ERBB3 is required for metastasis formation of melanoma cells

Melanoma is curable when it is at an early phase but is lethal once it becomes metastatic. The recent development of BRAF(V600E) inhibitors (BIs) showed great promise in treating metastatic melanoma, but resistance developed quickly in the treated patients, and these inhibitors are not effective on melanomas that express wild-type BRAF. Alternative therapeutic strategies for metastatic melanoma are urgently needed. Here we report that ERBB3, a member of the epidermal growth factor receptor family, is required for the formation of lung metastasis from both the BI-sensitive melanoma cell line, MA-2, and the BI-resistant melanoma cell line, 451Lu-R. Further analyses revealed that ERBB3 does not affect the initial seeding of melanoma cells in lung but is required for their further development into overt metastases, indicating that ERBB3 might be essential for the survival of melanoma cells after they reach the lung. Consistent with this, the ERBB3 ligand, NRG1, is highly expressed in mouse lungs and induces ERBB3-depdnent phosphorylation of AKT in both MA-2 and 451Lu-R cells in vitro. These findings suggest that ERBB3 may serve as a target for treating metastatic melanomas that are resistant to BIs. In support of this, administration of the pan-ERBB inhibitor, canertinib, significantly suppresses the metastasis formation of BI-resistant melanoma cell lines.

Quantifying physical decline in juvenile neuronal ceroid lipofuscinosis (Batten disease)

OBJECTIVE

To use the Unified Batten Disease Rating Scale (UBDRS) to measure the rate of decline in physical and functional capability domains in patients with juvenile neuronal ceroid lipofuscinosis (JNCL) or Batten disease, a neurodegenerative lysosomal storage disorder. We have evaluated the UBDRS in subjects with JNCL since 2002; during that time, the scale has been refined to improve reliability and validity. Now that therapies are being proposed to prevent, slow, or reverse the course of JNCL, the UBDRS will play an important role in quantitatively assessing clinical outcomes in research trials.

METHODS

We administered the UBDRS to 82 subjects with JNCL genetically confirmed by CLN3 mutational analysis. Forty-four subjects were seen for more than one annual visit. From these data, the rate of physical impairment over time was quantified using multivariate linear regression and repeated-measures analysis.

RESULTS

The UBDRS Physical Impairment subscale shows worsening over time that proceeds at a quantifiable linear rate in the years following initial onset of clinical symptoms. This deterioration correlates with functional capability and is not influenced by CLN3 genotype.

CONCLUSION

The UBDRS is a reliable and valid instrument that measures clinical progression in JNCL. Our data support the use of the UBDRS to quantify the rate of progression of physical impairment in subjects with JNCL in clinical trials.

Mixed chimerism in SCT: conflict or peaceful coexistence?

Stem cell transplants that follow both myeloablative and non-myeloablative conditioning regimens can result in states of mixed chimerism, which can be stable over time. With widespread availability of Y chromosome FISH in sex-mismatched transplantation and DNA-based methodologies for analysis of chimerism in other donor-recipient pairs, further insights have been gained regarding the implications of the mixed chimeric state. In transplants performed for inherited and acquired marrow failure disorders, disease status can be improved with only 10-20% donor cells, and it appears that stable mixed chimerism at that level is an acceptable outcome often leading to a state of tolerance, but an increasing level of recipient cells often precedes graft rejection. In transplants performed for malignant conditions, increasing levels of mixed chimerism may indicate disease relapse, but some cases with stable levels of mixed chimerism have been compatible with prolonged remission states. Understanding when mixed chimerism is an indication of secondary graft failure or impending graft rejection vs a state of tolerance and ongoing propensity for the establishment of a graft-vs-tumor effect is often difficult with currently available technologies and immunologic assays. The ability to understand the implication of mixed chimerism of multiple cell lineages and of varied lymphocyte subsets will remain important areas for future research to best harness the immunologic and other therapeutic benefits of allogeneic transplantation.

A clinical rating scale for Batten disease: Reliable and relevant for clinical trials

BACKGROUND

Batten disease (juvenile neuronal ceroid lipofuscinosis [JNCL]) is an autosomal recessive neurodegenerative disorder characterized by blindness, seizures, and relentless decline in cognitive, motor, and behavioral function. Onset is in the early school years, with progression to death typically by late adolescence. Development of a clinical instrument to quantify severity of illness is a prerequisite to eventual assessment of experimental therapeutic interventions.

OBJECTIVE

To develop a clinical rating instrument to assess motor, behavioral, and functional capability in JNCL.

METHODS

A clinical rating instrument, the Unified Batten Disease Rating Scale (UBDRS), was developed by the authors to assess motor, behavioral, and functional capability in JNCL. Children with verified JNCL were evaluated independently by three neurologists. Intraclass correlation coefficients (ICCs) were used to estimate the interrater reliability for total scores in each domain. Interrater reliability for scale items was assessed with weighted kappa statistics.

RESULTS

Thirty-one children with confirmed JNCL (10 boys, 21 girls) were evaluated. The mean age at symptom onset was 6.1 +/- 1.6 years, and the mean duration of illness was 9.0 +/- 4.4 years. The ICCs for the domains were as follows: motor = 0.83, behavioral = 0.68, and functional capability = 0.85.

CONCLUSIONS

The Unified Batten Disease Rating Scale (UBDRS) is a reliable instrument that effectively tests for neurologic function in blind and demented patients. In its current form, the UBDRS is useful for monitoring the diverse clinical findings seen in Batten disease.

Autoimmunity to glutamic acid decarboxylase in the neurodegenerative disorder Batten disease

The pathogenic mechanisms underlying Batten disease are unclear. Patients uniformly possess autoantibodies against glutamic acid decarboxylase (GAD) that are predominantly reactive with a region of GAD (amino acids 1 to 20) distinct from subjects with autoimmune type 1 diabetes or stiff-person syndrome. Batten patients did not possess autoantibodies against other type 1 diabetes-associated autoantigens and human leukocyte antigen genotypes revealed no specific associations with this disease.

Von Hippel-Lindau disease masquerading as autosomal dominant polycystic kidney disease

The diagnostic confusion in differentiating the various causes of renal cystic diseases in adults is well documented. This confusion can include misclassifications between autosomal dominant polycystic kidney disease (ADPKD) and von Hippel-Lindau disease (VHL). We describe such a case of VHL. A review of the literature and of the patients in our database regarding typical features of each disease, mean age of onset, and frequency of these features was undertaken to provide helpful differentiating features. Pancreatic cysts are one differentiating feature. In VHL, pancreatic cysts can occur in 70% of patients, often are multiple, and rarely may cause exocrine or endocrine insufficiency. Pancreatic islet cell tumors occur. In ADPKD, pancreatic cysts are found in only 9% of patients, usually are single and asymptomatic, generally occur in conjunction with cystic liver disease, and are not found in children or unaffected family members. Pancreatic malignancies do not occur with increased frequency in ADPKD. A different pattern, especially in patients without a strong family history of ADPKD, may be a clue to VHL masquerading as ADPKD. Genetic mutation screening of the VHL gene should be used in these patients.

Is the P25L a "real" VHL mutation?

BACKGROUND

The von Hippel-Lindau (VHL) gene has two translational initiation sites separated by 53 codons. Both proteins have been detected in cells and have equivalent activity. A mutation in the first 53 codons of the open reading frame has no effect on the structure of the smaller protein. As expected, the vast majority of VHL mutations are downstream of the second initiation site and alter both proteins. However, several candidate mutations have been found in the first 53 codons, including a substitution of leucine for proline at position 25 (P25L) of the larger protein.

METHODS AND RESULTS

DNA sequence analysis showed two VHL gene mutations, P25L and P86R, in an individual with a clinical diagnosis of VHL disease. Both mutations have been reported previously. P25L alters only the upstream protein, whereas P86R alters both VHL proteins. Based on the positions of the mutations, P86R is more likely to be pathogenically significant than the P25L mutation. A survey of anonymized DNAs for P25L, using allele-specific PCR, revealed that it is a variant with an allele frequency of approximately 0.5%.

CONCLUSION

P25L is a rare variant of the VHL gene and cannot be considered a cause of VHL disease. However, this work does not prove that P25L is entirely innocuous.

Two distinct phenotypes caused by two different missense mutations in the same codon of the VHL gene

We have identified a family segregating von Hippel-Lindau (VHL) disease with a previously unreported T547A mutation in exon 1 of the VHL gene that causes a Tyr112 to Asn missense alteration in the protein. The mutation was identified by nucleotide sequencing and confirmed by restriction enzyme digestion. The mutation cosegregated with the disease in all five tested affected individuals from the extended family. The family consists of more than 100 at-risk individuals over seven generations. To date, we have identified 13 affected individuals of whom seven have had renal cell carcinoma and one has had a pheochromocytoma. No other case of a neuroendocrine tumor of the pancreas or adrenal gland (pheochromocytoma) was found or recognized retrospectively. Other manifestations in this family include retinal angioma and hemangioblastoma of the central nervous system. We also found the T547A mutation in three asymptomatic members of the family, ages 12, 19, and 20. Another mutation, T547C, which causes Tyr112 to His, has been seen at the same position and has been associated with VHL type 2A (pheochromocytoma, but no renal cell carcinoma) in two families with a total of 22 affected individuals [Chen F, Slife L, Kishida T, Mulvihill J, Tisherman SE, Zbar B, 1996: J Med Genet 33:716-717]. Thus, different amino acid changes at the same position can cause very distinct clinical phenotypes. It will be interesting to elucidate the functional differences that underlie the different phenotypes.

Diminished energy metabolism and enhanced apoptosis in livers of B6C3F1 mice treated with the antihepatocarcinogen rotenone

Rotenone decreases the incidence of hepatocellular carcinoma and lowers rates of hepatocellular proliferation. In an effort to delineate mechanisms involved, the in vivo effect of rotenone on liver mitochondrial metabolism, apoptotic machinery as well as elements of the hepatic signal transduction pathways were investigated. Mitochondria from livers of male B6C3F1 mice fed a standard diet containing 600 ppm rotenone for 7 days were uncoupled or inhibited when succinate or glutamate plus malate were used as the substrate, respectively. These livers also showed a significant increase in apoptosis compared with control livers. Furthermore, rotenone increased the expression of c-myc mRNA to 5-fold of control values within 3 days, an effect which was still observed (3-fold) after 7 days. Levels of p53 mRNA were also increased 3-fold after 1 day, but declined to control levels by 7 days. Rotenone also caused a transient, yet marked increase in liver particulate glyceraldehyde phosphate dehydrogenase (GAPDH) protein expression, while it did not alter the expression of the cytosolic form of the enzyme. Conversely, mRNA of the proto-oncogene H-ras showed a decline of 35% after 3 days of rotenone treatment, and remained diminished for the duration of the experiment. These data suggest that rotenone may act as an anticancer agent by diminishing mitochondrial bioenergetics which prevents basal hepatocyte proliferation and lowers the threshold for liver cells with DNA damage to undergo apoptosis.

Posttransplant lymphoproliferative disorder in pediatric renal transplantation

Of 84 renal transplants performed in our center since 1986, six recipients (7.1%) developed posttransplant lymphoproliferative disorder (PTLD). All received quadruple immunosuppression with Minnesota anti-lymphoblastic globulin or anti-thymocyte globulin, methylprednisolone, cyclosporine, and azathioprine or mycophenolate mofetil. Five were seronegative for Epstein-Barr virus (EBV) when they received their renal transplant. All patients received prophylactic acyclovir treatment postrenal transplant and none developed a cytomegalovirus (CMV) infection. All patients were positive for EBV by serology and polymerase chain reaction at the time of diagnosis of PTLD. Clinical features at presentation included fever (6/6), adenopathy (4/6), hypertrophied adenoids (4/6), liver involvement (2/6), and allograft involvement (2/6), 2-78 months (4/6<6 months) postrenal transplant. Histopathology of PTLD tissue revealed T cell rich/ Hodgkin disease-like B cell PTLD in one patient, polymorphic PTLD in four, and monomorphic (large B cell lymphoma) PTLD in one. Immunophenotyping of the PTLD biopsy specimen revealed predominant T cells in three, mixed B and T cells in two patients, and B cell in one. No aneuploid populations were identified by flow cytometric DNA ploidy assay. DNA from the PTLD tissue revealed weak to moderate IgH gene rearrangement in four of six patients but no T cell receptor beta-chain or c-myc gene rearrangement on Southern blot analysis. The child with monomorphic (large B cell lymphoma) PTLD was clonal with lambda light chain restriction on immunophenotyping. Treatment consisted of reduced immunosuppression and ganciclovir/ acyclovir in all patients. CMV hyperimmune globulin was used as an adjunctive therapy in two patients. Chemotherapy was needed in only one patient. A single rejection episode occurred in two children following reduction in immunosuppression, which reversed following intravenous methylprednisolone therapy. PTLD resolved in all patients and at present all patients are alive with functional grafts 2-54 months post diagnosis. Our experience suggests that reduced immunosuppression and anti-viral treatment is adequate in most cases of PTLD, but chemotherapy and hyperimmune globulin therapy may be beneficial in cases resistant to first-line therapy. Since all but one of our patients were EBV seronegative at the time of transplant, vigilance is especially important for early detection of PTLD in this group of the pediatric renal transplant population.

Simultaneous detection of five mutations in the steroid 21-hydroxylase gene using nested allele-specific amplification

Congenital adrenal hyperplasia due to deficiency of steroid 21-hydroxylase (CYP21) is most frequently due to mutations that arise from the nearby CYP21 pseudogene. The mechanism involves either unequal crossing over, which deletes part of the CYP21 functional gene, or gene conversion which puts a mutation from the pseudogene into the functional gene. We have devised an assay to rapidly screen for five known mutations that are due to gene conversion within an 1,800 bp region of the CYP21 gene--I172N, V281L, Q318X, R356W, and a cluster of mutations in exon 6 (I236N, V237E, M239K). This method is based on a set of nested allele-specific polymerase chain reactions done simultaneously in one tube, for which we suggest the acronym NASA, for nested allele-specific amplification. The assay is capable of detecting the mutations individually as well as all combinations of mutations tested.

Cytokine-mediated stimulation of laminin expression and cell-growth arrest in a human submandibular gland duct-cell line (HSG)

Increased expression of laminin and various cytokines, including interferon-y (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha) has been demonstrated in minor salivary glands from patients with Sjögren's syndrome. Previous reports state that exposure of a human salivary-gland cell line (HSG) to IFN-gamma results in cellular changes similar to those in vivo Sjögren's syndrome. To begin studies of the cause of increased laminin expression in salivary glands in Sjögren's syndrome and laminin's role in the pathological process, the effects of IFN-gamma on laminin expression and growth of HSG cells were examined here. Subconfluent cultures of HSG cells were treated or not with IFN-gamma (1000 units/ml) for 1, 3 or 6 days. Immunoprecipitation showed that the expression of cell-associated laminin was significantly greater in IFN-gamma-treated cells at 3 or 6 days than in untreated cells, while no significant differences in laminin counts precipitated from the media were evident among any of the IFN-gamma-treated or untreated samples. Western blot analysis strongly suggested that this immunoprecipitated product is a dimer of the beta- and gamma-chains of laminin. Intracellular laminin was demonstrated immunocytochemically in a distinct, perinuclear pattern in both cytokine-treated and untreated cells. However, only faint staining for type IV collagen, and no staining for fibronectin were evident in untreated and cytokine-treated cells. An RNase protection assay showed only slight upregulation of the laminin beta-chain mRNA at 3 days, but no significant difference at 6 days of treatment. Taken together, these data suggest enhanced accumulation of a dimer of laminin beta- and gamma-chains in the cytoplasm of cytokine-treated HSG cells. However, mRNA for glyceraldehyde 3-phosphate dehydrogenase was significantly reduced at 6 days of treatment, suggestive of cytokine-mediated metabolic abnormalities. IFN-gamma treatment also resulted in significant reductions in cell numbers over time, in agreement with previous reports. Treatment of HSG cells for 3 days with IFN-gamma (1000 U/ml) and TNF-alpha (20 U/ml) resulted in no significant changes in cell proliferation or laminin protein and/or mRNA species compared to cells treated with IFN-gamma alone. Karyotype analysis of HSG cells revealed human chromosomes with triploid chromosome numbers and rearrangements, characteristic of transformed cells. These data demonstrate that IFN-gamma increases the amount of intracellular laminin beta-gamma dimers while decreasing cell growth. Further studies are required to define an interaction between laminin expression and the growth and viability of HSG cells.

Processed pseudogene from the von Hippel-Lindau disease gene is located on human chromosome 1

The von Hippel-Lindau (VHL) disease gene is a tumor suppressor located at 3p25-26. While amplifying intron 1 of this gene, a smaller-than-expected product was found. This fragment was sequenced and was approximately 78% similar in sequence to the VHL gene and completely lacked sequence from the intron. No stop codons were found in the sequenced region. Using this DNA fragment as a probe for Northern blot hybridization analysis, no evidence was found for expression of a unique RNA. Because of the lack of intron 1 sequence and the likely lack of expression, the new sequence is most probably a part of a VHL processed pseudogene. The putative pseudogene was mapped to human chromosome band 1q12 using the polymerase chain reaction with template DNA from human/rodent somatic cell hybrids, a radiation hybrid panel, and a set of primers that were chosen to be maximally divergent from the genuine VHL gene. The human/rodent somatic cell hybrid DNAs were then used on Southern blots to determine which human bands are from the pseudogene and which are from the functional gene. This knowledge is valuable in interpreting Southern blot evidence of VHL gene abnormalities.

A deletion polymorphism due to Alu-Alu recombination in intron 2 of the retinoblastoma gene: association with human gliomas

The retinoblastoma gene (RB) encodes a tumor suppressor that is inactivated in a number of different types of cancer. We searched for gross alterations of this gene in tumors of the central nervous system by using Southern blot hybridization. A common alteration was found in several tumors and was mapped to the region around exon 2. Nucleotide sequencing showed that the alteration was caused by a 799-bp deletion in intron 2 of the RB gene and was probably due to homologous recombination between two Alu repeats. Deletions of this type have not been found previously in the RB gene. The deletion turned out to be a polymorphism with an allele frequency estimated at 2.2% in 185 patients without cancer. The deletion was found in five of 48 patients with brain tumors (allele frequency of 5.2%). This difference is not statistically significant (P = 0.149, Fisher's exact test). Confining the analysis only to glioma brain tumors revealed a statistically significant difference compared with the cancer-free patient controls (P = 0.027, Fisher's exact test). Further study is needed to determine if the deletion is a weak brain cancer-predisposing mutation or a harmless polymorphism. Finding this mutation in a tumor and the germline DNA of a retinoblastoma patient could lead to incorrect estimation of the heritability of a tumor.

Use of DNA polymorphisms to monitor engraftment after allogeneic bone marrow transplantation

Bone marrow transplantation (BMT) has been established as a life-saving procedure in hematologic malignancies and bone marrow failure syndromes, and it may be valuable in other types of neoplastic disease. DNA polymorphisms are used to monitor engraftment after transplantation from a related or unrelated donor. DNA polymorphisms are not useful after autologous BMT or if the donor is an identical twin. The most valuable polymorphism for this purpose is caused by variation in certain repeated sequences that are known as variable number of tandem repeats (VNTR). The VNTRs are valuable because they each have several alleles increasing the probability of finding one that is useful in a given case. This method can be used to sensitively detect small amounts of residual recipient hematopoiesis. To accomplish this the laboratory must first find a polymorphic allele that is unique in the recipient. Detection of the unique allele in peripheral blood or bone marrow after BMT is tantamount to finding recipient hematopoiesis. The presence of both donor and recipient hematopoiesis can result in a state of stable mixed chimerism and not necessarily presage a relapse after BMT for leukemia; however, the presence of residual recipient cells in some cases may indicate an increased probability of relapse, particularly in chronic myelogenous leukemia.

Influence of protein tyrosine phosphorylation on the expression of the c-myc oncogene in cancer of the large bowel

We tested the potential impact of tyrosine phosphorylation on the expression of the c-myc gene in two colon cancer cell lines, HCT8 and SW837. We found that the protein tyrosine kinase inhibitor genistein causes a decrease in the abundance of c-myc RNA and an inhibition of proliferation with a similar dose response. Geldanamycin, a mechanistically different tyrosine kinase inhibitor, also causes a decrease in both the expression of c-myc RNA and proliferation. Genistein has also been found to inhibit topoisomerase II, but the topoisomerase II inhibitor novobiocin did not lower the expression of c-myc. The most likely interpretation is that inhibition of protein tyrosine kinase activity caused a decrease in c-myc expression in these cells. The impact of tyrosine phosphorylation on the expression of the c-myc gene is further supported by the finding that inhibition of phosphotyrosine phosphatase using orthovanadate causes an increase in the level of c-myc RNA. The effect of genistein on HCT8 cells is not dependent on the synthesis of new protein and does not involve an alteration in the stability of the message. Analysis of transcription in the c-myc gene reveals a more complicated picture with a decrease in initiation and an increase in elongation but no net change in transcription. We speculate that the genistein induced reduction in myc expression is the result of a posttranscriptional intranuclear event(s).

Clonal, nonconstitutional rearrangements of the MLL gene in infant twins with acute lymphoblastic leukemia: in utero chromosome rearrangement of 11q23

Rearrangements of chromosome band 11q23 are common in infant leukemias, comprising more than 70% of the observed chromosome abnormalities in children less than 1 year of age. The MLL gene, which is located at the 11q23 breakpoint in infant, childhood, and adult acute leukemias, has been cloned and has homology to the Drosophila trithorax gene. The breakpoints in MLL are restricted to an 8.3-kilobase pair (kb) region of the gene that is involved in translocations with as many as 29 other chromosomal regions in a number of phenotypically distinct acute leukemias. We have detected an identical, clonal, nonconstitutional rearrangement of the MLL gene in peripheral blood cells from a pair of female infants twins with acute lymphoblastic leukemia (ALL) and a t(11;19)(q23;p13.3). The detection of nonidentical IGH rearrangements suggests that the MLL rearrangement took place in a B-cell precursor or hematopoietic stem cell in one twin which was transferred in utero to the other fetus resulting in ALL with an identical aneuploid karyotype in both infants. We speculate that the other MLL-related infant leukemias may also develop in utero, and that the rearrangements may occur consistently in stem cells or early precursor cells, accounting for the frequency of mixed-lineage leukemia in infants.

The effects of dystrophin gene mutations on the ERG in mice and humans

PURPOSE

The authors' earlier findings of a negative electroretinogram (ERG) in a boy with Duchenne muscular dystrophy (DMD) led them to investigate dystrophin gene deletions and ERGs in five boys with DMD. The authors wanted to determined whether there were similar ERG findings in an animal model for DMD, the mdx mouse.

METHODS

Ganzfeld ERGs were recorded in five boys with DMD after a complete ophthalmic examination. The dystrophin gene was analyzed by Southern blot hybridization. ERGs were recorded in anesthetized mdx and control mice with a modified Grass photostimulator (Grass Instrument Company, Quincy, MA).

RESULTS

Ophthalmic examinations in all five boys had normal findings, yet an abnormal negative ERG was recorded for each subject. The subjects' gene deletions were variable, ranging from large deletions to no detectable deletions. The ERGs of the mdx mice were normal and did not differ significantly from those of the control mice.

CONCLUSIONS

The authors believe the unique ERG recorded for the human subjects is a manifestation of DMD associated with defects at the dystrophin gene locus and represents a new clinical entity. The ERG of the mdx mouse may be spared for several reasons, including milder effects of the mouse gene defect, differences in muscle and retinal gene product, or species differences in the biochemical role of dystrophin. The ERG shows promise of becoming a noninvasive diagnostic tool for DMD and its milder allelic forms.

Sodium butyrate causes an increase in the block to transcriptional elongation in the c-myc gene in SW837 rectal carcinoma cells

Elevated expression of the c-myc oncogene is a frequent finding in tumors and cell lines derived from carcinomas of the colon and rectum. In a previous study we demonstrated that the differentiation agent sodium butyrate causes a rapid reduction in the expression of c-myc RNA in the rectal carcinoma cell line SW837. This effect was blocked by inhibitors of protein synthesis, suggesting that butyrate causes the induction of an activity that has a negative effect on c-myc expression. In the present work we demonstrate that the rapid decrease in the level of c-myc RNA, upon treatment of SW837 cells with 2 mM butyrate, is followed by a slower decrease in the level of p53 RNA and an increase in the RNA levels for fibronectin and a placental type alkaline phosphatase. Using in vitro elongation of nascent transcripts to measure transcription and actinomycin D chase experiments to measure RNA stability, we show that the reduction in expression of c-myc RNA is due to an increase in the block to transcriptional elongation, rather than a decrease in transcriptional initiation or an increase in degradation of the RNA. We conclude that sodium butyrate induces an activity that increases the transcriptional block in SW837 cells, and that regulation of transcriptional elongation is an important mechanism for regulating c-myc expression in this cell type. A shift in relative usage of the two major promoters in the c-myc gene accompanies the reduction in expression. The potential significance of this finding with respect to transcriptional elongation is discussed. Mutations in the exon 1/intron 1 boundary region of the c-myc gene cause an increase in transcriptional elongation in Burkitt lymphoma. We sequenced this region in a series of cell lines derived from colorectal carcinomas, all of which had an elevated level of c-myc expression, to determine if a similar mutational mechanism is at work in this disease. All of the lines examined had a normal c-myc DNA sequence, suggesting that the deregulation of c-myc expression in colon cancer is not due to a cis mutation in this region.

Hypermutation of the MYC gene in diffuse large cell lymphomas with translocations involving band 8q24

The sequence of the exon 1/intron 1 boundary region of the MYC gene was determined in two diffuse large cell lymphomas (DLCL), one with t(8;14) (q24;q32) and the other with t(8;22) (q24;q11). Both tumors had multiple mutations in this region. Also, both tumors had mutations in the protein binding site in intron 1, which is a frequent target for mutational inactivation in endemic Burkitt's lymphoma (eBL). The translocations at 8q24, and multiple mutations in the exon 1/intron 1 boundary region, are reminiscent of similar findings in eBL. The same underlying oncogenic event that occurs in most eBLs is thus found in some DLCLs.

Extended electrophoresis resolves the dystrophin gene 5.2-kbp cDMD4-5a/HindIII fragment into two bands

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Bilateral choroidal neonatal neuroblastoma

We treated a bilateral, well-differentiated neuroblastoma of the choroid in a patient who had congenital abdominal neuroblastoma. Although orbital metastasis of neuroblastoma is common, intraocular metastasis is not. In our patient, there was no amplification of the N-myc oncogene in the tumor of either eye. This is consistent with early-stage primary neuroblastoma. Histologically, the tumors were identical in each eye and well differentiated with Homer Wright rosettes; most neuroblastoma metastases have few rosettes and are composed of more undifferentiated, anaplastic cells. We believe that our patient had bilateral primary tumors and not metastatic tumors.

Somatic mutation and transcriptional deregulation of myc in endemic Burkitt's lymphoma disease: heptamer-nonamer recognition mistakes?

We examined the structure and expression of the myc protooncogene in DNA extracted from a primary (uncultured) endemic Burkitt's lymphoma sample designated eBL3. Dot and Northern (RNA) blot analyses demonstrated extreme levels of myc RNA in the eBL3 sample. Nearly complete sequence data of the altered myc locus isolated from eBL3 DNA demonstrated extensive mutations (duplications, insertions, and deletions) in critical myc regulatory regions. Taken together, the data support the idea that myc transcriptional deregulation in Burkitt's lymphoma disease may be a consequence of the position and number of mutations produced within and around the myc locus. Furthermore, the myc exon-1-intron-1 hypermutable PvuII site is part of a potential heptamer-nonamer recognition sequence, suggesting a mechanism for mutation in endemic Burkitt's lymphoma disease.

Evidence for a labile intermediate in the butyrate induced reduction of the level of c-myc RNA in SW837 rectal carcinoma cells

We have found that the differentiation inducer butyric acid causes the synthesis of a cellular protein(s) that mediates a rapid decline in the level of myc RNA in SW837, a cell line derived from a human adenocarcinoma of the rectum. This effect was dose-dependent and was maximal at 1 mM. Among the short chain fatty acids tested, butyric acid was found to be the most potent. Valeric acid was less effective, and acetic, propionic, isobutyric, and caproic acids did not cause a significant change in myc RNA level. Dimethylsulfoxide, another inducer of differentiation, also caused a marked diminution of myc RNA level, but was only tested at a relatively high dose (282 mM). The reduction in myc RNA level caused by butyrate was blocked by inhibitors of protein synthesis, and was rapidly reversed by removing the inducer. This suggests that butyrate causes the induction of a labile activity that has a negative effect on myc RNA abundance.

The role of the oncogene c-myc in sporadic large bowel cancer and familial polyposis coli

The human myc gene is homologous to the v-myc gene, which was discovered in the avian oncogenic retrovirus MC29. Abnormally high expression of the cellular oncogenes is suspected to be involved in nonviral carcinogenesis. This article reviews the evidence that elevated expression of the human myc gene is involved in sporadic colon carcinoma and familial polyposis coli. The abundance of myc RNA and protein is frequently higher in colorectal cancer than in normal mucosa. The mechanism of this altered expression is obscure because the structure and quantity of myc DNA are very rarely disturbed. The COLO320 cell line is discussed as one unusual example of myc DNA rearrangement and amplification. There is a correlation between tumor-specific elevated myc RNA level and location in the bowel; tumors distal to the transverse colon are more likely to have elevated myc expression. The site distribution of unselected colorectal malignancies with an elevated myc RNA level is similar to the site distribution of familial polyposis coli tumors. With this observation it is suggested that elevated myc RNA may be a marker of a distinct type of colorectal cancer that involves the same genetic events as precede familial polyposis coli cancer.

Enhanced expression of the c-myc gene in bovine leukemia virus-induced bovine tumors

We have detected elevated levels of c-myc gene expression in neoplastic cells from all seven bovine leukemia virus (BLV)-induced bovine tumors examined, but not in BLV-infected, nonneoplastic lymphoid cells. No rearrangement or amplification of the c-myc gene could be demonstrated in any of the BLV-induced tumors. Furthermore, BLV proviral DNA was found to have no preferred site of integration in these tumors. The possible mechanisms of enhanced expression of the c-myc gene in BLV-induced tumors have been discussed.

Evidence that c-myc expression defines two genetically distinct forms of colorectal adenocarcinoma

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Deregulation of c-myc gene expression in human colon carcinoma is not accompanied by amplification or rearrangement of the gene

The structure and expression of the c-myc oncogene were examined in 29 primary human colon adenocarcinomas. Dot blot hybridization of total RNA showed that 21 tumors (72%) had considerably elevated expression of c-myc (5- to 40-fold) relative to normal colonic mucosa. These data were corroborated by Northern blots of polyadenylated RNA, which showed a 2.3-kilobase transcript. Southern analysis of the c-myc locus in these tumors indicated the absence of amplification or DNA rearrangement in a 35-kilobase region encompassing the gene. In a parallel study, elevated expression of c-myc without amplification or DNA rearrangement was also observed in three of six colon carcinoma cell lines examined; in addition, unlike a normal colon cell line control, these three cell lines exhibited constitutive, high-level expression of the gene during their growth in cultures. These results indicate that elevated expression of the c-myc oncogene occurs frequently in primary human colon carcinomas and that the mechanism involved in the regulation of c-myc expression is altered in tumor-derived cell lines.

Structure and expression of the oncogene c-myc in fresh tumor material from patients with hematopoietic malignancies

c-myc is the cellular gene homologous to the transforming sequence of MC29, an acute avian retrovirus. The human c-myc gene was cloned and used to study the structure and expression of c-myc in a variety of human hematopoietic malignancies. In a careful study of 106 patients, c-myc RNA was found to be expressed at elevated levels in tumor cells of 17 leukemia patients and five lymphoma patients. The c-myc gene was found to be rearranged in two lymphomas, an African Burkitt's lymphoma and a non-Hodgkins lymphoma in leukemic phase. The Burkitt's rearrangement involved the insertion of new DNA sequences upstream from the c-myc 5' coding region, presumably replacing the normal c-myc transcriptional promoter. None of the other 104 patients, including 20 with elevated myc expression, exhibited any evidence of a genetic rearrangement involving the c-myc gene. Our results show that there is a subset of hematopoietic malignancies characterized by elevated expression of c-myc. This elevated expression in most cases is not due to obvious genetic changes (rearrangement, amplification) at the c-myc locus nor to chromosomal translocations in the vicinity of this gene.

The role of promoter insertion in the induction of neoplasia

It has been shown in several retroviral systems that proviral DNA can integrate into the host genome in such a manner that expression of a nearby oncogene is enhanced. This enhancement results from either a direct promotion of transcription from a strong promoter within the proviral 3' LTR or from less well defined activation in which sequences known as 'enhancers' mediate an increase in the transcription of nearby genes. As a result of this observation, potential oncogenes can now be found by identifying genes whose activity is modulated by the nearby insertion of transcriptional activating elements during oncogenesis. It has also been shown that the genome of a retroviral-like IAP can similarly become integrated adjacent to an oncogene and produce an increase in transcription of that gene. Other examples of possible nonviral promoter insertion events that take place in the oncogenesis of the human Burkitt's lymphoma are discussed elsewhere in this volume.

Regulation of myc gene expression in HL-60 leukaemia cells by a vitamin D metabolite

HL-60, a cell line established from a patient with promyelocytic leukaemia, responds to a variety of inducing agents by ceasing division and acquiring some of the characteristics of either granulocytes or monocytes. Among the agents so far tested, only a comparative few occur naturally in vertebrates and would appear to have significant clinical potential in the treatment of leukaemic patients. One of the most promising of these is the dihydroxymetabolite of vitamin D3, 1,25(OH)2D3. This compound circulates in normal man and has a major role in calcium homeostasis. Moreover, it has recently been reported that 1,25(OH)2D3 increases the survival time of mice injected with myeloid leukaemia cells. We and McCarthy et al. have previously shown that HL-60 cells respond to near physiological levels of 1,25(OH)2D3 by rapidly acquiring a number of monocyte-like features. Here we document that these phenotypic changes are preceded by a marked decrement in the expression of the c-myc oncogene. In fact, the diminution in the level of c-myc mRNA parallels the dose dependency and metabolite specificity shown by the various other indicators of phenotypic change. In addition, we demonstrate that removal of vitamin D3, after the onset of maturational change, results in the reappearance of elevated myc mRNA levels. We believe this to be the first demonstration of a sequential relationship between the application of an exogenous inducing agent, a reduction in myc mRNA levels and the development of characteristics associated with normal cell maturation.

Mononucleotide and dinucleotide frequencies, and codon usage in poliovirion RNA

The polio type 1 (Mahoney) RNA sequence (1) has been analyzed in terms of the distribution of its mononucleotides, dinucleotides and trinucleotides (codons). The distribution of adenosine in the sequence is nonuniform, being lower at the 5' end and higher at the 3' end. The dinucleotide CG is relatively rare and the dinucleotides UG and CA are relatively more common than expected. Codon usage is decidedly nonrandom. Codons containing CG are avoided and those ending in adenosine are favored. The asymmetric use of mononucleotides, dinucleotides and codons in polio RNA is unexplained at the present time although the lowered CG frequency may be the result of a DNA origin for polio RNA.

Molecular cloning of the genome of poliovirus type 1

Poliovirus cDNA.RNA hybrids were prepared from the Mahoney strain of poliovirus type 1 by using reverse transcriptase (RNA-dependent DNA nucleotidyltransferase) and cloned in the Escherichia coli plasmid pBR322. Bacteria colonies carrying recombinant plasmids were selected by in situ hybridization with virus-specific RNase T1-resistant oligonucleotides. Analysis of the cDNA inserts by restriction mapping and electron microscopy showed that the cloned cDNAs, the longest of which was 3.2 kilobase pairs, originated from various parts of the viral RNA, covering at least 99% of the genome length. Due to overlapping of the clones, the restriction map of the poliovirus genome could be reconstructed. The complete 5' end of the genome was successfully cloned in at least one of the recombinant plasmids, pPV1-366.

Primary structure, gene organization and polypeptide expression of poliovirus RNA

The primary structure of the poliovirus genome has been determined. The RNA molecule is 7,433 nucleotides long, polyadenylated at the 3' terminus, and covalently linked to a small protein (VPg) at the 5' terminus. An open reading frame of 2,207 consecutive triplets spans over 89% of the nucleotide sequence and codes for the viral polyprotein NCVPOO. Twelve viral polypeptides have been mapped by amino acid sequence analysis and were found to be proteolytic cleavage products of the polyprotein, cleavages occurring predominantly at Gln-Gly pairs.

Poliovirus replication proteins: RNA sequence encoding P3-1b and the sites of proteolytic processing

A partial amino-terminal amino acid sequence of each of the major proteins encoded by the replicase region (P3) of the poliovirus genome has been determined. A comparison of this sequence information with the amino acid sequence predicted from the RNA sequence that has been determined for the 3' region of the poliovirus genome has allowed us to locate precisely the proteolytic cleavage sites at which the initial polyprotein is processed to create the poliovirus products P3-1b (NCVP1b), P3-2 (NCVP2), P3-4b (NCVP4b), and P3-7c (NCVP7c). For each of these products, as well as for the small genome-linked protein VPg, proteolytic cleavage occurs between a glutamine and a glycine residue to create the amino terminus of each protein. This result suggests that a single proteinase may be responsible for all of these cleavages. The sequence data also allow the precise positioning of the genome-linked protein VPg within the precursor P3-1b just proximal to the amino terminus of polypeptide P3-2.

The genome-linked protein of picornaviruses. VII. Genetic mapping of poliovirus VPg by protein and RNA sequence studies

The poliovirus genome-linked protein (VPg) has been subjected to radiochemical microsequence analysis. Sequence studies of virion RNA by a modification of Sanger's dideoxy method have revealed a base sequence corresponding to the amino acid analysis. This result proves that VPg is virus-encoded. The RNA sequence has allowed us to predict the total amino acid sequence of VPg and part of its precursor. VPg is, at most, 27 amino acids long. It maps within the 3' terminal segment of the viral genome that encodes the precursor polypeptide NCVP1b for the virus-specific RNA polymerase NCVP4.

O4-(5'-uridylyl)tyrosine is the bond between the genome-linked protein and the RNA of poliovirus

Virion RNA of poliovirus type 1 has been analyzed for the linkage between genome-protein VPg and the polyribonucleotide chain. Hydrolysis of the linkage with acid or alkali and enzymatic degradation lead to the conclusion that the bond is neither a phosphodiester such as nucleotidyl-(P-O)-serine (or threonine) nor a phosphoramidate such as nucleotidyl-(P-N)-amino acid. VPg-RNA can be iodinated by the Bolton and Hunter reagent [iodinated 3-(4-hydroxyphenyl)propionic acid N-hydroxysuccinimide ester] but not by the chloramine-T or lactoperoxidase procedures, an observation suggesting that VPg does not contain accessible tyrosine. However, VPg can be labeled with [3H]tyrosine in vivo. Hydrolysis of VPg-[32P]pUp with 5.6 M HCl at 110 degrees yielded 32P-labeled O4-(3'-phospho-5'-uridylyl)tyrosine that could be cleaved with micrococcal nuclease to O4-[32P]phosphotyrosine and uridine 3'-[32P]phosphate. These data establish that VPg is linked to the poliovirus genome by a bond between the O4 of tyrosine and the 5'-P atom of the terminal uridylic acid residue. The 5' end of polio genome RNA can now be described as VPg(Tyr-O)-pU-U-A-A-A-A-C-A-G.