Sequence diversity of hepatitis D virus in Mongolia.

Introduction: The Hepatitis Delta Virus (HDV) is a defective, single-stranded RNA virusoid encoding for a single protein, the Hepatitis Delta Antigen (HDAg), which requires the hepatitis B virus (HBV) envelope protein (HBsAg) for its transmission. Currently, hepatitis D is the most aggressive form of viral hepatitis and treatment options are limited. Worldwide 12 million people are chronically infected with HDV being at high risk for progression to cirrhosis and development of liver cancer. Objectives: Although it is well established that Mongolia is the country with the highest prevalence of HDV infections, the information on the molecular epidemiology and factors contributing to HDV sequence diversity are largely unclear. The aim of the study was to characterize the sequence diversity of HDV in rural areas from Mongolia and to determine the extent of HLA class I-associated selection pressure. Patients and methods: From the HepMongolia cohort from rural areas in Mongolia, 451 HBsAg-positive individuals were selected and anti-HDV, HDV-RNA and the sequence of the large HDAg was determined. For all individuals the HLA class I locus was genotyped. Residues under selection pressure in the presence of individual HLA class I types were identified with the recently published analysis tool HAMdetector. Results: Of 431 HBsAg positive patients, 281 were anti-HDV positive (65%), and HDV-RNA could be detected in 207 of 281 (74%) of patients. The complete large HDAg was successfully sequenced from 131 samples. Phylogenetic analysis revealed that all Mongolian HDV isolates belong to genotype 1, however, they separate into several different clusters without clear regional association. In turn, from phylogeny there is strong evidence for recent local transmission events. Importantly, we found multiple residues with strong support for HLA class I-associated selection pressure consistent with a functional CD8+ T cell response directed against HDV. Conclusion: HDV isolates from Mongolia are highly diverse. The molecular epidemiology suggests circulation of multiple subtypes and provides evidence for ongoing recent transmissions.

Interleukin-7-dependent nonclassical monocytes and CD40 expression are affected in children with type 1 diabetes.

The important role of IL-7 in the generation of self-reactive T-cells in autoimmune diseases is well established. Recent studies on autoimmunity-associated genetic polymorphisms indicated that differential IL-7 receptor (IL-7R) expression of monocytes may play a role in the underlying pathogenesis. The relevance of IL-7-mediated monocyte functions in type 1 diabetes remains elusive. In the present study, we characterized monocyte phenotype and IL-7-mediated effects in children with type 1 diabetes and healthy controls with multicolor flow cytometry and t-distributed Stochastic Neighbor-Embedded (t-SNE)-analyses. IL-7R expression of monocytes rapidly increased in vitro and was boosted through LPS. In the presence of IL-7, we detected lower monocyte IL-7R expression in type 1 diabetes patients as compared to healthy controls. This difference was most evident for the subset of nonclassical monocytes, which increased after IL-7 stimulation. t-SNE analyses revealed IL-7-dependent differences in monocyte subset distribution and expression of activation and maturation markers (i.e., HLA-DR, CD80, CD86, CD40). Notably, monocyte CD40 expression increased considerably by IL-7 and CD40/IL-7R co-expression differed between patients and controls. This study shows the unique effects of IL-7 on monocyte phenotype and functions. Lower IL-7R expression on IL-7-induced CD40high monocytes and impaired IL-7 response characterize monocytes from patients with type 1 diabetes.

CD33 Delineates Two Functionally Distinct NK Cell Populations Divergent in Cytokine Production and Antibody-Mediated Cellular Cytotoxicity.

The generation and expansion of functionally competent NK cells in vitro is of great interest for their application in immunotherapy of cancer. Since CD33 constitutes a promising target for immunotherapy of myeloid malignancies, NK cells expressing a CD33-specific chimeric antigen receptor (CAR) were generated. Unexpectedly, we noted that CD33-CAR NK cells could not be efficiently expanded in vitro due to a fratricide-like process in which CD33-CAR NK cells killed other CD33-CAR NK cells that had upregulated CD33 in culture. This upregulation was dependent on the stimulation protocol and encompassed up to 50% of NK cells including CD56dim NK cells that do generally not express CD33 in vivo. RNAseq analysis revealed that upregulation of CD33+ NK cells was accompanied by a unique transcriptional signature combining features of canonical CD56bright (CD117high, CD16low) and CD56dim NK cells (high expression of granzyme B and perforin). CD33+ NK cells exhibited significantly higher mobilization of cytotoxic granula and comparable levels of cytotoxicity against different leukemic target cells compared to the CD33- subset. Moreover, CD33+ NK cells showed superior production of IFNγ and TNFα, whereas CD33- NK cells exerted increased antibody-dependent cellular cytotoxicity (ADCC). In summary, the study delineates a novel functional divergence between NK cell subsets upon in vitro stimulation that is marked by CD33 expression. By choosing suitable stimulation protocols, it is possible to preferentially generate CD33+ NK cells combining efficient target cell killing and cytokine production, or alternatively CD33- NK cells, which produce less cytokines but are more efficient in antibody-dependent applications.

A novel HLA-B variant, HLA-B*14:02:16, discovered by amplicon-based next-generation sequencing.

HLA-B*14:02:16 differs from B*14:02:01:01 by a synonymous nucleotide substitution in codon 141.

Mutational and Functional Analysis of FANCB as a Candidate Gene for Sporadic Head and Neck Squamous Cell Carcinomas.

BACKGROUND/AIM: Head and neck squamous cell carcinomas (HNSCCs) form a heterogeneous tumor entity located throughout the oral cavity, pharynx and larynx that is caused predominantly by chemically or virally induced carcinogenesis. Heterozygous germline mutations in cancer susceptibility genes might also lead to increased incidence of HNSCCs. As DNA stability is typically impaired in HNSCC cells and genes of the Fanconi anemia/BRCA DNA repair pathway can be mutated or down-regulated in HNSCCs, we investigated here whether germline mutations occur in the X-chromosomal FANCB as candidate gene. MATERIALS AND METHODS: Germline DNA of 85 consecutive HNSCC patients was sequenced. Missense alterations in FANCB were functionally tested in reference cells. RESULTS AND CONCLUSION: Four single nucleotide polymorphisms were identified, three of which were located in untranslated regions of FANCB (rs2188383, rs2375729, rs2905223) and predicted to be associated with normal function. One missense alteration, c.1004G>A resulting in p.G335E (rs41309679), in exon 4 was detected in five men in homozygous and in five women in heterozygous state. Four in silico prediction programs uniformally predicted p.G335E to be associated with loss-of-function of the protein. To clarify these predictions, we expressed the FANCB p.G335E protein in primary human FANCB deficient fibroblasts. Cell cycle analysis of these fibroblasts established that the FANCB p.G335E was functionally indistinguishable from the wildtype FANCB protein. Thus, functional studies in genetically defined cells showed that the p.G335E germline alteration in FANCB is not associated with impaired function.

RAD51C--a new human cancer susceptibility gene for sporadic squamous cell carcinoma of the head and neck (HNSCC).

INTRODUCTION: Head and neck squamous cell carcinomas (HNSSCs) are one of the leading causes of cancer-associated death worldwide. Although certain behavioral risk factors are well recognized as tumor promoting, there is very little known about the presence of predisposing germline mutations in HNSCC patients. METHODS: In this study, we analyzed 121 individuals with HNSCCs collected at our institution for germline alterations in the newly identified cancer susceptibility gene RAD51C. RESULTS: Sequencing of all exons and the adjacent introns revealed five distinct heterozygous sequence deviations in RAD51C in seven patients (5.8%). A female patient without any other risk factors carried a germline mutation that disrupted the canonical splice acceptor site of exon 5 (c.706-2A>G). CONCLUSIONS: As there are only a few publications in the literature identifying germline mutations in head and neck cancer patients, our results provide the first indication that paralogs of RAD51, recently described as mutated in breast and ovarian cancer patients, might also be candidates for genetic risk factors in sporadic squamous cell carcinomas of the head and neck.

Analysis of the functional integrity of the p53 tumor-suppressor gene in malignant melanoma.

Derogation of the p53 pathway is a hallmark in human malignancies but its implication in melanomas remains unclear. p53 is frequently accumulated in melanomas despite protein stabilizing mutations being rare. For a panel of six melanoma cell lines we performed transcript sequence analysis of the entire coding region and determined p53 protein stability and messenger RNA stability by western blot experiments and quantitative reverse-transcription-PCR, respectively. Transcript levels of p53 modifying genes as well as p53 target genes were investigated after ultraviolet irradiation, interferon-α-2b, and chemotherapy (cisplatin or dacarbazine) by quantitative reverse-transcription-PCR. Transcript sequence analysis identified three aberrations in three of six melanomas. Four of six melanomas showed high-constitutive p53 protein levels. p53 transcripts remained stable in four of six melanomas. All p53-expressing melanomas displayed high p53 protein stability. Constitutively, and after ultraviolet irradiation, mouse double min-2 expression was reduced in melanomas. We detected high homeodomain-interacting protein kinase-2 level in melanomas-expressing mutant p53. Most experimental conditions resulted in lower expression of p21, GADD45A, and PUMA, and a higher expression of CDC2 in melanomas. Altogether, accumulation of p53 protein is due to posttranslational modification or aberrant expression of p53 modifiers. p53 is functionally disrupted although the p53 upstream signaling pathway remains inducible.

The checkpointkinase 2 (CHK2) 1100delC germ line mutation is not associated with the development of squamous cell carcinoma of the head and neck (SCCHN).

BACKGROUND: The checkpointkinase 2 (CHK2) is part of the highly conserved ATM-CHK2 signaling pathway, which is activated in response to DNA damage, in particular after double strand breaks which can be caused by carcinogens like smoking. After induction of downstream targets, e.g. the tumor suppressor p53, its activation leads to cell cycle arrest and apoptosis. Recently, the presence of CHK2 germ line mutations, primarily the 1100delC variant, has been reported to be involved in carcinogenesis. The CHK2 1100delC variant results in a truncated protein which is instable and inactive. Carriers of this variant have been shown to have an increased risk to develop breast cancer and probably also other tumors. Our purpose was to investigate the role of CHK2 germ line mutations in patients with squamous cell carcinoma of the head and neck (SCCHN). MATERIALS AND METHODS: We investigated 91 patients suffering from SCCHN including all tumor sites (oropharynx, hypopharynx, larynx) for the presence of the germ line mutation 1100delC by direct sequence analysis. Patients were characterized by their tumor localization, tumor stage, age, the presence of additional malignant tumors and predisposing carcinogens (smoking, alcohol abuse). RESULTS: None of the patients, independently of the tumor site, age, the abuse of predisposing carcinogens, or the presence of other kinds of tumors, carried the CHK2 1100delC variant. CONCLUSIONS: The germ line CHK2 1100delC variant does not seem to have a major impact on the development of SCCHN.

A novel mechanism for anti-EGFR antibody action involves chemokine-mediated leukocyte infiltration.

Overexpression of the epidermal growth factor receptor (EGFR) is a hallmark of squamous cell carcinoma of the head and neck (SCCHN). Monoclonal antibodies (mAbs) against EGFR are currently used for therapy of recurrent or metastatic disease; however, their mode of action is not completely understood. To investigate the immunological effects of anti-EGFR mAb, we generated a three-dimensional spheroid model of EGFR-expressing SCCHN and used this model to study the effect of anti-EGFR mAb on leukocyte migration toward tumors. Pretreatment with the blocking anti-EGFR mAb EMD 72000, its F(ab')2 fragments or an EGFR tyrosine kinase inhibitor led to substantially increased leukocyte infiltration into EGFR overexpressing tumor spheroids, but not into those with low EGFR expression. Nonblocking anti-EGFR mAb or fibroblast-specific mAb did not affect leukocyte infiltration, suggesting that the observed increase in leukocyte infiltration depends on interference with EGFR activation. Using a human cytokine macroarray, we demonstrated that the blockade of EGFR by anti-EGFR mAb in EGFR-overexpressing SCCHN cells leads to differential expression of several cytokines and chemokines, including the chemokine MCP-1/CCL-2. The significant upregulation of MCP-1/CCL2 on exposure to anti-EGFR mAb was confirmed by quantitative PCR and enzyme-linked immunospot analyses. Moreover, blocking anti-MCP-1 antibody inhibited leukocyte migration toward tumor cells induced by anti-EGFR mAb, pointing to an important role of MCP-1/CCL2 in anti-EGFR mAb-induced leukocyte migration. Our findings demonstrate that anti-EGFR mAb induces leukocyte infiltration to tumor spheroids by upregulating chemokine expression. This novel mechanism for anti-EGFR mAb action may contribute to the antitumor effects of anti-EGFR mAb in vivo.

Is there a role for the Fas-/Fas-Ligand pathway in chemoresistance of human squamous cell carcinomas of the head and neck (SCCHN)?

The aim of the present investigation was to determine the expression of the Fas-receptor/ligand system in established cell lines of squamous cell carcinomas of the head and neck (SCCHN), and to study it's functional impact on chemotherapy-induced apoptosis in these SCCHN cell lines. We observed constitutive expression of Fas and FasL in 13 SCCHN cell lines by RT-PCR, Southern-blotting and immunocytochemistry, respectively. Administration of the agonistic Fas-antibody CH-11 led to a significant reduction of viable cells in the colorimetric MTT-assay in 5 out of 13 (38%) cell lines tested and preincubation with Interferon-gamma (IFN-gamma) rendered 3 (23%) primarily resistant cell lines sensitive. Cisplatin (cDDP) and bleomycin (BLM) caused dose-dependent cytotoxicity in all cell lines as determined by the 50% inhibitory concentration (IC(50)) and induction of apoptosis. Furthermore, both antineoplastic agents led to an enhanced surface expression of Fas and FasL in all cell lines, and this effect was independent of the respective p53-status. This upregulation of Fas/FasL surface expression increased preexisting Fas-sensitivity only, but failed to make primarily resistant cell lines undergo Fas-mediated growth reduction or apoptosis. Vice versa, blockade of Fas-receptor-ligand-interactions by monoclonal antibodies directed against FasL was able to attenuate the cytotoxic effect of cDDP and BLM in 2 out of 5 (40%) cell lines tested only. In conclusion, in contrast to many other solid tumors, the Fas/FasL-system does not seem to play an exclusive role in anticancer drug mediated apoptosis in SCCHN.

Alterations in the p53 pathway and their association with radio- and chemosensitivity in head and neck squamous cell carcinoma.

Chemotherapy and/or radiotherapy are established measures in treatment protocols of head and neck squamous cell carcinoma (HNSCC). However, we still lack reliable predictive markers for the response to radio- and chemotherapy. The p53 pathway is involved in stress response and thus might influence chemo-/radiosensitivity. Using 29 HNSCC cell lines previously characterized for p53 mutations, we simultaneously analyzed several key players in the p53 pathway by RT-PCR, transcript sequencing and immunohistochemistry, and investigated their association with chemosensitivity and radiosensitivity. Cell lines with p53 mutations were slightly more sensitive to cisplatin than those with wild-type p53. The type of mutation did not influence radio- or chemosensitivity. p14(ARF), an activator of p53, was lost or mutated in all cell lines. Three cell lines showed overexpression of HDM-2, a major negative regulator of p53; however, HDM-2 levels did not correlate with radio- or chemosensitivity. HPV-16 oncoproteins were detected in one highly chemoresistant cell line. Our findings suggest that molecular events resulting in the inactivation of the p53 pathway occur in all HNSCC cell lines. However, single alterations in the p53 pathway are not reliable predictors for the response to radio- or chemotherapy in HNSCC.

Immunological characterization of missense mutations occurring within cytotoxic T cell-defined p53 epitopes in HLA-A*0201+ squamous cell carcinomas of the head and neck.

Previous analyses of p53 in 40 HLA-A*0201(HLA-A2)(+) squamous cell carcinomas of the head and neck (SCCHN) indicated that 6/13 p53 missense mutations that were detected, S149C, T150R, V157F, Y220C, Y220H and E271K, occurred within HLA-A2-restricted cytotoxic T lymphocyte (CTL)-defined p53 epitopes. Of the 6, the p53 S149C, Y220C and Y220H peptides were immunogenic. Anti-p53 mutant S149C and Y220H effector cells cross-reacted against the parental wild type sequence (wt) p53 peptides, whereas anti-p53 Y220C effector cells were specific for the mutant peptide, p53 Y220C cDNA-transfected HLA-A2(+) SaOS cells, and an HLA-A2(+) SCCHN cell line naturally expressing the mutation. These results indicate that the p53 Y220C mutation can be processed and presented for CD8(+) T cell recognition. Furthermore, using an autologous PBMC/tumor system, anti-p53 Y220C peptide-effector cells recognizing the autologous tumor could also be generated. Our analysis of p53 in 10 additional HLA-A2(+) SCCHN tumors detected the p53 Y220C in 2/10 tumors raising the overall frequency of the p53 Y220C mutation to 6/50 (12%) HLA-A2(+) SCCHN tumors. In contrast, independent of their HLA class I genotypes, the p53 Y220C mutation frequency for all human tumors analyzed to date is approximately 1.5%. This unexpectedly high frequency of the p53 Y220C mutation in HLA-A2(+) SCCHN suggests that vaccines targeting this mutation would not only be expected to induce robust anti-tumor immune responses in HLA-A2(+) subjects, but also be more widely applicable than previously envisioned for any given p53 missense mutation.

Gamma-delta T-cells in patients with squamous cell carcinoma of the head and neck.

In our attempt to characterize a general immune-suppression found in patients with squamous cell carcinoma of the head and neck (SCCHN) we now focused on a subset of CD3 lymphocytes described as gamma/delta-T-cells, a cell type with potential relevance in non-MHC restricted anti-tumor immune responses. Peripheral blood of 33 SCCHN patients and 33 age-matched controls (CON) was evaluated for the frequency of gamma/delta-T-cells among CD3+ T-cells and their onset of apoptosis (Annexin V binding) by multicolor flow cytometry. Results were correlated with clinical parameters. Patients with SCCHN had a significantly higher proportion of gamma/delta-T-cells compared to healthy controls (4.4+/-0.4% for SCCHN vs. 3.0+/-0.3% for CON, p=0.01). However, this increase was not paralleled with a difference in the onset of apoptosis if compared to CON. There was also no correlation between the proportion of gamma/delta-T-cells and tumor stage. However, a significantly higher proportion of gamma/delta-T-cells was found in patients with recurrent or metachronous second primary SCCHN (6.0+/-1.0%) if compared to the other SCCHN (3.8+/-0.4%, p=0.02). In a follow up 3-6 months post-treatment patients showed a decrease of gamma/delta-T-cells among CD3+cells (2.7+/-0.4%, n=4) if they were operated only and an increase if primary radio-chemotherapy (6.7+/-1.7%, n=8) or a combination of operation plus radio-chemotherapy (6.8+/-2.3%, n=3) was applied. Furthermore, patients receiving palliative treatment including radio-chemotherapy had highest values of gamma/delta-T-cells (9.1+/-2.7%, n=4) overall implicating that the treatment modality significantly influences the proportion of gamma/delta-T-cells. Since patients with SCCHN, particularly those with recurrent or second primary disease after treatment, had a higher proportion of gamma/delta-T-cells without signs of a reduced onset of apoptosis this could be due to an increased de novo generation. The current study implies that increased frequencies of gamma/delta-T-cells in patients with SCCHN may not only be the result of tumor-host interactions but the consequence of applied treatment modalities.

Comprehensive analysis of the p53 status in mucosal and cutaneous melanomas.

The abrogation of the function of the "gatekeeper of the genome", p53, is the most prevalent molecular alteration in solid human tumors. Regarding melanomas the involvement of p53 alterations is discussed controversially to date. In order to evaluate the status of p53 in detail, primary tumors and metastases of 63 sporadic cutaneous (CM) and mucosal (MuM) melanomas were examined by immunohistochemistry and sequence analysis of the entire coding region of the p53 transcript, i.e., exons 2 to 11. In addition, loss of heterozygosity (LOH) and loss of allele-specific transcription (LOT) were determined. Accumulation of the p53 protein occurred in most of the CM and MuM specimens (71% and 58%, respectively). In contrast, protein stabilizing p53 mutations were observed in 14% of the CM and no mutation was found in MuM specimens. Two of the aberrations located outside the core domain. LOH was detected in 22% CM and 58% MuM, and LOT in 25% of the CM specimens. The genotype distribution at the polymorphic p53 codon 72 in melanoma patients differed significantly from control subjects. The calculation of odds ratios (OR) and 95% confidence intervals (CI) indicated an increased risk for developing cutaneous melanomas in individuals carrying the Pro-coding allele. Altogether, aberrant p53 expression appears to be a common event in both CM and MuM.

T cells specific for HPV16 E7 epitopes in patients with squamous cell carcinoma of the oropharynx.

Squamous cell carcinomas of the oropharynx (SCCO) are often infected with oncogenic human papilloma virus (HPV) subtype 16. To determine the frequency of T cells specific for human leukocyte antigen (HLA)-A2.1 restricted HPV16 E7 protein-derived epitopes, tetramer analysis was performed using peripheral blood lymphocytes of 20 HLA-A2.1+ patients and 20 HLA-A2.1+ healthy individuals. Tetramers specific for 3 HPV16 peptides (E711-20, E782-90 and E786-93), an influenza matrix peptide (a model recall antigen) or an HIV reverse transcriptase peptide (a model novel antigen) were used in multicolor flow analysis. The HPV-specific T-cell frequencies were correlated with the HPV16 E7 and p16 status in tumor sections. In vitro stimulation (IVS) with autologous dendritic cells (DC) pulsed with HPV16 E7 epitopes was performed to demonstrate proliferation and antitumor activity of the HPV-responsive T cells. Frequencies of CD8+ T cells specific for HPV16 E7 peptides were not significantly different in patients with SCCO relative to normal donors. However, patients with tumors expressing HPV16 E7 (60%) and p16 (50%) had an increased frequency (p<0.05) of T cells specific for the E711-20 epitope compared to those with tumors negative for both markers. HPV16 E711-20 and HPV16 E786-93 specific T cells were expandable upon IVS with cognate peptide-pulsed DC and were reactive against peptide-pulsed targets or, in case of the E711-20 epitope-specific T cells, against HPV16 E7 expressing CaSki cell line. Thus, in patients with HPV16+ SCCO, precursor T cells specific for E711-20 epitope are present (1/3,947) in the circulation, are responsive to stimulation with the cognate viral peptide and recognize in vitro HPV16 E7+ tumor cells. Further studies have to elucidate why those T cells are unable to eliminate the tumor in vivo and this might also allow for finding potential strategies that will increase the chances of developing a future HPV-based vaccine in patients with SCCO.

Homozygous deletions of CDKN2A caused by alternative mechanisms in various human cancer cell lines.

The CDKN2A tumor-suppressor locus on chromosome band 9p21, which encodes p16(INK4A), a negative regulator of cyclin-dependent kinases, and p14(ARF1), an activator of TP53, is inactivated in many human cancers by point mutation, promoter hypermethylation, and, often, deletion. Homozygous deletions are unusually prevalent at this locus in very different human cancers. In the present study, we compared deletions in squamous cell carcinoma of the head and neck (SCCHN) cell lines to those in T-cell acute lymphatic leukemia (T-ALL), glioma, and bladder carcinoma (TCC) cell lines. Of 14 SCCHN lines, 10 showed homozygous deletions of CDKN2A, one displayed promoter hypermethylation with gene silencing, and one had a frameshift deletion in exon 2. Many deletion ends were in or proximal to the repetitive sequence clusters flanking the locus. Breakpoint junctions displayed variable microhomologies or insertions characteristic of DNA repair by nonhomologous end-joining. In general, deletions were much smaller in SCCHN than in TCC and glioma. In T-ALL, breakpoints were near consensus sites for recombination mediated by RAG (recombination activating genes) enzymes, and the structure of the junctions was consistent with this mechanism. We suggest that different mechanisms of CDKN2A deletion prevail in different human cancers. Aberrant RAG-mediated recombination may be responsible in T-ALL, and exuberant DNA repair by nonhomologous end-joining is the likely prevailing mechanism in SCCHN, but a distinct mechanism in TCC and glioma remains to be elucidated.

p53, p63 and p73 expression in squamous cell carcinomas of the head and neck and their response to cisplatin exposure.

p63 and p73 share significant structural and functional homologies with the tumour suppressor p53. Unlike the p53 gene, both encode for several isoforms which vary in their NH2 and COOH termini with variable and, in part, opposed biological functions. The objective of the present study was to analyse the expression profiles of p53 family members in squamous cell carcinomas of the head and neck (HNSCC) and their alterations caused by exposure to the clinically active drug cisplatin. Using multiplex RT-PCR combined with the Southern technique, we determined transcription of p53 family members in 10 established HNSCC cell lines. In the majority of HNSCC, p53 and different p63/p73 isoforms were expressed with cell-line-specific patterns for composition and intensity of transcript expression. Exposure to cisplatin caused multiple alterations in the p63 and p73 profiles suggesting a complex regulation which may influence the sensitivity to chemotherapy.

p53 codon 72 polymorphic variants, loss of allele-specific transcription, and human papilloma virus 16 and/or 18 E6 messenger RNA expression in squamous cell carcinomas of the head and neck.

A polymorphism at codon 72 of the human tumor suppressor p53 determines translation into either arginine or proline. Yet, the impact of this amino acid variability on the risk to develop malignant tumors, particularly carcinomas associated with human papilloma virus (HPV) infections, remains unresolved because of contradictory results. To address a potential correlation between the different genotypes and the manifestation of squamous cell carcinomas of the head and neck (SCCHN), we determined the p53 codon 72 in 193 healthy subjects and 122 unselected SCCHN with known HPV status. Furthermore, loss of allele-specific transcription was analyzed in p53 codon 72 heterozygous (Arg/Pro) SCCHN and correlated with HPV 16 and/or 18 E6 transcript expression. We found a moderately increased risk (odds ratio, 1.86; 95% confidence interval, 1.0-3.3) for individuals with germ line heterozygosity to develop SCC of the pharynx. On the other hand, p53 codon 72 polymorphic variants, most notably the Arg/Arg genotype, showed no association with the presence of HPV 16 and/or 18 E6 transcript. Moreover, there was no evidence for HPV-driven selection in SCCHN with allele-specific loss of transcription. Our data suggest that the p53 codon 72 polymorphism has a minor impact on the development of SCCHN.

Is the p53 inactivation frequency in squamous cell carcinomas of the head and neck underestimated? Analysis of p53 exons 2-11 and human papillomavirus 16/18 E6 transcripts in 123 unselected tumor specimens.

Mutations and interaction with high-risk human papillomavirus (HPV) E6 oncoprotein are well-established mechanisms of p53 inactivation. In a series of 123 unselected squamous cell carcinomas of the head and neck (SCCHN), we performed sequence analysis of the entire coding region of p53 transcript and determined the presence of the E6 transcripts of HPV 16 and 18. Aberrant p53 transcripts were identified in 97 (79%) SCCHN. HPV 16 and/or 18 E6 transcripts were detected in 37 (30%) tumor specimens, including 20 (77%) of the 26 p53 wild-type tumors. The likely inactivation of p53 in 117 (95%) of the 123 SCCHN suggests that this event could be obligatory in the multistep process of carcinogenesis.

Analysis of BRCA1, TP53, and TSG101 germline mutations in German breast and/or ovarian cancer families.

About 5%-10% of breast cancers are considered to be hereditary and associated with germline mutations of specific genes. As yet, the most frequently affected genes identified are BRCA1 and BRCA2, but also other genes such as TP53 are supposed to influence the predisposition toward breast cancer. In the present study, we analyzed patients of 19 German families with early onset breast cancer and/or a family history of breast and/or ovarian cancer for the presence of mutations in BRCA1 and TP53. In addition, we screened for germline mutations in the putative tumor suppressor gene TSG101. For this purpose we used direct sequence analysis of the entire coding regions for all three genes and, in the case of BRCA1, single-strand conformation polymorphism analysis and protein transcription-translation assays. We identified eight previously described polymorphisms and several aberrations in BRCA1: 1 unclassified missense mutation, 3 small protein truncating mutations, 1 novel pseudoexon, and 5 splicing variants. No mutation was detected in TP53. Analysis of TSG101 transcripts revealed an aberrant transcript in two breast cancer patients belonging to the same family, suggesting TSG101 as a predisposing gene in hereditary breast cancer.