ANTICANCER RESEARCH 27: 2141-2154 (2007) Review Does Homeobox-related "Positional" Genomic Information Contribute to Implantation of Metastatic Cancer Cells at Non-random Sites? K.M. ANDERSON1, M. DARWEESH2, A. JAJAH2, P. TSUI1, P. GUINAN1 and M. RUBENSTEIN1 1Division of Cell Biology, Hektoen Medical Research Institute LLC, 627 S. Wood Street, Chicago; 2Division of Medical Oncology, Cook County Hospital, 1825 W. Harrison, Chicago, IL 60612, U.S.A. Abstract. Reasons for the lodgment of metastases from Do HOX or Homeobox-related Genes Contribute several types of solid cancer at apparently non-random sites Directly or Indirectly to Homing and Nidation of have not been established. Recently, a group of genes expressed Metastatic Cancer Cells? in human fibroblasts obtained from different anatomic locations was implicated in "positional" genomic information. Two basic models have been proposed to account for the Essentially, a Cartesian coordinate system identifying differential gene expression profile of fibroblasts located at fibroblasts originally resident at anterior or more posterior, different anatomical sites (1). In one model emphasizing the proximal or distal and dermal or non-dermal (heart, lung, etc.) persistence of embryonic "positioning", considerable innate locations was proposed. The determinants used for these homology in profiles of cognate cells located at comparable identifications included HOX genes, central to embryonic anatomical sites is predicted. In the second model, local segmental development, some of which are expressed in influences including epithelial-mesenchymal interactions are differentiated, post-embryonic cells. To the extent that HOX or considered to determine possible similarity. Of course, other homeobox genes are expressed in ectodermal, blending of these models might occur. mesodermal or endodermally-derived, malignantly transformed Rinn et al. (2) have provided further evidence for the former cells, they might contribute "positional" information to nidation hypothesis, in which the expression profile of fibroblasts at of specific malignant clones at non-random sites. As similar anatomical sites share features that identify the site understood in the past, interdiction of HOX or homeobox- from which they were harvested. Microarray gene expression related gene expression might reduce the probability of cancer profiles from 47 cultured human fibroblast samples, cell implantation or alter their destinations in complex ways. representing 43 different anatomical sites provided by 20 Ideally, by interfering with HOX or other homeobox gene- different donors were compared by a series of unsupervised related expression of antigenic determinants potentially and supervised hierarchical clustering studies. With successive contributing to their "homing" and nidation, reduced refinements, a group of 337 genes that included augmented implantation of circulating cancer cells could render them expression of functions associated with pattern and more susceptible to systemic chemotherapy or immunotherapy, intercellular matrix formation, cell to cell signaling and that as demonstrated in mice. Furthermore, HOX or other included a number of HOX genes, was identified. With this homeobox genes or their products could provide novel intra- information, the original anatomical sites of the cultured or extracellular targets for therapy. fibroblasts could be distinguished as to anterior or posterior (caudal), proximal or distal and dermal or non-dermal (heart, lungs, prostate, intestines) location of the sampling. In view of their importance in embryonic segmentation, Correspondence to: K.M. Anderson, Division of Cell Biology, the HOX genes were further studied. Forty-two Hektoen Medical Research Institute LLC, 627 S. Wood Street, homeodomain genes that included 12 HOX genes reflected Chicago, IL 60612, U.S.A. Tel: +1 312 864 0564, Fax: +1 312 864 the identification of fibroblasts according to their original 9569, e-mail: [email protected] location, suggesting a HOX "code" for positional Key Words: Homeobox-related genes, metastasis, metastatic sites, identification. The genes expressed included HOXB2, B4, review. B5, B6, B7 and B9, limited to the trunk and non-dermal 0250-7005/2007 $2.00+.40 2141 ANTICANCER RESEARCH 27: 2141-2154 (2007) samples, while HOXD4 and D8 were expressed in trunk and malignantly transformed or not, are subject to "positional" proximal leg samples. HOXD4 was found by controls comparable to those of fibroblasts. There is immunoblotting in fetal lung fibroblasts but not in evidence that myogenic (9) and endothelial (10) cells exhibit fibroblasts from the foreskin. HOXA13 was expressed only some features of positioning, but additional evidence for in fibroblasts from distal sites, including the fingers, "instructional" contributions, especially during early foreskin, feet and prostate. Confirming studies were development between discrete epithelial-mesenchymal performed with RT-PCR of several HOX genes and interactions contributing to localization and induction of immunoblotting of HOXA13 from in vivo samples. Thus, specific cell types at different anatomic sites provides an fibroblasts from cognate sampling sites expressed greater alternate or additional explanation for these events (11). transcriptional similarity than fibroblasts from anatomically distant sites. These results were considered consistent with a Homeodomain and Homeobox Gene-related "positional" form of instruction of adult fibroblasts related Antigenic Determinants to embryonic HOX gene expression and maintained by epigenetic mechanisms. Dorsal to ventral differences in In view of the many excellent reviews available (5, 12-21a,b), fibroblast gene expression present during embryonic we will not attempt to review the topic in detail, but a few development were not found, implying that epithelial general comments could be useful. In mice and men, the dominance dictated dorsal to ventral fates in the limbs. HOX family includes 39 genes in 4 linkage groups (A Details of the anterio-posterior axis are complicated. through D) including some of the 13 homology (paralogue) Expression of the engrailed (en) gene in the posterior groups, from nine to eleven members in each linkage group compartment mandates (P) identity; its absence yields (A) located on 4 different chromosomes, in order, A through D, identity in the anterior regions (3). The en gene can repress numbers 7, 17, 12 and 2. Human paralogue groups 1-8 are or activate target genes. P cells expressing the EN protein related to the antennapedia (Antp) and groups 9-13 with are associated with hedghog (hh) activation. To achieve A-P abdominal-B (abd-B) of Home-C Drosophilia genes. A larger identities, en, a factor ci and hh are correctly expressed in group of non-HOX homeobox genes, of which HOX genes the required compartments and finally the Polycomb group are a subset, are more variable and located at diverse loci. (PcG) genes maintain en repression in all embryonic Class I HOX genes include 180 base pair homeobox DNA segments, for example repressed hh in anterior segments. sequences, with a "signature" – ATTA – (and related -AT-) Left-right asymmetry across apparent boundaries has sequence(s), coding for 60 amino acid protein homeodomain been described for QL and QR neuronal cells in Chaenorh containing sequences complementary to appropriate abditis elegans (4). QL neuroblast lineages migrated transcription promoters. HOX-related proteins originate posteriorly, while QR neuroblast cells moved anteriorly, from the 39 HOX genes while the more numerous "class II" associated with HOX mab-5 gene expression in QL but not homeobox-containing non-HOX genes give rise to additional in QR cells, with an asymmetric response to a EGL-20/Wnt proteins, such as the TALE (three amino acid loop signal. A variety of mutants that disrupted these movements extension) superclass, including homeodomain-related were described. A basis for bilateral, right versus left proteins from genes denoted as PBC, MEIS, IRO, TGIF. symmetric positioning in chick embryos depends upon sonic Class II homeobox genes give rise to additional hedgehog activating the bone morphogenic antagonist, homeodomain sequences and related proteins that have been Cerebrus protein, with expression of nodal, activating the denoted as POU, LIM, PAX, NK-2, Hix, TCL, NEC, emsZF, homeobox pitx2 gene, a member of the POU DNA-binding prd-like, prd, eve, lab, Dll, msh, NK-1, en, Abd-b Antp and domain family, and repression of the snail gene, cSnR (5). the TALE superclass (18, 19, 21, 22). Individual classes In QR cells, activin and its receptor are expressed, Fgf8 is include families of related genes such as Antp containing activated, blocking expression of Cerebrus, allowing BMPO Dfd, Scr, Antp, Xiox and pd and TALE, mentioned above. to inhibit nodal, snail gene activity and repression of pitx2. This list is not in any sense meant to be complete and Similar events are considered to occur in human cells. additional divergent homeobox genes and regions of micro An additional concept is introduced in the HOX codes RNA have been identified. The approximately 200 identified believed to underlie organ and cell-specific development of homeobox-containing genes give rise to some 1000 related several organ systems, including the digestive tract (6), lung proteins identified in various species (13). Reference (13) (7) and hematopoietic system (8). Sequential, unimpeded includes the following sites for listings of HOX-like genes unfolding of HOX