Resistance to anticancer immunity in cancer patients: potential strategies to reverse resistance.

In the 1990s, the application of immunotherapy approaches to target cancer cells resulted in significant clinical responses in patients with advanced malignancies who were refractory to conventional therapies. While early immunotherapeutics were focused on T cell-mediated cytotoxic activity, subsequent efforts were centered on targeted antibody-mediated anticancer therapy. The initial success with antibody therapy encouraged further studies and, consequently, there are now more than 25 FDA-approved antibodies directed against a range of targets. Although both T cell and antibody therapies continue to result in significant clinical responses with minimal toxicity, a significant subset of patients does not respond to immunotherapy and another subset develops resistance following an initial response. This review is focused on describing examples showing that cancer resistance to immunotherapies indeed occurs. In addition, it reviews the mechanisms being used to overcome the resistance to immunotherapies by targeting the tumor cell directly and/or the tumor microenvironment.

Tumoral CD105 is a novel independent prognostic marker for prognosis in clear-cell renal cell carcinoma.

BACKGROUND: Angiogenesis is essential for tumour growth and metastasis. There are conflicting reports as to whether microvessel density (MVD) using the endothelial marker CD105 (cluster of differentiation molecule 105) in clear-cell renal cell carcinomas (ccRCC) is associated with prognosis. Recently, CD105 has been described as a RCC cancer stem cell marker. METHODS: A total of 102 ccRCC were analysed. Representative tumour sections were stained for CD105. Vascularity (endothelial CD105) was quantified by MVD. The immunohistochemistry analysis detected positive (if present) or negative (if absent) CD105 tumoral staining. This retrospective population-based study was evaluated using Kaplan-Meier method, t-test and Cox proportional hazard model. RESULTS: We found that the expression of endothelial CD105 (MVD) negatively correlated with nuclear grade (P<0.001), tumour stage (P<0.001) and Leibovitch score (P<0.001), whereas the expression of tumoral CD105 positively correlated with these three clinicopathological factors (P<0.001). In multivariate analysis, tumoral CD105 was found to be an independent predictor of poor overall survival (P=0.002). CONCLUSIONS: We have shown for the first time that tumoral CD105 is an independent predictive marker for death risk and unfavourable prognosis in patients with ccRCC after curative resection.

Tumor microenvironment-induced tumor cell plasticity: relationship with hypoxic stress and impact on tumor resistance.

The role of tumor interaction with stromal components during carcinogenesis is crucial for the design of efficient cancer treatment approaches. It is widely admitted that tumor hypoxic stress is associated with tumor aggressiveness and thus impacts susceptibility and resistance to different types of treatments. Notable biological processes that hypoxia functions in include its regulation of tumor heterogeneity and plasticity. While hypoxia has been reported as a major player in tumor survival and dissemination regulation, the significance of hypoxia inducible factors in cancer stem cell development remains poorly understood. Several reports indicate that the emergence of cancer stem cells in addition to their phenotype and function within a hypoxic tumor microenvironment impacts cancer progression. In this respect, evidence showed that cancer stem cells are key elements of intratumoral heterogeneity and more importantly are responsible for tumor relapse and escape to treatments. This paper briefly reviews our current knowledge of the interaction between tumor hypoxic stress and its role in stemness acquisition and maintenance. Our review extensively covers the influence of hypoxia on the formation and maintenance of cancer stem cells and discusses the potential of targeting hypoxia-induced alterations in the expression and function of the so far known stem cell markers in cancer therapy approaches. We believe that a better and integrated understanding of the effect of hypoxia on stemness during carcinogenesis might lead to new strategies for exploiting hypoxia-associated pathways and their targeting in the clinical setting in order to overcome resistance mechanisms. More importantly, at the present time, efforts are oriented towards the design of innovative therapeutical approaches that specifically target cancer stem cells.

The first alpha helix of interleukin (IL)-2 folds as a homotetramer, acts as an agonist of the IL-2 receptor beta chain, and induces lymphokine-activated killer cells.

Interleukin (IL)-2 interacts with two types of functional receptors (IL-2Ralphabetagamma and IL-2Rbetagamma) and acts on a broad range of target cells involved in inflammatory reactions and immune responses. For the first time, we show that a chemically synthesized fragment of the IL-2 sequence can fold into a molecule mimicking the quaternary structure of a hemopoietin. Indeed, peptide p1-30 (containing amino acids 1-30, covering the entire alpha helix A of IL-2) spontaneously folds into an alpha-helical homotetramer and stimulates the growth of T cell lines expressing human IL-2Rbeta, whereas shorter versions of the peptide lack helical structure and are inactive. We also demonstrate that this neocytokine interacts with a previously undescribed dimeric form of IL-2Rbeta. In agreement with its binding to IL-2Rbeta, p1-30 activates Shc and p56(lck) but unlike IL-2, fails to activate Janus kinase (Jak)1, Jak3, and signal transducer and activator of transcription 5 (STAT5). Unexpectedly, we also show that p1-30 activates Tyk2, thus suggesting that IL-2Rbeta may bind to different Jaks depending on its oligomerization. At the cellular level, p1-30 induces lymphokine-activated killer (LAK) cells and preferentially activates CD8(low) lymphocytes and natural killer cells, which constitutively express IL-2Rbeta. A significant interferon gamma production is also detected after p1-30 stimulation. A mutant form of p1-30 (Asp20-->Lys), which is likely unable to induce vascular leak syndrome, remains capable of generating LAK cells, like the original p1-30 peptide. Altogether, our data suggest that p1-30 has therapeutic potential.

Detection of a functional hybrid receptor gammac/GM-CSFRbeta in human hematopoietic CD34+ cells.

A functional hybrid receptor associating the common gamma chain (gammac) with the granulocyte/macrophage colony-stimulating factor receptor beta (GM-CSFRbeta) chain is found in mobilized human peripheral blood (MPB) CD34+ hematopoietic progenitors, SCF/Flt3-L primed cord blood (CB) precursors (CBPr CD34+/CD56-), and CD34+ myeloid cell lines, but not in normal natural killer (NK) cells, the cytolytic NK-L cell line or nonhematopoietic cells. We demonstrated, using CD34+ TF1beta cells, which express an interleukin (IL)-15Ralpha/beta/gammac receptor, that within the hybrid receptor, the GM-CSFRbeta chain inhibits the IL-15-triggered gammac/JAK3-specific signaling controlling TF1beta cell proliferation. However, the gammac chain is part of a functional GM-CSFR, activating GM-CSF-dependent STAT5 nuclear translocation and the proliferation of TF1beta cells. The hybrid receptor is functional in normal hematopoietic progenitors in which both subunits control STAT5 activation. Finally, the parental TF1 cell line, which lacks the IL-15Rbeta chain, nevertheless expresses both a functional hybrid receptor that controls JAK3 phosphorylation and a novel IL-15alpha/gammac/TRAF2 complex that triggers nuclear factor kappaB activation. The lineage-dependent distribution and function of these receptors suggest that they are involved in hematopoiesis because they modify transduction pathways that play a major role in the differentiation of hematopoietic progenitors.

Immune surveillance of human cancer: if the cytotoxic T-lymphocytes play the music, does the tumoral system call the tune?

Accumulating evidence indicates that the innate and adaptive immune systems participate in the recognition and destruction of cancer cells by a process known as cancer immunosurveillance. Tumor antigen-specific cytotoxic T-lymphocytes (CTL) are the major effectors in the immune response against tumor cells. The identification of tumor-associated antigen (TAA) recognized primarily by CD 8(+) T-lymphocytes has led to the development of several vaccination strategies that induce or potentiate specific immune responses. However, large established tumors, which are associated with the acquisition of tumor resistance to specific lysis, are usually not fully controlled by the immune system. Recently, it has become clear that the immune system not only protects the host against tumor development but also sculpts the immunogenic phenotype of a developing tumor and can favor the emergence of resistant tumor cell variants. Moreover, it has become obvious that the evasion of immunosurveillance by tumor cells is under the control of the tumor microenvironment complexity and plasticity. In this review, we will focus on some new mechanisms associated with the acquisition of tumor resistance to specific lysis during tumor progression, involving genetic instability, structural changes in cytoskeleton, and hypoxic stress. We will also discuss the interaction between CTLs and tumor endothelial cells, a major component of tumor stroma.

Seroprevalence of Helicobacter pylori among Tunisian blood donors (outpatients), symptomatic patients and control subjects.

OBJECTIVES: Helicobacter pylori is a worldwide infection, although little data are available in the Tunisian population. The aims of our study were to detect the prevalence of H. pylori in a blood-donor population (n=250) and in another population of hospital-consulting patients comprising 87 symptomatic patients and 59 controls, and to determine the factors that influence the prevalence. MATERIALS AND METHODS: Study subjects answered a standardized questionnaire, and IgG anti-H. pylori and anti-cag were detected by ELISA. In the second population, culture and cagA polymerase chain reaction were performed. RESULTS: The seroprevalence of H. pylori in blood donors was 64%, and 11% had anti-cag. All patients positive for anti-cag were also positive for anti-H. pylori antibodies. The seroprevalence of H. pylori was 99.3% in the hospital-consulting patients, of whom 55.5% were positive for anti-cag. The difference between the anti-cag and symptomatic patients (66.7%) and controls (39%) was significant. Symptomatic patients had a higher rate of anti-cag (66.7%) compared with the controls (39%) and blood donors (11%). CONCLUSION: H. pylori seroprevalence in blood donors is low (64%) compared with symptomatic patients (99.3%), and anti-cag was statistically associated with symptomatic patients and pathology. Also, some environmental factors were correlated with H. pylori seroprevalence.

[Peritoneal tuberculosis--report of 43 cases]. / La tuberculose péritonéale--a propos de 43 observations.

BACKGROUND: Peritoneal tuberculosis represents 0, 1 to 4% of all forms of tuberculosis. AIM: The aim of our study is to describe clinical, therapeutic characteristics and the outcome of peritoneal tuberculosis. METHODS: Retrospective study of all cases of peritoneal tuberculosis diagnosed in gastroenterology B department - Rabta Hospital during a 12 years period (1996 to 2007). RESULTS: Forty three cases of peritoneal tuberculosis were included: 15 male and 28 female with mean age of 38years (extremes: 16 to 85years). Five patients were cirrhotic. Clinical manifestations were dominated by ascitis (83%). Ascitic fluid were exsudative in 97% of cases and lymphocytic in all cases. The diagnostic was based on coelioscopy with peritoneal biopsy in 26 cases demonstrating caseating granulomatous lesions in 64% of cases. Extra peritoneal tuberculosis was noted in 60, 4% dominated by pleuro-pulmonary localisations. Patients were given antituberculous therapy for a mean duration of 9, 8 months and the outcome was favourable in 93%. CONCLUSION: Peritoneal tuberculosis is still a medical problem in Tunisia. It is more common in young female. Diagnosis is based on the results of peritoneal biopsies during celioscopy. The outcome is good in most cases after antituberculous treatment.

Distinctive role of integrin-mediated adhesion in TNF-induced PKB/Akt and NF-kappaB activation and endothelial cell survival.

Tumor necrosis factor (TNF) is a pro-inflammatory cytokine exerting pleiotropic effects on endothelial cells. Depending on the vascular context it can induce endothelial cell activation and survival or death. The microenvironmental cues determining whether endothelial cells will survive or die, however, have remained elusive. Here we report that integrin ligation acts permissive for TNF-induced protein kinase B (PKB/Akt) but not nuclear factor (NF)-kappaB activation. Concomitant activation of PKB/Akt and NF-kappaB is essential for the survival of endothelial cells exposed to TNF. Active PKB/Akt strengthens integrin-dependent endothelial cell adhesion, whereas disruption of actin stress fibers abolishes the protective effect of PKB/Akt. Integrin-mediated adhesion also represses TNF-induced JNK activation, but JNK activity is not required for cell death. The alphaVbeta3/alphaVbeta5 integrin inhibitor EMD121974 sensitizes endothelial cells to TNF-dependent cytotoxicity and active PKB/Akt attenuates this effect. Interferon gamma synergistically enhanced TNF-induced endothelial cell death in all conditions tested. Taken together, these observations reveal a novel permissive role for integrins in TNF-induced PKB/Akt activation and prevention of TNF-induced death distinct of NF-kappaB, and implicate the actin cytoskeleton in PKB/Akt-mediated cell survival. The sensitizing effect of EMD121974 on TNF cytotoxicity may open new perspectives to the therapeutic use of TNF as anticancer agent.

p53 status correlates with histopathological response in patients with soft tissue sarcomas treated using isolated limb perfusion with TNF-alpha and melphalan.

BACKGROUND: Recombinant tumor necrosis factor-alpha (TNF-alpha) combined to melphalan is clinically administered through isolated limb perfusion (ILP) for regionally advanced soft tissue sarcomas of the limbs. In preclinical studies, wild-type p53 gene is involved in the regulation of cytotoxic action of TNF-alpha and loss of p53 function contributes to the resistance of tumour cells to TNF-alpha. The relationship between p53 status and response to TNF-alpha and melphalan in patients undergoing ILP is unknown. PATIENTS AND METHODS: We studied 110 cases of unresectable limbs sarcomas treated by ILP. Immunohistochemistry was carried out using DO7mAb, which reacts with an antigenic determinant from the N-terminal region of both the wild-type and mutant forms of the p53 protein, and PAb1620mAb, which reacts with the 1620 epitope characteristic of the wild-type native conformation of the p53 protein. The immunohistochemistry data were then correlated with various clinical parameters. RESULTS: P53DO7 was found expressed at high levels in 28 patients, whereas PAb1620 was negative in 20. The tumours with poor histological response to ILP with TNF-alpha and melphalan showed significantly higher levels of p53-mutated protein. CONCLUSIONS: Our results might be a clue to a role of p53 protein status in TNF-alpha and melphalan response in clinical use.

Imatinib enhances human melanoma cell susceptibility to TRAIL-induced cell death: Relationship to Bcl-2 family and caspase activation.

In order to define genetic determinants of primary and metastatic melanoma cell susceptibility to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), we have applied oligonucleotide microarrays to TRAIL-sensitive primary T1 cells and TRAIL-resistant metastatic G1 cells treated or not with TRAIL. T1 and G1 cells are isogenic melanoma cell subclones. We examined 22 000 spots, 4.2% of which displayed differential expression in G1 and T1 cells. Cell susceptibility to TRAIL-mediated apoptosis was found to be correlated with gene expression signatures in this model. Some of the differentially expressed genes were identified as involved in ATP-binding and signaling pathways, based on previously published data. Further analysis provided evidences that c-kit was overexpressed in G1 cells while it was absent in T1 cells. The c-kit inhibitor, imatinib, did not restore TRAIL sensitivity, excluding a role for c-kit in TRAIL resistance in G1 cells. Surprisingly, imatinib inhibited cell proliferation and TRAIL-mediated apoptosis in melanoma cells. We investigated the possible involvement of several molecules, including c-ABL, platelet-derived growth factor receptor (PDGFR), cellular FADD-like interleukin-1 alpha-converting enzyme-like inhibitory protein (c-FLIP)(L/S), Fas-associated DD kinase, p53, p21(WAF1), proteins of B-cell leukemia/lymphoma 2 (Bcl-2) family and cytochrome c. Imatinib did not modulate the expression or activation of its own targets, such as c-ABL, PDGFRalpha and PDGFRbeta, but it did affect the expression of c-FLIP(L), BCL2-associated X protein (Bax) and Bcl-2. Moreover, c-FLIP(L) knockdown sensitized T1 cells to TRAIL-mediated apoptosis, with a sensitivity similar to that of cells previously treated with imatinib. More notably, we found that the resistance to TRAIL in G1 cells was correlated with constitutive c-FLIP(L) recruitment to the DISC and the inhibition of caspase 8, 3 and 9 processing. Moreover, c-FLIP(L) knockdown partly restored TRAIL sensitivity in G1 cells, indicating that the expression level of c-FLIP(L) and its interaction with TRAIL receptor2 play a crucial role in determining TRAIL resistance in metastatic melanoma cells. Our results also show that imatinib enhances TRAIL-induced cell death independently of BH3-interacting domain death agonist translocation, in a process involving the Bax:Bcl-X(L) ratio, Bax:Bcl-X(L)/Bcl-2 translocation, cytochrome c release and caspase activation. Our data indicate that imatinib sensitizes T1 cells by directly downregulating c-FLIP(L), with the use of an alternative pathway for antitumor activity, because PDGFRalpha is not activated in T1 cells and these cells do not express c-kit, c-ABL or PDGFRbeta. Caspase cascade activation and mitochondria also play a key role in the imatinib-mediated sensitization of melanoma cells to the proapoptotic action of TRAIL.

Analysis of prostaglandin E2 effect on T lymphocyte activation. Abrogation of prostaglandin E2 inhibitory effect by the tumor promotor 12.0 tetradecanoyl phorbol-13 acetate.

We have investigated the inhibitory potential of prostaglandin E2 (PGE2) with respect to intracellular messengers implicated in the signaling system of T-lymphocyte activation pathway. Using the fluorescent indicator Quin 2, it is demonstrated that PGE2 inhibits the increase in cytosolic-free calcium concentration [Ca2+]i. Reconstitution of calcium mobilization in the presence of PGE2 by the calcium ionophore A23187 results in a partial restoration of both interleukin 2 (IL2) production and cell proliferation and has no effect on the inhibition of transferrin receptor expression. In contrast, the treatment of cell cultures with the tumor promotor 12.0 tetra decanoyl phorbol-13-acetate (TPA) abrogates the suppressor activity of PGE2. When T lymphocyte stimulation is provided by the combination of A23187 and TPA, the PGE2 inhibitory effect does not occur. These data also indicate that the down regulation of transferrin receptor by PGE2 is proximal to protein kinase C activation and is not associated with decreased expression of the functional IL2 receptor.

Involvement of cyclic adenosine monophosphate in the interleukin 4 inhibitory effect on interleukin 2-induced lymphokine-activated killer generation.

In previous studies, IL-4 has been reported to interfere with IL-2-driven generation of lymphokine-activated killer (LAK) activity. In this investigation, we have demonstrated that IL-4 inhibited the IL-2-induced differentiation of large granular lymphocytes (LGL) into LAK effectors by a mechanism involving, at least in part, an increase in LGL intracellular cAMP levels. In contrast, with its capacity to induce cAMP accumulation in resting LGL, IL-4 had a very negligible effect on LAK activity induction, and cAMP levels increase in LGL that had been preincubated with IL-2. Furthermore, the inhibitory effect of IL-4 on LAK activity generation also correlated with a marked decrease in N-CBZ-L-lysine thiobenzylester esterase activity, with an inhibition of tumor necrosis factor (TNF) mRNA expression and TNF production by IL-2-stimulated LGL. These results strongly suggest that complex signaling processes could be ascribed to the dual activities of cytokines and their interplay in LAK promotion.

Efficacy of adjuvant chemotherapy according to Prion protein expression in patients with estrogen receptor-negative breast cancer.

BACKGROUND: Prion protein (PrPc) has been previously reported to be associated with resistance to proapoptotic stimuli. We evaluated whether the expression of PrPc was associated with the resistance to adjuvant chemotherapy in patients with estrogen receptor (ER) -negative breast cancer. PATIENTS AND METHODS: The expression of PrPc by primary tumors was assessed by immunohistochemistry in a series of 756 patients included in two randomized trials that compared anthracycline-based chemotherapy to no chemotherapy. The PrPc expression was correlated with ER expression and the benefit of adjuvant chemotherapy was assessed according to PrPc expression in patients with ER-negative tumors. RESULTS: Immunostaining analysis showed that PrPc was mainly expressed by myoepithelial cells in normal breast tissue. Tissue microarray analysis from 756 breast tumors showed that PrPc was associated with ER-negative breast cancer subsets (P < 0.001). Adjuvant chemotherapy was not associated with a significant risk reduction for death in patients with ER-negative/PrPc-positive disease [adjusted hazard ratio (HR) for death = 0.98, 95% confidence interval (CI) 0.45-2.1, P = 0.95], while it decreased the risk for death (HR = 0.39, 95% CI 0.2-0.74, P = 0.004) in patients with ER-negative/PrPc-negative tumors. CONCLUSION: These data indicate that ER-negative/PrPc-negative phenotype is associated with a high sensitivity to adjuvant chemotherapy.

Cytolytic function and survival of natural killer cells are severely altered in myelodysplastic syndromes.

Natural Killer (NK) cells are critical in host defense against malignant transformation and are potent antileukemic cytotoxic effectors. In the present study, we investigated the peripheral NK function in patients with myelodysplastic syndromes (MDS). We demonstrated that the peripheral NK cell population was quantitatively normal in MDS patients. Furthermore, NK cells displayed an expression of the activating natural cytotoxicity receptors (NCR) NKp46 and NKp30 as well as NKG2D similar to that observed in donors, but exert a highly decreased constitutive cytolytic activity compared to resting normal NK cells. Although activation with IL-2 resulted in the upregulation of NKp46 expression by MDS-NK cells, their cytolytic function remained deeply altered as compared to activated donor NK cells. In addition, MDS NK cells did not proliferate in vitro, and displayed an increased rate of apoptosis in response to IL-2 stimulation although the spontaneous apoptosis was not significantly increased. Interestingly, a proportion of peripheral MDS-NK cells were derived from the MDS clone as the cytogenetic anomaly found in bone marrow karyotype was also detected in 20-50% of circulating NK cells. In conclusion, NK cells' cytolytic function and proliferative capacities in response to activation by cytokines are profoundly altered in MDS.

Hypoxic stress: obstacles and opportunities for innovative immunotherapy of cancer.

Tumors use several strategies to evade the host immune response, including creation of an immune-suppressive and hostile tumor environment. Tissue hypoxia due to inadequate blood supply is reported to develop very early during tumor establishment. Hypoxic stress has a strong impact on tumor cell biology. In particular, tissue hypoxia contributes to therapeutic resistance, heterogeneity and progression. It also interferes with immune plasticity, promotes the differentiation and expansion of immune-suppressive stromal cells, and remodels the metabolic landscape to support immune privilege. Therefore, tissue hypoxia has been regarded as a central factor for tumor aggressiveness and metastasis. In this regard, manipulating host-tumor interactions in the context of the hypoxic tumor microenvironment may be important in preventing or reverting malignant conversion. We will discuss how tumor microenvironment-driven transient compositional tumor heterogeneity involves hypoxic stress. Tumor hypoxia is a therapeutic concern since it can reduce the effectiveness of conventional therapies as well as cancer immunotherapy. Thus, understanding how tumor and stromal cells respond to hypoxia will allow for the design of innovative cancer therapies that can overcome these barriers. A better understanding of hypoxia-dependent mechanisms involved in the regulation of immune tolerance could lead to new strategies to enhance antitumor immunity. Therefore, discovery and validation of therapeutic targets derived from the hypoxic tumor microenvironment is of major importance. In this context, critical hypoxia-associated pathways are attractive targets for immunotherapy of cancer. In this review, we summarize current knowledge regarding the molecular mechanisms induced by tumor cell hypoxia with a special emphasis on therapeutic resistance and immune suppression. We emphasize mechanisms of manipulating hypoxic stress and its associated pathways, which may support the development of more durable and successful cancer immunotherapy approaches in the future.

Resistance to TNF-alpha and adriamycin in the human breast cancer MCF-7 cell line: relationship to MDR1, MnSOD, and TNF gene expression.

The molecular basis of cross-resistance to tumor necrosis factor (TNF) and Adriamycin has been investigated using the breast adenocarcinoma cell line MCF7/p, its Adriamycin-resistant counterpart MCF7AdrR, and the MDR1 gene-transduced MCF-7 cells (MCF7/MDR1). While the parental cell line MCF7/p was TNF-sensitive, MCF7AdrR was TNF-resistant. The TNF resistance exhibited by MCF7AdrR cells was not due to a lack of TNF receptor expression because both cell lines express comparable levels of p75 and p55 receptors as revealed by immunofluorescence analysis. NF-kappa B translocation, which is an essential transducing signal of the TNF-induced lysis pathway, does not appear to be involved in this resistance as assessed by gel shift experiments. In order to determine the role of MDR1 gene expression in the development of this cross-resistance, MCF7/p cells transfected by the MDR1 gene were examined. Our data showed that the expression of the MDR1 gene in these cells resulted in a relative resistance of these cells to Adriamycin without affecting their susceptibility to TNF killing. The implication of the manganese superoxide dismutase and endogenous TNF expression in the cross-resistance by MCF7AdrR cells to Adriamycin and TNF has also been investigated. Northern blot analysis indicated that following TNF stimulation, the expression of 4-kilobase and 1-kilobase manganese superoxide dismutase mRNAs were 9- to 10-fold induced in MCF7AdrR cells as compared to MCF7/p and MCF7/MDR1 cells. This suggests a possible involvement of this enzyme in the Adriamycin-induced resistance to TNF. Although TNF-treatment of MCF7/p and MDR-cells induced endogenous TNF expression in these cells, the level of mRNA induction was selectively enhanced in MCF7AdrR cells (7- to 8-fold greater in MCF7AdrR cells as compared to MCF7/p and MCF7/MDR1 cells). Collectively, these data indicate that the expression of the MDR1 gene in MCF7/p cells following gene transfection is not sufficient for the acquisition of TNF resistance by MCF7/MDR1 cells. Furthermore, our data provide the first evidence that Adriamycin-induced resistance to TNF in MCF7AdrR cells may, in part, involve an overexpression of endogenous TNF and manganese superoxide dismutase genes.

Tumor cells regulate the lytic activity of tumor-specific cytotoxic t lymphocytes by modulating the inhibitory natural killer receptor function.

Tumor-infiltrating p58+ T cells from a renal tumor were specifically expanded in response to tumor cell stimulation and cloned. These p58+ T cells were found to express a memory phenotype and corresponded to clonal TCRBV3 T-cell expansion. Functionally, p58(+) CTLs displayed a low lytic activity for HLA-A2 tumor and normal cells. However, this lytic activity was significantly increased after blockade of p58 with specific monoclonal antibodies. Interestingly, we demonstrated that stimulation by tumor cells was required to trigger the inhibitory effect of p58 on the lytic activity of antigen-specific CTLs and that stimulation of the inhibitory function of p58 by tumor cells correlated with an inhibition of nuclear factor-kappaB activation in p58+ tumor-specific CTLS.

A point mutation in the alpha-actinin-4 gene generates an antigenic peptide recognized by autologous cytolytic T lymphocytes on a human lung carcinoma.

We have identified an antigen recognized on a human large cell carcinoma by an autologous tumor-specific CTL clone that was derived from mononuclear cells infiltrating the primary tumor. The antigenic peptide is presented by HLA-A2 molecules and is encoded by the alpha-actinin-4 gene, which is expressed ubiquitously. In the tumor cells, a point mutation generates an amino-acid change that is essential for recognition by the CTLS: The mutation was not found in alpha-actinin-4 cDNA sequences from about 50 lung carcinoma cell lines, suggesting that it is unique to this patient. Although he did not receive chemotherapy or radiotherapy, the patient has been without evidence of tumor since the resection of the primary lesion in 1996. Using tetramers of soluble HLA-A2 molecules loaded with the mutated antigenic peptide, anti-alpha-actinin-4 CTLs could be derived from blood samples collected from the patient in 1998 and 2000. It is possible that these CTLs, recognizing a truly tumor-specific antigen, play a role in the clinical evolution of this lung cancer patient.

Stable inhibition of nuclear factor kappaB in cancer cells does not increase sensitivity to cytotoxic drugs.

Several reports indicated that nuclear factor kappaB (NF-kappaB) activation by cytokines, cytotoxic drugs, or ionizing radiation protects cells against apoptosis. Therefore, we investigated the consequence of NF-kappaB inhibition on the efficiency of antineoplastic agents. HPB, HCT116, MCF7, and OVCAR-3 cells stably expressing a dominant negative IkappaBalpha inhibitor showed a decreased NF-kappaB activation following treatment with tumor necrosis factor a and various chemotherapeutic agents. However, there was no difference in survival between parental cells and cells expressing mutated IkappaBalpha. These studies suggest that, at least in these cell lines, stable NF-kappaB inhibition did not modify the response to cytotoxic drugs.