Using autologous serum for the immunoscreening of a cDNA expression library derived from tissue involved by Hodgkin's disease, a new 36-kDa protein with the characteristics of galectins (S-type lectins) was detected. Sequence analysis of the cDNA clone HOM-HD-21 revealed two homologous motifs known as lectin domains with galactoside binding capacity. The two domains are linked by a stretch of about 30 amino acid residues and share a sequence homology of 39%. While the N-terminal lectin domain shows merely moderate homologies with known galectins, the C-terminal lectin domain is highly homologous to rat galectin-5 with an amino acid sequence identity of 70%. We ruled out mutations of the tumor-derived transcript by sequence comparison with the respective cDNA cloned from normal peripheral blood leukocytes. Recombinant protein expressed in Chinese hamster ovary cells was purified from lysates by lactose and galactose affinity chromatography, proving the galactoside binding capacity of this new galectin. Northern blot analysis revealed an expression spectrum restricted to peripheral blood leukocytes and lymphatic tissues. In accordance with the nomenclature of known galectins, we suggest to designate this novel galactoside binding protein galectin-9.Galectins, formerly known as S-type lectins or S-Lac lectins (1, 2), are a growing family of soluble animal ␤-galactosidebinding proteins. Members of the galectin family are defined by two characteristic features: affinity to ␤-galactosides and a specific sequence motif called lectin domain. Based on the number of lectin domains two groups of galectins are distinguished. The majority of galectins, including galectin-1, -2, -3, -5, and -7 (3-9), have a single lectin domain. The second group of galectins, which includes rat galectin-4 (10), rat galectin-8 (11), and the 32-kDa galactoside-binding protein of Caenorhabditis elegans (12) is characterized by two tandemly arranged lectin domains connected by a linker peptide. Although none of the galectins contains a typical secretion signal, several galectins are externalized by nonclassical secretory mechanisms (13,14) and play a role in modulating cell-to-cell or cell-to-matrix interactions. Galectins are involved in a number of different cellular events, including physiological (15, 16) and malignant cell adhesion (17, 18), activation and proliferation of immune cells (19,20), as well as induction (21) and inhibition (22) of programmed cell death.Recently, we established SEREX 1 (serological identification of antigens by recombinant expression cloning), a novel approach for the molecular definition of human tumor antigens using autologous serum from tumor patients. For SEREX, tumor-derived -phage expression libraries are screened for reactivity with high-titered IgG antibodies present in the autologous serum of the analyzed patient. By applying this method to several human neoplasms we identified numerous new tumor antigens (23,24). In a cDNA library derived from the Hodgkin's disease-involved spleen of a 28-year-old female...

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Mutations in the adenomatous polyposis coli (APC) gene are linked to the dysplastic transformation of colorectal polyps and represent an early step in the development of colorectal tumors. Ninety-four percent of all mutations result in the expression of a truncated APC protein lacking the C-terminal region. The C-terminal region of the APC protein may have a tumor suppressor function as its absence appears to be linked to the development of dysplastic lesions. Recently, we discovered and characterized a protein called RP1 which binds specifically to the C-terminal region of the APC protein. We show now that RP1 and the other known members of the EB/RP family (EB1 and RP3) also bind directly to tubulin, both in vitro and in vivo. Immunohistochemical analyses reveal a distinct staining pattern during interphase as well as an association of RP1/EB1 with mitotic microtubule structures. The previously described puncta of the APC protein at the leading edge of membrane protrusions contact microtubule fibers that contain RP1 or EB1. Int.

Antigenic targets of monoclonal gammopathy of undetermined significance (MGUS) and multiple myeloma (MM) paraproteins might play a role in the pathogenesis of these neoplasms. We screened a human fetal brain-derived macroarray with the IgA or IgG containing sera of 192 consecutive MGUS and MM patients. Twenty-nine of 192 (15.1%) paraproteins reacted with paratarg-7, a protein of unknown function which is expressed in all human tissues. Paratarg-7 reactivity was similarly frequent among IgA and IgG paraproteins, but all paratarg-7 reactive IgG paraproteins belonged to the IgG3 subtype with 24/57 IgG3 (42.1%) paraproteins displaying this specificity. Sequence analysis of paratarg-7 derived from patients having a paraprotein with specificity for paratarg-7 revealed no differences to paratarg-7 derived from patients with paraproteins of other specificities or healthy controls, excluding mutations or polymorphisms as a reason for its autoimmunogenicity. Similarly, Western-blot analysis showed identical bands for paratarg-7 derived from patients and controls. The above-random frequency of paratarg-7 as a paraprotein target suggests that paratarg-7 might be involved in the development of the respective clonal proliferations. The identification of paratarg-7 as an antigenic target enables the more detailed analysis of tumor-host interactions in these patients and their role in the pathogenesis of MM and MGUS. ' 2009 UICC

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