Impairment of Fas-antigen expression in adriamycin-resistant but not TNF-resistant MCF7 tumor cells

Prolactin-induced protein (PIP) increases the sensitivity of breast cancer cells to drug-induced apoptosis

We have previously shown that high expression of prolactin-induced protein (PIP) correlates with the response of breast cancer (BC) patients to standard adjuvant chemotherapy (doxorubicin and cyclophosphamide), which suggests that the absence of this glycoprotein is associated with resistance of tumor cells to chemotherapy. Therefore, in the present study, we analyzed the impact of PIP expression on resistance of BC cells to anti-cancer drugs and its biological role in BC progression. Expression of PIP and apoptotic genes in BC cell lines was analyzed using real-time PCR and Western blotting. PIP was detected in BC tissue specimens using immunohistochemistry. The tumorigenicity of cancer cells was analyzed by the in vivo tumor growth assay. Apoptotic cells were detected based on caspase-3 activation, Annexin V binding and TUNEL assay. The interaction of PIP with BC cells was analyzed using flow cytometry. Using two cellular models of BC (i.e. T47D cells with the knockdown of the PIP gene and MDA-MB-231 cells overexpressing PIP), we found that high expression of PIP resulted in (1) increased sensitivity of BC cells to apoptosis induced by doxorubicin (DOX), 4-hydroperoxycyclophosphamide (4-HC), and paclitaxel (PAX), and (2) improved efficacy of anti-cancer therapy with DOX in the xenograft mice model. Accordingly, a clinical study revealed that BC patients with higher PIP expression were characterized by longer 5-year overall survival and disease-free survival. Subsequent studies showed that PIP up-regulated the expression of the following pro-apoptotic genes: CRADD, DAPK1, FASLG, CD40 and BNIP2. This pro-apoptotic activity is mediated by secreted PIP and most probably involves the specific surface receptor. This study demonstrates that a high expression level of PIP sensitizes BC cells to anti-cancer drugs. Increased sensitivity to chemotherapy is the result of pro-apoptotic activity of PIP, which is evidenced by up-regulation of specific pro-apoptotic genes. As high expression of PIP significantly correlated with a better response of patients to anti-cancer drugs, this glycoprotein can be a marker for the prognostic evaluation of adjuvant chemotherapy.

Polymorphisms in tumor necrosis factor-alpha (-863C>A, -857C>T and +488G>A) are associated with idiopathic recurrent pregnancy loss in Korean women

Polymorphisms in TNF-a have been reported as genetic risk factors for recurrent spontaneous abortion and TNF-α may be immunologically important. We therefore examined the contribution of several TNF-a mutations to this phenomenon. The study participants consisted of 388 patients with idiopathic recurrent pregnancy loss (RPL), which was diagnosed on the basis of at least two consecutive spontaneous abortions; control subjects were 224 healthy women with a history of successful pregnancies. Polymerase chain reaction-restriction fragment length polymorphism analysis was performed to determine the TNF-α -863C>A, -857C>T, and +488G>A genotypes. The TNF-α -863C>A variants correlated with increased risk of RPL (CA+AA; adjusted odds ratio [AOR], 2.142; 95% confidence interval [CI], 1.493-3.074). These data did not differ in a stratified analysis according to number of consecutive spontaneous abortions. In haplotype analysis, there were similar trends of data for combination analysis, but in patients with 3+ pregnancy losses, a stratified analysis revealed that this correlation did not increase directly with the number of pregnancy losses. The TNF-α -863C>A variant is a possible genetic risk factor for idiopathic RPL in Korean women.

Tumor necrosis factor-α gene polymorphisms in Korean patients with recurrent spontaneous abortion

The objective of this study was to investigate the contribution of the tumor necrosis factor-α (TNF-α) gene polymorphisms to recurrent spontaneous abortion (RSA). The study participants consisted of 357 Korean women with RSA and 236 fertile women controls. Four TNF-α gene variants of all participants were analyzed by polymerase chain reaction-restriction fragment length polymorphism assay. The TNF-α -1031T>C and TNF-α -238G>A variants increased the risk of RSA TNF-α -1031TC+CC; adjusted odds ratio [AOR], 2.292; 95% confidence interval [CI], 1.547-3.395; P < .001; TNF-α -238GA+AA; AOR, 2.327; 95% CI, 1.038-5.217; P = .040), and these data were not different in a stratified analysis according to the number of consecutive spontaneous abortions. Also, the mutant genotypes of TNF-α -1031 and TNF-α -238 showed synergistic effects on increased RSA risk (-1031TC+CC/-238GA+AA; AOR, 4.054; 95% CI, 1.520-10.812; P = .005). In haplotype analysis, there were similar trends of data for combination analysis. In conclusion, the TNF-α -1031T>C and TNF-α -238G>A variants are possible genetic risk factors for RSA.

Polymorphisms of tumor necrosis factor-alpha and breast cancer risk: a meta-analysis

We conducted a meta-analysis to assess the association between tumor necrosis factor-alpha (TNF-alpha) gene TNFA -308 (G>A), TNFA -238 (G>A), TNFA -857 (C>T), TNFA -863 (C>A), TNFA -1031 (T>C), TNFA -1210 (A>T) polymorphisms and breast cancer(BC) susceptibility. We also performed subgroup analyses based on ethnicity (Caucasian, Asian, and African). An extensive search was performed to identify all case-control studies investigating such association. Thirteen eligible studies, including 10,236 BC patients and 13,143 controls, were identified. No significant association was observed in all genotypes in worldwide populations, but stratification by ethnicity indicated that the TNFA -308 A allele was associated with a decreased risk of BC compared with the G allele in Caucasian individuals (OR = 0.927, 95%CI = 0.879-0.978). Similar results were obtained when the A/A +A/G genotype was compared with the G/G genotype. In addition, meta-analysis results indicated that the A/A genotype of TNFA -308 was a risk factor for BC in African (A/A vs. G/G OR = 4.085 95%CI = 1.460-11.425; A/A vs. G/A OR = 4.861 95%CI = 1.746-13.527; A/A vs. G/A + G/G OR = 4.246 95%CI = 1.551-11.625), but not in Caucasian or Asian individuals. In conclusion, the results of this meta-analysis indicate that the TNFA -308 A allele may be an important protective factor for BC in European individuals, but it is not likely to confer susceptibility to BC in worldwide populations. In addition, the AA genotype of TNFA -308 may be a risk factor for BC in African individuals. Besides, other polymorphisms were not associated with BC susceptibility.

Gene expression profiles as biomarkers for the prediction of chemotherapy drug response in human tumour cells

Genome profiling approaches such as cDNA microarray analysis and quantitative reverse transcription polymerase chain reaction are playing ever-increasing roles in the classification of human cancers and in the discovery of biomarkers for the prediction of prognosis in cancer patients. Increasing research efforts are also being directed at identifying set of genes whose expression can be correlated with response to specific drugs or drug combinations. Such genes hold the prospect of tailoring chemotherapy regimens to the individual patient, based on tumour or host gene expression profiles. This review outlines recent advances and challenges in using genome profiling for the identification of tumour or host genes whose expression correlates with response to chemotherapy drugs both in vitro and in clinical studies. Genetic predictors of response to a variety of anticancer agents are discussed, including the anthracyclines, taxanes, topoisomerase I and II inhibitors, nucleoside analogs, alkylating agents, and vinca alkaloids.

Cellular metabolism as a basis for immune privilege

We hypothesize that the energy strategy of a cell is a key factor for determining how, or if, the immune system interacts with that cell. Cells have a limited number of metabolic states, in part, depending on the type of fuels the cell consumes. Cellular fuels include glucose (carbohydrates), lipids (fats), and proteins. We propose that the cell's ability to switch to, and efficiently use, fat for fuel confers immune privilege. Additionally, because uncoupling proteins are involved in the fat burning process and reportedly in protection from free radicals, we hypothesize that uncoupling proteins play an important role in immune privilege. Thus, changes in metabolism (caused by oxidative stresses, fuel availability, age, hormones, radiation, or drugs) will dictate and initiate changes in immune recognition and in the nature of the immune response. This has profound implications for controlling the symptoms of autoimmune diseases, for preventing graft rejection, and for targeting tumor cells for destruction.

Schisandrin B enhances doxorubicin-induced apoptosis of cancer cells but not normal cells

The dose-dependent cardiotoxicities of doxorubicin (DOX) significantly limits its anti-cancer efficacies. One of the ways to augment the efficacies of DOX at a relatively low cumulative dose is to use a chemical sensitizer. Here, we demonstrated that schisandrin B (Sch B) significantly enhanced DOX-induced apoptosis of SMMC7721, a human hepatic carcinoma cell line, and of MCF-7, a human breast cancer cell line. This enhancement was irrelevant to the action of Sch B on P-glycoprotein or other drug-transporters, but associated with the activation of caspase-9 rather than caspase-8. The loss of mitochondria membrane potential was observed when cells were treated with DOX and Sch B combined. On the other hand, at the same experimental conditions, Sch B did not enhance the DOX-induced apoptosis of primary rat cardiomyocytes and primary human fibroblasts. Therefore, it is speculative that Sch B may bring benefit to clinical chemotherapy by reducing significantly the cumulative doses of DOX and its associated cardiotoxicities.

Effect of organ-specific fibroblasts on proliferation and differentiation of breast cancer cells

Breast carcinomas contain both tumor cells and stromal cells, including fibroblasts, endothelial cells, and lymphocytes. Proliferation of breast cancer cells may be controlled partly by mesenchymal cells, especially fibroblasts. We studied effects of fibroblasts on tumorigenicity and histologic features of breast cancer cells vivo, and analyzed fibroblast-produced growth-promoting factors in vitro. Breast carcinoma cells from four lines, and fibroblasts from lines obtained from skin and breast tissue of four patients with breast cancer were used. A suitable number of breast tumor cells and fibroblasts were inoculated subcutaneously into nude mice; resulting tumors were examined. Then conditioned medium from fibroblasts was added to cultures of breast cancer cells to study growth effects, and growth-promoting factors from breast fibroblasts were analyzed. Co-inoculation of breast cancer cells with breast fibroblasts into mice significantly increased tumorigenicity and tumor size beyond those obtained with breast cancer cells alone. Histologically, tumors resulting from co-inoculation with breast fibroblasts showed a scirrhous pattern with extensive fibrosis, while those formed by breast cancer cells injected alone or co-inoculation with skin fibroblasts showed a solid pattern. Medium from breast fibroblasts significantly increased breast cancer cell growth in vitro, while the various skin fibroblasts did not all show this effect. Structural and functional interactions between organ-specific fibroblasts and breast cancer cells may importantly regulate breast cancer growth and progression.

Polymorphism in the genes of alpha and beta tumor necrosis factors (TNF-alpha and TNF-beta) and gamma interferon (IFN-gamma) among Iranian women with breast cancer

The association of the polymorphism in the genes of TNF-alpha, TNF-beta and IFN-gamma with breast cancer was investigated in the present study. There were no differences in the TNF-alpha and TNF-beta alleles and genotypes frequencies between breast cancer patients (n=223) and control subjects (n=267). The correlations between TNFA or TNFB alleles or genotypes and clinicopathological indices were also insignificant. However, the frequency of IFN-gamma+874 T/T genotype was significantly higher in breast cancer patients compared to those of controls (P<0.002; OR=2.03, 95% CI=1.28-3.2) which indicates that Iranian women carrying the IFN-gamma+874 T/T genotype may be exposed to an increased risk of breast cancer development.

Cross-resistance studies of isogenic drug-resistant breast tumor cell lines support recent clinical evidence suggesting that sensitivity to paclitaxel may be strongly compromised by prior doxorubicin exposure

Less than half of breast cancer patients respond to second-line chemotherapy with paclitaxel after failing treatment with anthracyclines such as doxorubicin. A recent clinical trial by Paridaens et al. [J. Clin. Oncol. 18 : 724-733, 2000] examined whether patients may derive a better clinical benefit if paclitaxel was administered before doxorubicin. While overall survival was similar regardless of the order of drug administration, a >4-fold reduction in the response rate to paclitaxel was observed after late crossover from doxorubicin, compared to the response rate to doxorubicin after late crossover from paclitaxel. This may be related to differences in the ability of the drugs to induce cross-resistance to each other. To test this hypothesis, we examined whether isogenic breast tumor cells selected for resistance to doxorubicin exhibit greater cross-resistance to paclitaxel and other drugs than identical cells selected for resistance to paclitaxel. We found that cells selected for resistance to paclitaxel showed strong resistance (>/=40-fold) to paclitaxel and docetaxel, with little cross-resistance (4-fold) to doxorubicin. In contrast, cells selected for resistance to doxorubicin exhibited 50-fold resistance to doxorubicin and a dramatic 4700-fold and 14,600-fold cross-resistance to paclitaxel and docetaxel, respectively. Doxorubicin-resistant cells exhibited higher P-glycoprotein and breast cancer resistance protein (BCRP) levels than paclitaxel-resistant cells. In addition, procaspase-9 was strongly downregulated in doxorubicin-resistant cells but not in paclitaxel-resistant cells. These differences may account for the contrasting cross-resistance profiles observed for the two cell lines and may help to explain why treatment of breast cancer patients with paclitaxel appears to be compromized by prior doxorubicin exposure.

Altered Expression of FAS System Is Related to Adverse Clinical Outcome in Stage I-II Breast Cancer Patients Treated with Adjuvant Anthracycline-Based Chemotherapy

PURPOSE

To determine the prognostic value of Fas receptor and Fas ligand (FasL) as apoptosis-related biomarkers in the context of chemoresponsiveness in breast cancer (BC) patients submitted to anthracycline-based adjuvant therapy.

EXPERIMENTAL DESIGN

Fas and FasL were investigated by immunohistochemistry in surgical samples collected from 167 stage I-IIa-b BC patients enrolled in a prospective clinical trial using epirubicin plus cyclophosphamide in the adjuvant setting.

RESULTS

Fas and FasL were significantly associated with tumor stage (P < 0.0001). Multivariate analysis indicated that stage, loss of Fas (relative risk, 8.5 and 9.12; P < 0.0001) and FasL up-regulation (relative risk, 2.38 and 2.88; P = 0.01) were independent prognostic variables influencing both disease-free survival (DFS) and overall survival (OS). A Cox analysis using a four-category Fas/FasL phenotype (+/-, +/+, -/+, -/-) as a stratification factor evidenced a highly positive association between Fas/FasL phenotype and the cumulative hazard of relapse and death in the entire series of patients. We also estimated the DFS and OS for different combinations of the pathological-tumor-node-metastasis (TNM) stage and Fas/FasL by using the K sample log-rank exact test demonstrating that significantly shorter DFS and OS were observed in Fas-negative and FasL-positive patients in both stage I-IIa and IIb.

CONCLUSIONS

Data presented herein demonstrated that, according to a number of in vitro studies, the prognosis for BC patients receiving adjuvant anthracycline-based chemotherapy strongly depends on the Fas/FasL status. Therefore, a concomitant altered pattern of Fas/FasL expression seems to configure an aggressive tumor phenotype linked to disease progression.

The effects of chemotherapeutics on cellular metabolism and consequent immune recognition

Awidely held view is that oncolytic agents induce death of tumor cells directly. In this report we review and discuss the apoptosis-inducing effects of chemotherapeutics, the effects of chemotherapeutics on metabolic function, and the consequent effects of metabolic function on immune recognition. Finally, we propose that effective chemotherapeutic and/or apoptosis-inducing agents, at concentrations that can be achieved physiologically, do not kill tumor cells directly. Rather, we suggest that effective oncolytic agents sensitize immunologically altered tumor cells to immune recognition and immune-directed cell death.

Expression patterns of biologic markers in small breast cancers and preneoplastic breast lesions

When does proliferating breast epithelium turn malignant? Single parameter analyses have not answered this question. We have tried to answer this through an analysis of immunohistochemical staining patterns in the following morphologically defined breast lesions: atypical ductal hyperplasia (ADH, 23 cases), papilloma (12 cases), ductal cancer in situ (DCIS, 28 cases), and mammographically detected small primary cancers (34 cases). The seven antibodies used were c-neu, bcl-2, p53, p21, CD44, MIB 1, and FAS. Staining patterns were compared within groups and between groups of lesions. Interesting differences in staining patterns were seen between invasive ductal cancer and invasive lobular cancer: invasive lobular cancer was less p53-positive and more CD44-positive than invasive ductal cancer. We found no common pattern in the different proliferating epithelia to show when they become malignant.

Global genome repair is required to activate KIN17, a UVC-responsive gene involved in DNA replication

UV light provokes DNA lesions that interfere with replication and transcription. These lesions may compromise cell viability and usually are removed by nucleotide excision repair (NER). In humans, inactivation of NER is associated with three rare autosomal recessive inherited disorders: xeroderma pigmentosum (XP), Cockayne syndrome, and trichothiodystrophy. The NER earliest step is lesion recognition by a complex formed by XPC and HHR23B proteins. In a subsequent step, XPA protein becomes associated to the repair complex. Here we investigate whether XPA and XPC proteins, involved in global genome repair, may contribute to a signal transduction pathway regulating the response to UVC-induced lesions. We monitored the expression of several UVC-induced genes in cells deficient in either a transduction pathway or mutated on an NER gene. Expression of the KIN17 gene is induced after UVC irradiation independently of p53 and of activating transcription factor 2. However, in human cells derived from XPA or XPC patients the UVC-induced accumulation of KIN17 RNA and protein is abolished. Our results indicate that the presence of functional XPA and XPC proteins is essential for the up-regulation of the KIN17 gene after UVC irradiation. They also show that the integrity of global genome repair is required to trigger KIN17 gene expression and probably other UVC-responsive genes.

Expression of Fas and FasL in human serous ovarian epithelial tumors

The expression of Fas and FasL was studied in 86 patients with benign, borderline, and malignant serous ovarian lesions. Four normal ovaries, and monolayer epithelial cultures from a human fetal ovary, a borderline, and a serous adenocarcinoma were used for comparison. Expression of Fas and FasL was studied immunohistochemically and flowcytometrically. Fas was expressed in all 90 lesions; FasL in 57 lesions, including 2 normal ovaries. Fas expression was significantly increased in borderline tumors compared with benign (P = 0.005, t = -2.94) or malignant serous tumors (P = 0.0001, t = 4.15). FasL expression was significantly increased in malignant tumors compared with benign (P = 0.039, t = -2.10) and borderline tumors (P = 0.0016, t = -3.33). Flow cytometry showed a range of Fas expression in short-term cultures isolated from normal, borderline, and malignant ovarian serous tissue; in the few samples studied, FasL was not expressed. Expression in three serous ovarian cell lines was similar. Fas and FasL expression differed throughout the spectrum of ovarian lesions. FasL expression was increased in malignant tumors, and Fas expression was increased in borderline tumors. Changes in Fas/FasL expression in ovarian surface epithelium might play a functional role in the biology of ovarian tumors.

Identification of KIN (KIN17), a human gene encoding a nuclear DNA-binding protein, as a novel component of the TP53-independent response to ionizing radiation

Ionizing radiation elicits a genetic response in human cells that allows cell survival. The human KIN (also known as KIN17) gene encodes a 45-kDa nuclear DNA-binding protein that participates in the response to UVC radiation and is immunologically related to the bacterial RecA protein. We report for the first time that ionizing radiation and bleomycin, a radiomimetic drug, which produce single- and double-strand breaks, increased expression of KIN in human cells established from tumors, including MeWo melanoma, MCF7 breast adenocarcinoma, and ATM+ GM3657 lymphoblast cells. KIN expression increased rapidly in a dose-dependent manner after irradiation. Under the same conditions, several genes controlled by TP53 were induced with kinetics similar to that of KIN. Using the CDKN1A gene as a marker of TP53 responsiveness, we analyzed the up-regulation of KIN and showed that is independent of the status of TP53 and ATM. In contrast, the presence of a dominant mutant for activating transcription factor 2 (ATF2) completely abolished the up-regulation of KIN. Our results suggest a role for ATF2 in the TP53-independent increase in KIN expression after gamma irradiation.

Signaling pathways activated by daunorubicin

The anthracycline daunorubicin is widely used in the treatment of acute nonlymphocytic leukemia. The drug has, of course, been the object of intense basic research, as well as preclinical and clinical study. As reviewed in this article, evidence stemming from this research clearly demonstrates that cell response to daunorubicin is highly regulated by multiple signaling events, including a sphingomyelinase-initiated sphingomyelin-ceramide pathway, mitogen-activated kinase and stress-activated protein/c-Jun N-terminal kinase activation, transcription factors such as nuclear factor kappa B, as well as the Fas/Fas-ligand system. These pathways are themselves influenced by a number of lipid products (diacylglycerol, sphingosine-1 phosphate, and glucosyl ceramide), reactive oxygen species, oncogenes (such as the tumor suppressor gene p53), protein kinases (protein kinase C and phosphoinositide-3 kinase), and external stimuli (hematopoietic growth factors and the extracellular matrix). In light of the complexity and diversity of these observations, a comprehensive review has been attempted toward the understanding of their individual implication (and regulation) in daunorubicin-induced signaling. (Blood. 2001;98:913-924)

Suppression of P-gp induced multiple drug resistance in a drug resistant gastric cancer cell line by overexpression of Fas

AIM: To observe the drug sensitizing effect and related mechanisms of fas gene transduction on human drug-resistant gastric cancer cell SGC7901/VCR (resistant to Vincristine).

METHODS: The cell cycle alteration was observed by FACS. The sensitivity of gastric cancer cells to apoptosis was determined by in vitro apoptosis assay. The drug sensitization of cells to several anti-tumor drugs was observed by MTT assay. Immunochemical method was used to show expression of P-gp and Topo II in gastric cancer cells.

RESULTS: Comparing to SGC7901 and pBK-SGC7901/VCR, fas-SGC7901/VCR showed decreasing G2 cells and increasing S cells, the G2 phase fraction of pBK-SGC7901/VCR was about 3.0 times that of fas-SGC7901/VCR, but S phase fraction of fas-SGC7901/VCR was about 1.9 times that of pBK-SGC7901/VCR, indicating S phase arrest of fas-SGC7901/VCR. FACS also suggested apoptosis of fas-SGC7901/VCR. fas-SGC7901/VCR was more sensitive to apoptosis inducing agent VM-26 than pBK-SGC7901/VCR. MTT assay showed increased sensitization of fas-SGC7901/VCR to DDP, MMC and 5-FU, but same sensitization to VCR according to pBK-SGC7901/VCR. SGC7901, pBK-SGC7901/VCR and fas-SGC7901/VCR had positively stained Topo II equally. P-gp staining in pBK-SGC7901/VCR was stronger than in SGC7901, but there was little staining of Pgp in fas-SGC7901/VCR.

CONCLUSION: fas gene transduction could reverse the MDR of human drug-resistant gastric cancer cell SGC7901/VCR to a degree, possibly because of higher sensitization to apoptosis and decreased expression of P-gp.

Role of specific apoptotic pathways in the restoration of paclitaxel-induced apoptosis by valspodar in doxorubicin-resistant MCF-7 breast cancer cells

Paclitaxel (Taxol) kills tumor cells by inducing both cellular necrosis and apoptosis. A major impediment to paclitaxel cytotoxicity is the establishment of multidrug resistance whereby exposure to one chemotherapeutic agent results in cross-resistance to a wide variety of other drugs. For example, selection of MCF-7 breast cancer cells for resistance to doxorubicin (MCF-7ADR cells) results in cross-resistance to paclitaxel. This appears to involve the overexpression of the drug transporter P-glycoprotein which can efflux both drugs from tumor cells. However, MCF-7ADR cells possess a deletion mutation in p53 and have considerably reduced levels of the Fas receptor, Fas ligand, caspase-2, caspase-6, and caspase-8, suggesting that paclitaxel resistance may also stem from a bona fide block in paclitaxel-induced apoptosis in these cells. To address this issue, we examined the ability of the P-glycoprotein inhibitor valspodar to restore paclitaxel accumulation, paclitaxel cytotoxicity, and paclitaxel-induced apoptosis. Compared to drug sensitive MCF-7 cells, MCF-7ADR cells accumulated >6-fold less paclitaxel, were approximately 100-fold more resistant to killing by the drug, and were highly resistant to paclitaxel-induced apoptosis. In contrast, MCF-7ADR cells pretreated with valspodar were indistinguishable from drug-sensitive cells in their ability to accumulate paclitaxel, in their chemosensitivity to the drug, and in their ability to undergo paclitaxel-induced apoptosis. Valspodar, by itself, did not affect these parameters. This suggests that the enhancement of paclitaxel toxicity in MCF-7ADR cells involves a restoration of apoptosis and not solely through enhanced drug-induced necrosis. Morever, it appears that changes in the levels/activity of p53, the Fas receptor, Fas ligand, caspase-2, caspase-6, or caspase-8 activity have little effect on paclitaxel-induced cytotoxicity and apoptosis in human breast cancer cells.

CD95 ligand expression as a mechanism of immune escape in breast cancer

Interaction of CD95 (Apo-1/Fas) and its ligand (CD95L) plays an important role in the regulation of the immune response, since CD95+ lymphocytes may be killed after engagement of the CD95 receptor. Studying the CD95/CD95L system in 40 cases of breast cancer, the malignant cells expressed CD95L, but lost CD95 expression, when compared with non-malignant mammary tissue. Jurkat T cells incubated on breast cancer sections underwent CD95L-specific apoptosis. The rate of apoptosis correlated with the CD95L mRNA levels of the tissue samples. In four breast cancer cell lines, CD95L expression was increased by interferon-gamma (IFN-gamma), which resulted in higher levels of CD95L-specific apoptosis in co-cultured Jurkat T cells. Since IFN-gamma is mainly secreted by activated T cells, up-regulation of CD95L in breast cancer cells in response to IFN-gamma may thus counterselect activated tumour-infiltrating T cells and favour the immune escape of breast cancer. As demonstrated by inhibition of matrix metalloproteinases, CD95L expressed on breast cancer cells can also be shed from the cell membrane into the culture supernatant. Supernatants derived from cultured breast cancer cells induced apoptosis in Jurkat T cells via CD95L. In breast cancer patients, depletion of CD4+ and CD8+ peripheral blood lymphocytes was significantly correlated with CD95L expression in the tumours. This might be suggestive for a relationship between CD95L expression by breast cancer and systemic immunosuppression.

CD95 ligand expression in dedifferentiated breast cancer

CD95 ligand expression has been observed in various malignancies. Studying the CD95 ligand (CD95L) and receptor (CD95) system in eight non-malignant mammary tissues and 40 breast cancer tissues, mRNA and protein expression was determined by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and immunofluorescence. mRNA levels of CD95L correlated positively (r=0.90; p< 0.01) and transmembrane CD95 inversely (r=-0.88; p< 0.01) with histopathological grading of the breast tumours: CD95L mRNA levels were low in adenomas, but increased by 20-fold in grade I, 120-fold in grade II, and 310-fold in grade III breast cancer. In contrast, CD95 mRNA levels were low in high-grade carcinomas, but high in benign mammary tissues. Since CD95L acts as an efficient inducer of apoptosis in CD95(+) cells, apoptotic cells were identified on the tissue sections. Tumour-infiltrating lymphocytes and stromal cells in close proximity to CD95L-expressing breast cancer underwent apoptosis. As a functional test, CD95(+) target cells were cultured on breast cancer tissue sections. The target cells underwent apoptosis when cultured on breast cancer sections, but could be rescued when CD95L was specifically blocked by a CD95-Fc fusion molecule. The data suggest an inverse regulation of CD95 ligand and receptor expression during dedifferentiation of breast cancer. Killing of bystander cells by the CD95L-expressing breast tumour could be involved in tissue invasion.

Two distinct modes of oncoprotein expression during apoptosis resistance in vincristine and daunorubicin multidrug-resistant HL60 cells

Apoptosis is a genetically regulated cell death process which results in a variety of morphological changes like chromatin condensation and DNA fragmentation. The decision between survival or death in response to an apoptotic stimulus is determined and regulated in part by oncoproteins which include proteins of the Bcl-2 family (bcl-2, bax, bcl-xL) and bcr-abl. We investigated the effect of these proteins on the induction of this phenomenon in human promyelocytic leukemic HL60 cells and two multidrug resistant homologues selected respectively with vincristine (HL60/VCR) and daunorubicin (HL60R/DNR). We show that sensitive cells at 1 micron and HL60/VCR cells at DNR IC50 were able to undergo apoptosis while HL60R/DNR did not even at much higher concentration of DNR. However, treatment with synthetic C2-ceramide did not sensitize HL60/DNR cells to apoptosis. Cell death through apoptosis or necrosis was accompanied by acidification of the cytosol without mitochondrial membrane depolarization. Western blotting analysis shows that bax is expressed at slightly elevated level in HL60S/VCR in comparison with the other cells lines. Bcl-2 is overexpressed in HL60/VCR but not in HL60R/DNR. However, this cell line displayed a higher expression of bcl-xL. Interestingly, bcr-abl, a dysregulated tyrosine kinase was detected only in HL60R/DNR cells. DNR at the IC50, has no effect on expression of the oncoproteins. These data suggest that in addition of the multidrug resistance phenotype, bcr-abl translocation and bcl-xL overexpression could also account for the development of resistance to cell death induced by anthracyclines in leukemic cells.

Control of tumor development by intratumoral cytokines

The local immune reactions may influence the clinical outcome of human tumors. In carcinoma of the cervix, high gene expression of IL6 with tumor invasiveness whereas lack of gene expression of IFNbeta is correlated with poor prognosis. In colorectal cancer, lack of expression of IFNbeta is associated with the presence of distant metastasis and poor survival. The production of IL17 and IL18, inducers of IL6 and IFNbeta respectively is regulated in these tumors and may control the levels of the effector cytokines, i.e. IL6 and IFNbeta. The mechanisms by which these cytokines act are linked to the recruitment of effector cells such as macrophages.

Nitric oxide sensitizes ovarian tumor cells to Fas-induced apoptosis

Fas-mediated apoptosis represents one major mechanism by which tumor cells can be eliminated by activated cytotoxic immune lymphocytes. Previously, we have reported that interferon-gamma (IFN-gamma) sensitizes human ovarian carcinoma cell lines to Fas-mediated apoptosis. Furthermore, IFN-gamma, together with many other proinflammatory cytokines (TNF-alpha, IL-1beta, LPS, etc.), can stimulate the induction of inducible nitric oxide synthase (iNOS) and the generation of nitric oxide (NO). In this study, we examined whether nitric oxide is a mediator of IFN-gamma-induced sensitization of human ovarian carcinoma cell lines (A2780 and AD10) to Fas-mediated apoptosis and whether NO regulates the expression of the Fas receptor. Treatment of quiescent A2780 and AD10 ovarian carcinoma cells with IFN-gamma alone induced the expression of iNOS mRNA as examined by RT-PCR. There was accumulation of nitrite in the culture medium of IFN-gamma-treated cells, suggesting the generation of NOx. Like IFN-gamma, the use of exogenous sources of NO (S-nitroso-N-acetylpenicillamine (SNAP)) mimicked the sensitization of both cell lines to anti-Fas cytotoxic antibody (CH11) by IFN-gamma. Endogenously produced NO, by IFN-gamma pretreatment or exogenous nitrodonors, resulted in the upregulation of Fas receptor mRNA and protein expression. Blocking iNOS activity by NG-monomethyl-l-arginine (l-NMA) significantly reduced the sensitization, Fas mRNA, and protein expression observed with IFN-gamma pretreatment of the tumor cells. These findings demonstrate that sensitization of human ovarian carcinoma cell lines to Fas-mediated apoptosis by IFN-gamma can be due, in part, to the induction of iNOS and the subsequent upregulation of Fas gene expression by reactive nitrogen intermediates. Thus, the sensitivity of tumor cells to Fas-L-mediated cytotoxic immune lymphocytes can be regulated by the induction of NO or intermediates.

Is primary chemotherapy useful for all patients with primary invasive breast cancer?

Chemotherapy dose intensification in breast tumours is being evaluated in many multicentre trials, its indication being based on a clinical response in high-risk patients, thus selecting for tumours with rapid proliferation and low resistance. However, results from randomized trials are still pending. Clinical and pathological responses to therapy are valuable surrogate endpoints following primary chemotherapy. They will make it possible to distinguish at an early stage between patients who still retain an apoptotic response to chemotherapy and those patients whose disease will progress rapidly due to resistance mechanisms. For practical purposes, patients at risk and capable of responding represent the population of choice for primary systemic chemotherapy. Thus, by investigating mechanisms of response and resistance during the first courses of treatment we may target chemotherapy at those patients likely to benefit most from this treatment. A number of immunotherapy and vaccination trials are being conducted in many different centres. There is a lot of anecdotal evidence that cancer vaccines could help patients, but little yet in the way of solid, reproducible clinical data. Best responses to clinical testing would ideally be expected in early-stage disease because there is less tumour bulk and the patient's immune system is still able to respond. Patients with early breast cancer who are at high risk of recurrence and who have failed to respond to primary chemotherapy might be given the option of participating in adjuvant vaccination trials following the completion of local therapy.

Further characterization of cyclophosphamide resistance: expression of CD95 and of bcl-2 in a CML cell line

Drug resistance is a common cause of treatment failure in oncology. In addition to the resistance caused by over-expression of p-glycoprotein and similar molecules other mechanisms are involved in the selection or induction of drug resistant tumor cells. In this study, we characterized a CML cell line made resistant to cyclophosphamide (KBM7-B5-1803) further for the expression of apoptosis promoting and inhibiting molecules. We found that KBM7-B5-1803 has a 3 4-fold over-expression of the receptor CD95 (Fas/Apo-1) compared with the parent line. The regulation of CD95 by cytokines was comparable to other types of cells. Despite the inducibility and over-expression of CD95, CD95 failed to trigger apoptosis in both the parent and the drug resistant line. The drug resistant line has a particular pattern of the expression of bcl-2 family members: bcl-2 protein and message were expressed to a similar extent, however, compared with the parent line, the message for bclx short was decreased. P-glycoprotein was not expressed in either cell line. Taken together we show here in a leukemia cell line that the phenotype of cyclophosphamide resistance is associated with a particular pattern of apoptosis-related molecules.

Mutation of CD95 (Fas/Apo-1) Gene in Adult T-Cell Leukemia Cells

CD95 antigen (also known as Fas or Apo-1) and Fas ligand play key roles in apoptosis of cells of the immune system, function as effector molecules of cytotoxic T lymphocytes, and function in the elimination of activated lymphocytes during the downregulation of the immune response. The critical roles of the Fas-Fas ligand system in apoptosis suggest that its inactivation may be involved in malignant transformation. We analyzed the expression of Fas antigen on adult T-cell leukemia (ATL) cells by flow cytometry and found that Fas antigen expression was absent in a case of ATL and markedly decreased in another case among 47 cases examined. Apoptosis could not be induced in the Fas-negative ATL cells by antibody against Fas antigen. Sequencing of reverse transcription-polymerase chain reaction products of the Fas genes in the Fas negative cells showed two types of aberrant transcripts: one had a 5-bp deletion and a 1-bp insertion in exon 2, and the other transcript lacked exon 4. These mutations caused the premature termination of both alleles, resulting in the loss of expression of surface Fas antigen. These aberrant transcripts were not detected in a nonleukemic B-cell line from the same patient. An RNase protection assay of the Fas gene showed mutations in 2 additional cases with Fas-positive ATL cells of 35 cases examined: 1 case lacked exon 4 and the other was a silent mutation. In the Fas antigen-negative case, leukemic cells were resistant to anticancer drugs in vivo, indicating that the loss of expression of Fas antigen may be associated with a poor response to anticancer drugs. Indeed, Fas-negative ATL cells were resistant to adriamycin-induced apoptosis in vitro, which is consistent with the finding that ATL in this case was resistant to chemotherapy. These findings indicate that mutation of the Fas gene may be associated with the progression of ATL and with resistance to anticancer drugs.

Mutation of CD95 (Fas/Apo-1) Gene in Adult T-Cell Leukemia Cells

CD95 antigen (also known as Fas or Apo-1) and Fas ligand play key roles in apoptosis of cells of the immune system, function as effector molecules of cytotoxic T lymphocytes, and function in the elimination of activated lymphocytes during the downregulation of the immune response. The critical roles of the Fas-Fas ligand system in apoptosis suggest that its inactivation may be involved in malignant transformation. We analyzed the expression of Fas antigen on adult T-cell leukemia (ATL) cells by flow cytometry and found that Fas antigen expression was absent in a case of ATL and markedly decreased in another case among 47 cases examined. Apoptosis could not be induced in the Fas-negative ATL cells by antibody against Fas antigen. Sequencing of reverse transcription-polymerase chain reaction products of the Fas genes in the Fas negative cells showed two types of aberrant transcripts: one had a 5-bp deletion and a 1-bp insertion in exon 2, and the other transcript lacked exon 4. These mutations caused the premature termination of both alleles, resulting in the loss of expression of surface Fas antigen. These aberrant transcripts were not detected in a nonleukemic B-cell line from the same patient. An RNase protection assay of the Fas gene showed mutations in 2 additional cases with Fas-positive ATL cells of 35 cases examined: 1 case lacked exon 4 and the other was a silent mutation. In the Fas antigen-negative case, leukemic cells were resistant to anticancer drugs in vivo, indicating that the loss of expression of Fas antigen may be associated with a poor response to anticancer drugs. Indeed, Fas-negative ATL cells were resistant to adriamycin-induced apoptosis in vitro, which is consistent with the finding that ATL in this case was resistant to chemotherapy. These findings indicate that mutation of the Fas gene may be associated with the progression of ATL and with resistance to anticancer drugs.

Lack of cell surface Fas/APO-1 expression in pulmonary adenocarcinomas

The Fas receptor and ligand initiate an apoptotic pathway. Alterations in this pathway within tumor cells can result in escape from apoptosis and immune surveillance. We evaluated Fas protein expression in 42 primary pulmonary adenocarcinomas, and Fas expression and function in the lung adenocarcinoma cell lines A549 and A427. Immunohistochemical analysis demonstrated Fas protein expression in 47.6% of the tumors; however, Fas-positive tumors demonstrated cytoplasmic staining without cell surface expression. Northern blot analysis indicated that levels of Fas mRNA were similar in Fas protein-positive tumors to levels in normal lung tissue, but were reduced in Fas protein-negative tumors. Soluble form Fas was not detected in the majority of these tumors either by RT-PCR or Western blot analysis. Cell surface Fas protein expression was minimal in A549 and A427 cell lines as determined by flow cytometry. Both cell lines demonstrated Fas mRNA expression by Northern blot analysis and abundant protein expression by Western blot analysis. Transfection of the Fas cDNA derived from A549 cells induced surface Fas protein in COS cells; however, stable transfection of a native Fas cDNA into A549 cells failed to induce surface Fas protein expression. Parental A549 cells and A549 cells transfected with a Fas expression vector were resistant to Fas-mediated apoptosis. Transgenic expression of a FLAG-tagged Fas cDNA in A549 cells, with visualization of the Fas-FLAG protein using confocal microscopy, demonstrated that the Fas-FLAG protein was retained within cytoplasmic portions of the cell and was not translocated to the cell surface. These findings suggest that the Fas protein is reduced or not present on the cell surface in the primary lung tumors and is sequestered within A549 tumorigenic lung cells, and these alterations directly affect the cells resistance to Fas-mediated apoptosis.

The host-tumor immune conflict: from immunosuppression to resistance and destruction

A successful immune response against a tumor is dependent on the cytokine repertoire present at the tumor site. Salem Chouaib and colleagues discuss evidence that, to escape the immune system, tumor cells not only produce immunosuppressive cytokines but also employ strategies involving altered susceptibility to tumor necrosis factor and Fas cytotoxic pathways and, in some circumstances, use of the Fas ligand to neutralize effector cells.