Abstract P2-08-01: Loss of function of Brca1 or Gata3 induces basal-like breast cancer

BACKGROUND:

Breast cancer is mainly divided into estrogen receptor (ER)-positive luminal and ER-negative basal-like tumors. Luminal-type tumors are associated with better survival and respond to hormone therapies whereas basal-like tumors are more aggressive and associated with a poor prognosis. Mammary epithelia are mainly composed of luminal and basal cells that are maintained by luminal and basal progenitors, respectively. The maintenance of luminal cell fate is orchestrated by networks of transcription factors, including BRCA1 and GATA3. Functional loss of BRCA1 by germline or somatic mutation or by promoter methylation is associated with more than one third of basal-like breast cancers. GATA3 expression is reduced in basal-like breast cancers and cancers that metastasize. Overexpression of GATA3 in cancer cells inhibits tumor formation. Deletion of Brca1 or Gata3 in mice results in early lethality or growth defects. How BRCA1 and GATA3 suppress breast cancer remains elusive.

METHODS:

We generated mice lacking Brca1 or Gata3 in mammary epithelia. Due to the proliferative defects and induction of p18Ink4c (p18), an inhibitor of CDK4/6, in mammary epithelial cells of these mice, we then generated mice lacking Brca1 or Gata3 in p18 deficient mammary epithelia. We determined spontaneous mammary tumor development in mutant mice and the mechanisms underlying the role of Brca1 and Gata3 in suppressing tumorigenesis and progression.

RESULTS:

Depletion of Brca1 or Gata3 led to growth defects of mammary epithelial cells, which was rescued by loss of p18. Depletion of Brca1 or Gata3 in a p18 null background induced heterogeneous mammary tumors with less luminal and more basal-like features and accelerated metastasis. Deletion of Brca1 eliminated Gata3 expression in human and mouse mammary tissues and cells. How Brca1 interacts with Gata3 to control mammary tumor development and progression is currently under investigation.

CONCLUSION: Our results suggest that loss of function of either Brca1 or Gata3 induces basal-like mammary tumors in p18 deficient background.

Citation Format: Pei X-H, Chan HL, Zhang L, Wang C, Robbins DJ, Capobianco T, Bai F. Loss of function of Brca1 or Gata3 induces basal-like breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-08-01.

Abstract P6-08-08: GATA3 inhibits breast basal-like tumorigenesis

BACKGROUND: Breast cancer can be broadly categorized into two groups depending on the cell type affected. Luminal-type tumors are typically estrogen receptor (ER) positive that are associated with better survival and respond to hormone therapies whereas basal-like tumors are ER negative, more aggressive, and associated with a poor prognosis. GATA3 is a transcription factor well studied for its role as a master regulator of cellular differentiation and stem cell self renewal. Loss of Gata3 in mouse mammary glands blocks luminal cell differentiation and induces growth defects, and low levels of GATA3 are associated with basal-like and metastatic human breast cancers with epithelial-to-mesenchymal transition (EMT). Importantly, luminal cells have been shown to be the origin of some basal-like breast cancers. Due to the proliferation defects caused by GATA3 deficiency, it remains elusive how loss of function of GATA3 contributes to breast cancers development and progression.

METHODS: We previously demonstrated that p18Ink4c (p18), a cell cycle inhibitor, is a downstream target of GATA3 in regulating mammary luminal cell proliferation and loss of p18 leads to luminal type tumorigenesis. To test the role of Gata3 deficiency in tumorigenesis, we generated p18-/-;Gata3+/- mice. Mammary gland development and tumorigenesis were characterized in vivo using a panel of cellular and molecular assays. Results were further confirmed in vitro with well established cell lines.

RESULTS: Loss of p18 rescued mammary growth defects caused by Gata3 heterozygosity. Gata3 heterozygosity impaired luminal, but promoted basal gene expression in mammary epithelial cells. Gata3 heterozygosity in p18 null mice accelerated spontaneous mammary tumorigenesis, reducing the average latency of tumor onset. More importantly, Gata3 heterozygosity transformed the luminal type tumors of p18 null mice into heterogeneous basal-like breast cancers with activated EMT. Conversely, reintroduction of GATA3 inhibited tumor growth and reduced expression of EMT markers in basal-like tumor xenografts. We discovered that expression of GATA3 and Vimentin, an EMT marker, is inversely related in human breast cancers.

CONCLUSION: Our data indicates that GATA3 promotes luminal but suppresses basal cell differentiation in the mammary gland and in tumor development.

Mechanisms underlying the role of GATA3 in suppressing basal-like tumor development are under investigation.BACKGROUND: Breast cancer can be broadly categorized into two groups depending on the cell type affected. Luminal-type tumors are typically estrogen receptor (ER) positive that are associated with better survival and respond to hormone therapies whereas basal-like tumors are ER negative, more aggressive, and associated with a poor prognosis. GATA3 is a transcription factor well studied for its role as a master regulator of cellular differentiation and stem cell self renewal. Loss of Gata3 in mouse mammary glands blocks luminal cell differentiation and induces growth defects, and low levels of GATA3 are associated with basal-like and metastatic human breast cancers with epithelial-to-mesenchymal transition (EMT). Importantly, luminal cells have been shown to be the origin of some basal-like breast cancers. Due to the proliferation defects caused by GATA3 deficiency, it remains elusive how loss of function of GATA3 contributes to breast cancers development and progression.

METHODS: We previously demonstrated that p18Ink4c (p18), a cell cycle inhibitor, is a downstream target of GATA3 in regulating mammary luminal cell proliferation and loss of p18 leads to luminal type tumorigenesis. To test the role of Gata3 deficiency in tumorigenesis, we generated p18-/-;Gata3+/- mice. Mammary gland development and tumorigenesis were characterized in vivo using a panel of cellular and molecular assays. Results were further confirmed in vitro with well established cell lines.

RESULTS: Loss of p18 rescued mammary growth defects caused by Gata3 heterozygosity. Gata3 heterozygosity impaired luminal, but promoted basal gene expression in mammary epithelial cells. Gata3 heterozygosity in p18 null mice accelerated spontaneous mammary tumorigenesis, reducing the average latency of tumor onset. More importantly, Gata3 heterozygosity transformed the luminal type tumors of p18 null mice into heterogeneous basal-like breast cancers with activated EMT. Conversely, reintroduction of GATA3 inhibited tumor growth and reduced expression of EMT markers in basal-like tumor xenografts. We discovered that expression of GATA3 and Vimentin, an EMT marker, is inversely related in human breast cancers.

CONCLUSION: Our data indicates that GATA3 promotes luminal but suppresses basal cell differentiation in the mammary gland and in tumor development.

Mechanisms underlying the role of GATA3 in suppressing basal-like tumor development are under investigation.

Citation Format: Pei X-H, Chan HL, Liu S, Scott A, Pimentel E, Slingerland J, Robbins D, Capobianco A, Bai F. GATA3 inhibits breast basal-like tumorigenesis [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P6-08-08.

Genetic variation in ERCC1 and XPF genes and breast cancer risk

Breast cancer is one of the most frequently diagnosed cancer in women worldwide, and we conducted a case-control study by genotyping seven potentially functional SNPs, three in ERCC1 and four in XPF, in a Chinese population of 417 breast cancer cases and 417 cancer-free controls. Three SNPs in ERCC1 and four SNPs in XPF were genotyped by using the Taqman Universal PCR Master Mix in the GeneAmp(®) PCR System 9700 with Dual 384-Well Sample Block Module, and assays were performed on a 384-well plate on the Sequenom MassARRAY platform. We found that elevated breast cancer risk was associated with those who had a family history of breast cancer and history of breast disease, and those who were over 25 years old at first full-term pregnancy. We found that decreased risk of breast cancer was associated with those who had a history of full-term pregnancies. Compared with the ERCC1 rs11615 T/T genotype, a significantly higher risk of breast cancer was found in the C/C genotype in codominant and dominant models after adjusting for potential risk factors. Similarly, we found that ERCC1 rs3212986 C/C genotype was associated with an increased risk of breast cancer in codominant, dominant and recessive models. Our study indicated that the ERCC1 rs11615 and rs2298881 polymorphisms are associated with breast cancer in a Chinese population. Further studies with large sample size are greatly needed to elucidate the SNPs of ERCC1 and XPF genes in the development of breast cancer.

Germline mutation of Brca1 alters the fate of mammary luminal cells and causes luminal-to-basal mammary tumor transformation

Breast cancer developed in familial BRCA1 mutation carriers bears striking similarities to sporadic basal-like breast tumors. The mechanism underlying the function of BRCA1 in suppressing basal-like breast cancer remains unclear. We previously reported that the deletion of p18(Ink4c) (p18), an inhibitor of G1 cyclin Ds-dependent CDK4 and CDK6, stimulates mammary luminal progenitor cell proliferation and leads to spontaneous luminal tumor development. We report here that germline mutation of Brca1 in p18-deficient mice blocks the increase of luminal progenitor cells, impairs luminal gene expression and promotes malignant transformation of mammary tumors. Instead of the luminal mammary tumors developed in p18 single-mutant mice, mammary tumors developed in the p18;Brca1 mice, similar to breast cancer developed in familial BRCA1 carriers, exhibited extensive basal-like features and lost the remaining wild-type allele of Brca1. These results reveal distinct functions of the RB and BRCA1 pathways in suppressing luminal and basal-like mammary tumors, respectively. These results also suggest a novel mechanism--causing luminal-to-basal transformation--for the development of basal-like breast cancer in familial BRCA1 carriers and establish a unique mouse model for developing therapeutic strategies to target both luminal and basal-like breast cancers.

Transfer of IkappaBalpha gene increase the sensitivity of paclitaxel mediated with caspase 3 activation in human lung cancer cell

In oncogenic therapies, apoptosis seems to be the important mechanism of deciding chemotherapy effect. NF-kappaB transcription factors are implicated in the control of cell proliferation and apoptosis. NF-kappaB is activated by chemotherapy and by irradiation, and this pathway has been shown to protect cells potently from their stimuli-induced apoptosis. Furthermore, inhibition of NF-kappaB leads to enhanced apoptosis in response to various stimuli. However, because the role of NF-kappaB as a modifier of the intrinsic chemosensitivity of cancer cells is less clear, we have studied the impact of IkappaBalpha (an inhibitor of NF-kappaB) on the chemosensitivity of human lung cancer cells. We used adenoviral vectors expressing human IkappaBalpha (AdIkappaBalpha) and investigated the effects of IkappaBalpha gene transfer in combination with 6 anticancer agents on a human pulmonary adenocarcinoma cell line, A549. Solutions containing anticancer agents at various concentrations were added followed by the addition of recombinant adenovirus solutions, and each IC50 was calculated based on the dose-response curves. The gene transfer of AdIkappaBalpha decreased IC50 from 12.0 to 2.2 nM on paclitaxel and increased IC50 from 0.27 to 16.0 microM on SM5887 compared with the transfer of control gene, AdLacZ. The IC50 did not change clearly on the other anticancer drugs. To investigate this molecular mechanism, we measured caspase 3 activity by the transfer of IkappaBalpha gene. On result, paclitaxel increased caspase 3 activity and SM5887 decreased the activity. These results indicate that the cell killing effect of anticancer drug is influenced by the inhibition of NF-kappaB activity and may, at least in part, depend on the regulation of caspase 3 activation. Adenovirus mediated IkappaBalpha gene transfer improve the anti-cancer effect of paclitaxel to lung cancer cells through the regulation of caspase 3 activation.

Polychlorinated biphenyls promote 1-nitropyrene-induced lung tumorigenesis without the induction of K-ras gene mutation in A/J mice

Although the effects of polychlorinated biphenyls (PCBs) on human lung carcinogenesis are suggested from the massive PCBs poisoning that occurred in Japan designated "Yusho," the detailed molecular mechanism are unknown. 1 nitropyrene (1-NP), an ubiquitous and abundant environmental pollutant, is known to be detected in lung tissues derived from patients with lung cancer in Japan, and its relation to lung carcinogenesis is also suggested. We investigated the effects of PCBs (Kanechlor-400) on 1-NP-induced lung tumorigenesis in A/J mice. PCBs were administered intraperitoneally followed by ip injection of 1-NP. The lung lesions were examined 18 weeks after the final treatment. In the control group, no neoplastic lesions were induced in the lung. In the PCB group, preneoplastic lesions such as hyperplasia and adenoma were induced in 2/10 (20%) mice. In 1-NP group and in PCB + 1-NP group, lung lesions including adenocarcinoma were induced in 16/20 (80%) and 13/13 (100%) mice, respectively. Both the number and the size of tumors in PCB + 1-NP group were significantly greater than those in 1-NP group. K-ras gene mutation, CAA to CGA in codon 61 or GGT to GAT in codon 12, was found in either 1-NP group or PCB + 1-NP group but not in the PCB group. There was no difference in the pattern of K-ras mutation associated with the pretreatment with PCBs. These results suggest that PCBs promote 1-NP-induced lung tumorigenesis and may support, at least in part, the mechanism of the high incidence of lung cancer in patients with Yusho.

Polycyclic aromatic hydrocarbon carcinogens increase ubiquitination of p21 protein after the stabilization of p53 and the expression of p21

Polycyclic aromatic hydrocarbon carcinogens (PAHs) and their metabolites have been found to result in a rapid accumulation of p53 gene product in human and mouse cells. However, the induced p53 protein was reported to be transcriptionally inactive. In the present study, the induction of p53 target gene expression after the treatment with either benzo(a)pyrene (B[a]P) or 1-nitropyrene (1-NP) was investigated. A marked induction of messenger RNA (mRNA) expressions of Mdm2, Bax, and p21 was detected in wild-type p53-expressing cells after the treatment with either B[a]P or 1-NP, whereas no significant change in mRNA expression of these genes was observed in p53-negative and mutant cells. 1-NP activated the p21 promoter in a p53-dependent manner. Binding activity of p53 to a p53 consensus sequence increased after the treatment in wild-type p53-expressing cells. Nevertheless, the induced mRNA levels of the p21 did not result in a proportional p21 protein increase, indicating the possibility of post-transcriptional regulation of the protein. With the addition of MG-132, a proteasome inhibitor, to B[a]P or 1-NP treatments, both p21 and p53 protein levels were increased; however, the increase in p21 protein levels was significantly larger than the increase in p53 protein levels. PAHs treatment increased the level of ubiquitinated p21. These results suggest that the p21 product is degraded by the ubiquitin-proteasome system. We conclude that PAHs-induced p53 protein is transcriptionally active.

Analysis of Fas and Fas ligand expression and function in lung cancer cell lines

The aim of this study was to investigate the expression of Fas and Fas ligand (FasL) and to determine the significance of these molecules in lung cancer cell lines. Immunoblotting, RT-PCR and flow cytometric analyses were carried out to measure the expression of Fas and FasL and to examine their interactions and effects on cell growth and apoptosis. Fas and FasL were co-expressed in most of the cell lines but to varying degrees. Apoptosis induced by the agonistic anti-Fas antibody was significantly correlated with Fas expression (P=0.0075), whereas cisplatin-induced apoptosis was not. Upregulation of Fas and FasL expression by the administration of cisplatin was found in 7 of 11 (64%) and 9 of 11 (82%) cell lines, respectively. However, cisplatin-induced apoptosis was not suppressed by antagonistic anti-FasL antibody. Thus, our data indicated that Fas and FasL were co-expressed in lung cancer cell lines, and that Fas ligation induced by agonistic anti-Fas antibody is functional and induced apoptosis that was dependent on the levels of Fas expression. In contrast, Fas-FasL interactions appeared to be non-functional. Furthermore, our results suggest that cisplatin-induced apoptosis in lung cancer cells was independent of the Fas-FasL interaction.

Alteration of drug chemosensitivity caused by the adenovirus-mediated transfer of the wild-type p53 gene in human lung cancer cells

The aim of the present study is to identify the optimal anticancer agents for use in combination with gene therapy using wild-type (wt) p53 gene transfer. We used adenoviral vectors expressing human wt p53 (AdCAp53) and investigated the effects of wt p53 gene transfer in combination with 12 anticancer agents on a human pulmonary squamous cell carcinoma cell line, NCI-H157, and a human pulmonary large cell carcinoma cell line, NCI-H1299. Solutions containing anticancer agents at various concentrations were added followed by the addition of recombinant adenovirus solutions; after a 5-day incubation period, the anticancer activity was then evaluated by a 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carbo xanilide assay. Each 50% inhibitory concentration was calculated based on the dose-response curves. The agents showing a high degree of effectiveness on NCI-H157 cells were cisplatin (CDDP), 5-fluorouracil (5-FU), bleomycin, and 7-ethyl-10-hydroxy-camptothecin (SN-38), an active metabolite of irinotecan (CPT-11); conversely, cyclophosphamide and paclitaxel showed a low degree of effectiveness. Based on these data, an isobologram was performed to investigate the interaction between AdCAp53 and some anticancer agents. A supra-additive effect was thus observed for 5-FU and SN-38 on NCI-H157 cells. An additive effect was also observed for CDDP, paclitaxel, bleomycin, and cyclophosphamide on NCI-H157 cells. CDDP, paclitaxel, 5-FU, and SN-38 had an additive effect on NCI-H1299 cells. No drug showed any subadditive or protective effects. These findings suggest that CPT-11 and 5-FU may thus be useful as possible anticancer agents for use in a combination therapy regimen using wt p53 gene transfer. CDDP and CPT-11 had a significant antitumoral effect on H157 cell xenografts of nude mice in vivo. These results indicate that CPT-11 as well as CDDP would be a candidate for the combination of chemotherapy and gene therapy for non-small cell lung cancer.

Benzo[a]pyrene activates the human p53 gene through induction of nuclear factor kappaB activity

p53 is known to be recruited in response to DNA-damaging genotoxic stress and plays an important role in maintaining the integrity of the genome. In the present study, the effect of a potent lung cancer carcinogen, benzo[a]pyrene (B[a]P) on p53 expression was investigated. We showed that exposure of A549 and NIH 3T3 cells to B[a]P resulted in an increase in p53 mRNA levels and in p53 promoter activation, indicating that B[a]P-induced p53 expression is partly regulated at the transcriptional level. The p53 promoter region which extends from -58 to -43, overlapping the kappaB motif, is essential for both the p53 basal promoter activity and p53 promoter activation induced by B[a]P. Nuclear factor kappaB (NF-kappaB) proteins have been revealed to be activated in B[a]P-induced p53 expression. Activated NF-kappaB complexes were shown to contain predominantly p50 and p65 subunit components in A549 cells and p65 subunit in NIH 3T3 cells. In addition, the overexpression of IkappaBalpha completely inhibited NF-kappaB activation, p53 promoter transactivation and the stimulatory effect on p53 transcription induced by B[a]P. We therefore conclude that B[a]P transcriptionally activates the human p53 gene through the induction of NF-kappaB activity.

Expression of p53 and glutathione S-transferase-pi relates to clinical drug resistance in non-small cell lung cancer

To determine the predictive value of the expression of p53 and glutathione S-transferase-pi (GST-pi) with respect to chemotherapy response, immunostaining was performed on transbronchial biopsy specimens from previously untreated patients with non-small cell lung cancer. Of the 54 patients, 34 patients (63%) and 37 patients (69%) were positive for p53 and GST-pi, respectively. The response rates in the p53-positive and p53-negative group were 15 and 45%, and those in GST-pi-positive and GST-pi-negative groups were 16 and 47%, respectively. A multiple logistic regression analysis revealed that positive immunostaining for GST-pi was a significant risk factor for clinical chemotherapy resistance. The combination of these two markers was the most important independent factor in predicting a response to chemotherapy in multiple logistic regression analysis. Immunohistochemical expression of p53 and GST-pi was independently related to clinical chemoresistance in patients with non-small cell lung cancer. Combined use of these two biomarkers may be a useful predictor of clinical chemoresistance.

[Effect of PCBs on mouse lung tumorigenesis induced by 1-nitropyrene: a preliminary report]

We have analyzed the effect of polychlorinated biphenyls (PCB, Kanechlor-400) on 1-nitropyrene (1-NP) induced lung tumor. Male A/J mice (6 weeks old) were used for the experiment. A total of 2.5 mg/kg PCB was administered intraperitoneally (PCB group), a total of 0.38 mmol/kg 1-NP was administered intraperitoneally for 17 times (1-NP group), PCB was administered followed by i.p. injection of 1-NP (PCB + 1-NP group), and only vehicle was administered (control group). The lung lesions induced were examined 18 weeks after the final treatment with 1-NP or vehicle. In control group, no neoplastic lesion in the lung was induced. In PCB group, only one lesion with adenoma was induced. In 1-NP group, various kinds of lung neoplastic lesions including hyperplasia, adenoma and adenocarcinoma were induced. In PCB + 1-NP group, both the number and size of tumors induced were significantly more than those in 1-NP group. In addition, the number of adenocarcinoma formed was more in PCB + 1-NP group than in 1-NP group. Each lesion was microdissected to collect and analyze DNA of the targeted tissue. K-ras gene mutation was detected in part of adenoma lesions and all the carcinoma lesions. The mutation was found in either 1-NP or PCB + 1-NP group, but not in control and PCB group. The pattern of K-ras mutation was CAA to CGA in codon 61 or GGT to GAT in codon 12. There was no difference in the pattern of K-ras mutation despite of the pretreatment with PCB. Although the present data are from small sample size, it was suggested that PCB may promote (but not initiate) 1-NP induced lung tumorigenesis, and may not induce K-ras mutation directly in the experimental system.

Granulocyte, granulocyte-macrophage, and macrophage colony-stimulating factors can stimulate the invasive capacity of human lung cancer cells

We and other researchers have previously found that colony-stimulating factors (CSFs), which generally include granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF) and macrophage colony-stimulating factor (M-CSF), promote invasion by lung cancer cells. In the present study, we studied the effects of these CSFs on gelatinase production, urokinase plasminogen activator (uPA) production and their activity in human lung cancer cells. Gelatin zymographs of conditioned media derived from human lung adenocarcinoma cell lines revealed two major bands of gelatinase activity at 68 and 92 kDa, which were characterized as matrix metalloproteinase (MMP)-2 and MMP-9 respectively. Treatment with CSFs increased the 68- and 92-kDa activity and converted some of a 92-kDa proenzyme to an 82-kDa enzyme that was consistent with an active form of the MMP-9. Plasminogen activator zymographs of the conditioned media from the cancer cells showed that CSF treatment resulted in an increase in a 48-55 kDa plasminogen-dependent gelatinolytic activity that was characterized as human uPA. The conditioned medium from the cancer cells treated with CSFs stimulated the conversion of plasminogen to plasmin, providing a direct demonstration of the ability of enhanced uPA to increase plasmin-dependent proteolysis. The enhanced invasive behaviour of the cancer cells stimulated by CSFs was well correlated with the increase in MMPs and uPA activities. These data suggest that the enhanced production of extracellular matrix-degrading proteinases by the cancer cells in response to CSF treatment may represent a biochemical mechanism which promotes the invasive behaviour of the cancer cells.

G-CSF increases secretion of urokinase-type plasminogen activator by human lung cancer cells

We reported previously that granulocyte colony-stimulating factor (G-CSF) can promote the invasion of human lung cancer cell lines in vitro. However, the exact mechanism of its stimulatory effect on invasion remains to be elucidated. In the present study we mainly focused our attention on the components of the plasminogen activation system in human lung cancer cell lines, because of the central role that plasminogen activators play in regulating extracellular proteolysis. We showed that G-CSF induced a dose-dependent increase in the urokinase-type plasminogen activator (uPA) activity in the conditioned medium of a PC-9 lung cancer cell line. When the amounts of uPA activity were quantitated by densitometry, we found that even at a concentration of 0.01 microg/ml, G-CSF had a stimulatory effect on the uPA release, while high concentrations caused a 3.6-fold increase at a maximum concentration of 1 microg/ml. A Western blot analysis of the conditioned medium confirmed the findings observed in a zymographic analysis. The observed increase in uPA protein was paralleled by a significant increase in the uPA mRNA levels after treatment with G-CSF. However, our experiments failed to identify any alteration in the plasminogen activator inhibitor (PAI) secretion caused by G-CSF. In addition, we also found the expression of G-CSF receptor by PC-9 cells, suggesting the possible pathway activated by G-CSF.

Ki-ras mutation and cell proliferation of lung lesions induced by 1-nitropyrene in A/J mice

In this study, lung lesions were found in male A/J mice 24 wk after intraperitoneal injection of 1-nitropyrene (1-NP). The lesions were classified into three categories: alveolar/bronchiolar hyperplasia, adenoma, and adenocarcinoma. The proliferation kinetics of cells in the lesions were evaluated by assessing proliferating cell nuclear antigen (PCNA) expression and silver-staining nucleolar organizer regions (AgNORs). Furthermore, the role of the Ki-ras gene in tumorigenesis was studied by detecting point mutations in Ki-ras codons 12, 13, and 61 by polymerase chain reaction and sequence analysis. The PCNA-positive rates (+/- standard deviations) in various samples were as follows: 0% for specimens from six untreated animals and six uninvolved areas, 4.26 +/- 3.94% for 19 hyperplasias (hyperplasias vs normal lung tissue, P < 0.01), 13.24 +/- 6.35% for 25 adenomas (adenomas vs hyperplasias, P < 0.01), and 38.0 +/- 9.63% for four adenocarcinomas (adenocarcinomas vs adenomas, P < 0.01). The corresponding mean AgNOR scores were as follows: 1.10 +/- 0.05 for the untreated animals, 1.32 +/- 0.09 for the uninvolved areas, 1.72 +/- 0.59 for the hyperplasias (hyperplasias vs normal lung tissue, P > 0.05), 2.74 +/- 0.70 for the adenomas (adenomas vs hyperplasias, P < 0.01), and 5.22 +/- 0.62 for the adenocarcinomas (adenocarcinomas vs adenomas, P < 0.01). Ki-ras gene mutations were identified in three of four (75%) adenocarcinomas, six of 23 (26%) adenomas, and two of 17 (12%) hyperplasias. No mutations were found in normal lung tissue. The most frequent Ki-ras mutation was an arginine (CGA)AT --> GC transition at codon 61 in exon 2. The PCNA-positive rates and AgNOR scores of cases with Ki-ras mutations were higher than those without an identified mutation (P < 0.05). Ki-ras mutations at codon 61 (Arg) may therefore influence the growth or development of 1-NP-induced lung lesions in A/J mice.

The levels of integrin alpha v beta 5 may predict the susceptibility to adenovirus-mediated gene transfer in human lung cancer cells

Adenovirus mediated transfer of growth-inhibiting molecules, such as p53 shows promise as an effective method of suppressing the growth of cancer cells. As the basis for in vivo studies, we examined transfection efficiency using 15 human lung cancer cell lines that differ in their endogenous p53 status. When infected with an adenovirus expressing bacterial beta-galactosidase, the different cell lines showed different levels of beta-galactosidase activity. We found a correlation between the level of integrin alpha v beta 5, which is thought to be an adherence receptor for adenoviruses, and the expression level of the transferred gene, suggesting that gene expression is largely dependent on the infection efficiency. Growth inhibition was induced in all cell lines tested following infection with an adenovirus containing p53, regardless of the genetic status of their endogenous p53 provided a sufficient amount of p53 protein was expressed. Our results (1) confirm that the examination of the susceptibility of target cancer cells to an adenovirus is important when considering performing adenovirus-mediated gene transfer and for evaluating its therapeutic effects; and (2) suggest that the quantification of integrin alpha v beta 5 may be a good way of predicting the susceptibility of cells to adenoviral vectors.

Effect of CPT-11 in combination with other anticancer agents in lung cancer cells

To determine the optimal combination of commonly used anticancer agents with 7-ethyl-10-hydroxy-camptothecin (SN-38), an active metabolite of 7-ethyl-10-[4(1-piperidino)-1-piperidino] carbonyloxy camptothecin (CPT-11), for chemotherapy of lung cancer, we studied the effects of SN-38 in combination with six representative anticancer agents on the human small cell lung cancer (SCLC) cell line, NCl N417, and the non-small cell lung cancer (NSCLC) cell line, PC-9. The anticancer activity was evaluated by MTT assay and the effects of drug combinations on ID50 were analyzed by an improved isobologram method. In the SCLC cell line, supra-additive effect was observed for SN-38 in combination with cisplatin, etoposide (VP-16) and paclitaxel (Taxol). An additive effect was observed for its combination with bleomycin. Sub-additive and protective effects were found in combination with adriamycin (ADR) and 5-fluorouracil (5-FU). In the NSCLC cell line, supra-additive and marginal supra-additive effects were found for SN-38 in combination with VP-16, ADR, 5-FU and bleomycin. The others showed additive effects with SN-38. No drug showed sub-additive and protective effects with SN-38. These results suggest that all the drugs we selected can be used with SN-38 simultaneously for NSCLC, while for SCLC, cisplatin, VP-16 and Taxol are the most suitable for combination with SN-38.

Granulocyte-colony stimulating factor promotes invasion by human lung cancer cell lines in vitro

The effects of exogenous and endogenous granulocyte colony-stimulating factor (G-CSF) on invasion by cancer cells were studied, using lung cancer cell lines that produce G-CSF (NCI-H157) and lines that do not (PC-9 and NCI-H23). The invasive capacity of NCI-H157 cells was 26- to 27-fold higher than that of PC-9 and NCI-H23 cells. The invasiveness of PC-9 cells was stimulated by exogenous G-CSF, while that of NCI-H157 cells was not. Antibodies against G-CSF blocked the stimulation of PC-9 cell invasiveness by exogenous G-CSF. Anti G-CSF antibodies also inhibited invasion by NCI-H157 cells in the absence of exogenous G-CSF. These results suggest that endogenous and exogenous G-CSF both stimulate invasion by lung cancer cells.

Immunohistochemical expression of glutathione S-transferase-Pi can predict chemotherapy response in patients with nonsmall cell lung carcinoma

BACKGROUND

Resistance to chemotherapy agents is a major problem in the treatment of patients with nonsmall cell lung carcinoma (NSCLC). Recent studies have indicated that glutathione S-transferase-Pi (GST-Pi) may play an important role in the resistance of cancer cells to alkylating agents, including cisplatin compounds.

METHODS

The expression of GST-Pi in tissues obtained by bronchoscopic biopsy from 38 NSCLC patients was investigated immunohistochemically. These patients were treated with a combination of cisplatin-based chemotherapy and were evaluated to determine the relationship between GST-Pi expression and chemotherapy response.

RESULTS

Of the 38 patients, 25 (66%) were GST-Pi-positive and 13 (34%) were negative. There was no significant correlation between GST-Pi expression and the clinicopathologic factors examined (age, sex, performance status, histology, differentiation grade, and stage). Of the 38 patients treated with cisplatin-based chemotherapy, 12 patients responded to chemotherapy (overall response rate, 32%). For the patients with negative GST-Pi expression, the response rate was 69% (9 of 13 patients). In the patients with positive GST-Pi expression, the response rate was 12% (3 of 25 patients). This difference was statistically significant (P=0.0012).

CONCLUSIONS

The expression of GST-Pi in NSCLC patients was significantly related to response to cisplatin-based chemotherapy, and may be a useful predictor of chemotherapy response.