Disseminated tumor cells and their prognostic significance in nonmetastatic prostate cancer patients

Detection of pretreatment disseminated cells (pre-DTC) reflecting its homing to bone marrow (BM) in prostate cancer (PCa) might improve the current model to predict recurrence or survival in men with nonmetastatic disease despite of primary treatment. Thereby, pre-DTC may serve as an early prognostic biomarker. Post-treatment DTCs (post-DTC) finding may supply the clinician with additional predictive information about the possible course of PCa. To assess the prognostic impact of DTCs in BM aspirates sampled before initiation of primary therapy (pre-DTC) and at least 2 years after (post-DTC) to established prognostic factors and survival in patients with PCa. Available BM of 129 long-term follow-up patients with T1-3N0M0 PCa was assessed in addition to 100 BM of those in whom a pretreatment BM was sampled. Patients received either combined therapy [n = 81 (63%)], radiotherapy (RT) with different duration of hormone treatment (HT) or monotherapy with RT or HT alone [n = 48 (37%)] adapted to the criteria of the SPCG-7 trial. Mononuclear cells were deposited on slides according to the cytospin methodology and DTCs were identified by immunocytochemistry using the pancytokeratin antibodies AE1/AE3. The median age of men at diagnosis was 64.5 years (range 49.5-73.4 years). The median long-term follow-up from first BM sampling to last observation was 11 years. Categorized clinically relevant factors in PCa showed only pre-DTC status as the statistically independent parameter for survival in the multivariate analysis. Pre-DTCs homing to BM are significantly associated with clinically relevant outcome independent to the patient's treatment at diagnosis with nonmetastatic PCa.

ER stress-mediated autophagy promotes Myc-dependent transformation and tumor growth

The proto-oncogene c-Myc paradoxically activates both proliferation and apoptosis. In the pathogenic state, c-Myc-induced apoptosis is bypassed via a critical, yet poorly understood escape mechanism that promotes cellular transformation and tumorigenesis. The accumulation of unfolded proteins in the ER initiates a cellular stress program termed the unfolded protein response (UPR) to support cell survival. Analysis of spontaneous mouse and human lymphomas demonstrated significantly higher levels of UPR activation compared with normal tissues. Using multiple genetic models, we demonstrated that c-Myc and N-Myc activated the PERK/eIF2α/ATF4 arm of the UPR, leading to increased cell survival via the induction of cytoprotective autophagy. Inhibition of PERK significantly reduced Myc-induced autophagy, colony formation, and tumor formation. Moreover, pharmacologic or genetic inhibition of autophagy resulted in increased Myc-dependent apoptosis. Mechanistically, we demonstrated an important link between Myc-dependent increases in protein synthesis and UPR activation. Specifically, by employing a mouse minute (L24+/-) mutant, which resulted in wild-type levels of protein synthesis and attenuation of Myc-induced lymphomagenesis, we showed that Myc-induced UPR activation was reversed. Our findings establish a role for UPR as an enhancer of c-Myc-induced transformation and suggest that UPR inhibition may be particularly effective against malignancies characterized by c-Myc overexpression.

Tumor necrosis factor receptor expression and signaling in renal cell carcinoma

Clear cell renal cell carcinoma (ccRCC), a tubular epithelial cell (TEC) malignancy, frequently secretes tumor necrosis factor (TNF). TNF signals via two distinct receptors (TNFRs). TNFR1, expressed in normal kidney primarily on endothelial cells, activates apoptotic signaling kinase 1 and nuclear factor-kappaB (NF-kappaB) and induces cell death, whereas TNFR2, inducibly expressed on endothelial cells and on TECs by injury, activates endothelial/epithelial tyrosine kinase (Etk), which trans-activates vascular endothelial growth factor receptor 2 (VEGFR2) to promote cell proliferation. We investigated TNFR expression in clinical samples and function in short-term organ cultures of ccRCC tissue treated with wild-type TNF or specific muteins selective for TNFR1 (R1-TNF) or TNFR2 (R2-TNF). There is a significant increase in TNFR2 but not TNFR1 expression on malignant TECs that correlates with increasing malignant grade. In ccRCC organ cultures, R1-TNF increases TNFR1, activates apoptotic signaling kinase and NF-kappaB, and promotes apoptosis in malignant TECs. R2-TNF increases TNFR2, activates NF-kappaB, Etk, and VEGFR2 and increases entry into the cell cycle. Wild-type TNF induces both sets of responses. R2-TNF actions are blocked by pretreatment with a VEGFR2 kinase inhibitor. We conclude that TNF, acting through TNFR2, is an autocrine growth factor for ccRCC acting via Etk-VEGFR2 cross-talk, insights that may provide a more effective therapeutic approach to this disease.

Integrin genetic variants and stage-specific tumor recurrence in patients with stage II and III colon cancer

Integrins (ITGs) are key elements in cancer biology, regulating tumor growth, angiogenesis and lymphangiogenesis through interactions of the tumor cells with the microenvironment. Moving from the hypothesis that ITGs could have different effects in stage II and III colon cancer, we tested whether a comprehensive panel of germline single-nucleotide polymorphisms (SNPs) in ITG genes could predict stage-specific time to tumor recurrence (TTR). A total of 234 patients treated with 5-fluorouracil-based chemotherapy at the University of Southern California were included in this study. Whole-blood samples were analyzed for germline SNPs in ITG genes using PCR-restriction fragment length polymorphism or direct DNA sequencing. In the multivariable analysis, stage II colon cancer patients with at least one G allele for ITGB3 rs4642 had higher risk of recurrence (hazard ratio (HR)=4.027, 95% confidence interval (95% CI) 1.556-10.421, P=0.004). This association was also significant in the combined stage II-III cohort (HR=1.975, 95% CI 1.194-3.269, P=0.008). The predominant role of ITGB3 rs4642 in stage II diseases was confirmed using recursive partitioning, showing that ITGB3 rs4642 was the most important factor in stage II diseases. In contrast, in stage III diseases the combined analysis of ITGB1 rs2298141 and ITGA4 rs7562325 allowed to identify three distinct prognostic subgroups (P=0.009). The interaction between stage and the combined ITGB1 rs2298141 and ITGA4 rs7562325 on TTR was significant (P=0.025). This study identifies germline polymorphisms in ITG genes as independent stage-specific prognostic markers for stage II and III colon cancer. These data may help to select subgroups of patients who may benefit from ITG-targeted treatments.

Tumor suppressor Ras-association domain family 1 isoform A is a novel regulator of cardiac hypertrophy

BACKGROUND: Ras signaling regulates a number of important processes in the heart, including cell growth and hypertrophy. Although it is known that defective Ras signaling is associated with Noonan, Costello, and other syndromes that are characterized by tumor formation and cardiac hypertrophy, little is known about factors that may control it. Here we investigate the role of Ras effector Ras-association domain family 1 isoform A (RASSF1A) in regulating myocardial hypertrophy.

METHODS AND RESULTS: A significant downregulation of RASSF1A expression was observed in hypertrophic mouse hearts, as well as in failing human hearts. To further investigate the role of RASSF1A in cardiac (patho)physiology, we used RASSF1A knock-out (RASSF1A(-)(/)(-)) mice and neonatal rat cardiomyocytes with adenoviral overexpression of RASSF1A. Ablation of RASSF1A in mice significantly enhanced the hypertrophic response to transverse aortic constriction (64.2% increase in heart weight/body weight ratio in RASSF1A(-)(/)(-) mice compared with 32.4% in wild type). Consistent with the in vivo data, overexpression of RASSF1A in cardiomyocytes markedly reduced the cellular hypertrophic response to phenylephrine stimulation. Analysis of molecular signaling events in isolated cardiomyocytes indicated that RASSF1A inhibited extracellular regulated kinase 1/2 activation, likely by blocking the binding of Raf1 to active Ras.

CONCLUSIONS: Our data establish RASSF1A as a novel inhibitor of cardiac hypertrophy by modulating the extracellular regulated kinase 1/2 pathway.

Novel functional interaction between the plasma membrane Ca2+ pump 4b and the proapoptotic tumor suppressor Ras-associated factor 1 (RASSF1)

Plasma membrane calmodulin-dependent calcium ATPases (PMCAs) are enzymatic systems implicated in the extrusion of calcium from the cell. We and others have previously identified molecular interactions between the cytoplasmic COOH-terminal end of PMCA and PDZ domain-containing proteins. These interactions suggested a new role for PMCA as a modulator of signal transduction pathways. The existence of other intracellular regions in the PMCA molecule prompted us to investigate the possible participation of other domains in interactions with different partner proteins. A two-hybrid screen of a human fetal heart cDNA library, using the region 652-840 of human PMCA4b (located in the catalytic, second intracellular loop) as bait, revealed a novel interaction between PMCA4b and the tumor suppressor RASSF1, a Ras effector protein involved in H-Ras-mediated apoptosis. Immunofluorescence co-localization, immunoprecipitation, and glutathione S-transferase pull-down experiments performed in mammalian cells provided further confirmation of the physical interaction between the two proteins. The interaction domain has been narrowed down to region 74-123 of RASSF1C (144-193 in RASSF1A) and 652-748 of human PMCA4b. The functionality of this interaction was demonstrated by the inhibition of the epidermal growth factor-dependent activation of the Erk pathway when PMCA4b and RASSF1 were co-expressed. This inhibition was abolished by blocking PMCA/RASSSF1 association with an excess of a green fluorescent protein fusion protein containing the region 50-123 of RASSF1C. This work describes a novel protein-protein interaction involving a domain of PMCA other than the COOH terminus. It suggests a function for PMCA4b as an organizer of macromolecular protein complexes, where PMCA4b could recruit diverse proteins through interaction with different domains. Furthermore, the functional association with RASSF1 indicates a role for PMCA4b in the modulation of Ras-mediated signaling.

IGF-Binding Protein 2 - Oncogene or Tumor Suppressor?

The role of insulin-like growth factor binding protein 2 (IGFBP2) in cancer is unclear. In general, IGFBP2 is considered to be oncogenic and its expression is often observed to be elevated in cancer. However, there are a number of conflicting reports in vitro and in vivo where IGFBP2 acts in a tumor suppressor manner. In this mini-review, we discuss the factors influencing the variation in IGFBP2 expression in cancer and our interpretation of these findings.

Low-grade malignant Triton tumor of the oral cavity:a case report

Malignant Triton tumor (MTT) is a malignant peripheral nerve sheath tumor showing rhabdomyoblastic differentiation. It is considered a high-grade neoplasm with poor outcome. This report describes an MTT appearing in the oral cavity. On histologic examination the encapsulated lesion was composed of interlacing fascicles of spindle cells and scattered, large, strap-like pleomorphic cells with abundant eosinophilic cytoplasm. No cross striations were seen. Examination of levels through the tissue showed a total of only 4 normal mitoses and no necrosis. Immunohistochemistry demonstrated diffuse S100 positivity in the spindle cells. The large pleomorphic cells were weakly positive for alpha-sarcomeric actin and myoglobin, although variably but strongly positive for desmin. Management involved a small en bloc resection of the maxilla. After 33 months there was no sign of recurrence or distant metastasis. It was concluded that low-grade variants of MTT occur that do not have an aggressive clinical course.