ALK translocation is the 3rd most frequent genetic aberration in lung adenocarcinoma, and several... more ALK translocation is the 3rd most frequent genetic aberration in lung adenocarcinoma, and several inhibitors are now clinically available in first and second line settings. Accordingly, molecular diagnostics of ALK-positive lung cancer is very important and can be done with the rational combination of several methods. All international recommendations suggest that, except for cytological samples, screening technology for ALK-positive tumors is immunohistochemistry using a validated test. It is highly recommended that in case of ALK protein positive samples gene translocation must be confirmed by fluorescent in situ hybridization (FISH). In case of cytological samples FISH technique must be used as ALK diagnostics. In equivocal cases the genetic alteration of ALK can be confirmed by alternative molecular techniques such as next generation sequencing or RNAbased PCR methods. Upon administration of ALK inhibitors, acquired resistance is frequent which is mostly due to ALK amplification and/or mutation. It is evident that the diagnostics of these secondary ALK gene alterations must be done from recurrent tumors or circulating nucleic acids.
The role of alphaIIbbeta3 integrin in regulating platelet function is well appreciated, whereas i... more The role of alphaIIbbeta3 integrin in regulating platelet function is well appreciated, whereas its role in tumor progression and metastasis is not. The purpose of our study was to determine a functional relevance to expression of alphaIIbbeta3 integrin in cells derived from human solid tumors. A study of human melanoma biopsies (n = 24) showed that alphaIIbbeta3 expression increased with tumor thickness, which is indicative of metastatic propensity. Expression of alphaIIbbeta3 was 8% (+/-1.8), 33% (+/-10.4) and 62% (+/-5) in melanomas ranging in thickness from 0-1.5 mm, 1.5-4.0 mm and >4 mm, respectively; alphavbeta3 was equally high all categories. To determine biological function, we stably transfected alphaIIbbeta3 into human melanoma cells that express alphavbeta3, but not alphaIIbbeta3. Surface expression of alphavbeta3 remained unaltered between alphaIIbbeta3 (+) and mock transfected counterparts. The alphaIIbbeta3 (+) cells possessed increased ability to adhere, spread and migrate on fibrinogen. They had decreased ability to attach, spread and migrate on vitronectin. Immunocytochemistry showed that expression of alphaIIbbeta3 displaced alphavbeta3 from focal contact points. When implanted subcutaneously into SCID mice, the alphaIIbbeta3 (+) cells developed approximately 4-fold larger tumors when compared to their mock counterparts and the level of apoptosis was reduced within the tumors. Results suggest that co-expression of the 2 beta3 integrins, alphavbeta3 and alphaIIbbeta3, in human melanoma cells enhanced cell survival and promoted growth in vivo.
3328 Introduction : Human monoclonal antibodies against tumor-associated ganglioside antigens hav... more 3328 Introduction : Human monoclonal antibodies against tumor-associated ganglioside antigens have the potential for tumor therapeutic reagents. We report here a novel strategy to obtain such antibodies. We aimed to investigate and compare B cells infiltrating breast carcinomas and melanomas (TIL-B), in terms of tumor antigen specific binding potential. We questioned the characteristics of these different tumor types and how the immunoglobuline repertoire of their TIL-B parallels the distinguished features.Description of the work: Different types of breast carcinoma and melanoma tumor tissues were processed for further cellular and molecular studies. Heavy (VH) and light chain (Vκ, Vλ) immunoglobulin variable region genes were amplified. Single chain Fv (scFv) antibody fragments were constructed and phage display libraries generated. We compared our previously developed method to other techniques. The effectiveness of the selection process in respect of tumor associated ganglioside specific antibody fragments was tested against various tumor cell membranes. Selected tumor binder antibody fragments of breast cancer and melanoma TIL-B libraries were investigated in cell ELISA, immunofluorescence FACS analysis, confocal microscopy. DNA sequence analysis and biochemical investigations were done to define the targeted tumor associated antigens. Summary of results: Heavy and light chain immunoglobulin variable region genes could be amplified from any of the investigated tissues. This way single chain Fv antibody fragment phage libraries could be generated and specific tumor binders could be selected.With our technique we obtained human antibody fragmenst with unique GD3 ganglioside specificities on breast carcinomas and melanomas. The anti-GD3 antibody pattern was selective for the cancerous tissues and showed apoptotic effects in different tumor cell cultures. Conclusion: Our results suggest that B cells accumulated in breast carcinomas or melanomas have the potential to reveal key tumor associated antigens. Acknowledgements:Supporting grants (Fulbright Research Scholarship 26.0911, OTKA T048933, OTKA T030380, NATO CLG 978639, Rajko Medenica Research Foundation). Key words: antibody fragments, breast carcinomas, ganglioside, melanoma
Cancer Epidemiology and Prevention Biomarkers, Dec 1, 2006
Background: A great variety of solid tumors is characterized by lymphocytic infiltrates, especial... more Background: A great variety of solid tumors is characterized by lymphocytic infiltrates, especially T cells. The amount of B lymphocytes in tumors is variable. In some breast cancers heavy B cell infiltration (TIL-B) could be correlated with improved patient survival. Objectives: We ...
Molecular epidemiology of mismatch repair deficiency (dMMR)/microsatellite instability (MSI) are ... more Molecular epidemiology of mismatch repair deficiency (dMMR)/microsatellite instability (MSI) are different in various ethnic groups; accordingly, our aim was to test this in a large single-center Hungarian cancer patient cohort. We have found that dMMR/MSI incidence correlates well with TCGA data in case of colorectal, gastric and endometrial cancers. We have also observed that immunohistochemistry- based dMMR incidences are higher as compared to MSI. We suggest that the testing guidelines must be fine-tuned for immune-oncology indications. Nádorvári ML, Kiss A, Barbai T, Rásó E, Tímár J. Molecular epidemiology of mismatch repair deficiency, microsatellite instability in a large single diagnostic center cancer cohort.
Despite experimental findings suggesting the prognostic significance of Aquaporin 1 (AQP1) in hum... more Despite experimental findings suggesting the prognostic significance of Aquaporin 1 (AQP1) in human melanoma, no published clinical data are available. We studied the expression of AQP1 protein in cutaneous melanoma, correlated our findings with standard histological and genetic markers, and long-term clinical follow-up. Our study evaluated the AQP1 protein expression in 78 melanoma patients, representing two predefined risk cohorts using the immune labeling technique with commercially available anti-AQP1 antibodies on routinely formalin-fixed and paraffin-embedded tumor tissue samples. BRAF V600E mutation analyses were carried out successfully in 70 patients using PCR and restriction fragment length polymorphism analyses, followed by confirmatory analysis with the Sanger sequencing technique. AQP1-expressing melanoma cells were found in 52 cases (66.7%, median H-score=124.24). Significantly higher AQP1 H-scores (P=0.047) were found in the 'high-risk' patients. No correlations were found with the established histological markers, such as mitotic index (P=0.42), Clark level (P=0.95), and Breslow thickness (P=0.51). BRAF V600 mutation analyses were successful in 89%, and showed a two times higher mutation frequency in the 'high-risk' group. The BRAF V600 mutations were significantly associated with AQP1 expression (P=0.014). Long-term follow-up indicated a reduced progression-free survival (P=0.036) and overall survival (P=0.017) for the AQP1-positive cutaneous melanoma patients. AQP1 expression is likely to be associated with an adverse prognosis in cutaneous melanoma.
The therapeutic impact of KRAS mutations remains controversial in bone metastatic lung adenocarci... more The therapeutic impact of KRAS mutations remains controversial in bone metastatic lung adenocarcinoma (LADC). Therefore, our aim was to investigate the effects of KRAS mutational status on overall survival (OS) in these patients according to bisphosphonate therapy (BTx) and radiation therapy (RTx). In total, 134 LADC patients diagnosed with simultaneous bone metastasis were included in this study. The results of the univariate (p=0.008) and multivariate (p=0.004) survival analyses indicated that KRAS mutation is a negative prognostic factor. Both BTx and RTx can increase the OS with a pronounced benefit for patients with KRAS wild-type tumors. Importantly, the concomitant use of BTx and RTx might increase the OS irrespective of KRAS status compared to BTx or RTx alone. In summary, our results might contribute to the development of new therapeutic approaches with regards to KRAS mutational status in bone metastatic LADC.
Head and neck squamous cell carcinomas (HNSCC) take many lifes worldwide. Patients with recurrent... more Head and neck squamous cell carcinomas (HNSCC) take many lifes worldwide. Patients with recurrent/metastatic disease receive combination chemotherapy containing anti-EGFR antibody cetuximab. However, resistance often hurdles therapy. The mechanism is yet to unveil, although EGFR extracellular alterations and activity of c-Met signaling were accused. We investigated the effects of EGFR-vIII and EGFR-R521K on cetuximab efficacy in HNSCC in cellular, xenograft, and clinical setup. Furthermore, we investigated the efficacy of c-Met inhibition in HNSCC in vitro and in vivo. We showed that EGFR-vIII is very rare in HNSCC, while the common R521K polymorphism abolishes antibody-dependent cellular cytotoxicity and in vivo antitumor effect of cetuximab. This selectivity was not reflected in immunophenotype or survival data of HNSCC patients, suggesting a more complex mechanism behind. Interestingly, c-Met inhibitor SU11274 was more effective in cetuximab-resistant, EGFR R521K heterozygous cells and xenografts, raising the possible importance of simultaneous targeting of the two receptors.
The aims of this study were to assess the sex hormone receptor status of head and neck (HNC) canc... more The aims of this study were to assess the sex hormone receptor status of head and neck (HNC) cancers. Frozen surgical samples (n = 67) of HNC patients were analyzed. Protein expression of estrogen receptor (ER)alpha, ERbeta and progesterone receptor (PgR) of tumor cells was determined by immunocytochemistry. Data were confirmed at mRNA level by nested-PCR and sequencing. ER and PgR expressions confirmed by PCR analysis were frequent in HNC: 50.7 and 49.3% respectively. Concerning the ER isoforms, ERalpha expression was predominant over ERbeta in both of oral cavity- as well as laryngeal/hypopharyngeal (LH) cancers. The delta3 splice variant of ERalpha was detected at low frequency, while the delta5 splice variant of ERbeta was frequent in HNC. The incidence of functional receptor expression (coexpression of ER and PgR) was relatively frequent also in HNC (27/67, 40.3%) which was independent of the anatomical location of the tumor. Sex hormone receptor expressions did not affect survival of HNC patients, however, in the LH cancer subgroup ER expression was associated with a trend of shortened survival (p = 0.0636, Mantel-Cox generalized savage). ERalpha,beta and PgR expressions are frequent in HNC and may affect the prognosis of the disease, at least in case of LH cancers.
4320 NM23-H1 was first identified by virtue of its reduced expression in highly metastatic melano... more 4320 NM23-H1 was first identified by virtue of its reduced expression in highly metastatic melanoma and breast carcinoma cells, and the ability of forced NM23-H1 expression to inhibit metastatic potential without significant impact on the transformed phenotype. NM23-H1 exhibits nucleoside diphosphate kinase (NDPK) activity, catalyzing the transfer of γ-phosphate between nucleoside triphosphate and nucleoside diphosphate via a “ping-pong” mechanism. In addition to NDPK activity, NM23-H1 also exhibits both protein histidine kinase and 3’-5’exonuclease activities. Generally, enzymes that contain 3’-5’ exonuclease activity are involved directly in DNA repair processes and the maintenance of genomic stability. We hypothesized that loss of the 3’-5’ exonuclease activity of NM23-H1 during tumor progression impairs genomic integrity, thereby enhancing metastatic potential. In an effort to quantify the contribution of NM23-H1 to DNA repair, we have initiated experiments in the yeast Saccharomyces cerevisiae. Yeast provide excellent eukaryotic models for DNA repair research, since knockout strains are available for essentially all genes and DNA repair mechanisms are relatively well-characterized. In this project, we measured the extent to which expression of ynk1(the yeast homologue of the human metastasis suppressor NM23-H1) is required for genomic integrity. Mutation rates were measured in a haploid ynk1 knockout (ynk1Δ) strain using the standard CAN1 forward mutation assay. The ynk1 deletion had no effect on spontaneous mutation rate, but did result in increased mutations (2.2-fold) upon treatment with the DNA methylating agent, methyl methanesulfonate. Moreover, UV radiation induced a more marked (7-fold) deficit of DNA repair in the ynk1Δ strain as compared with the wild-type counterpart. Current efforts are being devoted to analyzing DNA repair activity in ynk1Δ strains that harbor second knockouts in a variety of known DNA repair genes (e.g. Ddc1, Rad17, Mec3, Msh2 and Fen1). Such double-knockout strains may magnify the ynk1-dependent mutator phenotype, as well as facilitate identification of the relevant biochemical activity(s) of the NM23-H1 molecule by complementation with wild-type and enzymatically-defective mutant forms of the protein.
ALK translocation is the 3rd most frequent genetic aberration in lung adenocarcinoma, and several... more ALK translocation is the 3rd most frequent genetic aberration in lung adenocarcinoma, and several inhibitors are now clinically available in first and second line settings. Accordingly, molecular diagnostics of ALK-positive lung cancer is very important and can be done with the rational combination of several methods. All international recommendations suggest that, except for cytological samples, screening technology for ALK-positive tumors is immunohistochemistry using a validated test. It is highly recommended that in case of ALK protein positive samples gene translocation must be confirmed by fluorescent in situ hybridization (FISH). In case of cytological samples FISH technique must be used as ALK diagnostics. In equivocal cases the genetic alteration of ALK can be confirmed by alternative molecular techniques such as next generation sequencing or RNAbased PCR methods. Upon administration of ALK inhibitors, acquired resistance is frequent which is mostly due to ALK amplification and/or mutation. It is evident that the diagnostics of these secondary ALK gene alterations must be done from recurrent tumors or circulating nucleic acids.
The role of alphaIIbbeta3 integrin in regulating platelet function is well appreciated, whereas i... more The role of alphaIIbbeta3 integrin in regulating platelet function is well appreciated, whereas its role in tumor progression and metastasis is not. The purpose of our study was to determine a functional relevance to expression of alphaIIbbeta3 integrin in cells derived from human solid tumors. A study of human melanoma biopsies (n = 24) showed that alphaIIbbeta3 expression increased with tumor thickness, which is indicative of metastatic propensity. Expression of alphaIIbbeta3 was 8% (+/-1.8), 33% (+/-10.4) and 62% (+/-5) in melanomas ranging in thickness from 0-1.5 mm, 1.5-4.0 mm and >4 mm, respectively; alphavbeta3 was equally high all categories. To determine biological function, we stably transfected alphaIIbbeta3 into human melanoma cells that express alphavbeta3, but not alphaIIbbeta3. Surface expression of alphavbeta3 remained unaltered between alphaIIbbeta3 (+) and mock transfected counterparts. The alphaIIbbeta3 (+) cells possessed increased ability to adhere, spread and migrate on fibrinogen. They had decreased ability to attach, spread and migrate on vitronectin. Immunocytochemistry showed that expression of alphaIIbbeta3 displaced alphavbeta3 from focal contact points. When implanted subcutaneously into SCID mice, the alphaIIbbeta3 (+) cells developed approximately 4-fold larger tumors when compared to their mock counterparts and the level of apoptosis was reduced within the tumors. Results suggest that co-expression of the 2 beta3 integrins, alphavbeta3 and alphaIIbbeta3, in human melanoma cells enhanced cell survival and promoted growth in vivo.
3328 Introduction : Human monoclonal antibodies against tumor-associated ganglioside antigens hav... more 3328 Introduction : Human monoclonal antibodies against tumor-associated ganglioside antigens have the potential for tumor therapeutic reagents. We report here a novel strategy to obtain such antibodies. We aimed to investigate and compare B cells infiltrating breast carcinomas and melanomas (TIL-B), in terms of tumor antigen specific binding potential. We questioned the characteristics of these different tumor types and how the immunoglobuline repertoire of their TIL-B parallels the distinguished features.Description of the work: Different types of breast carcinoma and melanoma tumor tissues were processed for further cellular and molecular studies. Heavy (VH) and light chain (Vκ, Vλ) immunoglobulin variable region genes were amplified. Single chain Fv (scFv) antibody fragments were constructed and phage display libraries generated. We compared our previously developed method to other techniques. The effectiveness of the selection process in respect of tumor associated ganglioside specific antibody fragments was tested against various tumor cell membranes. Selected tumor binder antibody fragments of breast cancer and melanoma TIL-B libraries were investigated in cell ELISA, immunofluorescence FACS analysis, confocal microscopy. DNA sequence analysis and biochemical investigations were done to define the targeted tumor associated antigens. Summary of results: Heavy and light chain immunoglobulin variable region genes could be amplified from any of the investigated tissues. This way single chain Fv antibody fragment phage libraries could be generated and specific tumor binders could be selected.With our technique we obtained human antibody fragmenst with unique GD3 ganglioside specificities on breast carcinomas and melanomas. The anti-GD3 antibody pattern was selective for the cancerous tissues and showed apoptotic effects in different tumor cell cultures. Conclusion: Our results suggest that B cells accumulated in breast carcinomas or melanomas have the potential to reveal key tumor associated antigens. Acknowledgements:Supporting grants (Fulbright Research Scholarship 26.0911, OTKA T048933, OTKA T030380, NATO CLG 978639, Rajko Medenica Research Foundation). Key words: antibody fragments, breast carcinomas, ganglioside, melanoma
Cancer Epidemiology and Prevention Biomarkers, Dec 1, 2006
Background: A great variety of solid tumors is characterized by lymphocytic infiltrates, especial... more Background: A great variety of solid tumors is characterized by lymphocytic infiltrates, especially T cells. The amount of B lymphocytes in tumors is variable. In some breast cancers heavy B cell infiltration (TIL-B) could be correlated with improved patient survival. Objectives: We ...
Molecular epidemiology of mismatch repair deficiency (dMMR)/microsatellite instability (MSI) are ... more Molecular epidemiology of mismatch repair deficiency (dMMR)/microsatellite instability (MSI) are different in various ethnic groups; accordingly, our aim was to test this in a large single-center Hungarian cancer patient cohort. We have found that dMMR/MSI incidence correlates well with TCGA data in case of colorectal, gastric and endometrial cancers. We have also observed that immunohistochemistry- based dMMR incidences are higher as compared to MSI. We suggest that the testing guidelines must be fine-tuned for immune-oncology indications. Nádorvári ML, Kiss A, Barbai T, Rásó E, Tímár J. Molecular epidemiology of mismatch repair deficiency, microsatellite instability in a large single diagnostic center cancer cohort.
Despite experimental findings suggesting the prognostic significance of Aquaporin 1 (AQP1) in hum... more Despite experimental findings suggesting the prognostic significance of Aquaporin 1 (AQP1) in human melanoma, no published clinical data are available. We studied the expression of AQP1 protein in cutaneous melanoma, correlated our findings with standard histological and genetic markers, and long-term clinical follow-up. Our study evaluated the AQP1 protein expression in 78 melanoma patients, representing two predefined risk cohorts using the immune labeling technique with commercially available anti-AQP1 antibodies on routinely formalin-fixed and paraffin-embedded tumor tissue samples. BRAF V600E mutation analyses were carried out successfully in 70 patients using PCR and restriction fragment length polymorphism analyses, followed by confirmatory analysis with the Sanger sequencing technique. AQP1-expressing melanoma cells were found in 52 cases (66.7%, median H-score=124.24). Significantly higher AQP1 H-scores (P=0.047) were found in the 'high-risk' patients. No correlations were found with the established histological markers, such as mitotic index (P=0.42), Clark level (P=0.95), and Breslow thickness (P=0.51). BRAF V600 mutation analyses were successful in 89%, and showed a two times higher mutation frequency in the 'high-risk' group. The BRAF V600 mutations were significantly associated with AQP1 expression (P=0.014). Long-term follow-up indicated a reduced progression-free survival (P=0.036) and overall survival (P=0.017) for the AQP1-positive cutaneous melanoma patients. AQP1 expression is likely to be associated with an adverse prognosis in cutaneous melanoma.
The therapeutic impact of KRAS mutations remains controversial in bone metastatic lung adenocarci... more The therapeutic impact of KRAS mutations remains controversial in bone metastatic lung adenocarcinoma (LADC). Therefore, our aim was to investigate the effects of KRAS mutational status on overall survival (OS) in these patients according to bisphosphonate therapy (BTx) and radiation therapy (RTx). In total, 134 LADC patients diagnosed with simultaneous bone metastasis were included in this study. The results of the univariate (p=0.008) and multivariate (p=0.004) survival analyses indicated that KRAS mutation is a negative prognostic factor. Both BTx and RTx can increase the OS with a pronounced benefit for patients with KRAS wild-type tumors. Importantly, the concomitant use of BTx and RTx might increase the OS irrespective of KRAS status compared to BTx or RTx alone. In summary, our results might contribute to the development of new therapeutic approaches with regards to KRAS mutational status in bone metastatic LADC.
Head and neck squamous cell carcinomas (HNSCC) take many lifes worldwide. Patients with recurrent... more Head and neck squamous cell carcinomas (HNSCC) take many lifes worldwide. Patients with recurrent/metastatic disease receive combination chemotherapy containing anti-EGFR antibody cetuximab. However, resistance often hurdles therapy. The mechanism is yet to unveil, although EGFR extracellular alterations and activity of c-Met signaling were accused. We investigated the effects of EGFR-vIII and EGFR-R521K on cetuximab efficacy in HNSCC in cellular, xenograft, and clinical setup. Furthermore, we investigated the efficacy of c-Met inhibition in HNSCC in vitro and in vivo. We showed that EGFR-vIII is very rare in HNSCC, while the common R521K polymorphism abolishes antibody-dependent cellular cytotoxicity and in vivo antitumor effect of cetuximab. This selectivity was not reflected in immunophenotype or survival data of HNSCC patients, suggesting a more complex mechanism behind. Interestingly, c-Met inhibitor SU11274 was more effective in cetuximab-resistant, EGFR R521K heterozygous cells and xenografts, raising the possible importance of simultaneous targeting of the two receptors.
The aims of this study were to assess the sex hormone receptor status of head and neck (HNC) canc... more The aims of this study were to assess the sex hormone receptor status of head and neck (HNC) cancers. Frozen surgical samples (n = 67) of HNC patients were analyzed. Protein expression of estrogen receptor (ER)alpha, ERbeta and progesterone receptor (PgR) of tumor cells was determined by immunocytochemistry. Data were confirmed at mRNA level by nested-PCR and sequencing. ER and PgR expressions confirmed by PCR analysis were frequent in HNC: 50.7 and 49.3% respectively. Concerning the ER isoforms, ERalpha expression was predominant over ERbeta in both of oral cavity- as well as laryngeal/hypopharyngeal (LH) cancers. The delta3 splice variant of ERalpha was detected at low frequency, while the delta5 splice variant of ERbeta was frequent in HNC. The incidence of functional receptor expression (coexpression of ER and PgR) was relatively frequent also in HNC (27/67, 40.3%) which was independent of the anatomical location of the tumor. Sex hormone receptor expressions did not affect survival of HNC patients, however, in the LH cancer subgroup ER expression was associated with a trend of shortened survival (p = 0.0636, Mantel-Cox generalized savage). ERalpha,beta and PgR expressions are frequent in HNC and may affect the prognosis of the disease, at least in case of LH cancers.
4320 NM23-H1 was first identified by virtue of its reduced expression in highly metastatic melano... more 4320 NM23-H1 was first identified by virtue of its reduced expression in highly metastatic melanoma and breast carcinoma cells, and the ability of forced NM23-H1 expression to inhibit metastatic potential without significant impact on the transformed phenotype. NM23-H1 exhibits nucleoside diphosphate kinase (NDPK) activity, catalyzing the transfer of γ-phosphate between nucleoside triphosphate and nucleoside diphosphate via a “ping-pong” mechanism. In addition to NDPK activity, NM23-H1 also exhibits both protein histidine kinase and 3’-5’exonuclease activities. Generally, enzymes that contain 3’-5’ exonuclease activity are involved directly in DNA repair processes and the maintenance of genomic stability. We hypothesized that loss of the 3’-5’ exonuclease activity of NM23-H1 during tumor progression impairs genomic integrity, thereby enhancing metastatic potential. In an effort to quantify the contribution of NM23-H1 to DNA repair, we have initiated experiments in the yeast Saccharomyces cerevisiae. Yeast provide excellent eukaryotic models for DNA repair research, since knockout strains are available for essentially all genes and DNA repair mechanisms are relatively well-characterized. In this project, we measured the extent to which expression of ynk1(the yeast homologue of the human metastasis suppressor NM23-H1) is required for genomic integrity. Mutation rates were measured in a haploid ynk1 knockout (ynk1Δ) strain using the standard CAN1 forward mutation assay. The ynk1 deletion had no effect on spontaneous mutation rate, but did result in increased mutations (2.2-fold) upon treatment with the DNA methylating agent, methyl methanesulfonate. Moreover, UV radiation induced a more marked (7-fold) deficit of DNA repair in the ynk1Δ strain as compared with the wild-type counterpart. Current efforts are being devoted to analyzing DNA repair activity in ynk1Δ strains that harbor second knockouts in a variety of known DNA repair genes (e.g. Ddc1, Rad17, Mec3, Msh2 and Fen1). Such double-knockout strains may magnify the ynk1-dependent mutator phenotype, as well as facilitate identification of the relevant biochemical activity(s) of the NM23-H1 molecule by complementation with wild-type and enzymatically-defective mutant forms of the protein.
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Papers by Erzsebet Raso