A constitutional balanced t(3;8)(p14;q24.1) translocation results in disruption of the TRC8 gene and predisposition to clear cell renal cell carcinoma

The Pathologic and Molecular Genetic Landscape of the Hereditary Renal Cancer Predisposition Syndromes

It is estimated that 5-8% of renal tumors are hereditary in nature with many inherited as autosomal dominant. These tumors carry a unique spectrum of pathologic and molecular alterations, the knowledge of which is expanding in the recent years. Indebted to this knowledge, many advances in treatment of these tumors have been achieved. In this review, we summarize the current understanding of the genetic renal neoplasia syndromes, the clinical and pathologic presentations, their molecular pathogenesis, the advances in therapeutic implications and targeted therapy.

Characterization of renal cell carcinoma-associated constitutional chromosome abnormalities by genome sequencing

Constitutional translocations, typically involving chromosome 3, have been recognized as a rare cause of inherited predisposition to renal cell carcinoma (RCC) for four decades. However, knowledge of the molecular basis of this association is limited. We have characterized the breakpoints by genome sequencing (GS) of constitutional chromosome abnormalities in five individuals who presented with RCC. In one individual with constitutional t(10;17)(q11.21;p11.2), the translocation breakpoint disrupted two genes: the known renal tumor suppressor gene (TSG) FLCN (and clinical features of Birt‐Hogg‐Dubé syndrome were detected) and RASGEF1A. In four cases, the rearrangement breakpoints did not disrupt known inherited RCC genes. In the second case without chromosome 3 involvement, the translocation breakpoint in an individual with a constitutional t(2;17)(q21.1;q11.2) mapped 12 Kb upstream of NLK. Interestingly, NLK has been reported to interact indirectly with FBXW7 and a previously reported RCC‐associated translocation breakpoint disrupted FBXW7. In two cases of constitutional chromosome 3 translocations, no candidate TSGs were identified in the vicinity of the breakpoints. However, in an individual with a constitutional chromosome 3 inversion, the 3p breakpoint disrupted the FHIT TSG (which has been reported previously to be disrupted in two apparently unrelated families with an RCC‐associated t(3;8)(p14.2;q24.1). These findings (a) expand the range of constitutional chromosome rearrangements that may be associated with predisposition to RCC, (b) confirm that chromosome rearrangements not involving chromosome 3 can predispose to RCC, (c) suggest that a variety of molecular mechanisms are involved the pathogenesis of translocation‐associated RCC, and (d) demonstrate the utility of GS for investigating such cases.

Dropping in on lipid droplets: insights into cellular stress and cancer

Lipid droplets (LD) have increasingly become a major topic of research in recent years following its establishment as a highly dynamic organelle. Contrary to the initial view of LDs being passive cytoplasmic structures for lipid storage, studies have provided support on how they act in concert with different organelles to exert functions in various cellular processes. Although lipid dysregulation resulting from aberrant LD homeostasis has been well characterised, how this translates and contributes to cancer progression is poorly understood. This review summarises the different paradigms on how LDs function in the regulation of cellular stress as a contributing factor to cancer progression. Mechanisms employed by a broad range of cancer cell types in differentially utilising LDs for tumourigenesis will also be highlighted. Finally, we discuss the potential of targeting LDs in the context of cancer therapeutics.

Clinical Utility of Fluorescence In Situ Hybridization (FISH) for Deletion of Chromosome 3p in the Work-up of Renal Masses

Chromosome 3p deletion is a well-established genetic aberration in clear cell renal cell carcinoma (RCC). We aimed to evaluate the clinical utility of 3p fluorescence in situ hybridization (FISH) on formalin-fixed paraffin-embedded tissue in surgical pathology specimens. 3p:3q <0.8 was established as the cut-off for 3p loss. The 2015 Medicare allowable billing rates were used to estimate the cost. Over 2.5 years (2013 to 2015), 3p FISH was performed on 18 cases per year. Among tested cases, 70% (30/43) were nephrectomies and 30% (14/43) metastases. 3p loss was detected in 44% (19/43) of cases, with a higher rate of loss in radical compared with partial nephrectomies (71% vs. 15%; P=0.003). A definitive RCC subtype was assigned in 65% (28/43) of cases. More partial nephrectomies had a definitive subtype assigned, compared with radical nephrectomies (92% vs. 59%; P=0.04), possibly related to more high-grade, high-stage tumors in submitted radical nephrectomies. Tested nephrectomies were most commonly diagnosed as clear cell (41%) or clear cell papillary RCC (32%). Half of unclassifiable RCCs had 3p loss (53%, 8/15). Annual 3p FISH costs were $3446.64, with 79% of costs from ancillary studies attributable to immunostains. 3p FISH was performed infrequently in nephrectomy specimens and was not cost prohibitive. RCC cases that are unclassifiable by morphology and other ancillary tests, but which have 3p FISH deletion may merit a comment in the pathology report, raising the possibility of clear cell RCC, as the oncologic approach may be altered despite the lack of a definitive RCC subtype.

Lysosomal acid lipase promotes cholesterol ester metabolism and drives clear cell renal cell carcinoma progression

OBJECTIVES

Clear cell renal cell carcinoma (ccRCC) is characterized histologically by accumulation of cholesterol esters, cholesterol and other neutral lipids. Lysosomal acid lipase (LAL) is a critical enzyme involved in the cholesterol ester metabolism. Here, we sought to determine whether LAL could orchestrate metabolism of cholesterol esters in order to promote ccRCC progression.

MATERIALS AND METHODS

Quantitative reverse-transcription PCR and western blots were conducted to assess the expression of LAL in human ccRCC tissues. We analysed the relationship between LAL levels and patient survival using tissue microarrays. We used cell proliferation assays, colony formation assays, cell death assays, metabolic assays and xenograft tumour models to evaluate the biological function and underlying mechanisms.

RESULTS

LAL was up-regulated in ccRCC tissue. Tissue microarray analysis revealed higher levels of LAL in advanced grades of ccRCC, and high LAL expression indicated lower patient survival. Suppressing LAL expression not only blocked the utilization of cholesterol esters but also impaired proliferation and cellular survival. Furthermore, immunohistochemistry staining showed that LAL expression was correlated with Akt phosphorylation. Suppressing LAL expression decreased the phosphorylation level of Akt and Src and reduced the level of 14,15-epoxyeicosatrienoic acids in ccRCC cells. Supplement of 14,15-epoxyeicosatrienoic acids rescued proliferation in vitro and in vivo.

CONCLUSIONS

LAL promoted cell proliferation and survival via metabolism of epoxyeicosatrienoic acids and activation of the Src/Akt pathway.

Constitutional t(8;22)(q24;q11.2) that mimics the variant Burkitt-type translocation in Philadelphia chromosome-positive chronic myeloid leukemia

Constitutional translocations that coincide with t(9;22)(q34;q11.2) may lead to unnecessary treatments in chronic myeloid leukemia (CML) patients, as, under the standard criteria, a diagnosis of CML with additional chromosomal abnormalities indicates an accelerated phase (AP). In the present report, a 47-year-old male had pain in the right foot due to gout. Peripheral blood examination showed leukocytosis with left shift. Bone marrow aspiration revealed myeloid hyperplasia with megakaryocytosis. RT-PCR revealed the major BCR-ABL fusion transcript, and CML in the chronic phase was diagnosed, followed by nilotinib treatment. Although WBC counts decreased immediately, G-banding analysis showed 46,XY,t(8;22)(q24;q11.2),t(9;22)(q34;q11.2) [20]. The t(8;22)(q24;q11.2) translocation is known to be recurrent in Burkitt's lymphoma. The diagnosis was changed to CML in AP, leading to B-lymphoid crisis. Unexpectedly, the karyotype was 46,XY,t(8;22)(q24;q11.2) [20] in hematological complete remission, even after 3 months. Fluorescence in situ hybridization on metaphase spreads revealed the MYC signal on the der(22)t(8;22), indicating that the 8q24 breakpoint was centromeric to MYC at 8q24.21. G-banding analysis of phytohemagglutinin-stimulated peripheral blood T-lymphocytes also indicated 46,XY,t(8;22)(q24.1;q11.2). We conclude that the t(8;22) is constitutional in this patient. As the tumor suppressor gene TRC8/RNF139 is disrupted by constitutional t(8;22)(q24.13;q11.21) in dysgerminoma, it may be associated with the onset of CML.

Glioblastomas with copy number gains in EGFR and RNF139 show increased expressions of carbonic anhydrase genes transformed by ENO1

Background

Prominence of glycolysis in glioblastomas may be non-specific or a feature of oncogene-related subgroups (i.e. amplified EGFR, etc.). Relationships between amplified oncogenes and expressions of metabolic genes associated with glycolysis, directly or indirectly via pH, were therefore investigated.

Methods

Using multiplex ligation-dependent probe amplification, copy numbers (CN) of 78 oncogenes were quantified in 24 glioblastomas. Related expressions of metabolic genes encoding lactate dehydrogenases (LDHA, LDHC), carbonic anhydrases (CA3, CA12), monocarboxylate transporters (SLC16A3 or MCT4, SLC16A4 or MCT5), ATP citrate lyase (ACLY), glycogen synthase1 (GYS1), hypoxia inducible factor-1A (HIF1A), and enolase1 (ENO1) were determined in 22 by RT-qPCR. To obtain supra-glycolytic levels and adjust for heterogeneity, concurrent ENO1 expression was used to mathematically transform the expression levels of metabolic genes already normalized with delta-delta crossing threshold methodology.

Results

Positive correlations with EGFR occurred for all metabolic genes. Significant differences (Wilcoxon Rank Sum) for oncogene CN gains in tumors of at least 2.00-fold versus less than 2.00-fold occurred for EGFR with CA3's expression (p < 0.03) and for RNF139 with CA12 (p < 0.004). Increased CN of XIAP associated negatively. Tumors with less than 2.00-fold CN gains differed from those with gains for XIAP with CA12 (p < 0.05). Male gender associated with CA12 (p < 0.05).

Conclusions

Glioblastomas with CN increases in EGFR had elevated CA3 expression. Similarly, tumors with RNF149 CN gains had elevated CA12 expression.

General significance

In larger studies, subgroups of glioblastomas may emerge according to oncogene-related effects on glycolysis, such as control of pH via effects on carbonic anhydrases, with prognostic and treatment implications.

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PCR of glioblastomas show oncogene copy numbers relate to metabolic gene expressions.

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ENO1(ENOLASE1) transformations yielded “supra-glycolytic” metabolic gene expressions.

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EGFR, RNF139, and XIAP associated with expressions of two carbonic anhydrase genes.

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Male gender associated (+) with the transformed expression of carbonic anhydrase 12.

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Oncogene amplifications may aid control of pH to protect glycolysis in glioblastomas.

Identifying gene disruptions in novel balanced de novo constitutional translocations in childhood cancer patients by whole-genome sequencing

Purpose

We applied whole genome sequencing to children diagnosed with neoplasms and found to carry apparently balanced constitutional translocations, to discover novel genic disruptions.

Methods

We applied SV calling programs CREST, Break Dancer, SV-STAT and CGAP-CNV, and developed an annotative filtering strategy to achieve nucleotide resolution at the translocations.

Results

We identified the breakpoints for t(6;12) (p21.1;q24.31) disrupting HNF1A in a patient diagnosed with hepatic adenomas and Maturity Onset Diabetes of the Young (MODY). Translocation as the disruptive event of HNF1A, a gene known to be involved in MODY3, has not been previously reported. In a subject with Hodgkin’s lymphoma and subsequent low-grade glioma, we identified t(5;18) (q35.1;q21.2), disrupting both SLIT3 and DCC, genes previously implicated in both glioma and lymphoma.

Conclusions

These examples suggest that implementing clinical whole genome sequencing in the diagnostic work-up of patients with novel but apparently balanced translocations may reveal unanticipated disruption of disease-associated genes and aid in prediction of the clinical phenotype.

Analysis of the t(3;8) of hereditary renal cell carcinoma: a palindrome-mediated translocation

It has emerged that palindrome-mediated genomic instability generates DNA-based rearrangements. The presence of palindromic AT-rich repeats (PATRRs) at the translocation breakpoints suggested a palindrome-mediated mechanism in the generation of several recurrent constitutional rearrangements: the t(11;22), t(17;22), and t(8;22). To date, all reported PATRR-mediated translocations include the PATRR on chromosome 22 (PATRR22) as a translocation partner. Here, the constitutional rearrangement, t(3;8)(p14.2;q24.1), segregating with renal cell carcinoma in two families, is examined. The chromosome 8 breakpoint lies in PATRR8 in the first intron of the RNF139 (TRC8) gene, whereas the chromosome 3 breakpoint is located in an AT-rich palindromic sequence in intron 3 of the FHIT gene (PATRR3). Thus, the t(3;8) is the first PATRR-mediated, recurrent, constitutional translocation that does not involve PATRR22. Furthermore, we detect de novo translocations similar to the t(11;22) and t(8;22), involving PATRR3 in normal sperm. The breakpoint on chromosome 3 is in proximity to FRA3B, the most common fragile site in the human genome and a site of frequent deletions in tumor cells. However, the lack of involvement of PATRR3 sequence in numerous FRA3B-related deletions suggests that there are several different DNA sequence-based etiologies responsible for chromosome 3p14.2 genomic rearrangements.

Identifying potential cancer driver genes by genomic data integration

Cancer is a genomic disease associated with a plethora of gene mutations resulting in a loss of control over vital cellular functions. Among these mutated genes, driver genes are defined as being causally linked to oncogenesis, while passenger genes are thought to be irrelevant for cancer development. With increasing numbers of large-scale genomic datasets available, integrating these genomic data to identify driver genes from aberration regions of cancer genomes becomes an important goal of cancer genome analysis and investigations into mechanisms responsible for cancer development. A computational method, MAXDRIVER, is proposed here to identify potential driver genes on the basis of copy number aberration (CNA) regions of cancer genomes, by integrating publicly available human genomic data. MAXDRIVER employs several optimization strategies to construct a heterogeneous network, by means of combining a fused gene functional similarity network, gene-disease associations and a disease phenotypic similarity network. MAXDRIVER was validated to effectively recall known associations among genes and cancers. Previously identified as well as novel driver genes were detected by scanning CNAs of breast cancer, melanoma and liver carcinoma. Three predicted driver genes (CDKN2A, AKT1, RNF139) were found common in these three cancers by comparative analysis.

Chromosomal characterization of cryopreserved mesenchymal stem cells from the human subendothelium umbilical cord vein

AIMS

To conduct a morphological, functional and chromosomal characterization of mesenchymal stem cell populations from the human subendothelium umbilical cord vein after cryopreservation.

MATERIAL & METHODS

Five human umbilical cords were processed in order to obtain mesenchymal stem cells. Flow cytometry, differentiation assays and cytogenetic analysis were carried out before and after the cryopreservation process.

RESULTS

Flow cytometry revealed that CD105, CD73 and CD90 markers were expressed by the cells, which lacked the expression of hematopoietic lineage markers, such as CD14, CD34 and CD45. The mesenchymal stem cells demonstrated capacity for osteogenic, adipogenic and chondrogenic differentiation. Chromosome analysis showed no clonal chromosome changes in the cells in either situation. However, a significant number of nonclonal chromosomal aberrations were apparent after cryopreservation, including monosomies and structural changes. Cells isolated from one umbilical cord exhibited a rare balanced paracentric inversion, likely a cytogenetic constitutional alteration. This was present both before and after experimental procedures.

CONCLUSION

These findings show that using mesenchymal stem cells for clinical approaches requires careful investigation and sensitive tests in order to ensure cellular therapy biosafety.

Cholesterol and the development of clear-cell renal carcinoma

The majority of kidney cancers are clear-cell carcinomas (ccRCC), characterized by the accumulation of cholesterol, cholesterol esters, other neutral lipids and glycogen. Rather than being a passive bystander, the clear-cell phenotype is suggested to be a biomarker of deregulated cholesterol and lipid biosynthesis, which plays an important role in development of the disease. One clue to this relationship has come from the elucidation of the hereditary kidney cancer gene, TRC8, which functions partly to degrade key regulators of endogenous cholesterol and lipid biosynthesis. In addition, deregulation of the mevalonate pathway has been shown to play a key role in cellular transformation and invasion. These findings are supported by considerable epidemiologic data linking obesity and the deregulation of lipid biosynthesis to ccRCC.

TRC8 suppresses tumorigenesis through targeting heme oxygenase-1 for ubiquitination and degradation

The TRC8 gene, which was previously shown to be disrupted by a 3;8 chromosomal translocation in hereditary kidney cancer, encodes for an endoplasmic reticulum-resident E3 ligase. Studies have shown that TRC8 exhibits a tumor-suppressive effect through its E3-ligase activity. Therefore, the identification of its physiological substrates will provide important insights into the molecular mechanism underlying TRC8-mediated tumor suppression. Here we show that TRC8 targets heme oxygenase-1 (HO-1), an antioxidant enzyme highly expressed in various cancers, for ubiquitination and degradation. Ectopic TRC8 expression suppresses HO-1-induced cancer cell growth and migration/invasion. Conversely, HO-1 depletion reduced the tumorigenic and invasive capacities promoted by TRC8 knockdown. HO-1 downregulation in renal carcinoma cells induces a mitotic delay at G2/M phase by increasing the intracellular reactive oxygen species and the DNA-damage-induced checkpoint activation. These results highlight the tumorigenic role of HO-1 and the importance of TRC8-mediated HO-1 degradation in the control of cancer growth.

Chromosomal translocations and palindromic AT-rich repeats

Repetitive DNA sequences constitute 30% of the human genome, and are often sites of genomic rearrangement. Recently, it has been found that several constitutional translocations, especially those that involve chromosome 22, take place utilizing palindromic sequences on 22q11 and on the partner chromosome. Analysis of translocation junction fragments shows that the breakpoints of such palindrome-mediated translocations are localized at the center of palindromic AT-rich repeats (PATRRs). The presence of PATRRs at the breakpoints indicates a palindrome-mediated mechanism involved in the generation of these constitutional translocations. Identification of these PATRR-mediated translocations suggests a universal pathway for gross chromosomal rearrangement in the human genome. De novo occurrences of PATRR-mediated translocations can be detected by PCR in normal sperm samples but not somatic cells. Polymorphisms of various PATRRs influence their propensity for adopting a secondary structure, which in turn affects de novo translocation frequency. We propose that the PATRRs form an unstable secondary structure, which leads to double-strand breaks at the center of the PATRR. The double-strand breaks appear to be followed by a non-homologous end-joining repair pathway, ultimately leading to the translocations. This review considers recent findings concerning the mechanism of meiosis-specific, PATRR-mediated translocations.

Case report: renal cell carcinoma segregating with a t(2;3)(q37.3;q13.2) chromosomal translocation in an Ashkenazi Jewish family

Chromosome translocations involving chromosome 3 have previously been associated with the development of renal cell carcinoma. In this report we describe an Ashkenazi Jewish family with a previously unreported balanced constitutional translocation (t(2;3)(q37.3;q13.2)) segregating with the development of clear cell renal carcinomata in three family members spanning two generations. We outline the difficulties with the clinical utility of this finding for genetic counselling and risk management strategies. We suggest that an additional renal cancer susceptibility gene may exist at 3q13.2, and review known breakpoints in the autosomes which are associated with clear cell renal cell carcinoma.

Clinical genomics of renal epithelial tumors

Kidney and upper urinary tract cancers account for approximately 54,000 cases every year in the United States, and represent about 3.7% of adult malignancies, with more than 13,000 annual deaths. Classification of renal tumors is typically based on histomorphologic characteristics but, on occasion, morphologic characteristics are not sufficient. Each of the most common histologic subtypes harbors specific recurrent genetic abnormalities, such as deletion of 3p in conventional clear cell carcinoma, trisomy 7 and 17 in papillary renal cell carcinoma, multiple monosomies in chromophobe renal cell carcinoma, and a nearly diploid genome in benign oncocytomas. Knowledge of this information can provide diagnostic support and prognostic refinement in renal epithelial tumors. Identification of the specific subtype of a renal tumor is critical in guiding surveillance for recurrence and the appropriate use of targeted therapies. Cytogenomic arrays are increasingly being used as a clinical tool for genome-wide assessment of copy number and loss of heterozygosity in renal tumors. In addition, the improved understanding of the hereditary causes of renal tumors and their role in sporadic malignancies has led to the development of more effective targeted therapies. This review summarizes the genetic and genomic changes in the most common types of renal epithelial tumors and highlights the clinical implications of these aberrations.

Renal cell cancer among African Americans: an epidemiologic review

Incidence rates for renal cell cancer, which accounts for 85% of kidney cancers, have been rising more rapidly among blacks than whites, almost entirely accounted for by an excess of localized disease. This excess dates back to the 1970s, despite less access among blacks to imaging procedures in the past. In contrast, mortality rates for this cancer have been virtually identical among blacks and whites since the early 1990s, despite the fact that nephrectomy rates, regardless of stage, are lower among blacks than among whites. These observations suggest that renal cell cancer may be a less aggressive tumor in blacks. We have reviewed the epidemiology of renal cell cancer, with emphasis on factors which may potentially play a role in the observed differences in incidence and mortality patterns of renal cell cancer among blacks and whites. To date, the factors most consistently, albeit modestly, associated with increased renal cell cancer risk in epidemiologic studies among whites--obesity, hypertension, cigarette smoking--likely account for less than half of these cancers, and there is virtually no epidemiologic evidence in the literature pertaining to their association with renal cell cancer among blacks. There is a long overdue need for detailed etiologic cohort and case-control studies of renal cell cancer among blacks, as they now represent the population at highest risk in the United States. In particular, investigation of the influence on renal cell cancer development of hypertension and chronic kidney disease, both of which occur substantially more frequently among blacks, is warranted, as well as investigations into the biology and natural history of this cancer among blacks.

A palindrome-mediated recurrent translocation with 3:1 meiotic nondisjunction: the t(8;22)(q24.13;q11.21)

Palindrome-mediated genomic instability has been associated with chromosomal translocations, including the recurrent t(11;22)(q23;q11). We report a syndrome characterized by extremity anomalies, mild dysmorphia, and intellectual impairment caused by 3:1 meiotic segregation of a previously unrecognized recurrent palindrome-mediated rearrangement, the t(8;22)(q24.13;q11.21). There are at least ten prior reports of this translocation, and nearly identical PATRR8 and PATRR22 breakpoints were validated in several of these published cases. PCR analysis of sperm DNA from healthy males indicates that the t(8;22) arises de novo during gametogenesis in some, but not all, individuals. Furthermore, demonstration that de novo PATRR8-to-PATRR11 translocations occur in sperm suggests that palindrome-mediated translocation is a universal mechanism producing chromosomal rearrangements.

Obesity, cholesterol, and clear-cell renal cell carcinoma (RCC)

Multiple epidemiologic studies have linked the development of renal cancer to obesity. In this chapter, we begin with a review of selected population studies, followed by recent mechanistic discoveries that further link lipid deregulation to the RCC development. The upregulation of leptin and downregulation of adiponectin pathways in obesity fit well with our molecular understanding of RCC pathogenesis. In addition, two forms of hereditary RCC involve proteins, Folliculin and TRC8, that are positioned to coordinately regulate lipid and protein biosynthesis. Both of these biosynthetic pathways have important downstream consequences on HIF-1/2alpha levels and angiogenesis, key aspects in the disease pathogenesis. The role of lipid biology and its interface with protein translation regulation represents a new dimension in RCC research with potential therapeutic implications.

Fragile histidine triad protein: structure, function, and its association with tumorogenesis

BACKGROUND

The human fragile histidine triad (FHIT) gene is a putative tumor suppressor gene, which is located at chromosome region 3p14.2. It was suggested that the loss of heterozygosity (LOH), homozygous deletions, and abnormal expression of the FHIT gene were involved in several types of human malignancies.

MATERIALS AND METHODS

To determine the role of FHIT in various cancers, we have performed structural and functional analysis of FHIT in detail.

RESULTS AND DISCUSSION

The protein FHIT catalyzes the Mg(2+) dependent hydrolysis of P1-5 cent-O-adenosine-P3-5 cent-O-adenosine triphosphate, Ap3A, to AMP, and ADP. The reaction is thought to follow a two-step mechanism. Histidine triad proteins, named for a motif related to the sequence H-cent-H-cent-H-cent-cent- (cent, a hydrophobic amino acid), belong to superfamily of nucleotide hydrolases and transferases. This enzyme acts on the R-phosphate of ribonucleotides, and contain a approximately 30-kDa domain that is typically a homodimer of approximately 15 kDa polypeptides with catalytic site.

CONCLUSION

Here we have gathered information is known about biological activities of FHIT, the structural and biochemical bases for their functions. Our approach may provide a comparative framework for further investigation of FHIT.

Population-based survey of cancer risks in chromosome 3 translocation carriers

Familial renal cell carcinoma (RCC) is genetically heterogeneous and may be associated with germline mutations in a number of genes. Twelve different constitutional translocations involving chromosome 3 have also been described in association with inherited RCC. In some families the lifetime risk of RCC in chromosome 3 translocation carriers has been estimated to be more than 80%; however the cancer risks in patients with chromosome 3 translocations not ascertained because of a family history of RCC are not well defined. We report a retrospective population-based study using Danish national cytogenetic and cancer registries to clarify tumor risks associated with constitutional translocations involving chromosome 3. We identified 222 (105 females, 117 males) individuals with a constitutional chromosome 3 translocation and compared their cancer risks to those of the Danish population. None of the chromosome 3 translocation carriers had developed RCC at the time of study (female 95% CIs 0.000-0.042, male 95% CIs 0.000-0.038) (P = 1.0 and P = 0.498 for females and males compared to Danish population). Fourteen translocation carriers had developed cancer but there was no evidence of an excess of early onset disease and lifetime cancer risks in chromosome 3 translocation carriers were similar that in the Danish population. There was no association between cancer risk and location of the chromosome 3 breakpoint (HR = 1.322, P = 0.673). These findings suggest that, in the absence of a family history of RCC or evidence of disruption of a specific tumor suppressor gene, chromosome 3 translocations carriers are not at high risk of developing RCC.

The TRC8 ubiquitin ligase is sterol regulated and interacts with lipid and protein biosynthetic pathways

TRC8/RNF139 encodes an endoplasmic reticulum-resident E3 ubiquitin ligase that inhibits growth in a RING- and ubiquitylation-dependent manner. TRC8 also contains a predicted sterol-sensing domain. Here, we report that TRC8 protein levels are sterol responsive and that it binds and stimulates ubiquitylation of the endoplasmic reticulum anchor protein INSIG. Induction of TRC8 destabilized the precursor forms of the transcription factors SREBP-1 and SREBP-2. Loss of SREBP precursors was proteasome dependent, required a functional RING domain, occurred without generating processed nuclear forms, and suppressed SREBP target genes. TRC8 knockdown had opposite effects in sterol-deprived cells. In Drosophila, growth inhibition by DTrc8 was genetically suppressed by loss of specific Mprlp, Padlp N-terminal domain-containing proteins found in the COP9 signalosome and eIF3. DTrc8 genetically and physically interacted with two eIF3 subunits: eIF3f and eIF3h. Coimmunoprecipitation experiments confirmed these interactions in mammalian cells, and TRC8 overexpression suppressed polysome profiles. Moreover, high-molecular weight ubiquitylated proteins were observed in eIF3 immunoprecipitations from TRC8-overexpressing cells. Thus, TRC8 function may provide a regulatory link between the lipid and protein biosynthetic pathways.

The TRC8 E3 ligase ubiquitinates MHC class I molecules before dislocation from the ER

The US2 and US11 gene products of human cytomegalovirus promote viral evasion by hijacking the endoplasmic reticulum (ER)-associated degradation (ERAD) pathway. US2 and US11 initiate dislocation of newly translocated major histocompatibility complex class I (MHC I) from the ER to the cytosol for proteasome-mediated degradation, thereby decreasing cell surface MHC I. Despite being instrumental in elucidating the mammalian ERAD pathway, the responsible E3 ligase or ligases remain unknown. Using a functional small interfering RNA library screen, we now identify TRC8 (translocation in renal carcinoma, chromosome 8 gene), an ER-resident E3 ligase previously implicated as a hereditary kidney cancer gene, as required for US2-mediated MHC I ubiquitination. Depletion of TRC8 prevents MHC I ubiquitination and dislocation by US2 and restores cell surface MHC I. TRC8 forms an integral part of a novel multiprotein ER complex that contains MHC I, US2, and signal peptide peptidase. Our data show that the TRC8 E3 ligase is required for MHC I dislocation from the ER and identify a new complex associated with mammalian ERAD.

The tumor suppressor gene TRC8/RNF139 is disrupted by a constitutional balanced translocation t(8;22)(q24.13;q11.21) in a young girl with dysgerminoma

Background

RNF139/TRC8 is a potential tumor suppressor gene with similarity to PTCH, a tumor suppressor implicated in basal cell carcinomas and glioblastomas. TRC8 has the potential to act in a novel regulatory relationship linking the cholesterol/lipid biosynthetic pathway with cellular growth control and has been identified in families with hereditary renal (RCC) and thyroid cancers. Haploinsufficiency of TRC8 may facilitate development of clear cell-RCC in association with VHL mutations, and may increase risk for other tumor types. We report a paternally inherited balanced translocation t(8;22) in a proposita with dysgerminoma.

Methods

The translocation was characterized by FISH and the breakpoints cloned, sequenced, and compared. DNA isolated from normal and tumor cells was checked for abnormalities by array-CGH. Expression of genes TRC8 and TSN was tested both on dysgerminoma and in the proposita and her father.

Results

The breakpoints of the translocation are located within the LCR-B low copy repeat on chromosome 22q11.21, containing the palindromic AT-rich repeat (PATRR) involved in recurrent and non-recurrent translocations, and in an AT-rich sequence inside intron 1 of the TRC8 tumor-suppressor gene at 8q24.13. TRC8 was strongly underexpressed in the dysgerminoma. Translin is underexpressed in the dysgerminoma compared to normal ovary.

TRC8 is a target of Translin (TSN), a posttranscriptional regulator of genes transcribed by the transcription factor CREM-tau in postmeiotic male germ cells.

Conclusion

A role for TRC8 in dysgerminoma may relate to its interaction with Translin. We propose a model in which one copy of TRC8 is disrupted by a palindrome-mediated translocation followed by complete loss of expression through suppression, possibly mediated by miRNA.

Overexpression of ZNF342 by juxtaposition with MPO promoter/enhancer in the novel translocation t(17;19)(q23;q13.32) in pediatric acute myeloid leukemia and analysis of ZNF342 expression in leukemia

We report a novel translocation t(17;19)(q22;q13.32) found in 100% of blast cells from a pediatric acute myeloid leukemia (AML) patient. Fluorescence in situ hybridization and vectorette polymerase chain reaction were used to precisely map the chromosomal breakpoint located on the derivative chromosome 17 at 352 bp 5' of MPO, encoding myeloperoxidase a highly expressed protein in myeloid cells, and 2,085 bp 5' of ZNF342 on 19q, encoding a transcription factor expressed in human stem cells and previously implicated in mouse models of leukemia. Analysis of RNA levels from the patient sample revealed significant overexpression of ZNF342, potentially contributing to AML formation. This is the first report of a translocation in myeloid leukemia occurring only in the promoter/enhancer regions of the two genes involved, similar to translocations commonly found in lymphoid malignancies. Analysis of ZNF342 protein levels in a large dataset of leukemia samples by reverse phase protein array showed that higher levels of ZNF342 expression in acute lymphoblastic leukemia was associated with poorer outcome (P = 0.033). In the myeloid leukemia samples with the highest ZNF342 expression, there was overrepresentation of FLT3 internal tandem duplication (P = 0.0016) and AML subtype M7 (P = 0.0002). Thus, overexpression of ZNF342 by translocation or other mechanisms contributes to leukemia biology in multiple hematopoietic compartments.

Is there an association with constitutional structural chromosomal abnormalities and hematologic neoplastic process? A short review

The occasional observation of constitutional chromosomal abnormalities in patients with a malignant disease has led to a number of studies on their potential role in cancer development. Investigations of families with hereditary cancers and constitutional chromosomal abnormalities have been key observations leading to the molecular identification of specific genes implicated in tumorigenesis. Large studies have been reported on the incidence of constitutional chromosomal aberrations in patients with hematologic malignancies, but they could not confirm an increased risk for hematologic malignancy among carriers of structural chromosomal changes. However, it is of particular interest that constitutional structural aberrations with breakpoints similar to leukemia-associated specific breakpoints have been reported in patients with hematologic malignancies. Because of insufficient data, it remains still unclear if these aberrations represent random events or are associated with malignancy. There has been a substantial discussion about mechanisms involved in constitutional structural chromosomal changes in the literature. The documentation of more patients with constitutional structural chromosomal changes could be of major importance. Most importantly, the molecular investigation of chromosomal regions involved in rearrangements could give useful information on the genetic events underlying constitutional anomalies, contributing to isolation of genes important in the development of the neoplastic process. Regarding constitutional anomalies in patients with hematologic disorders, a survey of the cytogenetic data of our cytogenetics unit is herein also presented.

Clinical utility of array comparative genomic hybridization for detection of chromosomal abnormalities in pediatric acute lymphoblastic leukemia

BACKGROUND

Accurate detection of recurrent chromosomal abnormalities is critical to assign patients to risk-based therapeutic regimens for pediatric acute lymphoblastic leukemia (ALL).

PROCEDURE

We investigated the utility of array comparative genomic hybridization (aCGH) for detection of chromosomal abnormalities compared to standard clinical evaluation with karyotype and fluorescent in situ hybridization (FISH). Fifty pediatric ALL diagnostic bone marrows were analyzed by bacterial artificial chromosome (BAC) array and findings compared to standard clinical evaluation.

RESULTS

Sensitivity of aCGH was 79% to detect karyotypic findings other than balanced translocations, which cannot be detected by aCGH because they involve no copy number change. aCGH also missed abnormalities occurring in subclones constituting less than 25% of cells. aCGH detected 44 additional abnormalities undetected or misidentified by karyotype with 21 subsequently validated by FISH, including abnormalities in 4 of 10 cases with uninformative cytogenetics. aCGH detected concurrent terminal deletions of both 9p and 20q in three cases, in two of which the 20q deletion was undetected by karyotype. A narrow region of loss at 7p21 was detected in two cases.

CONCLUSIONS

aCGH detects the majority of karyotypic findings other than balanced translocations, and may provide key prognostic information in the approximately 35% of cases with uninformative cytogenetics.

Renal cell carcinoma: new developments in molecular biology and potential for targeted therapies

Renal cell carcinoma (RCC) affects 38,000 individuals in the U.S. yearly. Seventy-five percent of cases are clear-cell carcinomas, and a majority is driven by dysfunction of the von Hippel-Lindau (VHL) gene. VHL loss of function and other non-VHL pathways leading to RCC share aberrant activation of the hypoxic response, such as upregulation of vascular endothelial growth factor (VEGF) and consequent neoangiogenesis. Metastatic RCC has been notoriously resistant to therapy. For decades, its treatment has been based on nephrectomy and limited use of toxic and often inefficient immunotherapy with interleukin-2 or interferon-alpha. However, new biologic agents are beginning to break the resistance barrier. Small-molecule multikinase inhibitors that target VEGF receptors (sunitinib and sorafenib) have a favorable toxicity profile and can prolong time to progression and preserve quality of life when used in newly diagnosed or previously treated patients. The anti-VEGF antibody bevacizumab enhances the response rate and prolongs disease control when added to interferon-alpha. Temsirolimus, a mammalian target of rapamycin inhibitor, prolongs the survival duration of patients with poor-risk disease. Despite three new drugs being approved for RCC in the past 2 years, responses are mostly partial and of limited duration. Multiple new drugs and drug combinations are undergoing clinical trials and will likely impact the treatment of RCC in future years. Compounds found to be active in the metastatic setting are now being tried in earlier stage disease in an attempt to improve curability. However, no method has yet been validated to predict patient response to these newer treatments.