Analysis of colorectal cancer by comparative genomic hybridization: evidence for induction of the metastatic phenotype by loss of tumor suppressor genes.

Current models suggest that colon cancer initiation and progression are secondary to both the activation of oncogenes and the deletion of tumor suppressor genes. The role of each, however, is still poorly understood, particularly with regard to the induction of metastasis. We hypothesized that genetic differences exist between tumors that metastasize distantly and those that do not, and that oncogenes and tumor suppressor genes participate equally in this process. To address this hypothesis, human tumor specimens from localized [tumor-node-metastasis (TNM) stage I-III] and primary colon cancers (n = 10) were directly compared with metastatic (TNM stage IV) lesions (n = 10) using comparative genomic hybridization analysis. Although several alterations were shared equally between primary tumors and metastases (+7q, +19q, and +20q), two patterns of distinguishing alterations were observed: (a) alterations that were more extensive in liver metastases than in primary tumors (+8q, +13q, -4p, -8p, -15q, -17p, -18q, -21q, and -22q); and (b) alterations that were unique to metastatic lesions (-9q, -11q, and -17q). Overall, genetic losses were more common than gains, and, more importantly, the number of losses/tumor was significantly higher for metastases than for primary tumors (9.3 + 1.3 versus 4.1 + 0.7; P = 0.00062, Wilcoxon's rank-sum test). The distinct predominance of genetic losses in the metastatic lesions when compared with the primary localized tumors provides evidence that the metastatic phenotype is induced by the deletion of tumor suppressor genes and permits the construction of physical maps targeting regions where novel tumor suppressor genes are likely to exist.

Complex chromosome rearrangement with ankyloblepharon filiforme adnatum.

A Caucasian boy with a de novo complex chromosome rearrangement owing to six chromosome breaks was small for gestation with microcephaly, complex heart defect, hypotonia, left auricular pit, simian creases, and ankyloblepharon filiforme adnatum. The rearrangement included two translocation, t(15;21) (q22;q22) and t(3;11)(q21;q11), with the derivative 3 showing in addition pericentric inversion (p11q11) and interstitial deletion (q11q21). Based on parental satellite polymorphisms of chromosomes 15 and 21, the paternal gamete appeared to be the source of the chromosome rearrangement. There was no evidence of mitotic chromosome instability. A review of 36 reported patients with complex chromosome rearrangements secondary to more than four breaks indicates that complex chromosome rearrangements are compatible with gamete survival, zygote formation, and postnatal life. The latter is usually compromised by structural defects, growth retardation, and often mental retardation.

Cleft palate and complex chromosome rearrangements.

Two of three unrelated children with de novo congenital complex chromosome rearrangements (CCR) with more than four chromosome breaks had cleft lip and palate as one of several congenital anomalies. In patient 1, unilateral complete cleft of the primary and secondary palates accompanied severe ectrodactyly, bilateral posterior choanal atresia and several minor congenital anomalies. Karyotypes of peripheral lymphocytes and skin fibroblasts showed five derivative chromosomes with six break points. There were two translocations, t(2;5), t(3;11) and an interstitial deletion, del(13)(q12q14). Patient 2 had a bilateral complete cleft of the lip and palate, in addition to slow pre- and postnatal growth and minor congenital anomalies. Peripheral lymphocytes and palatal mucosa fibroblasts karyotypes showed five derivative chromosomes with six break points. A partial deletion of 10p, two translocations, t(2;3), t(7;18) and an inversion of the derivative chromosome 2 were present. In both patients, a "major catastrophe" of unknown etiology in one of the parental gametes appeared to be the event leading to the stable CCR without evidence of persistent chromosome instability. All four parents had normal karyotypes. The presence of palatal clefts in these patients indicates that dysmorphologists and pediatricians have to consider CCR whenever taking care of a patient with cleft palate, particularly if additional anomalies, no matter how subtle, are present. The detection and interpretation of the latter anomalies are essential for the diagnosis and management of these patients. Accurate cytogenetic diagnosis determines the short- and long-term prognosis and facilitates genetic counseling in regard to life-span, quality of life and reproductive plans of patients and parents.

Lowe oculocerebrorenal syndrome in a female with a balanced X;20 translocation: mapping of the X chromosome breakpoint.

A Hispanic girl with Lowe oculocerebrorenal syndrome (OCRL), an X-linked recessive condition characterized by cataracts, glaucoma, mental retardation, and proteinuria, is reported. A balanced X;20 chromosomal translocation with the X chromosome breakpoint at q26.1 was found with high-resolution trypsin-Giemsa banding. Somatic cell hybridization was used to separate the X chromosome derivative and the chromosome 20 derivative in order to position, with respect to the translocation breakpoint, several DNA loci that are linked to the Lowe syndrome locus (Xq24-q26). DXS10 and DXS53 were found to be distal to the breakpoint, whereas DXS37 and DXS42 were located proximal to it. These studies suggest that the OCRL locus lies in the region between these probes. The translocation chromosome originated from an unaffected male without a visible translocation, indicating that the most likely cause of OCRL in this patient is the de novo translocation that disrupted the OCRL locus.

Argyrophilic nucleolar organizer regions in Wilms' tumors and related lesions: a histologic and chromosomal correlation.

The argyrophilic nucleolar organizer regions (AgNORs) have been extensively investigated in different neoplasms, and their increased number has been frequently linked to aggressive tumor behavior. To evaluate this association, 22 specimens from 21 patients with Wilms' tumors and related lesions were stained by the AgNOR silver-staining technique in formalin-fixed, paraffin-embedded tissue. The aim of the study was to assess the significance of AgNOR count independently or in relation to histology in predicting the behavior of these neoplasms. Eleven nonneoplastic pediatric kidneys were used as controls. The controls had a range of 1.55 to 2.26 AgNOR/nucleus with a mean +/- SD of 1.91 +/- 0.22. The tumors showed a range of 1.25 to 2.86 AgNOR/nucleus with a mean +/- SD of 2.10 +/- 0.38 with obvious overlap between tumors and controls. The two unfavorable histology Wilms' tumors and the malignant rhabdoid tumor showed no increase in the number of AgNOR (1.66, 2.04, and 2.05, respectively). We further quantitated the nucleolar organizer regions (NOR) in metaphase spreads of three of the neoplasms, compared those with the patients' peripheral blood, and showed no difference in NOR numbers except for an occasional decrease in G-group NORs in the tumor cells. Tumors that had metaphase NOR counts of 6 to 9/nucleus had a mean interphase AgNOR count of less than 2.5. These results suggest that quantitative analysis of AgNORs in Wilms' tumors and related lesions is not a reliable predictor of aggressive tumor behavior. The discrepancy between metaphase and interphase NOR counts indicates that AgNOR counts are merely the reflection of the spatial arrangement of NOR-bearing chromosomes.

Trisomy 3p23----pter and monosomy 11q23----qter in an infant with two translocation carrier parents.

A newborn male infant with multiple congenital abnormalities was found to be trisomic for 3p23----pter and monosomic for 11q23----qter. His parents were both carriers of a balanced reciprocal translocation. Considerable overlap in phenotype-karyotype correlations was found between the two chromosomal syndromes in the patient.

Monosomy, trisomy, fragile sites, and rearrangements of chromosome no. 1 in a mentally retarded male with multiple congenital anomalies.

A 17-year-old male was referred for evaluation because of short stature and severe mental retardation. Major clinical findings included microphthalmia, micrognathia, low-set ears, a prominent beaked nose, clubbing of digits, and premature graying of hair. Cytogenetic analysis revealed a 45,XY,-1/46,XY/47,XY,+1 mosaicism in lymphocytic culture, a 45,XY,-1/46,XY mosaicism in skin fibroblasts, and fra(1p) sites in 2% of the metaphases from lymphocyte, fibroblast and bone marrow cultures. Post-zygotic non-disjunction causing this mosaicism is believed to be responsible for the patient's phenotype.

Ultrasound identification of apparently normal male genitalia in a 46,X,+mar fetus.

A level II ultrasound examination revealed a scrotum and penis in a fetus with a 46,X,+mar chromosome complement. The marker was subsequently considered to be a del(Y)(q11). A phenotypically normal male infant was born. Detailed ultrasound examination of similar cases for visualisation of the genitalia is recommended.

Complex chromosome rearrangements and congenital anomalies.

Congenital complex chromosome rearrangements (CCR) compatible with life are rare in man. Thus patients with CCR usually present considerable diagnostic difficulties both clinically and cytogenetically. We studied a 12-year-old mentally retarded male with minor congenital anomalies as described below and his first-degree relatives. The propositus had an unbalanced karyotype with eight break points and seven derivative chromosomes; two deletions, del(6) (q25----qter) and del(14) (q31----qter), and four translocations, t(2;11), t(5;15), t(6;11), t(6;20) were present. Parental chromosomes were normal; however, the mother had a few metaphases with abnormal chromosomes suggestive of chromosome instability. These findings and a review of reported patients with CCR are presented with regard to speculations about etiology, pathogenesis, phenotypic expression, and prognosis. Physicians should be aware of CCR and broader indications for cytogenetic studies appear warranted in view of these data.