Daniel Martinez

Dual CDK4/CDK6 Inhibition Induces Cell-Cycle Arrest and Senescence in Neuroblastoma

Purpose: Neuroblastoma is a pediatric cancer that continues to exact significant morbidity and mortality. Recently, a number of cell-cycle proteins, particularly those within the Cyclin D/CDK4/CDK6/RB network, have been shown to exert oncogenic roles in neuroblastoma, suggesting that their therapeutic exploitation might improve patient outcomes. Experimental Procedures: We evaluated the effect of dual CDK4/CDK6 inhibition on neuroblastoma viability using LEE011 (Novartis Oncology), a highly specific CDK4/6 inhibitor. Results: Treatment with LEE011 significantly reduced proliferation in 12 of 17 human neuroblastoma-derived cell lines by inducing cytostasis at nanomolar concentrations (mean IC50 = 307 ± 68 nmol/L in sensitive lines). LEE011 caused cell-cycle arrest and cellular senescence that was attributed to dose-dependent decreases in phosphorylated RB and FOXM1, respectively. In addition, responsiveness of neuroblastoma xenografts to LEE011 translated to the in vivo setting in that there was a direct correlation of in vitro IC50 values with degree of subcutaneous xenograft growth delay. Although our data indicate that neuroblastomas sensitive to LEE011 were more likely to contain genomic amplification of MYCN (P = 0.01), the identification of additional clinically accessible biomarkers is of high importance. Conclusions: Taken together, our data show that LEE011 is active in a large subset of neuroblastoma cell line and xenograft models, and supports the clinical development of this CDK4/6 inhibitor as a therapy for patients with this disease. Clin Cancer Res; 19(22); 6173–82. ©2013 AACR.

DJ-1 Colocalizes with Tau Inclusions: A Link between Parkinsonism and Dementia

Two novel mutations recently have been identified in the DJ‐1 gene that cause a new form of autosomal recessive, early‐onset parkinsonism. Because the pathological role of this protein is unknown, we examined the issue here and report the colocalization of DJ‐1 protein within a subset of pathological tau inclusions in a diverse group of neurodegenerative disorders known as tauopathies. Our study extends the view that different neurodegenerative diseases may have similar pathological mechanisms, and that these processes likely include DJ‐1.

MYC protein expression and genetic alterations have prognostic impact in patients with diffuse large B-cell lymphoma treated with immunochemotherapy.

MYC alterations influence the survival of patients with diffuse large B-cell lymphoma. Most studies have focused on MYC translocations but there is little information regarding the impact of numerical alterations and protein expression. We analyzed the genetic alterations and protein expression of MYC, BCL2, BCL6, and MALT1 in 219 cases of diffuse large B-cell lymphoma. MYC rearrangement occurred as the sole abnormality (MYC single-hit) in 3% of cases, MYC and concurrent BCL2 and/or BCL6 rearrangements (MYC double/triple-hit) in 4%, MYC amplifications in 2% and MYC gains in 19%. MYC single-hit, MYC double/triple-hit and MYC amplifications, but not MYC gains or other gene rearrangements, were associated with unfavorable progression-free survival and overall survival. MYC protein expression, evaluated using computerized image analysis, captured the unfavorable prognosis of MYC translocations/amplifications and identified an additional subset of patients without gene alterations but with similar poor prognosis. Patients with tumors expressing both MYC/BCL2 had the worst prognosis, whereas those with double-negative tumors had the best outcome. High MYC expression was associated with shorter overall survival irrespectively of the International Prognostic Index and BCL2 expression. In conclusion, MYC protein expression identifies a subset of diffuse large B-cell lymphoma with very poor prognosis independently of gene alterations and other prognostic parameters.

Evaluation of Histone 3 Lysine 27 Trimethylation (H3K27me3) and Enhancer of Zest 2 (EZH2) in Pediatric Glial and Glioneuronal Tumors Shows Decreased H3K27me3 in H3F3A K27M Mutant Glioblastomas

H3F3A mutations are seen in ∼30% of pediatric glioblastoma (GBMs) and involve either the lysine residue at position 27 (K27M) or glycine at position 34 (G34R/V). Sixteen genes encode histone H3, each variant differing in only a few amino acids. Therefore, how mutations in a single H3 gene contribute to carcinogenesis is unknown. H3F3A K27M mutations are predicted to alter methylation of H3K27. H3K27me3 is a repressive mark critical to stem cell maintenance and is mediated by EZH2, a member of the polycomb‐group (PcG) family. We evaluated H3K27me3 and EZH2 expression using immunohistochemistry in 76 pediatric brain tumors. H3K27me3 was lowered/absent in tumor cells but preserved in endothelial cells and infiltrating lymphocytes in six out of 20 GBMs. H3K27me3 showed strong immunoreactivity in all other tumor subtypes. Sequencing of GBMs showed H3F3A K27M mutations in all six cases with lowered/absent H3K27me3. EZH2 expression was high in GBMs, but absent/focal in other tumors. However, no significant differences in EZH2 expression were observed between H3F3A K27M mutant and wild type GBMs, suggesting that EZH2 mediated trimethylation of H3K27 is inhibited in GBM harboring K27M mutations. Our results indicate that H3F3A K27M mutant GBMs show decreased H3K27me3 that may be of both diagnostic and biological relevance.

Expanded and highly active proliferation centers identify a histological subtype of chronic lymphocytic leukemia ("accelerated" chronic lymphocytic leukemia) with aggressive clinical behavior.

Background The concept of “accelerated” chronic lymphocytic leukemia is frequently used by both pathologists and clinicians. However, neither histological criteria to define this form of chronic lymphocytic leukemia nor its clinical correlates and prognostic impact have been formally defined in large series of patients. Design and Methods Tissue biopsies from 100 patients with chronic lymphocytic leukemia were analyzed for the size of proliferation centers and their proliferation rate as assessed by mitosis count and Ki-67 immunostaining. Histological patterns were correlated with main clinico-biological features and outcome. Results A suspicion of disease transformation was the main reason for carrying out tissue biopsy, which was performed at a median time of 14 months (range, 0 to 204 months) after the diagnosis of chronic lymphocytic leukemia. The biopsy showed histological transformation to diffuse large B-cell lymphoma in 22 cases. In the remaining 78 patients, the presence of expanded proliferation centers (broader than a 20x field) and high proliferation rate (either >2.4 mitoses/proliferation center or Ki-67 >40%/proliferation center) predicted a poor outcome and were selected to define a highly proliferative group. Thus, 23 patients with either expanded proliferation centers or high proliferation rate were considered as having “accelerated” chronic lymphocytic leukemia. These patients displayed particular features, including higher serum lactate dehydrogenase levels and more frequently elevated ZAP-70 than “non-accelerated” cases. The median survival from biopsy of patients with “non-accelerated” chronic lymphocytic leukemia, “accelerated” chronic lymphocytic leukemia and transformation to diffuse large B-cell leukemia was 76, 34, and 4.3 months, respectively (P<0.001). Conclusions The presence of expanded and/or highly active proliferation centers identifies a group of patients with “accelerated” chronic lymphocytic leukemia characterized by an aggressive clinical behavior.

Immunohistochemical heterogeneity of breast carcinomas negative for estrogen receptors, progesterone receptors and Her2/neu (basal-like breast carcinomas).

Basal breast carcinomas triple negative for estrogen receptors, progesterone receptors and Her2/neu breast carcinomas are more aggressive than conventional neoplasms. We studied 64 cases with immunohistochemistry, using 23 antibodies, to characterize diverse pathological pathways. A basal cytokeratin was identified in 81% of tumors and vimentin was identified in 55%. The mean Ki67 index was 46% (range, 10–90%). Coincident expression of p50 and p65, which suggests an active nuclear factor-κB factor, was present in 13% of neoplasms. Epithelial growth factor receptor (EGFR), insulin-like growth factor-I receptor (IGF-IR) or c-kit (CD117) was identified in 77% of tumors. Loss of protein tyrosine phosphatase was found in 14%, whereas Akt activation was present in 28%. Several differences were identified between two subtypes of basal breast carcinomas: the pure variant (negative S-100 and actin) was more frequently associated with ‘in situ carcinoma’ (P=0.019) and pBad overexpression (P=0.098), whereas the myoepithelial variant (positive S-100 or actin) showed more frequent tumor necrosis (P=0.048), vimentin expression (P=0.0001), CD117 expression (P=0.001) and activated caspase-3 (P=0.089). IGF-IR could be as important as EGFR for the growth of these neoplasms. Basal cell carcinoma has at least two subtypes with distinct microscopic and immunohistochemical features.

Combination Therapy Targeting the Chk1 and Wee1 Kinases Shows Therapeutic Efficacy in Neuroblastoma

Neuroblastoma is uniquely sensitive to single-agent inhibition of the DNA damage checkpoint kinase Chk1, leading us to examine downstream effectors of this pathway and identify mitotic regulator Wee1 as an additional therapeutic target in this disease. Wee1 was overexpressed in both neuroblastoma cell lines and high-risk patient tumors. Genetic or pharmacologic abrogation of Wee1 signaling results in marked cytotoxicity in 10 of 11 neuroblastoma cell lines with a median IC(50) of 300 nmol/L for the Wee1-selective small-molecule inhibitor MK-1775. Murine tumor lines derived from mice that were either heterozygous or homozygous for MycN were particularly sensitive to single-agent inhibition of Wee1 (IC(50)s of 160 and 62 nmol/L, respectively). Simultaneous pharmacologic inhibition of Chk1 and Wee1 acted in a synergistic fashion to further impede neuroblastoma cell growth in vitro, in a manner greater than the individual inhibitors either alone or combined with chemotherapy. Combination Chk1 and Wee1 inhibition also revealed in vivo efficacy in neuroblastoma xenografts. Taken together, our results show that neuroblastoma cells depend on Wee1 activity for growth and that inhibition of this kinase may serve as a therapeutic for patients with neuroblastoma.

Coexisting follicular and mantle cell lymphoma with each having an in situ component: A novel, curious, and complex consultation case of coincidental, composite, colonizing lymphoma.

A diagnosis of composite lymphoma is typically prompted by the observation of morphologic discordance. We present a case of a spleen revealing histologic features of follicular lymphoma, without any indication of a second lymphoma. Immunohistochemical stains supported this diagnosis and showed the follicular lymphoma to be BCL2-. However, these studies revealed 2 additional unexpected findings: cyclin D1+ mantle zone cells surrounding neoplastic and reactive follicles (indicative of in situ mantle cell lymphoma) and BCL2-bright, histologically nonneoplastic follicles (indicative of in situ follicular lymphoma). ImmunoFISH and microdissection and polymerase chain reaction analysis documented the clonal nature of the cyclin D1+ mantle zones and illustrated clonal independence from the follicular lymphoma. This case illustrates an uncommon and unusual composite follicular and mantle cell lymphoma, with the follicular lymphoma accompanied by an in situ component, whereas the only manifestation of the mantle cell lymphoma was in situ.

Malignant rhabdoid tumors express stem cell factors, which relate to the expression of Ezh2 and Id proteins

Malignant rhabdoid tumors (MRTs) are highly aggressive pediatric tumors associated with loss of expression of SMARCB1, commonly occurring in the central nervous system [referred to as atypical teratoid/rhabdoid tumors (AT/RTs)] and in the kidney and soft tissues. Histologically, MRTs are characterized by immunohistochemical evidence of primitive neuroectodermal, mesenchymal, and epithelial differentiation. The ability of MRTs to differentiate along multiple lines, as evidenced by both histologic features and polyphenotypic immunohistochemical staining, and the proliferative nature of MRT cells are characteristics shared with the self-renewal and plasticity of embryonic stem cells (ES). To test the hypothesis that MRTs share similarities with ES, we used immunohistochemistry to evaluate the expression of various stem cell markers in a tissue microarray containing 26 AT/RTs and 16 non-central nervous system MRTs (NCMRTs). Staining intensity was scored as negative (0), low (1+), moderate (2+), and strong (3+) and was multiplied by the percentage of positive tumor cells to establish a semiquantitative measure for each marker. In AT/RT, strong-to-low expression was noted with glypican-3 (20 of 26, 77%), Sall4 (23 of 26, 88%), T-cell leukemia/lymphoma 1 (25 of 26, 96%), and undifferentiated embryonic cell transcription factor 1 (19 of 26, 73%). Markers that showed low expression in AT/RT were Sox2 (8 of 26, 31%), Nanog (7 of 26, 27%), Klf4 (10 of 26, 38%), Zfp206 (5 of 26, 19%), and musashi-1 (21 of 26, 81%). Similarly, in NCMRT, expression was noted with glypican-3 (12 of 16, 75%), Sall4 (13 of 16, 81%), T-cell leukemia/lymphoma 1 (16 of 16, 100%), undifferentiated embryonic cell transcription factor 1 (12 of 16, 75%), Sox2 (5 of 16, 31%), Nanog (8 of 16, 50%), Klf4 (8 of 16, 50%), Zfp206 (13 of 16, 81%), and musashi-1 (11 of 16, 75%). Placental alkaline phosphatase, Oct4, c-KIT, CD30, &agr;-fetoprotein, and &bgr;-−human chorionic gonadotrophin were not expressed in all cases. Markers that regulate the expression of stem cell transcription factors were also expressed in MRT. AT/RT cases showed expression of Id proteins: Id1 (17 of 26, 65%), Id2 (24 of 26, 92%), Id3 (22 of 26, 85%), and Id4 (22 of 26, 85%). Low expression was observed with EZH2 (15 of 26, 58%). Similarly, NCMRT cases showed expression of Id1 (15 of 16, 94%), Id2 (16 of 16, 100%), Id3 (16 of 16, 100%), Id4 (13 of 16, 81%), and EZH2 (13 of 16, 81%). Finally, regression analysis revealed a significant relationship between the expression of stem cell markers and EZH2 (P<0.0001), Id1 (P=0.0087), Id2 (P=0.0002), Id3 (P=0.0033), and Id4 (P<0.0001). These data suggest that MRTs express many stem cell-associated transcription factors, which may be regulated by the expression of EZH2 and the Id family of proteins. This study underscores similarities between MRTs and stem cells and may help elucidate common biologic pathways that could serve in advancing more effective therapeutic strategies to treat MRTs.

Antibody targeting of anaplastic lymphoma kinase induces cytotoxicity of human neuroblastoma

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase aberrantly expressed in neuroblastoma, a devastating pediatric cancer of the sympathetic nervous system. Germline and somatically acquired ALK aberrations induce increased autophosphorylation, constitutive ALK activation and increased downstream signaling. Thus, ALK is a tractable therapeutic target in neuroblastoma, likely to be susceptible to both small-molecule tyrosine kinase inhibitors and therapeutic antibodies—as has been shown for other receptor tyrosine kinases in malignancies such as breast and lung cancer. Small-molecule inhibitors of ALK are currently being studied in the clinic, but common ALK mutations in neuroblastoma appear to show de novo insensitivity, arguing that complementary therapeutic approaches must be developed. We therefore hypothesized that antibody targeting of ALK may be a relevant strategy for the majority of neuroblastoma patients likely to have ALK-positive tumors. We show here that an antagonistic ALK antibody inhibits cell growth and induces in vitro antibody-dependent cellular cytotoxicity of human neuroblastoma-derived cell lines. Cytotoxicity was induced in cell lines harboring either wild type or mutated forms of ALK. Treatment of neuroblastoma cells with the dual Met/ALK inhibitor crizotinib sensitized cells to antibody-induced growth inhibition by promoting cell surface accumulation of ALK and thus increasing the accessibility of antigen for antibody binding. These data support the concept of ALK-targeted immunotherapy as a highly promising therapeutic strategy for neuroblastomas with mutated or wild-type ALK.