled HR of the progression free survival provided in 5 articles was 2.28 (95% CI: 1.78-2.93, p = 0.001) with heterogeneity (I2 39.8% p = 0.156). No publication bias was found among the included studies, and sensitivity analysis suggested that the combined HRs were stable after any of the studies was excluded from our meta-analysis. This study identified the prognostic significance of TP53 mutation that varied in different NHL subgroups. The group with a mutated TP53 was significantly associated with poor prognosis in patients with NHL. This parameter is a valuable basis for accurate individual therapeutic regimens.

P53 expression correlates with poorer survival and augments the negative prognostic effect of MYC rearrangement, expression or concurrent MYC/BCL2 expression in diffuse large B-cell lymphoma

In patients with diffuse large B-cell lymphoma, MYC rearrangement (MYC-R), MYC expression, or concurrent expression of MYC and BCL2 is associated with a poorer prognosis. P53 expression also has been shown to confer inferior survival in diffuse large B-cell lymphoma patients, but less is known about the role of P53 expression in those with MYC-R, MYC expression (MYC+), or MYC&BCL2 co-expression (MYC+/BCL2+). We studied P53 expression in 201 patients with untreated de novo diffuse large B-cell lymphoma. Sixty-seven (33%) cases were P53 positive, 56 (28%) had MYC-R (including 17 MYC/BCL2 double hit lymphoma), 86 (45%) were MYC+/BCL2+, and 47 (24%) were positive for both MYC and P53. Compared with patients with P53 negative lymphoma, the P53 positive group had a poorer overall survival (P=0.004). In patients with lymphoma harboring MYC-R, MYC expression or MYC+/BCL2+, P53 expression was associated with a significantly worse overall survival (P<0.0001, P=0.01, and P=0.035, respectively). Patients with lymphoma showing concurrent P53 expression and MYC-R had a worse prognosis compared with patients with either P53 expression or MYC-R alone (P<0.0001). Similarly, P53 enhanced the negative prognostic effect of MYC expression in DLBCL patients. In addition, among patients with lymphoma with concurrent MYC and P53 expression, MYC and BCL2 or BCL2 & P53 expression, those patients with tumors with MYC and P53 expression had the worst overall survival (P=0.005), regardless of BCL2 expression status. Multivariate analysis demonstrated that both MYC-R and P53 expression were independent prognostic factors in this patient cohort. In conclusion, our data suggest that P53 expression and MYC -R or MYC expression have an additive negative prognostic effect in diffuse large B-cell lymphoma patients. Assessment of P53 expression adds additional prognostic information in de novo diffuse large B-cell lymphoma patients, especially in subgroups with MYC-R, MYC expression and MYC and BCL2 double expression.

Oncogenic Signaling Pathways and Pathway-Based Therapeutic Biomarkers in Lymphoid Malignancies

Lymphoma is characterized by heterogeneous biology, pathologic features, and clinical outcome. This has been proven by accumulating pathologic and molecular evidence attributed to underlying aberrant alterations at genetic, epigenetic, transcriptional, protein, microenvironmental levels, and dysregulated oncogenic signaling pathways. In the era of precision medicine, targeting oncogenic pathways to design drugs and to optimize treatment regimens for the lymphoma patients is feasible and clinically significant. As such, further understanding of the biology and the mechanisms behind lymphoma development and identification of oncogenic pathway activation and pathway-based biomarkers to better design precise therapies are challenging but hopeful. Furthermore, pathway-based targeted therapies in combination with traditional chemotherapy, single specific targeted antibody therapy, and immunotherapy might raise the hope for the patients with lymphoma, especially for relapsed and refractory lymphoma patients.

The role of p53 in myelodysplastic syndromes and acute myeloid leukemia: molecular aspects and clinical implications

TP53 gene mutations occurring in patients with myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) are associated with high-risk karyotypes including 17p abnormalities, monosomal and complex cytogenetics. TP53 mutations in these disorders portend rapid disease progression and resistance to conventional therapeutics. Notably, the size of the TP53 mutant clone as measured by mutation allele burden is directly linked to overall survival (OS) confirming the importance of p53 as a negative prognostic variable. In nucleolar stress-induced ribosomopathies, such as del(5q) MDS, disassociation of MDM2 and p53 results in p53 accumulation in erythroid precursors manifested as erythroid hypoplasia. P53 antagonism by lenalidomide or other therapeutics such as antisense oligonucleotides, repopulates erythroid precursors and enhances effective erythropoiesis. These findings demonstrate that p53 is an intriguing therapeutic target that is currently under investigation in MDS and AML. This study reviews molecular advances in understanding the role of p53 in MDS and AML, and explores potential therapeutic strategies in this era of personalized medicine.

Molecular Mechanisms of p53 Deregulation in Cancer: An Overview in Multiple Myeloma

The p53 pathway is inactivated in the majority of human cancers. Although this perturbation frequently occurs through the mutation or deletion of p53 itself, there are other mechanisms that can attenuate the pathway and contribute to tumorigenesis. For example, overexpression of important p53 negative regulators, such as murine double minute 2 (MDM2) or murine double minute 4 (MDM4), epigenetic deregulation, or even alterations in TP53 mRNA splicing. In this work, we will review the different mechanisms of p53 pathway inhibition in cancer with special focus on multiple myeloma (MM), the second most common hematological malignancy, with low incidence of p53 mutations/deletions but growing evidence of indirect p53 pathway deregulation. Translational implications for MM and cancer prognosis and treatment are also reviewed.

TP53 Gene Status Affects Survival in Advanced Mycosis Fungoides

TP53 is frequently mutated in different types of neoplasms including leukemia and lymphomas. Mutations of TP53 have also been reported in mycosis fungoides (MF), the most common type of cutaneous lymphoma. However, little is known about the frequency, spectrum of mutations, and their prognostic significance in MF. In this study, we have optimized the protocol for Sanger sequencing of TP53 using DNA extracted from archival paraffin-embedded biopsies. Of 19 samples from patients with stage IIB MF or higher, 31% harbored mutations in TP53. Overall survival of the patients with mutated TP53 was significantly shorter than median survival in the age- and stage-matched patients treated in our Institution. Distribution of mutations was heterogenous in TP53 exons; however, C > T transitions were common suggesting the causal role of ultraviolet radiation. We propose that TP53 mutation status would be useful for risk stratification of patients with advanced MF.

Diagnostic and predictive biomarkers for lymphoma diagnosis and treatment in the era of precision medicine

Lymphomas are a group of hematological malignancies derived from lymphocytes. Lymphomas are clinically and biologically heterogeneous and have overlapping diagnostic features. With the advance of new technologies and the application of efficient and feasible detection platforms, an unprecedented number of novel biomarkers have been discovered or are under investigation at the genetic, epigenetic, and protein level as well as the tumor microenvironment. These biomarkers have enabled new clinical and pathological insights into the mechanisms underlying lymphomagenesis and also have facilitated improvements in the diagnostic workup, sub-classification, outcome stratification, and personalized therapy for lymphoma patients. However, integrating these biomarkers into clinical practice effectively and precisely in daily practice is challenging. More in-depth studies are required to further validate these novel biomarkers and to assess other parameters that can affect the reproducibility of these biomarkers such as the selection of detection methods, biological reagents, interpretation of data, and cost efficiency. Despite these challenges, there are many reasons to be optimistic that novel biomarkers will facilitate better algorithms and strategies as we enter a new era of precision medicine to better refine diagnosis, prognostication, and rational treatment design for patients with lymphomas.

High-grade B-cell Lymphoma With MYC Rearrangement and Without BCL2 and BCL6 Rearrangements Is Associated With High P53 Expression and a Poor Prognosis

Patients with MYC/BCL2 double-hit lymphoma (DHL) are known to have an aggressive clinical course and to respond poorly to various therapies including intensive chemotherapy and stem cell transplant. Less is known about high-grade B-cell lymphoma with MYC rearrangement without concomitant BCL2 and BCL6 rearrangement, designated here as single-hit lymphoma (SHL). In this study, we assessed 61 cases of SHL and compared them with 83 cases of DHL, all confirmed by MYC, BCL2, and BCL6 fluorescence in situ hybridization studies. Although many clinicopathologic features overlap between patients with SHL and those with DHL, distinct features were observed in SHL. Patients with SHL had tumors with a higher prevalence of p53 overexpression (P=0.047), less frequent expression of CD10, BCL2, and BCL6 (P<0.05), and less often had a history of low-grade B-cell lymphoma (P=0.01). In addition, MYC was more frequently partnered with IGH in SHL than in DHL (P=0.04). With a median follow-up of 25 months, the overall survival of 61 SHL patients was poor and similar to that of DHL patients (2-y overall survival rate of 41% in SHL vs. 48% in DHL; P=0.35) and significantly worse than patients with diffuse large B-cell lymphoma and B-cell lymphoma, unclassifiable, with features intermediate between diffuse large B-cell lymphoma and Burkitt lymphoma, without MYC and BCL2 rearrangements (P<0.0001). In conclusion, patients with SHL have distinct clinicopathologic features but a similar poor prognosis compared with patients with MYC/BCL2 DHL. The poor prognosis of patients with SHL may be partially related to the higher frequency and level of p53 expression in these tumors.

TP53 hotspot mutations are predictive of survival in primary central nervous system lymphoma patients treated with combination chemotherapy

Primary central nervous system lymphoma (PCNSL) is an aggressive variant of diffuse large B-cell lymphoma (DLBCL) confined to the CNS. TP53 mutations (MUT-TP53) were investigated in the context of MIR34A/B/C- and DAPK promoter methylation status, and associated with clinical outcomes in PCNSL patients. In a total of 107 PCNSL patients clinical data were recorded, histopathology reassessed, and genetic and epigenetic aberrations of the p53-miR34-DAPK network studied. TP53 mutational status (exon 5-8), with structural classification of single nucleotide variations according to the IARC-TP53-Database, methylation status of MIR34A/B/C and DAPK, and p53-protein expression were assessed. The 57/107 (53.2 %) patients that were treated with combination chemotherapy +/- rituximab (CCT-treated) had a significantly better median overall survival (OS) (31.3 months) than patients treated with other regimens (high-dose methotrexate/whole brain radiation therapy, 6.0 months, or no therapy, 0.83 months), P < 0.0001. TP53 mutations were identified in 32/86 (37.2 %), among which 12 patients had hotspot/direct DNA contact mutations. CCT-treated patients with PCNSL harboring a hotspot/direct DNA contact MUT-TP53 (n = 9) had a significantly worse OS and progression free survival (PFS) compared to patients with non-hotspot/non-direct DNA contact MUT-TP53 or wild-type TP53 (median PFS 4.6 versus 18.2 or 45.7 months), P = 0.041 and P = 0.00076, respectively. Multivariate Cox regression analysis confirmed that hotspot/direct DNA contact MUT-TP53 was predictive of poor outcome in CCT-treated PCNSL patients, P = 0.012 and P = 0.008; HR: 1.86 and 1.95, for OS and PFS, respectively. MIR34A, MIR34B/C, and DAPK promoter methylation were detected in 53/93 (57.0 %), 80/84 (95.2 %), and 70/75 (93.3 %) of the PCNSL patients with no influence on survival. Combined MUT-TP53 and MIR34A methylation was associated with poor PFS (median 6.4 versus 38.0 months), P = 0.0070. This study suggests that disruption of the p53-pathway by MUT-TP53in hotspot/direct DNA contact codons is predictive of outcome in CCT-treated PCNSL patients, and concomitant MUT-TP53 and MIR34A methylation are associated with poor PFS.

Evidence for a role of the histone deacetylase SIRT6 in DNA damage response of multiple myeloma cells

Multiple myeloma (MM) is characterized by a highly unstable genome, with aneuploidy observed in nearly all patients. The mechanism causing this karyotypic instability is largely unknown, but recent observations have correlated these abnormalities with dysfunctional DNA damage response. Here, we show that the NAD(+)-dependent deacetylase SIRT6 is highly expressed in MM cells, as an adaptive response to genomic stability, and that high SIRT6 levels are associated with adverse prognosis. Mechanistically, SIRT6 interacts with the transcription factor ELK1 and with the ERK signaling-related gene. By binding to their promoters and deacetylating H3K9 at these sites, SIRT6 downregulates the expression of mitogen-activated protein kinase (MAPK) pathway genes, MAPK signaling, and proliferation. In addition, inactivation of ERK2/p90RSK signaling triggered by high SIRT6 levels increases DNA repair via Chk1 and confers resistance to DNA damage. Using genetic and biochemical studies in vitro and in human MM xenograft models, we show that SIRT6 depletion both enhances proliferation and confers sensitization to DNA-damaging agents. Our findings therefore provide insights into the functional interplay between SIRT6 and DNA repair mechanisms, with implications for both tumorigenesis and the treatment of MM.

TP53 dysfunction in diffuse large B-cell lymphoma

The aberrations of TP53 gene and dysregulation of the TP53 pathway are important in the pathogenesis of many human cancers, including malignant lymphomas, especially for diffuse large B cell lymphoma (DLBCL). By regulating many downstream target genes or molecules, TP53 governs major defenses against tumor growth and promotes cellular DNA repair, apoptosis, autophagy, cell cycle arrest, signaling, transcription, immune or inflammatory responses and metabolism. Dysfunction of TP53, including microRNA regulations, copy number alterations of TP53 pathway and TP53 itself, dysregulation of TP53 regulators, and somatic mutations by abnormal TP53 function modes, play an important role in lymphoma generation, progression and invasion. The role of TP53 in DLBCL has been widely explored recently. In this review, we summarized recent advances on different mechanisms of TP53 in DLBCL and new therapeutic approaches to overcome TP53 inactivation.

Novel drug targets for personalized precision medicine in relapsed/refractory diffuse large B-cell lymphoma: a comprehensive review

Diffuse large B-cell lymphoma (DLBCL) is a clinically heterogeneous lymphoid malignancy and the most common subtype of non-Hodgkin's lymphoma in adults, with one of the highest mortality rates in most developed areas of the world. More than half of DLBLC patients can be cured with standard R-CHOP regimens, however approximately 30 to 40 % of patients will develop relapsed/refractory disease that remains a major cause of morbidity and mortality due to the limited therapeutic options.Recent advances in gene expression profiling have led to the identification of at least three distinct molecular subtypes of DLBCL: a germinal center B cell-like subtype, an activated B cell-like subtype, and a primary mediastinal B-cell lymphoma subtype. Moreover, recent findings have not only increased our understanding of the molecular basis of chemotherapy resistance but have also helped identify molecular subsets of DLBCL and rational targets for drug interventions that may allow for subtype/subset-specific molecularly targeted precision medicine and personalized combinations to both prevent and treat relapsed/refractory DLBCL. Novel agents such as lenalidomide, ibrutinib, bortezomib, CC-122, epratuzumab or pidilizumab used as single-agent or in combination with (rituximab-based) chemotherapy have already demonstrated promising activity in patients with relapsed/refractory DLBCL. Several novel potential drug targets have been recently identified such as the BET bromodomain protein (BRD)-4, phosphoribosyl-pyrophosphate synthetase (PRPS)-2, macrodomain-containing mono-ADP-ribosyltransferase (ARTD)-9 (also known as PARP9), deltex-3-like E3 ubiquitin ligase (DTX3L) (also known as BBAP), NF-kappaB inducing kinase (NIK) and transforming growth factor beta receptor (TGFβR).This review highlights the new insights into the molecular basis of relapsed/refractory DLBCL and summarizes the most promising drug targets and experimental treatments for relapsed/refractory DLBCL, including the use of novel agents such as lenalidomide, ibrutinib, bortezomib, pidilizumab, epratuzumab, brentuximab-vedotin or CAR T cells, dual inhibitors, as well as mechanism-based combinatorial experimental therapies. We also provide a comprehensive and updated list of current drugs, drug targets and preclinical and clinical experimental studies in DLBCL. A special focus is given on STAT1, ARTD9, DTX3L and ARTD8 (also known as PARP14) as novel potential drug targets in distinct molecular subsets of DLBCL.

miR-31 and miR-17-5p levels change during transformation of follicular lymphoma

The 30% of patients whose indolent follicular lymphoma transforms to aggressive diffuse large B-cell lymphoma (DLBCL) have poor survival. Reliable predictors of follicular B-cell lymphoma transformation to DLBCL are lacking, and diagnosis of those that will progress is challenging. MicroRNA, which regulates gene expression, has critical functions in the growth and progression of many cancers and contributes to the pathogenesis of lymphoma. Using 5 paired samples from patients who presented with follicular lymphoma and progressed to DLBCL, we identified specific microRNA differentially expressed between the two. Specifically, miR-17-5p levels were low in follicular lymphoma and increased as the disease transformed. In contrast, miR-31 expression was high in follicular lymphoma and decreased as the lymphoma progressed. These results were confirmed in additional unpaired cases of low-grade follicular lymphoma (n = 13) and high-grade follicular lymphoma grade 3 or DLBCL (n = 17). Loss of miR-31 expression in DLBCL was not due to deletion of the locus. Changes in miR-17-5p and miR-31 were not correlated with immunophenotype, genetics, or status of the MYC oncogene. However, increased miR-17-5p expression did significantly correlate with increased expression of p53 protein, which is indicative of mutant TP53. Two pro-proliferative genes, E2F2 and PI3KC2A, were identified as direct messenger RNA targets of miR-31, suggesting that these may contribute to follicular lymphoma transformation. Our results indicate that changes in miR-31 and miR-17-5p reflect the transformation of follicular lymphoma to an aggressive large B-cell lymphoma and may, along with their targets, be viable markers for this process.

Results of the Phase I Trial of RG7112, a Small-Molecule MDM2 Antagonist in Leukemia

PURPOSE

RG7112 is a small-molecule MDM2 antagonist. MDM2 is a negative regulator of the tumor suppressor p53 and frequently overexpressed in leukemias. Thus, a phase I study of RG7112 in patients with hematologic malignancies was conducted.

EXPERIMENTAL DESIGN

Primary study objectives included determination of the dose and safety profile of RG7112. Secondary objectives included evaluation of pharmacokinetics; pharmacodynamics, such as TP53-mutation status and MDM2 expression; and preliminary clinical activity. Patients were divided into two cohorts: Stratum A [relapsed/refractory acute myeloid leukemia (AML; except acute promyelocytic leukemia), acute lymphoblastic leukemia, and chronic myelogenous leukemia] and Stratum B (relapsed/refractory chronic lymphocytic leukemia/small cell lymphocytic leukemia; CLL/sCLL). Some Stratum A patients were treated at the MTD to assess clinical activity.

RESULTS

RG7112 was administered to 116 patients (96 patients in Stratum A and 20 patients in Stratum B). All patients experienced at least 1 adverse event, and 3 dose-limiting toxicities were reported. Pharmacokinetic analysis indicated that twice-daily dosing enhanced daily exposure. Antileukemia activity was observed in the 30 patients with AML assessed at the MTD, including 5 patients who met International Working Group (IWG) criteria for response. Exploratory analysis revealed TP53 mutations in 14% of Stratum A patients and in 40% of Stratum B patients. Two patients with TP53 mutations exhibited clinical activity. p53 target genes were induced only in TP53 wild-type leukemic cells. Baseline expression levels of MDM2 correlated positively with clinical response.

CONCLUSIONS

RG7112 demonstrated clinical activity against relapsed/refractory AML and CLL/sCLL. MDM2 inhibition resulted in p53 stabilization and transcriptional activation of p53-target genes. We provide proof-of-concept that MDM2 inhibition restores p53 function and generates clinical responses in hematologic malignancies.

To Each Its Own: Linking the Biology and Epidemiology of NHL Subtypes

Non-Hodgkin lymphoma (NHL) constitutes a diverse group of more than 40 subtypes, each characterized by distinct biologic and clinical features. Until recently, pinpointing genetic and epidemiologic risk factors for individual subtypes has been limited by the relative rarity of each. However, several large pooled case-control studies have provided sufficient statistical power for detecting etiologic differences and commonalities between subtypes and thus yield new insight into their unique epidemiologic backgrounds. Here, we review the subtype-specific medical, lifestyle, and biologic components identified in these studies, which suggest that a complex interplay between host genetics, autoimmune disorders, modifiable risk factors, and occupation contributes to lymphomagenesis.

PRMT5-dependent p53 escape in tumorigenesis

Extensive studies have characterized mutational disruption of p53 signaling in human cancers. However, the mechanism for bypass of p53 function in tumors retaining wild-type p53 has remained ambiguous. Recent studies suggest that PRMT5, which is frequently elevated in human cancers, cooperates with oncogenic cyclin D1 and leaves marks on p53 by way of arginine methylation, promoting the bypass of wild-type p53, and in doing so, evade apoptosis.

The role of aberrant proteolysis in lymphomagenesis

PURPOSE OF REVIEW

Deregulated proteolysis is increasingly being implicated in pathogenesis of lymphoma. In this review, we highlight the major cellular processes that are affected by deregulated proteolysis of critical substrates that promote lymphoproliferative disorders.

RECENT FINDINGS

Emerging evidence supports the role of aberrant proteolysis by the ubiquitin proteasome system (UPS) in lymphoproliferative disorders. Several UPS mediators are identified to be altered in lymphomagenesis. However, the precise role of their alteration and comprehensive knowledge of their target substrate critical for lymphomagenesis is far from complete.

SUMMARY

Many E3 ligase and deubiquitinases that contribute to regulated proteolysis of substrates critical for major cellular processes are altered in various lineages of lymphoma. Understanding of the proteolytic regulatory mechanisms of these major cellular pathways may offer novel biomarkers and targets for lymphoma therapy.

TP53 mutation characteristics in therapy-related myelodysplastic syndromes and acute myeloid leukemia is similar to de novo diseases

BACKGROUND

TP53 mutation is more prevalent in therapy-related myeloid neoplasms (t-MN) than their de novo counterparts; however, the pattern of mutations involving TP53 gene in t-MN versus de novo diseases is largely unknown.

METHODS

We collected 108 consecutive patients with therapy-related myelodysplastic syndrome (t-MDS)/acute myeloid leukemia (t-AML). Clinical, hematological, and cytogenetic data were collected by searching the electronic medical record. TP53 sequencing was performed in all patients using a clinically validated next-generation sequencing-based gene panel assay. A previously published patient cohort consisting of 428 patients with de novo MDS/AML was included for comparison.

RESULTS

We assessed 108 patients with t-MN, in which 40 patients (37%) had TP53 mutations. The mutation frequency was similar between t-MDS and t-AML; but significantly higher than de novo MDS/AML (62/428 patients, 14.5%) (p<0.0001). TP53 mutations in t-MN were mainly clustered in DNA-binding domains, with an allelic frequency of 37.0% (range, 7.1 to 98.8). Most mutations involved single nucleotide changes, of which, transitions (65.9%) were more common than transversions (34.1%). Missense mutations were the most frequent, followed by frameshift and nonsense mutations. This TP53 mutation pattern was strikingly similar to that observed in de novo MDS/AML. TP53 mutations in t-MN were associated with a complex karyotype (p<0.0001), a higher number of chromosomal abnormalities (p<0.0001), and an inferior overall survival in affected patients (6.1 vs 14.1 months) by univariate (p<0.0001) and multivariate analyses (p=0.0020).

CONCLUSIONS

Our findings support the recent notion that heterozygous TP53 mutation may be a function of normal aging and that mutated cells are subject to selection upon exposure to cytotoxic therapy. t-MN carrying TP53 mutation have an aggressive clinical course independent of other confounding factors.

Screening Feature Genes of Venous Thromboembolism with DNA Microarray

We aimed to explore the potential genes or pathways related to venous thromboembolism (VTE) and expected our findings could contribute to the development of new target drugs for VTE. The gene expression profile of GSE19151 was downloaded from Gene Expression Omnibus (GEO) database. The bioinformatics methods were applied to screen the feature genes and pathways related with VTE. A total of 115 DEGs were identified, including 25 downregulated genes and 90 upregulated genes. Function enrichment analysis showed that upregulated genes of VTE were mainly enriched in ribosome and translation-related pathways, while downregulated genes were mainly enriched in cytoskeletal protein binding and non-membrane-bounded organelle-related pathways. MCL1, TP53, and RERE were three outstanding genes involved in the interaction network. The most significant pathways enriched by module genes were ribosome and oxidative phosphorylation. Moreover, all the products of the 18 genes enriched in ribosome (hsa03010) were ribosomal proteins. Ribosome, translation, actin binding, and non-membrane-bounded organelle pathways were closely related to the development of VTE. Moreover, MCL1, TP53, and RERE might play key roles in the process of VTE.

PRMT5 is required for lymphomagenesis triggered by multiple oncogenic drivers

Protein arginine methyltransferase 5 (PRMT5) has been implicated as a key modulator of lymphomagenesis. Whether PRMT5 has overt oncogenic function in the context of leukemia/lymphoma and whether it represents a therapeutic target remains to be established. We demonstrate that inactivation of PRMT5 inhibits colony-forming activity by multiple oncogenic drivers, including cyclin D1, c-MYC, NOTCH1, and MLL-AF9. Furthermore, we demonstrate that PRMT5 overexpression specifically cooperates with cyclin D1 to drive lymphomagenesis in a mouse model, revealing inherent neoplastic activity. Molecular analysis of lymphomas revealed that arginine methylation of p53 selectively suppresses expression of crucial proapoptotic and antiproliferative target genes, thereby sustaining tumor cell self-renewal and proliferation and bypassing the need for the acquisition of inactivating p53 mutations. Critically, analysis of human tumor specimens reveals a strong correlation between cyclin D1 overexpression and p53 methylation, supporting the biomedical relevance of this pathway.

SIGNIFICANCE

We have identified and functionally validated a crucial role for PRMT5 for the inhibition of p53-dependent tumor suppression in response to oncogenic insults. The requisite role for PRMT5 in the context of multiple lymphoma/leukemia oncogenic drivers suggests a molecular rationale for therapeutic development.

TP53 mutations in human cancer: database reassessment and prospects for the next decade

More than 50% of human tumors carry TP53 gene mutations and in consequence more than 45,000 somatic and germline mutations have been gathered in the UMD TP53 database (http://p53.fr). Analyses of these mutations have been invaluable for bettering our knowledge on the structure-function relationships within the TP53 protein and the high degree of heterogeneity of the various TP53 mutants in human cancer. In this review, we discuss how with the release of the sequences of thousands of tumor genomes issued from high-throughput sequencing, the description of novel TP53 mutants is now reaching a plateau indicating that we are close to the full set of mutants that target the elusive tumor-suppressive activity of this protein. We performed an extensive and thorough analysis of the TP53 mutation database, focusing particularly on specific sets of mutations that were overlooked in the past because of their low frequencies, for example, synonymous mutations, splice mutations, or mutations-targeting residues subject to posttranslational modifications. We also discuss the evolution of the statistical methods used to differentiate TP53 passenger mutations and artifactual data from true mutations, a process vital to the release of an accurate TP53 mutation database that will in turn be an invaluable tool for both clinicians and researchers.