Regular Article

Journal of Investigative Dermatology (2000) 114, 122–126; doi:10.1046/j.1523-1747.2000.00819.x

Somatic Mutations of Fas (Apo-1/CD95) Gene in Cutaneous Squamous Cell Carcinoma Arising from a Burn Scar

Sug Hyung Lee1, Min Sun Shin1, Hong Sug Kim, Won Sang Park, Su Young Kim, Ja June Jang*, Kyung Jin Rhim†, Jin Jang, Hun Kyung Lee, Jik Young Park, Ro Ra Oh, Seo Young Han, Jong Heun Lee, Jung Young Lee and Nam Jin Yoo

  1. Department of Pathology, College of Medicine, The Catholic University of Korea, Socho-gu, Seoul, Korea
  2. *Department of Pathology and Cancer Research Center, Seoul National University College of Medicine, Seoul, Korea
  3. †Department of Dermatology, Korea Cancer Center Hospital, Seoul, Korea

Correspondence: Dr Nam Jin Yoo, Department of Pathology, College of Medicine, The Catholic University of Korea, 505 Banpo-dong, Socho-gu, Seoul 137-701, Korea

1Sug Hyung Lee and Min Sun Shin contributed equally to this work.

Received 26 August 1999; Revised 5 October 1999; Accepted 6 October 1999.

Top

Abstract

Fas (Apo-1/CD95) is a cell-surface receptor involved in cell death signaling, and recent reports have suggested that defects within the Fas receptor pathway such as Fas mutation play an important part in the development and progression of human tumors. Burn scar-related squamous cell carcinoma of skin is a unique subtype of cutaneous squamous cell carcinoma, and tends to be more aggressive in nature than conventional squamous cell carcinoma. The molecular mechanisms underlying the development and progression of burn scar-related squamous cell carcinoma, however, are not clear. In this study, we analyzed the entire coding region and all splice sites of the Fas gene for the detection of the somatic mutations in a series of 50 conventional squamous cell carcinomas and 21 burn scar-related squamous cell carcinomas by polymerase chain reaction, single strand conformation polymorphism, and DNA sequencing. We detected mis-sense mutations in three of 21 burn scar-related squamous cell carcinomas (14.3%), whereas no mutation was detected in 50 conventional squamous cell carcinomas. Of the three Fas mutations detected in the burn scar-related squamous cell carcinomas, one was found in Fas ligand-binding domain, another one was identified in the death domain known to be involved in the transduction of an apoptotic signal, and the other one was found in the transmembrane domain. Our data show that some burn scar-related squamous cell carcinomas have Fas gene mutations in important regions for the apoptosis function and suggest that these mutations might be involved in the pathogenesis of burn scar-related squamous cell carcinomas. In addition, our results provide an important clue to understanding the difference between burn scar-related squamous cell carcinoma and conventional squamous cell carcinoma at the molecular level.

Keywords:

apoptosis, loss of heterozygosity, skin, squamous cell carcinoma

Abbreviations:

BSCC, burn scar-related squamous cell carcinoma; CSCC, conventional squamous cell carcinoma; SSCP, single strand conformation polymorphism; FasL, Fas ligand

It is now believed that clonal expansion and tumor growth is the result of the deregulation of intrinsic proliferation (cell division) and cell death (apoptosis) (Nagata 1997). Failure of apoptosis could allow the survival of transformed cells that are prone to undergo further genetic damage and play an important part in the pathogenesis of tumors (Nagata 1997).

The Fas–Fas ligand (FasL) system has been recognized as a major pathway for the induction of apoptosis in cells and tissues (Nagata 1997). Fas is a member of the death receptor subfamily of the tumor necrosis factor receptor superfamily (Itoh & Nagata 1993;Nagata 1997). Ligation of Fas by either agonistic antibody or by its natural ligand transmits a ''death signal'' to the target cells, potentially triggering apoptosis (Trauth et al. 1989;Leithäuser et al. 1993;Owen-Schaub et al. 1994). Fas is widely expressed in normal and neoplastic cells (Leithäuser et al. 1993), but the expression of this protein does not necessarily predict susceptibility to killing (Owen-Schaub et al. 1994). This can reflect the presence of inhibiting mechanisms of Fas-mediated apoptosis. Fas-mediated apoptosis can be blocked by several mechanisms, including the mutation of the primary structure of Fas (Owen-Schaub et al. 1994;Nagata 1997).

There is mounting evidence that Fas gene mutation is involved in the pathogenesis of tumors. Mice bearing the germ line mutation of Fas gene (lpr) have been reported to have spontaneous development of plasmacytoid tumors (Davidson et al. 1998). Lymphomatogenesis driven by the Emu-myc transgene was shown to be markedly accelerated in lpr mice compared with wild-type mice, confirming a causal, rather than correlative, role for Fas loss in tumor development (Zörnig et al. 1995). Germline mutations of the Fas gene in human results in autoimmune lymphoproliferative syndrome, and some these patients have been reported to have malignancies (Drappa et al. 1996;Bettinardi et al. 1997;Infante et al. 1998;Martin et al. 1999), including multiple tumor development in one patient (Drappa et al. 1996). In cancer patients, somatic mutations of Fas gene have been mainly described in lymphoid tumors, including multiple myelomas (Landowsky et al. 1997), childhood T cell lymphoblastic leukemias (Beltinger et al. 1998), adult T cell leukemias (Tamiya et al. 1998;Maeda et al. 1999), and non-Hodgkin's lymphomas (Grønbæk et al. 1998). In adult T cell leukemia, the somatic mutation of Fas gene was found to contribute to lymph node metastasis of the tumor (Maeda et al. 1999). In nonlymphoid tumors, we previously reported Fas gene mutations in malignant melanomas (Shin et al. 1999), transitional cell carcinomas of urinary bladder (Lee et al. 1999a) and non-small cell lung cancers (Lee et al. 1999b). These data indicate that resistance against Fas-mediated apoptosis through the Fas gene mutation may contribute to the development and progression of human tumors.

There have been many case reports over the years describing the occurrence of cancers in burn scars which are most frequently squamous cell carcinoma (SCC) (Bartle et al. 1990). Burn scar-related SCC (BSCC) of skin is more aggressive in nature and carry a poorer prognosis than conventional SCC (CSCC), although the microscopic picture of BSCC is that of typical SCC (Bartle et al. 1990). It is believed that the mechanisms underlying the development and progression of BSCC is different from those of CSCC. There have been few data, however, explaining these mechanisms (Bartle et al. 1990;Harland et al. 1997;Sakatani et al. 1998). Because it is possible that Fas gene mutation is involved in the pathogenesis of nonlymphoid malignancies, we considered the possibility that Fas gene mutation might be involved in the pathogenesis of BSCC. In this study, we performed a polymerase chain reaction (PCR)-based mutational analysis of Fas gene in 21 BSCC and 50 CSCC. The data here demonstrate that some BSCC have Fas gene mutations and suggest that the Fas mutations might be one of the mechanisms involved in the pathogenesis of BSCC.

Top

MATERIALS AND METHODS

Tissue samples and microdissection

Paraffin-embedded tissues were obtained from BSCC (n = 21) and CSCC (n = 50) patients undergoing surgery. Each tumor was graded histologically according to the proportion of differentiated cells (grades 1–4) (Broders 1921). The CSCC samples consisted of 31 grade 1, 12 grade 2, seven grade 3 and no grade 4 tumors and the BSCC samples consisted of 17 grade 1, four grade 2, no grade 3, and no grade 4 tumors.

Malignant cells were selectively procured from hematoxylin and eosin-stained sections using a 30G1/2 hypodermic needle (Becton Dickinson, Franklin Lakes, NJ) affixed to a micromanipulator, as described previously (Lee et al. 1998). We also microdissected infiltrating lymphocytes from the slides and used them for corresponding normal DNA. This microdissection technique used in this study has been proven to be precise and effective for procurement of tumor cells without normal cell contamination (Lee et al. 1998). DNA extraction was performed by a modified single-step DNA extraction method, as described previously (Lee et al. 1998).

Single strand conformation polymorphism (SSCP) analysis for mutation and loss of heterozygosity (LOH)

Genomic DNA each from normal lymphocytes or tumor cells was amplified with the primer pairs of Fas gene described in our previous studies (Lee et al. 1999a,b;Shin et al. 1999). The primers were designed with the program Oligo (National Biosciences, Plymouth, MN) using sequences obtained from GenBank (accession number M67454) and cover the entire coding region and parts of the promoter region of Fas gene (Lee et al. 1999a,b;Shin et al. 1999). Each PCR reaction was performed under standard conditions in a 10 mul reaction mixture containing 1 mul of template DNA, 0.5 muM of each primer, 0.2 muM of each deoxynucleotide triphosphate, 1.5 mM MgCl2, 0.4 units of Taq polymerase, 0.5 muCi of [32P]dCTP (Amersham, Buckinghamshire, U.K.), and 1 mul of 10 times buffer. The reaction mixture was denatured for 1 min at 94°C and incubated for 40 cycles (denaturing for 40 s at 94°C, annealing for 40 s at 49–60°C, and extending for 40 s at 72°C). Final extension was continued for 5 min at 72°C. After amplification, PCR products were denatured 5 min at 95°C at a 1:1 dilution of sample buffer containing 98% formamide/5 mmol per l NaOH and were loaded on to a SSCP gel (FMC Mutation Detection Enhancement system; Intermountain Scientific, Kaysville, UT) with 10% glycerol. After electrophoresis, the gels were transferred to 3 mm Whatman paper and dried, and autoradiography was performed with Kodak X-OMAT film (Eastman Kodak, Rochester, NY). For the detection of mutations, DNAs showing mobility shifts were cut out from the dried gel, and re-amplified for 35 cycles using the same primer set. Sequencing of the PCR products was carried out using the cyclic sequencing kit (Perkin-Elmer, Foster City, CA) according to the manufacturer's recommendation.

Because it has been known that four bi-allelic polymorphisms at positions -1377 (promoter region), -670 (promoter region), 416 (exon 3), and 836 (exon 7) are located in Fas gene (Fiucci & Ruberti 1994;Huang et al. 1997), SSCP analysis at these polymorphic sites was used for the detection of LOH as well as for the detection of mutations. The PCR and SSCP conditions of LOH study were the same with the condition described above. Complete or nearly complete absence of one allele in tumor DNA of informative cases, as defined by direct visualization, was considered as LOH.

Immunohistochemistry

Antibody for human Fas (C-20, Santa Cruz Biotechnology, Santa Cruz, CA) was used to detect Fas on tissue sections. Immunohistochemical procedures were performed as described previously (Lee et al. 1999a,b;Shin et al. 1999). Tumors were interpreted as positive for Fas by immunohistochemistry when at least weak to moderate cytoplasmic staining was seen in greater than 30% of the neoplastic cells. The immunostaining with each antibody was judged to be antibody-specific by several criteria, including: (i) use of normal rabbit serum at the same dilution produced no consistent immunostaining of any cells; (ii) intensity of the signal diminished as the dilution of the antibody was increased; and (iii) preincubating the antibody with blocking peptides abrogated the positive immunostaining. The results were reviewed independently by three pathologists.

Top

RESULTS

Fas gene mutations

Through the microdissection technique, we successfully procured tumor cells from histologic sections of 71 SCC, including 21 BSCC and 50 CBSCC, as shown in Figure 1a,b. Genomic DNA was isolated and analyzed for potential mutations in all nine exons of the Fas gene by PCR–SSCP analysis. Enrichment and direct sequence analysis of aberrantly migrating bands led to the identification of mutations in three of 21 BSCC (14.3%) (Table 1 and Figure 2a), but no mutation was identified in 50 CSCC. None of the normal samples showed evidence of mutations by SSCP (Figure 2a), indicating the mutations detected in the BSCC specimens had risen somatically.

Figure 1.
Figure 1 - Unfortunately we are unable to provide accessible alternative text for this. If you require assistance to access this image, please contact help@nature.com or the author

Microdissection of BSCC. (A) Malignant cells are arranged in irregularly shaped nests in the dermis. The needle tip (arrow) is attached to a tumor cell nest. (B) Tumor cell nest was dissected leaving large holes behind. Original magnification, times 150.

Full figure and legend (241K)

Figure 2.
Figure 2 - Unfortunately we are unable to provide accessible alternative text for this. If you require assistance to access this image, please contact help@nature.com or the author

Mutations and deletions of Fas gene in cutaneous SCC. SSCP (A, D) and sequencing analysis (B, C) of DNA from tumors (lane T) and normal tissues (lane N). (A) Part of exon 9 was amplified using primer set 9A. SSCP of DNA from tumor (T) of case 7 (left) and case 16 (right) show wild-type bands and additional aberrant bands as compared with SSCP of DNA from the corresponding normal lymphocytes (N). (B) Sequencing analysis from aberrant band of case 7. There is an A–G transition at nucleotide 957 (arrow) in tumor tissue as compared with normal tissue. (C) Sequencing analysis from aberrant band of case 16. There is an A–G transition at nucleotide 547 (arrow) in tumor tissue as compared with normal tissue. (D) Detection of allelic loss by amplifying a region encompassing the bi-allelic polymorphism, -1377, in the Fas promoter with primer PA. Representative SSCP show ''not informative'' (left), ''retention of heterozygosity'' (middle), and ''loss of heterozygosity'' (right). Right: Loss of bands was observed in DNA from tumor cells (T) compared with the SSCP from normal cells (N).

Full figure and legend (56K)


All three mutations identified were mis-sense variants (Figure 2b,c and Table 1). One mutation was detected in exon 9 which encodes the death domain region of the Fas (Itoh & Nagata 1993). This mutation (case 7) affects codon 239. Another mutation (case 16) was identified in exon 4 and would result in the substitution of Asn to Ser at codon 102. The other mutation (case 13) observed in exon 6, affects codon 162. We repeated the experiments three times, including tissue microdissection, PCR, SSCP, and sequencing analysis to ensure the specificity of the results, and found that the data were consistent (data not shown). The demographic data and Fas mutation data in 21 BSCC are summarized in Table 1.

Allelic status

Because mis-sense mutations in the death domain of Fas in patients with autoimmune lymphoproliferative syndrome have been suggested to affect receptor function in a dominant-negative fashion (Drappa et al. 1996;Bettinardi et al. 1997;Infante et al. 1998;Martin et al. 1999), we examined the allelic status of Fas in the BSCC and the CSCC. Overall, 12 of 21 BSCC (57%) and 30 of 50 CSCC (60%) were informative for at least one of the four polymorphic markers, and four of 12 informative BSCC (33%) and three of 30 informative CSCC (10%) showed LOH with one or more markers (Table 1).

Of the three BSCC with the Fas gene mutations, two case (cases 7 and 13) showed LOH with the markers (Figure 2d and Table 1). The other case (case 16) with the Fas mutation was heterozygous for the markers PA and PB, but did not showed any LOH for these markers (Table 1).

Expression of Fas protein

We demonstrated Fas expressions in the BSCC and CBSCC by immunohistochemistry. The BSCC and CSCC showed immunoreactivity for Fas in 16 of 21 cases (76%), and in 40 of 50 cases (80%), respectively. As for the relationship between histologic grade and Fas immunoreactivity, the 16 Fas-positive BSCC consisted of 13 grade 1 and three grade 2 tumors, and 40 Fas-positive CSCC consisted of 26 grade 1, 10 grade 2, and four grade 3 tumors. Fas immunostaining, when present, was cytoplasmic and along the cell membranes; nuclei were clearly negative (data not shown). All BSCC with the Fas gene mutations expressed Fas (Table 1).

Top

DISCUSSION

In order to explore genetic basis for the differences between CSCC and BSCC, we analyzed somatic mutations of the Fas gene in these tumors. We detected three somatic mutations in BSCC, one in FasL binding domain, another one in the death domain, and the other one in transmembrane domain (Table 1). There were no Fas gene mutations in 50 CSCC, however. These findings, together with the recent demonstration of a similar frequency of Fas mutations in other human malignancies, indicate that Fas mutation is one of the mechanisms that mediate Fas resistance in BSCC.

Various postulates have been put forward to explain the development of cancer in burn scar and its aggressive biologic behavior, but there are few data to corroborate these suggestions (Bartle et al. 1990;Harland et al. 1997;Sakatani et al. 1998). Recently,Sakatani et al. (1998) reported somatic mutation of p53 gene in BSCC, which may be one of the underlying mechanisms in the pathogenesis of BSCC. Because p53 gene mutation is thought to be important in tumorigenesis of CSCC as well (Brash et al. 1991), however, there may be an additional mechanism by which the pathogenesis in BSCC is differentiated when compared with CSCC. We detected three mutations in the Fas gene that were exclusively observed in BSCC. These results suggest that mutant Fas may be involved in the process of development or progression of BSCC.

Although functional studies have not yet been performed, the mutations identified in this study are likely to disrupt or alter the normal function of Fas. To date, loss-of-function mutations of Fas have been identified in the promoter, exon 2, exon 3, exon 4, exon 6, exon 7, exon 8, and exon 9 (Watanabe-Fukunaga et al. 1992;Drappa et al. 1996;Bettinardi et al. 1997,Bettinardi et al. (1997;Infante et al. 1998;Tamiya et al. 1998;Maeda et al. 1999;Martin et al. 1999). Most of the mutations, however, have been detected in exon 9 which encodes the death domain of Fas (Itoh & Nagata 1993). The death domain is evolutionarily highly conserved and has been shown to be necessary and sufficient for the transduction of an apoptotic signal (Nagata 1997). In this study, one mutation (Asn 239 Asp) was identified in this conserved area, suggesting that the mutation might disrupt death signaling. Another mutation (Asn 102 Ser) was found in exon 4 (Table 1), which encodes part of FasL-binding domain of Fas (Starling et al. 1998). This mutation might impair the Fas pathway through inappropriate binding with its ligand. The other mutation (Cys 162 Arg) was found in exon 6, which encodes the transmembrane domain of Fas protein, but the functional significance of this mutation remains unknown at this stage.

The lprcg mice have a mis-sense mutation in exon 9 of Fas, which completely abolishes the signal transduction activities of Fas (Watanabe-Fukunaga et al. 1992). The human version of the lprcg mutation would results in amino-acid substitution at codon 238 (Watanabe-Fukunaga et al. 1992;Landowsky et al. 1997), which is close to the mutation identified in this study (amino acid substitution at codon 239). These data suggest that this area may be a potential hotspot in the Fas coding sequence.

Most of the patients with autoimmune lymphoproliferative syndrome carry a heterozygous mutation in the Fas gene (Drappa et al. 1996;Bettinardi et al. 1997;Infante et al. 1998;Martin et al. 1999). In these patients, the affected Fas protein seemed to work in a dominant-negative fashion, and T lymphocytes from these patients did not die upon activation. In our study, one Fas mutation (case 16) seemed to be a hemizygous mutation without allelic deletion (Table 1). In contrast, cases 7 and 13 showed evidence of alterations of both alleles (a mis-sense mutation and an allelic deletion), indicating potential bi-allelic inactivation of the Fas gene. The functional difference between mono-allelic and bi-allelic inactivations of Fas gene in the tumorigenesis of BSCC, however, remains unknown at this stage.

We observed Fas protein expression in 76% of BSCC. In the BSCC which were not shown to express Fas protein, loss or downregulation of the protein may be another way to avoid Fas-mediated apoptosis. The Fas gene mutations in three BSCC, which showed Fas expression by immunohistochemistry, may be involved in the mechanisms of Fas resistance of those tumors. The presence of Fas-resistance mechanisms in the remaining BSCC without Fas mutations remains to be studied.

Despite the small number of cases, the mutations in the death domain and ligand-binding domain of the Fas gene observed in BSCC suggest that mutant Fas may play an important part in the pathogenesis of BSCC, probably through protecting the tumor cells from host immune attack by FasL-bearing lymphocytes. Additional studies in a large patient population and examining the BSCC samples according to the progression, however, will be needed to verify these initial observations, and further identification of the role of apoptosis dysregulation in human tumorigenesis will certainly broaden our understanding of pathogenesis of not only BSCC but also other tumors deserving consideration.

Top

References

  1. Bartle, EJ, Sun, JH, Wang, XW, Schneider, BK: Cancers arising from burn scars. A literature review and report of twenty-one cases. J Burn Care Rehabil 1990 11:46–49,  | PubMed | ChemPort |
  2. Beltinger, C, Kurz, E, Bohler, T, Schrappe, M, Ludwig, WD, Debatin, KM: CD 95 (APO-1/Fas) mutations in childhood T-lineage acute lymphoblastic leukemia. Blood 1998 91:3943–3951,  | PubMed | ISI | ChemPort |
  3. Bettinardi, A, Brugnoni, B, Quiros-Roldan, E, Malagoli, A, Grutta, SL, Correra, A, Notarangelo, LD: Missense mutations in the Fas gene resulting in autoimmune lymphoproliferative syndrome: a molecular and immunological analysis. Blood 1997 89:902–909,  | PubMed | ISI | ChemPort |
  4. Brash, DE, Rudolph, JA, Simon, JA, et al.: A role for sunlight in skin cancer: UV-induced p53 mutations in squamous cell carcinoma. Proc Natl Acad Sci USA 1991 88:10124–10128,  | PubMed | ChemPort |
  5. Broders, AC: Squamous cell epithelioma of the skin. Ann Surg 1921 73:141–160,
  6. Davidson, WF, Giese, T, Fredrickson, TN: Spontaneous development of plasmacytoid tumors in mice with defective Fas–Fas ligand interactions. J Exp Med 1998 187:1825–1838,  | Article | PubMed | ISI | ChemPort |
  7. Drappa, J, Vaishnaw, AK, Sullivan, KE, Chu, JL, Elkon, KB: Fas gene mutations in the Canale–Smith syndrome, an inherited lymphoproliferative disorder associated with autoimmunity. N Engl J Med 1996 335:1643–1649,  | Article | PubMed | ISI | ChemPort |
  8. Fiucci, G Ruberti, G: Detection of polymorphisms within the Fas cDNA gene sequence by GC-clamp denaturing gradient gel electrophoresis. Immunogenetics 1994 39:437–439,  | PubMed | ISI | ChemPort |
  9. Grønbæk, K, Straten, PT, Ralfkiaer, E, et al.: Somatic Fas mutations in non-Hodgkin's lymphoma: association with extranodal disease and autoimmunity. Blood 1998 92:3018–3024,  | PubMed | ISI | ChemPort |
  10. Harland, DL, Robinson, WA, Franklin, WA: Deletion of the p53 gene in a patient with aggressive burn scar carcinoma. J Trauma 1997 42:104–107,  | PubMed | ISI | ChemPort |
  11. Huang, QR, Morris, D, Manolios, N: Identification and characterization of polymorphisms in the promoter region of the human Apo-1/fas (CD95) gene. Mol Immunol 1997 34:577–582,  | Article | PubMed | ISI | ChemPort |
  12. Infante, AJ, Britton, HA, DeNapoli, T, et al.: The clinical spectrum in a large kindred with autoimmune lymphoproliferative syndrome caused by a Fas mutation that impairs lymphocyte apoptosis. J Pediatr 1998 133:629–633,  | PubMed | ISI | ChemPort |
  13. Itoh, N Nagata, S: A novel protein domain required for apoptosis. Mutational analysis of human Fas antigen. J Biol Chem 1993 268:10932–10937,  | PubMed | ISI | ChemPort |
  14. Landowsky, TH, Qu, N, Buyuksal, I, Painter, JS, Dalton, WS: Mutations in the Fas antigen in patients with multiple myeloma. Blood 1997 90:4266–4270,  | PubMed | ISI | ChemPort |
  15. Lee, JY, Dong, SM, Kim, SY, Yoo, NJ, Lee, SH, Park, WS: A simple, precise and economical microdissection technique for analysis of genomic DNA from archival tissue sections. Virchows Arch 1998 433:305–309,  | Article | PubMed | ISI | ChemPort |
  16. Lee, SH, Shin, MS, Park, WS, et al.: Alterations of Fas (APO-1/CD95) gene in non-small cell lung cancer. Cancer Res 1999a 59:3068–3072,  | PubMed | ISI | ChemPort |
  17. Lee, SH, Shin, MS, Park, WS, et al.: Alterations of Fas (APO-1/CD95) gene in non-small cell lung cancer. Oncogene 1999b 18:3754–3760,  | Article | PubMed | ISI | ChemPort |
  18. Leithäuser, F, Dhein, J, Mechtersheimer, G, et al.: Constitutive and induced expression of APO-1, a new member of the new grow factor/tumor necrosis receptor superfamily, in normal and neoplastic cells. Lab Invest 1993 69:415–429,  | PubMed | ISI | ChemPort |
  19. Maeda, T, Yamada, Y, Moriuchi, R, et al.: Fas gene mutation in the progression of adult T cell leukemia. J Exp Med 1999 189:1063–1071,  | Article | PubMed | ISI | ChemPort |
  20. Martin, DA, Zheng, L, Siegel, RM, et al.: Defective CD95/APO-1/Fas signal complex formation in the human autoimmune lymphoproliferative syndrome, type Ia. Proc Natl Acad Sci USA 1999 96:4552–4557,  | Article | PubMed | ChemPort |
  21. Nagata, S: Apoptosis by death factor. Cell 1997 88:355–365,  | Article | PubMed | ISI | ChemPort |
  22. Owen-Schaub, LB, Radinsky, R, Kruzel, E, Berry, K, Yonehara, S: Anti-Fas on nonhematopoietic tumors: levels of Fas/APO-1 and bcl-2 are not predictive of biological responses. Cancer Res 1994 54:1580–1586,  | PubMed | ChemPort |
  23. Sakatani, S, Kusakabe, H, Kiyokane, K, Suzuki, K: p53 gene mutations in squamous cell carcinoma occurring in scars: comparison with p53 protein immunoreactivity. Am J Dermatopathol 1998 20:463–467,  | Article | PubMed | ISI | ChemPort |
  24. Shin, MS, Park, WS, Kim, SY, et al.: Alterations of Fas (APO-1/CD95) gene in cutaneous malignant melanoma. Am J Pathol 1999 154:1785–1791,  | PubMed | ISI | ChemPort |
  25. Starling, GC, Kiener, PA, Aruffo, A, Bajorath, J: Analysis of the ligand binding site in Fas (CD95) by site-directed mutagenesis and comparison with TNFR and CD40. Biochemistry 1998 37:3723–3726,  | Article | PubMed | ISI | ChemPort |
  26. Tamiya, S, Etoh, KI, Suzushima, H, Takatsuki, K, Matsuoka, M: Mutation of CD 95 (Fas/APO-1) gene in adult T-cell leukemia cells. Blood 1998 91:3935–3942,  | PubMed | ISI | ChemPort |
  27. Trauth, BC, Klas, C, Peters, AMJ, et al.: Monoclonal antibody-mediated tumor regression by induction of apoptosis. Science 1989 245:301–305,  | PubMed | ISI | ChemPort |
  28. Watanabe-Fukunaga, R, Brannan, CI, Copeland, NG, Jenkins, NA, Nagata, S: Lymphoproliferation disorder in mice explained by defects in Fas antigen that mediates apoptosis. Nature 1992 356:314–317,  | Article | PubMed | ChemPort |
  29. Zörnig, M, Grzeschiczek, A, Kowalski, M-B, Hartmann, K-U, Möröy, T: Loss of Fas/APO-1 receptor accelerates lymphomagenesis in Emu L-MYC transgenic mice but not in animals infected with MoMuLV. Oncogene 1995 10:2397–2401,  | PubMed | ISI | ChemPort |
Top

Acknowledgments

This work was supported by funding from the Korea Research Foundation made in the program year of 1998 (F-05).

Extra navigation

.
ADVERTISEMENT