Managing pediatric psoriasis: update on treatments and challenges-a review.

BACKGROUND: Psoriasis is a chronic, immune-mediated inflammatory disease with prominent cutaneous features, although the limited number of medications approved for pediatric psoriasis makes treating this population difficult. This review provides an overview of the challenges associated with diagnosing and treating pediatric psoriasis as well as the approved and off-label treatments for children and infants with psoriasis. METHODS: Articles relevant to pediatric psoriasis were identified using a series of PubMed searches. Topics relevant to pediatric psoriasis were explored, including disease characteristics, epidemiology, treatment efficacy and safety, and access to care. Publications previously known to the authors were also included. RESULTS: Clinical features of psoriasis can be challenging to identify clinically, and patients face challenges gaining access to treatment. Most medications that have been approved for adult psoriasis lack data and labeling to support safe and effective use in pediatric patients, and therefore access is limited. A growing number of clinical trials using biologic agents for pediatric psoriasis aim to broaden available treatment options but may also raise unique concerns associated with the use of these medications in children. CONCLUSION: Pediatric psoriasis is underrecognized and often undertreated. Clinicians must balance relative risks and potential benefits when developing a treatment strategy for these patients.

Oral and genital ulceration: a unique presentation of immunodeficiency in Athabascan-speaking American Indian children with severe combined immunodeficiency.

BACKGROUND: Oral and genital ulcerations have been previously reported in 3 Navajo children diagnosed with severe combined immunodeficiency disease with T- and B-cell lymphopenia (T-B(-)-SCID). OBJECTIVE: To evaluate the occurrence of oral and genital ulcerations in 12 Athabascan-speaking American Indians with a diagnosis of T-B(-)-SCID (SCIDA group) and to compare their occurrence in non-Athabascan-speaking children with SCID (control group). We also observed the course of these ulcerations in response to bone marrow transplantation (BMT). DESIGN: Retrospective survey of the medical records of patients with SCID admitted from December 1, 1986, through July 31, 1995. SETTING: Pediatric Bone Marrow Transplantation Division at a university hospital. PATIENTS: Twelve children in the SCIDA group and 21 in the control group. All patients had virtual absence of T- and B-cell numbers and function at time of diagnosis. RESULTS: Oral and/or genital ulcers developed as a presenting feature of the SCIDA group. These ulcerations were not observed in the 21 controls. All patients underwent BMT. Of the 10 patients with oral and/or genital ulcerations, 3 had poor T-cell reconstitution after BMT, with recurrences of ulcers requiring additional BMTs. CONCLUSIONS: Oral and/or genital ulcerations are common in Athabascan-speaking American Indian children with T-B(-)-SCID but are not seen in non-Athabascan-speaking children with SCID. Thus, oral and/or genital ulceration appears to be an important, distinctive finding, and often a presenting feature of immunodeficiency in Athabascan-speaking American Indian children with SCID. Bone marrow transplantation with successful T-cell engraftment appears to be curative in the resolution of the ulcers, with recurrences only in patients who had poor T-cell reconstitution.

Cloning of a gene that encodes a new member of the human cytotoxic cell protease family.

A family of unusual serine proteases that are believed to be involved in the effector mechanism of cell-mediated cytotoxicity have previously been described in the mouse. However, in the human only one gene encoding a member has been isolated. By use of a mixture of murine cDNAs as probes, a second human gene has now been isolated. The primary structures of the gene and the predicted protein are very similar to those of the mouse. In addition, in keeping with the postulated involvement in cytolysis, transcripts were detected only in cytotoxic cells. The organization of the coding and noncoding regions of the gene, the clustering of family members, and the chromosomal location, close to the alpha chain of the T cell antigen receptor, are all conserved between human and mouse.

Linkage relationships of the Wiskott-Aldrich syndrome to 10 loci in the pericentromeric region of the human X chromosome.

Twelve families with Wiskott-Aldrich syndrome (WAS) were studied by linkage analysis using 10 polymorphic marker loci from the X-chromosome pericentromeric region. The results confirm close linkage of WAS to the DXS14, DXS7, TIMP, and DXZ1 loci and are consistent with previous data suggesting that WAS maps to the proximal Xp and is flanked by the DXS14 and DXS7 loci. The strongest linkage (Z = 10.19 at theta = 0.00) was found to be between WAS and the hypervariable DXS255 locus, a marker locus already mapped between DXS7 and DXS14 and which was informative for all meioses included in this analysis. Linkage of the WAS to two pericentromeric Xq loci, DXS1 and PGK1, was also established. On the basis of these results, accurate predictive testing should now be feasible in the majority of WAS families.

S100 protein expression in human melanoma cells: comparison of levels of expression among different cell lines and individual cells in different phases of the cell cycle.

The synthesis of S100 protein in cultured human melanoma cells was examined using metabolic labeling with [35S]methionine, immunoprecipitation with anti-S100 protein antiserum, and polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Six of seven cell lines derived from melanomas synthesized relatively large amounts of S100 protein, whereas three cell lines derived from normal melanocytes synthesized lesser amounts. Synthesis of S100 protein was not detected in 10 human cell lines of nonneuroectodermal origin. Analysis of poly(A+) RNA from one melanoma cell line by Northern blot hybridization with a probe specific for the beta subunit of rat S100 protein revealed a single mRNA species of 1.0 kb coding for the human protein. Flow cytometric analysis of individual cells of two melanoma cell lines and the rat glioma cell line C6 indicated that G0/G1 cells were heterogeneous with respect to S100 protein expression, while almost all the cells in S + G2 + M expressed S100 protein. These results suggest that expression of S100 protein in G0/G1 could be a prerequisite for progression of the cells through the cell cycle.

A human anti-cardiolipin autoantibody is encoded by developementally restricted heavy and light chain variable region genes.

Based on recent structural analyses of monoclonal autoantibodies, it appears that a number of these antibodies express germ-line immunoglobulin variable region (V) genes with little or no somatic mutation. In addition, our group and others have noted the identity or near identity of some autoantibody-associated V genes to V genes apparently expressed preferentially in the fetal pre-B cell repertoire. To extend these data, we now report that the heavy and light chain V genes of an anti-cardiolipin antibody derived from a healthy individual display 99% nucleotide sequence homology with V genes expressed in early B cell ontogeny. Sequence comparisons indicate the likely use of fetal-restricted V genes by this autoantibody. Taken together with other data on autoantibody V gene usage, these findings provide further evidence for overlap between the autoantibody-associated and early ontogeny expressed V gene repertoires and suggest that natural autoreactivity may be instrumental in the development and maintenance of the normal immune repertoire.

A natural autoantibody is encoded by germline heavy and lambda light chain variable region genes without somatic mutation.

While nonmutated germline variable region (V) genes have been found to encode heavy or light chains of various human autoantibodies, the use of germline V genes by both chains of a given autoantibody has not been documented. Recently, we reported that the heavy chain V gene (designated Humha346) of the Kim4.6 anti-DNA antibody is identical to a germline VH gene, 1.9III. To investigate whether this autoantibody was entirely germline encoded, we searched for the germline counterpart to the Kim4.6 V lambda segment (designated Humla146) and isolated a V lambda I gene designated Humlv117, which was identical to Humla146. Together with the sequence identity of the Kim4.6/Humha346 and 1.9III VH genes, the current data provide the first direct proof that an autoantibody can be encoded entirely by germline V genes without any somatic change. In addition, Humlv117 is the first V lambda I germline gene that has been isolated, and is highly homologous to the V lambda genes expressed in two lymphomas. Thus, this V lambda I gene should provide a useful tool for investigating the expression of the human V lambda gene repertoire, particularly with regard to autoimmune and/or lymphoproliferative diseases.

Linkage studies of the Wiskott-Aldrich syndrome: polymorphisms at TIMP and the X chromosome centromere are informative markers for genetic prediction.

Eleven families segregating for the X-linked recessive immune deficiency disorder, Wiskott-Aldrich syndrome (WAS), were studied by linkage analysis with an alpha satellite DNA probe, pBamX-7, which detects polymorphisms at the X chromosome centromere, locus DXZ1, as well as three other polymorphic markers defining loci on the proximal short arm of the X chromosome. Linkage has been established between WAS and DXZ1 (zeta (theta) = 7.08 at theta = 0.03) and WAS and the TIMP gene locus (zeta (theta) = 5.09 at theta = 0.0). We have also confirmed close linkage between DXZ1 and two marker loci, DXS14 and DXS7, previously shown to be linked to the WAS locus. The probe pBamX-7 detected allelic variation in all females tested, reflecting the high frequency of polymorphism at the centromere. One WAS carrier revealed a recombination between WAS and both marker loci DXZ1 and DXS14, indicating that WAS does not map between these loci. In conjunction with previous data from genetic mapping studies of WAS, these results confirm the pericentromeric Xp localization of WAS and demonstrate the usefulness of alpha satellite DNA probes as tools for genetic prediction in WAS as well as other pericentric X-linked diseases.

Analysis of variable region genes encoding a human anti-DNA antibody of normal origin. Implications for the molecular basis of human autoimmune responses.

In order to investigate the genetic basis for natural anti-DNA immune responses, we isolated and sequenced the variable gene elements (VH and VL) encoding an anti-DNA antibody expressed by a human hybridoma of normal origin (Kim4.6) and compared these sequences with those reported for four other human anti-DNA antibodies. The Kim4.6 antibody leader and VH segments were identical in nucleotide sequence with the VH1.9III germ-line VH3 gene, and the Kim4.6VL segment showed 98% nucleotide sequence identity with a V lambda I subgroup gene expressed in a Burkitt's lymphoma. Comparative analysis of Kim4.6 and other human hybridoma anti-DNA antibodies indicated that anti-DNA immune responses are diverse in terms of VH and VL gene utilization but may exhibit a bias toward rearrangement of VH genes that are over-represented in the fetal pre-B cell repertoire. Moreover, Kim4.6 and three of four other sequenced human anti-DNA antibodies appear to use a germ-line diversity gene, DXP'1, which may represent a counterpart of the DFL16.1 segment utilized in murine responses to the hapten nitrophenyl. Taken together, our findings indicate that anti-DNA immune responses can be encoded by nonmutated VH genes and that the elements and molecular mechanisms which engender this response are essentially the same among natural and lupus-associated anti-DNA antibodies. Our data also suggest that natural autoimmune responses originate early in B cell ontogeny as is consistent with the hypothesis that autoreactivity plays a major role in shaping the normal immune repertoire.

X-chromosome inactivation in the Wiskott-Aldrich syndrome: a marker for detection of the carrier state and identification of cell lineages expressing the gene defect.

Recently developed techniques for the direct analysis of DNA have made possible the determination of patterns of cellular X-chromosome inactivation. These techniques provide a potential method for carrier detection for several X-linked human disorders in which obligate carriers show nonrandom X inactivation. By using restriction fragment length polymorphic (RFLP) gene-specific probes in conjunction with methylation-sensitive enzymes, we have characterized the patterns of X-chromosome inactivation in cell subsets from females belonging to 10 kindreds segregating for the X-linked immune deficiency disorder Wiskott-Aldrich syndrome (WAS). We show that selective inactivation of the X chromosome distinguishes obligate WAS carriers from noncarrier females and constitutes a valuable marker of the WAS carrier state. Selective inactivation phenomena were observed in the monocytes and T and B lymphocytes of obligate carriers, implying that the WAS gene defect is expressed in each of these cellular lineages. In conjunction with the use of linked DNA markers, RFLP-methylation analysis should render carrier detection feasible for the majority of females from WAS families. The results of such analyses also provide an initial step toward identifying the cellular level and molecular basis for WAS.

Cross-reactivity of murine anti-human high molecular weight-melanoma associated antigen monoclonal antibodies with guinea pig melanoma cells.

To identify melanoma associated antigens (MAAs) shared by human and guinea pig melanoma cells, a battery of murine monoclonal antibodies (MoAbs) to human MAA and an antiserum to S100 protein were tested with four newly established guinea pig melanoma cell lines. Only the monoclonal antibodies 149.53 and 225.28 which recognize distinct determinants of the human high molecular weight-MAA (HMW-MAA) reacted with all four guinea pig melanoma cell lines. To compare the binding site of MoAbs 149.53 and 225.28 with guinea pig and human melanoma cells, inhibition binding experiments were performed with antiidiotypic monoclonal antibodies which completely inhibit the binding of MoAbs 149.53 and 225.28 to human melanoma cells. The binding of MoAb 149.53 to guinea pig melanoma cells was partially inhibited by antiidiotypic MoAbs MF9-10 and MK1-180 which recognize distinct private idiotopes within the antigen combining site of MoAb 149.53. On the other hand the binding of MoAb 225.28 to guinea pig melanoma cells was completely inhibited by antiidiotypic MoAbs MF11-30 and TK1-F2 which recognize distinct private idiotopes within the antigen combining site of MoAb 225.28. These results suggest that the determinant recognized by MoAb 149.53 on guinea pig melanoma cells is similar but not identical to that recognized on human melanoma cells, while the determinants recognized by MoAb 225.28 on the two types of cells do not display any detectable differences under the experimental conditions tested. The target structure on the guinea pig melanoma cells identified by MoAbs 149.53 and 225.28 is a Mr 280,000 molecule which has the same apparent molecular weight as one of the two subunits of the HMW-MAA synthesized by human melanoma cells. Sequential immunoprecipitation experiments with guinea pig melanoma cells showed that the determinant recognized by MoAb 149.53 is expressed on a subpopulation of the molecules recognized by MoAb 225.28. Immunohistochemical staining with MoAb 225.28 of a variety of different tissues from normal adult guinea pigs showed that the corresponding antigenic determinant is detectable only in basal cells of epidermis and hair follicles of skin. S100 protein, which is a cytoplasmic constituent of normal human melanocytes, benign nevi, and malignant melanocytes, was also detected in the cytoplasm of the four cultured guinea pig melanoma cells lines. The results of the present investigation may lead to a better understanding of the phylogenetic evolution of the human HMW-MAA and suggest that guinea pig melanoma may serve as a useful animal model for immunobiological studies and carcinogen-induced tumorigenesis investigations.

Characterization of a Db-specific helper factor required for the induction of cytotoxic responses to alloantigens with the use of monoclonal antibodies specific for the helper factor or the T-cell antigen receptor.

A T helper clone (clone 9), isolated from a H-2d anti-H-2b mixed lymphocyte culture, was previously found to produce an antigen-specific helper factor (ASHF) that could be specifically absorbed out with BIO.A(2R) (KkAkEkDb), but not B10.A (KkAkEkDd), spleen cells. In order to characterize this ASHF further, we have constructed T-cell hybridoma lines by fusing clone 9 cells with the AKR thymoma, BW5147. One of these hybridoma clones, referred to as clone 25, produced an ASHF that was specific for the Db alloantigen. Immunization of allogeneic C57BL/6 mice with clone 9 cells and subsequent fusion of these immune spleen cells with non-secreting myeloma cells led to the isolation of a monoclonal antibody (mAb) (clone 30 IgM) that was capable of neutralizing the helper activity of clone 25 ASHF. Clone 30 IgM affinity column was found to retain clone 25 ASHF; clone 30 IgM column eluates augmented the cytotoxic responses of CBA/J thymocytes to B6(H-2b), but not D2(H-2d), alloantigens. Preabsorption of clone 25 ASHF with Db-bearing spleen cells prior to affinity purification over a clone 30 IgM column resulted in the abrogation of Db-specific helper activity as well as the loss of a 50,000 molecular weight (MW) band in SDS-polyacrylamide gels run under reducing conditions. Clone 25 ASHF was also retained by immunoadsorbents made with an IgG2a mAb (F23.1) the reactivity of which is against the beta chain of the T-cell receptor. Furthermore, affinity purification of clone 25 ASHF over a F23.1 affinity column, but not an irrelevant mAb column, also yielded a 50,000 MW molecule. These findings suggest that this particular ASHF may be intimately related to the T-cell antigen receptor.

Mechanism of action of a Db-specific helper clone and factor in cytotoxic responses to alloantigens.

The mechanism by which a Db-specific helper clone (clone 9) and a hybridoma-derived Db-specific helper factor, referred to as ASHF, induced cytotoxic T lymphocyte (CTL) responses to alloantigens was investigated. Clone 9 or ASHF helped CBA thymocytes to produce CTL against B6 (H-2b), but not D2 (H-2d), alloantigens. However, when BDF1 (H-2b/d) spleen cells or an equal mixture of B6 or D2 spleen cells were used as stimulator cells, CTL responses to both B6 and D2 were induced. This suggested that clone 9 cells or ASHF could induce the production of long-ranged, non-antigen-specific helper factor(s) in B6-stimulated cultures. One of these long-ranged factors produced in B6-stimulated cultures was found to be interleukin-2(IL-2). Thus, clone 9, which is a non-IL-2 producer, increased the production of IL-2 by irradiated B6 spleen cells and by CBA anti-B6 cultures by 4.7-and 5.7-fold, respectively. ASHF did not increase the amount of IL-2 produced by irradiated B6 spleen cells but increased the amount of IL-2 produced in CBA anti-B6 cultures by 3.8-fold. Clone 9 cells or ASHF did not increase IL-2 production in D2-stimulated cultures. Upon stimulation with concanavalin A or antigen, clone 9 cells also produced a non-antigen-specific helper factor. This factor (IL-X) synergized with excess human recombinant IL-2(rIL-2) in the polyclonal activation of BDF1 or D2 CTL precursors. A model that involves the participation of ASHF, clone 9 cells, IL-2 and IL-X in the induction of a cytotoxic response is proposed.

Difference in cell binding patterns of two monoclonal antibodies recognizing distinct epitopes on a human melanoma-associated oncofetal antigen.

Two monoclonal antibodies (MAbs), 140.240 and 96.5, generated independently in different laboratories, have been shown to detect the target structures of 87,000 (gp87) and 97,000 (p97) glycoproteins, respectively, both strongly expressed by melanoma cells and fetal small intestine. To determine whether MAb 140.240 and MAb 696.5 recognized a same target structure, they were tested in immunoprecipitation/SDS-PAGE using NP-40 lysates of melanoma cells labelled with [35S]methionine for 18 hr. Both antibodies precipitated a single band with Mr = 87,000. Reciprocal immunodepletion studies showed that neither of the two antibodies detected the 87,000 band in the lysate immuno depleted by either antibody, suggesting that these two antibodies recognize the same or extremely similar molecules. Two-dimensional tryptic peptide mapping analysis showed that the two identified molecules shared the same finger-printing pattern. A 40,000 fragment of the 87,000 molecule produced by protease digestion was precipitated by MAb 96.5 but not MAb 140.240, indicating that the epitopes recognized by the two antibodies are localized at discrete sites on the molecule. Serological studies on these two antibodies revealed slightly different binding patterns in the MAb 140.240 exhibited a more melanoma-restricted specificity, while MAb 96.5 had a specificity to melanoma and to some other cell types. The observed difference in epitope specificity may be important in the clinical applications of these antibodies.

Monoclonal antibody recognizing human melanoma-carcinoma cross-reacting oncofetal antigen epitopically associated with carcinoembryonic antigen.

By fusion of mouse NS1 myeloma cells with splenocytes from a BALB/c mouse immunized with human melanoma cells, an IgG1 monoclonal antibody, designated as 140.72, was produced. By the mixed hemadsorption antibody binding assay, 140.72 was shown to react with 17 of 20 melanoma cell lines and with 5 of 14 carcinoma cell lines. This antibody also reacted with 3 of 3 normal melanocyte cultures in much lower titers. It did not react with any of 35 other normal and malignant lines, including neuroblastoma, glioblastoma, sarcoma, teratoma, fibroblast, and lymphoid cell lines. Absorption with fresh melanoma and carcinoma homogenates confirmed the results of direct tests. Fetal reactivity of antibody 140.72 was determined by positive absorption with 10 of 11 tissue homogenates derived from different fetuses of 10-16 weeks' gestation. The reactivity of this antibody was completely removed by absorption with a highly purified preparation of carcinoembryonic antigen (CEA) derived from a colon carcinoma. The antigenic activity was detected in the culture medium of reactive cell lines. Immunoprecipitation analyses of melanoma and carcinoma cells indicated that the antigenic determinant recognized by antibody 140.72 is on a glycoprotein with an apparent molecular weight of 95,000-150,000 common to both serologically reactive cell types. Additionally, a 200,000-molecular-weight glycoprotein corresponding to the CEA molecule was detected only on the reactive carcinoma cells. These data confirmed previous findings obtained with polyclonal anti-CEA antisera for the existence of shared CEA-related antigenic determinants on human carcinomas and melanomas and provided additional molecular characterization of these glycoproteins. Further characterization of the molecules bearing the antigenic determinant recognized by antibody 140.72 should be performed with a view to exploring its potential in the immunodiagnosis and immunotherapy of patients with melanoma.

Immunopurification, characterization, and nature of membrane association of human melanoma-associated oncofetal antigen gp87 defined by monoclonal antibody 140.240.

A melanoma-associated oncofetal antigen, gp87 (a p97-like molecule), defined by the monoclonal antibody (MoAb) 140.240 has been purified to homogeneity from the spent medium of cultured melanoma cells by a two-step immunoadsorbent procedure. The first immunoadsorbent step using glutaraldehyde-insolubilized MoAb 140.240 (ascites fluid) resulted in a 13-fold enrichment with 93% recovery in the bound material. In the second immunoadsorbent step constructed by the purified IgG2a of MoAb 140.240 (culture fluid) coupled to CNBr-activated Sepharose 4B the bound material from the first step was further purified resulting in a 330-fold purification with 90% recovery. SDS-polyacrylamide gel electrophoretic analysis of the final purified material revealed a single band migrating as a polypeptide with an approximate molecular weight of 87 Kd, consistent with the size of the molecule immunoprecipitated by MoAb 140.240 from lysates of radiolabelled melanoma cells. Preliminary amino acid analysis indicates a particularly high proportion of phenylalanine in gp87. We have also compared gp87 with two well defined antigens, HLA-A,B,C (integral membrane protein) and "94K" melanoma/carcinoma-associated antigen (peripheral membrane protein) with respect to antigen extractability from melanoma cells using phosphate-buffered saline, 0.1 M urea, 3 M NaCl, or nonionic detergent (NP-40). The results showed that whereas 94K antigen was extractable by each of the four different solutions, gp87, similar to HLA-A,B,C antigens, could only be extracted with NP-40, strongly suggesting that gp87 is an integral melanoma cell component.

Induction of CTL responses to alloantigens by a Db-specific T helper clone.

A T cell helper clone was derived 2 yr ago from a mixed lymphocyte culture. This clone, referred to as clone 9, was propagated in interleukin 2 (IL 2)-containing medium in the presence of irradiated stimulator and irradiated syngeneic spleen cells. Clone 9 was of H-2d origin and was found to be Thy-1+ and Lyt-1-2-. Clone 9, as well as supernatant factor(s) derived from it, were able to enhance the primary cytotoxic responses of Db responder cells to alloantigens. Furthermore, clone 9 cells or its factor(s) were only active when added during the first 24 hr of a 5-day culture period. When a low stimulator cell dose (10(4) cells per 0.2 ml culture) was used, it was possible to demonstrate that clone 9 also required a source of irradiated allogeneic splenic accessory cells to exert its helper action. Under these conditions, clone 9 or its factor(s) could also synergize with IL 2-containing medium in mounting cytotoxic responses to alloantigens. Synergy between IL 2-containing medium and clone 9 or its factor(s) was observed only when Db responder cells were used. The helper activity in clone 9 supernatant was also specifically absorbed out by Con A-stimulated Db spleen cell blasts. Preincubation with clone 9 supernatant for 1 hr at room temperature also led to enhanced cytotoxic responses of Db responder cells to alloantigens. Clone 9 supernatant was also found to be devoid of detectable IL 2 activity. Thus, clone 9 or its helper factor(s) appear to exert its helper activity by an early interaction with Db cytotoxic T lymphocyte precursors (CTL-P).

Selective extraction by 1-butanol of surface glycoprotein antigens from human melanoma cells.

The butanol extraction method has previously been used to achieve selective release of tumor-specific transplantation antigens from mouse sarcoma cells. In this study we investigated the feasibility of this method for extracting four surface glycoprotein antigens (87K, 95-150K, HLA-DR, and HLA-A,B,C) from cultured human melanoma cells. Of the four antigens examined, only 95-150K and HLA-DR antigens could readily be detected in material extracted by 2%, 3%, or 5% butanol. The 3% butanol was found to be most effective in releasing these two antigens. Treatment of melanoma cells with less than or equal to 3% butanol did not decrease the viability of extracted cells as judged by either Trypan Blue dye exclusion or plating efficiency. Thus the noncytolytic butanol extraction method offers a promising approach to the isolation of certain glycoproteins such as 95-150K and HLA-DR from viable human melanoma cells for further purification and structural analysis.

Association of morphological differentiation with enhanced surface antigen expression and susceptibility to natural killer cell lysis in theophylline-treated human melanoma cells.

Human and animal melanomas undergo maturation spontaneously in vivo and in vitro, and as a result of experimental manipulation in vitro. To gain a better understanding of this phenomenon, we studied the effects of theophylline on a cultured human malignant melanoma cell line (CaCL 73-36). We observed a dose-dependent inhibition of cell growth with a reduction in plating efficiency of 16, 64, and 99% at concentrations of theophylline of 0.1, 1.0, and 2.0 mM, respectively. Theophylline-treated cells showed morphological changes consistent with a more differentiated state such as increased dendrite formation and contact inhibition. Expression of surface HLA-A,B,C antigens and beta-2-microglobulin was enhanced 15- and fivefold, respectively. Finally, cells treated with theophylline for 96 h showed a five- to eightfold increase in sensitivity to lysis by natural killer cells. These findings have obvious bearing on the potential use of theophylline in the treatment of malignant melanoma.