HER2 Copy Number and Resistance Mechanisms in Patients with HER2-positive Advanced Gastric Cancer Receiving Initial Trastuzumab-based Therapy in JACOB Trial

PURPOSE

In JACOB trial, pertuzumab added to trastuzumab-chemotherapy did not significantly improve survival of patients with HER2-positive metastatic gastric cancer, despite 3.3 months increase versus placebo. HER2 copy-number variation (CNV) and AMNESIA panel encompassing primary resistance alterations (KRAS/PIK3CA/MET mutations, KRAS/EGFR/MET amplifications) may improve patients' selection for HER2 inhibition.

EXPERIMENTAL DESIGN

In a post hoc analysis of JACOB on 327 samples successfully sequenced by next-generation sequencing (NGS; Oncomine Focus DNA), HER2 CNV, HER2 expression by IHC, and AMNESIA were correlated with overall response rate (ORR), progression-free survival (PFS), and overall survival (OS) by univariable/multivariable models.

RESULTS

Median HER2 CNV was 4.7 (interquartile range, 2.2-16.9). HER2 CNV-high versus low using the median as cutoff was associated with longer median PFS (10.5 vs. 6.4 months; HR = 0.48; 95% confidence interval: 0.38-0.62; P < 0.001) and OS (20.3 vs. 13.0 months; HR = 0.54; 0.42-0.72; P < 0.001). Combining HER2 CNV and IHC improved discriminative ability, with better outcomes restricted to HER2-high/HER2 3+ subgroup. AMNESIA positivity was found in 51 (16%), with unadjusted HR = 1.35 (0.98-1.86) for PFS; 1.43 (1.00-2.03) for OS.In multivariable models, only HER2 CNV status remained significant for PFS (P < 0.001) and OS (P = 0.004). Higher ORR was significantly associated with IHC 3+ [61% vs. 34% in 2+; OR = 3.11 (1.89-5.17)] and HER2-high [59% vs. 43% in HER2-low; OR = 1.84 (1.16-2.94)], with highest OR in the top CNV quartile. These biomarkers were not associated with treatment effect of pertuzumab.

CONCLUSIONS

HER2 CNV-high assessed by NGS may be associated with better ORR, PFS, and OS in a JACOB subgroup, especially if combined with HER2 3+. The negative prognostic role of AMNESIA requires further clinical validation.

Predictive Role of CD36 Expression in HER2-Positive Breast Cancer Patients Receiving Neoadjuvant Trastuzumab

BACKGROUND

Despite huge efforts to identify biomarkers associated with long-term clinical outcomes in patients with early-stage HER2-positive breast cancer (HER2+ BC) treated with (neo)adjuvant anti-HER2 therapy, no reliable predictors have been identified so far. Fatty acid uptake, a process mediated by the transmembrane transporter CD36, has recently emerged as a potential determinant of resistance to anti-HER2 treatments in preclinical HER2+ BC models.

METHODS

Here, we investigated the association between baseline intratumor CD36 gene expression and event-free survival in 180 patients enrolled in the phase III trial Neoadjuvant Lapatinib and/or Trastuzumab Treatment Optimization (NeoALTTO), which randomly assigned stage II-III HER2+ BC patients to receive neoadjuvant lapatinib, trastuzumab, or lapatinib-trastuzumab in combination with chemotherapy. To this aim, we selected NeoALTTO trial patients for whom pretreatment whole transcriptomic data were available. The main study results were validated in an independent cohort of patients enrolled in the neoadjuvant phase II trial NeoSphere.

RESULTS

In 180 NeoALTTO patients, high intratumor CD36 expression was independently associated with worse event-free survival in patients treated with trastuzumab-based therapy (hazard ratio [HR] = 1.72, 95% confidence interval [CI] = 1.20 to 2.46), but not with lapatinib-based (HR = 1.02, 95% CI = 0.68 to 1.53) or trastuzumab-lapatinib-based (HR = 1.08, 95% CI = 0.60 to 1.94) therapy. Among 331 NeoSphere patients evaluated, high CD36 expression was independently associated with worse patient disease-free survival in both the whole study cohort (HR = 1.197, 95% CI = 1.002 to 1.428) and patients receiving trastuzumab-based neoadjuvant therapy (HR = 1.282, 95% CI = 1.049 to 1.568).

CONCLUSIONS

High CD36 expression predicts worse clinical outcomes in early-stage HER2+ BC treated with trastuzumab-based neoadjuvant therapy.

A combination of extracellular matrix- and interferon-associated signatures identifies high-grade breast cancers with poor prognosis

Breast cancer (BC) is a heterogeneous disease in which the tumor microenvironment (TME) seems to impact the clinical outcome. Here, we investigated whether a combination of gene expression signatures relating to both the structural and immune TME aspects can help predict prognosis in women with high‐grade BC (HGBC). Thus, we focused on a combined molecular biomarker variable that involved extracellular matrix (ECM)‐associated gene expression (ECM3 signature) and interferon (IFN)‐associated metagene (IFN metagene) expression. In 97 chemo‐naive HGBCs from the METABRIC dataset, the dichotomous ECM3/IFN (dECIF) variable identified a group of high‐risk patients (ECM3⁺/IFN⁻ vs other; hazard ratio = 3.2, 95% confidence interval: 1.5–6.7). Notably, ECM3⁺/IFN⁻ tumors showed low tumor‐infiltrating lymphocytes, high levels of CD33‐positive cells, absence of PD‐1 expression, or low expression of PD‐L1, as suggested by immune profiles and immune‐histochemical analysis on an independent cohort of 131 HGBCs. To make our results transferable to clinical use, we refined the dECIF biomarker using reduced ECM3 and IFN signatures; notably, the prognostic value of this reduced dECIF was comparable to that of the original dECIF. After validation in a new BC cohort, reduced dECIF was translated into a robust qPCR classifier for real‐world clinical use.

Anticancer innovative therapy: Highlights from the ninth annual meeting

The Ninth Annual Conference of "Anticancer Innovative Therapy", organized by Fondazione IRCCS Istituto Nazionale dei Tumori di Milano (Fondazione IRCCS INT) and hosted by Hotel Michelangelo, was held in Milan on 25 January 2019. Cutting-edge science was presented in two main scientific sessions: i) pre-clinical evidences and new targets, and ii) clinical translation. The Keynote lecture entitled "Cancer stem cells (CSCs): metabolic strategies for their identification and eradication" presented by M. Lisanti, was one of the highlights of the conference. One key concept of the meeting was how the continuous advances in our knowledge about molecular mechanisms in various fields of research (cancer metabolism reprogramming, epigenetic regulation, transformation/invasiveness, and immunology, among others) are driving cancer research towards more effective personalized antineoplastic strategies. Specifically, recent preclinical data on the following topics were discussed: 1. Polycomb group proteins in cancer; 2. A d16HER2 splice variant is a flag of HER2 addiction across HER2-positive cancers; 3. Studying chromatin as a nexus between translational and basic research; 4. Metabolomic analysis in cancer patients; 5. CDK4-6 cyclin inhibitors: clinical activity and future perspectives as immunotherapy adjuvant; and 6. Cancer stem cells (CSCs): metabolic strategies for their identification and eradication. In terms of clinical translation, several novel approaches were presented: 1. Developing CAR-T cell therapies: an update of preclinical and clinical development at University of North Carolina; 2. Vγ9Vδ2 T-cell activation and immune suppression in multiple myeloma; 3. Predictive biomarkers for real-world immunotherapy: the cancer immunogram model in the clinical arena; and 4. Mechanisms of resistance to immune checkpoint blockade in solid tumors. Overall, the pre-clinical and clinical findings presented could pave the way to identify novel actionable therapeutic targets to significantly enhance the care of persons with cancer.

RET fusions in a small subset of advanced colorectal cancers at risk of being neglected

Background

Recognition of rare molecular subgroups is a challenge for precision oncology and may lead to tissue-agnostic approval of targeted agents. Here we aimed to comprehensively characterize the clinical, pathological and molecular landscape of RET rearranged metastatic colorectal cancer (mCRC).

Patients and methods

In this case series, we compared clinical, pathological and molecular characteristics of 24 RET rearranged mCRC patients with those of a control group of 291 patients with RET negative tumors. RET rearranged and RET negative mCRCs were retrieved by systematic literature review and by taking advantage of three screening sources: (i) Ignyta's phase 1/1b study on RXDX-105 (NCT01877811), (ii) cohorts screened at two Italian and one South Korean Institutions and (iii) Foundation Medicine Inc. database. Next-generation sequencing data were analyzed for RET rearranged cases.

Results

RET fusions were more frequent in older patients (median age of 66 versus 60 years, P = 0.052), with ECOG PS 1-2 (90% versus 50%, P = 0.02), right-sided (55% versus 32%, P = 0.013), previously unresected primary tumors (58% versus 21%, P < 0.001), RAS and BRAF wild-type (100% versus 40%, P < 0.001) and MSI-high (48% versus 7%, P < 0.001). Notably, 11 (26%) out of 43 patients with right-sided, RAS and BRAF wild-type tumors harbored a RET rearrangement. At a median follow-up of 45.8 months, patients with RET fusion-positive tumors showed a significantly worse OS when compared with RET-negative ones (median OS 14.0 versus 38.0 months, HR: 4.59; 95% CI, 3.64-32.66; P < 0.001). In the multivariable model, RET rearrangements were still associated with shorter OS (HR: 2.97; 95% CI, 1.25-7.07; P = 0.014), while primary tumor location, RAS and BRAF mutations and MSI status were not.

Conclusions

Though very rare, RET rearrangements define a new subtype of mCRC that shows poor prognosis with conventional treatments and is therefore worth of a specific management.

Innovative therapy, monoclonal antibodies, and beyond: Highlights from the eighth annual meeting

The eighth annual conference of "Innovative therapy, monoclonal antibodies, and beyond" was held in Milan on Jan. 26, 2018, and hosted by Fondazione IRCCS-Istituto Nazionale dei Tumori (Fondazione IRCCS INT). The conference was divided into two main scientific sessions, of i) pre-clinical assays and novel biotargets, and ii) clinical translation, as well as a third session of presentations from young investigators, which focused on recent achievements within Fondazione IRCCS INT on immunotherapy and targeted therapies. Presentations in the first session addressed the issue of cancer immunotherapy activity with respect to tumor heterogeneity, with key topics addressing: 1) tumor heterogeneity and targeted therapy, with the definition of the evolutionary Index as an indicator of tumor heterogeneity in both space and time; 2) the analysis of cancer evolution, with the introduction of the TRACERx Consortium-a multi-million pound UK research project focused on non-small cell lung cancer (NSCLC); 3) the use of anti-estrogen agents to boost immune recognition of breast cancer cells; and 4) the high degree of functional plasticity within the NK cell repertoire, including the expansion of adaptive NK cells following viral challenges. The second session addressed: 1) the effectiveness of radiotherapy to enhance the proportion of patients responsive to immune-checkpoint blockers (ICBs); 2) the use of MDSC scores in selecting melanoma patients with high probability to be responsive to ICBs; and 3) the relevance of the gut microbiome as a predictive factor, and the potential of its perturbation in increasing the immune response rate to ICBs. Overall, a picture emerged of tumor heterogeneity as the main limitation that impairs the effectiveness of anti-cancer therapies. Thus, the choice of a specific therapy based on reproducible and selective predictive biomarkers is an urgent unmet clinical need that should be addressed in order to increase the proportion of long-term responding patients and to improve the sustainability of novel drugs.

Innovative Therapy, Monoclonal Antibodies and Beyond

The seventh Edition of "Innovative Therapy, Monoclonal Antibodies and Beyond" Meeting took place in Milan, Italy, on January 27, 2017. The two sessions of the meeting were focused on: 1) Preclinical assays and novel biotargets; and 2) monoclonal antibodies, cell therapies and targeted molecules. Between these two sessions, a lecture entitled "HLA-antigens modulation and response to immune checkpoint inhibitor immunotherapy" was also presented. Despite the impressive successes in cancer immunotherapy in recent years, the response to immune based interventions occurs only in a minority of patients (∼20%). Several basic and translational mechanisms of resistance to immune checkpoint blockers (ICBs) were discussed during the meeting: 1. the impact of tumor microenvironment on the activity of immune system; 2. strategies to inhibit the cross-talk between extracellular matrix and myeloid-derived suppressor cells (MDSC) in the preclinical setting; 3. microRNA expression as a biomarker and as a target of therapy in non-small cell lung cancer (NSCLC); 4. the significance of complement activation pathways in response to immune checkpoint inhibitors; 5. the immunosuppressive activity of the microbiota by inducing IL-17 producing cells; and 6. modulation of HLA antigens as possible markers of response to ICB therapy. In order to overcome the deficiency in active anti-tumor T cells, several clinically applicable combination strategies were also discussed: 1. strategies to enhance the anticancer effects of immunogenic cell death inducing-chemotherapy; 2. the use of CAR T-cells in solid tumors; 3. the use of combination strategies involving oncolytic viruses and ICBs; 4. combinations of new ICBs with anti-PD-1/CTLA-4 therapy; and 4. combinations of targeted therapies and ICBs in melanoma. Overall, this conference emphasized the many novel strategies that are being investigated to improve the overall patient response to cancer immunotherapy. Optimization of biomarkers to accurately select patients who will respond to immunotherapy, coupled with combination strategies to improve long term patient survival remain critical challenges in the immuno-oncology field.

Pathobiological implications of the d16HER2 splice variant for stemness and aggressiveness of HER2-positive breast cancer

We have previously shown that the d16HER2 splice variant is linked to HER2-positive breast cancer (BC) tumorigenesis, progression and response to Trastuzumab. However, the mechanisms by which d16HER2 contributes to HER2-driven aggressiveness and targeted therapy susceptibility remain uncertain. Here, we report that the d16HER2-positive mammary tumor cell lines MI6 and MI7, derived from spontaneous lesions of d16HER2 transgenic (tg) mice and resembling the aggressive features of primary lesions, are enriched in the expression of Wnt, Notch and epithelial–mesenchymal transition pathways related genes compared with full-length wild-type (WT) HER2-positive cells (WTHER2_1 and WTHER2_2) derived from spontaneous tumors arising in WTHER2 tg mice. MI6 cells exhibited increased resistance to anoikis and significantly higher mammosphere-forming efficiency (MFE) and self-renewal capability than the WTHER2-positive counterpart. Furthermore, d16HER2-positive tumor cells expressed a higher fraction of CD29^High/CD24⁺/SCA1^Low cells and displayed greater in vivo tumor engraftment in serial dilution conditions than WTHER2_1 cells. Accordingly, NOTCH inhibitors impaired mammosphere formation only in MI6 cells. A comparative analysis of stemness-related features driven by d16HER2 and WTHER2 in ad hoc engineered human BC cells (MCF7 and T47D) revealed a higher MFE and aldehyde dehydrogenase-positive staining in d16HER2- vs WTHER2-infected cells, sustaining consistent BC-initiating cell enrichment in the human setting. Moreover, marked CD44 expression was found in MCF7_d16 and T47D_d16 cells vs their WTHER2 and Mock counterparts. Clinically, BC cases from two distinct HER2-positive cohorts characterized by high levels of expression of the activated-d16HER2 metagene were significantly enriched in the Notch family and signal transducer genes vs those with low levels of the metagene.

A Limited Autoimmunity to p185neu Elicited by DNA and Allogeneic Cell Vaccine Hampers the Progression of Preneoplastic Lesions in HER-2/NEU Transgenic Mice

Prevention of the progression of precancerous lesions by vaccines is a virtually uncharted territory. Their potential, however, is being assessed in transgenic mice which develop autochthonous tumors with defined stages of progression. In this paper we show that the DNA micro-array technology significantly helps assessment of the preventive efficacy of a combined DNA and cell vaccine. All female rat Her-2/neu transgenic BALB/c (BALB-neuT) mice develop an invasive carcinoma in each of their mammary glands within 25 weeks of age. This is elicited by the activated transforming rat Her-2/neu oncogene embedded in their genome. We have previously shown that vaccination of mice bearing multiple in situ carcinomas with DNA plasmids which code for the extracellular and transmembrane domain of rat p185neu, the product of the rat Her-2/neu oncogene, followed by a boost with rat p185neu+ allogeneic cells engineered to secrete interferon-γ, keeps 48% of mice tumor free until week 32. We have now extended our follow-up until mice reach one year of age and show that protection vanishes as time progresses. This observation suggests that the accuracy of the results studying immunotherapy against life-threatening tumors is a function of the length of the follow-up. The application of microarrays, and the concordance of morphologic and gene expression data led us to identify antibody as the main mechanism induced by vaccination. Protection is associated with a break of tolerance and a limited autoimmunity against the

Abstract P5-18-10: Chemotherapy can enhance trastuzumab-mediated ADCC

Trastuzumab, a recombinant humanized monoclonal antibody directed to the HER2 protein, has shown survival benefits in women with HER2-positive breast cancer, and treatment is now FDA-approved in combination with chemotherapy. However, some patients do not respond clinically to trastuzumab, pointing to the need for further definition of trastuzumab killing activity on tumor cells to optimize this therapy. Recent clinical data indicate a synergistic therapeutic effect between trastuzumab and taxanes in HER2-positive breast cancer patients, but the mechanism(s) underlying this synergy remains unclear. Because drug-stressed cells can dynamically regulate factors that favor activity of immune effector cells, and because trastuzumab-mediated ADCC is crucially dependent on NK cell activity, we hypothesize that this synergy reflects enhanced trastuzumab-mediated ADCC on tumor cells due to improved rather than impaired participation of immune effectors resulting from drug-induced stress. To test this hypothesis, we investigated the effect of chemotherapy in HER2-positive breast carcinoma models on NK receptor ligands and correlated the changes in these molecules with the ability of trastuzumab to mediate ADCC.

Flow cytometry revealed a 4-fold upmodulated surface expression of NKG2D (MICA, MICB, ULBP1, ULBP2) and DNAM-1 (CD112 and CD155) ligands in HER2-positive breast carcinoma cell lines BT474 and MDA-MB-361 treated for 6 hr with taxotere at a 72-hr IC50 dose, consistent with results of Western blot analysis using soluble lysates obtained from chemotherapy-treated HER2-positive breast carcinoma xenografts. The enhanced expression of NKG2D and DNAM-1 ligands in breast carcinoma cells was accompanied by about a 50% increase in trastuzumab-mediated in vitro ADCC in chemotherapy-treated versus untreated cells. Antibodies blocking NKG2D and DNAM-1, but not control monoclonal antibody, abolished the chemotherapy-induced increase of in vitro trastuzumab-dependent ADCC. Increased expression of NK ligands in taxotere-treated BT474 cells was associated with cytoskeletal damage assessed by confocal microscopy; at 72 hr after chemotherapy, NK ligands returned to basal levels, pointing to the importance of duration of NK ligand enhancement for the chemotherapy-induced trastuzumab-mediated ADCC.

Together, our results indicate that chemotherapy can modulate expression levels of NK-activating ligands on human breast carcinoma cells in correlation with trastuzumab-mediated ADCC, raising the possibility of identifying optimal chemotherapy administration schedules to maximize activity of trastuzumab-mediated ADCC effectors. (Partially supported by AIRC)

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P5-18-10.

P5-14-06: Interaction between Stoma and Tumor Characteristics as a New Prognostic and Predictive Marker in Breast Carcinomas

Background. We recently demonstrated that primary breast tumors can be classified based upon extracellular matrix composition (ECM) (Bergamaschi et al.) suggesting stroma characteristics could influence tumor progression.

Aim of this study is to further investigate the robustness of this classification and its impact in tumor progression and response to therapy.

Methods. The expression profile of ECM-related genes was analyzed by unsupervised hierarchical clustering in 10 independent datasets of breast tumors, counting more than 1000 samples and the prognostic and predictive value of this signature were evaluated in two datasets of not treated patients and in one dataset of neo-adjuvant treated patients, respectively.

Results. Only one of ECM subsets (ECM3) showed a homogeneous gene pattern that consistently allowed the classification of an independent group of tumors in all tested datasets. ECM3 is characterized by highly correlated over expression of 34 ECM genes encoding mainly structural proteins. From 24 to 38% of cases were ECM3-enriched and were mainly estrogen receptor-positive and low grade (p&lt;0.0001). The ECM3 showed inconsistent association with DMFS in the two data sets of not treated patients, whereas the interaction between ECM3 and grade showed strongly and significant association with DMFS (HR=5.35, p=0.0012). In particular, multivariate analysis of covariates available (size, ER, age and ECM) indicated that ECM3 is significantly associated with worse DMFS in grade III patients (HR=2.5, p=0.0386), whereas it is slightly correlated with better DMFS in grade I-II patients (HR=0.6, p=0.088). It is noteworthy that the probability of 10-year DMFS was 90% in ECM3 versus 74% in non-ECM3 patients in differentiated tumors, and 75% in non-ECM3 versus 41 % in ECM3 grade III tumors. The interaction between ECM3 and grade remained significantly associated with DMFS also in ER negative (HR=14.2, p=0.03) and ER positive (HR=3.34, p=0.079) subgroups. ECM3, indeed, was correlated with good and bad prognosis in differentiated and grade III tumors, respectively.

Moreover analysis of a data set of patients treated neoadjuvantly with chemotherapy revealed that, among the grade III tumors, pathological complete response was reached by 9% of ECM3 versus 74% of non-ECM3 tumors (p=0.04). In differentiated tumors no response difference was observed according to ECM.

Conclusions. Our results provide evidence that breast carcinoma progression and response to therapy are influenced by the interaction between tumor and stromal characteristics.

(Partially supported by AIRC).

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P5-14-06.

Role of exon-16-deleted HER2 in breast carcinomas

A splice variant of the human gene HER2, lacking exon-16 (DeltaHER2) which encodes a small extracellular region, has been described. This altered receptor forms disulfide bond-stabilized homodimers. We report here that the DeltaHER2 splice variant represents about 9% of the HER2 mRNA obtained from most of the 46 breast carcinoma samples with HER2 expression levels ranging from 3+ to 0 by HercepTest. Analysis of human cells transfected with DeltaHER2 or wild-type (WT) cDNA revealed no growth of WT cells in nude mice, whereas clones expressing 10-fold less DeltaHER2 were tumorigenic. Unlike WT transfectants, DeltaHER2-expressing cells showed low sensitivity to two new therapeutic drugs targeting receptors of the HER family (ZD1839 and Trastuzumab), whereas an inhibitor of the HER2 tyrosine kinase domain (Emodin) blocked activation of both DeltaHER2 and WT transfectants. Taken together, our findings indicate that the DeltaHER2 transcript encodes the transforming form of the oncoprotein. It is plausible that malignant transformation arises when a critical threshold of DeltaHER2 is reached in HER2-overexpressing tumors. Specific inhibitors of HER2 catalytic activity represent a promising approach to therapy of HER2-overexpressing tumors.

The 67 kDa laminin receptor increases tumor aggressiveness by remodeling laminin-1

The association between expression of the 67 kDa laminin receptor (67LR) and tumor aggressiveness has been convincingly demonstrated although the exact function of this molecule in the metastatic process has remained unclear. In this study, we tested whether the laminin-1, upon interaction with 67LR, promotes tumor cell aggressiveness; the investigation was based on: (i) the previous demonstration that soluble 67LR, as well as a 20-amino-acid peptide corresponding to the 67LR laminin binding site, changes the conformation of laminin upon interaction with this adhesion molecule and (ii) the known relevance of microenvironment remodeling by the tumor, leading to structural modification of extracellular matrix components in tumor progression. MDAMB231 breast carcinoma cells plated on peptide G-treated laminin-1 exhibited a polygonal array of actin filament bundles compared with cells seeded on native laminin-1 which presented the actin bundles organized as multiple cables parallel to margins. Furthermore, in cells seeded on peptide G-treated laminin-1, 67LR was distinct from the alpha6 integrin subunit in filopodia protrusions in addition to colocalizing with this integrin in focal adhesion plaques as it occurs when cells are plated on native laminin-1. In addition to differences in tumor cell adhesion and migration found in cells exposed to peptide G-treated vs native laminin-1, breast carcinoma cells seeded on modified laminin-1 showed a 6-fold increase in invasion capability compared with cells seeded on unmodified laminin-1. Alterations in actin organization as well as adhesion, migration and especially invasion observed in MDAMB231 cells in the presence of peptide G-treated laminin-1 were even found in MDAMB231 cells that, after selection for 67LR high expression, were seeded on native laminin-1. As the 67LR shedding is proportional to its expression level, these findings indicate a role for 67LR in changing laminin structure. Expression analysis of 97 genes encoding proteins that mediate cell matrix interactions, revealed significant differences between cells exposed to modified vs unmodified laminin-1 in 19 genes, 17 of which--including those encoding alpha3 integrin, extracellular matrix protein 1, proteolytic enzymes (such as MT1-MMP, stromelysin-3 and cathepsin L) and their inhibitors--were up-modulated in cells treated with modified laminin-1. Zymogram analysis clearly indicated a significant increase in the activity of the gelatinolytic enzyme MMP-2 in the culture supernatant from cells exposed to modified laminin-1, without an increase in mRNA abundance as observed in microarray analysis. Invasiveness of tumor cells conditioned by modified laminin-1, evaluated as the capability to cross Matrigel basement, was significantly more inhibited by MMPinhibitor TIMP-2 than invasiveness induced by native laminin-1. Taken together, our findings indicate that the role of 67LR in tumor aggressiveness rests in its ability to modify laminin-1 thereby activating proteolytic enzymes that promote tumor cell invasion through extracellular matrix degradation.

Role of HER2/neu in tumor progression and therapy

HER2 (human epidermal growth factor receptor-2; also known as erbB2) and its relatives HER1 (epidermal growth factor receptor; EGFR), HER3 and HER4 belong to the HER family of receptor tyrosine kinases. In normal cells, activation of this receptor tyrosine kinase family triggers a rich network of signaling pathways that control normal cell growth, differentiation, motility and adhesion in several cell lineages. The first tumor studied for an alteration of the HER2 oncogene is breast carcinoma, and so far the majority of studies have been performed on this oncotype. Although involvement of HER2 as a cause of human cell transformation needs to be further investigated, overexpression of the HER2 oncogene in human breast carcinomas has been associated with a more aggressive course of disease. It has been suggested that this association depends on HER2-driven proliferation, vessel formation and/or invasiveness; however, poor prognosis may not be directly related to the presence of the oncoprotein on the cell membrane but instead to the breast carcinoma subset identified by HER2 overexpression and characterized by a peculiar gene expression profile, as recently identified. HER2-positive tumors were recently shown to benefit from anthracyclin treatment and to be resistant to endocrine therapy. Despite the fact that many pathways interacting with HER2 are still not fully understood, this tyrosine kinase receptor is, to date, a promising molecule for targeted therapy.

Monoclonal antibody to fibulin-1 generated by genetic immunization

Fibulin-1 (Fbln-1) is an extracellular matrix (ECM) and plasma glycoprotein. Considering the growing evidence indicating that Fbln-1 plays a role in cancer we sought to develop monospecific antibodies to better facilitate further studies of the function of Fbln-1 in breast cancer. Using a plasmid expression vector encoding full-length human Fbln-1D as an immunogen and CpG oligodeoxyribonucleotides as adjuvant a monoclonal antibody (MAb) against Fbln-1 was produced. This MAb, designated MEM-2 was of IgM isotype and reacted with bacterially expressed Fbln-1. Furthermore, MEM-2 reacted with Fbln-1 expressed in the ECM released by cultured human breast carcinoma SKBR-3 cells in ELISA, and also with Fbln-1 present in SKBR-3 cell extract in immunoprecipitation and Western blotting. MEM-2 also reacted with Fbln-1 in human breast carcinoma specimens. These findings illustrate the utility of genetic immunization as a means of generating monoclonal antibodies to tumor-related ECM proteins. MEM-2 represents a useful new tool for the study of Fbln-1 in breast cancer.

Combined allogeneic tumor cell vaccination and systemic interleukin 12 prevents mammary carcinogenesis in HER-2/neu transgenic mice

Transgenic Balb/c mice expressing the transforming rat HER-2/neu oncogene develop early and multifocal mammary carcinomas. Within the first 5 months of life the tissue-specific expression of HER-2/neu causes a progression in all their 10 mammary glands from atypical hyperplasia to invasive carcinoma. It was previously observed that chronic administration of interleukin (IL)-12 increased tumor latency, but every mouse eventually succumbed to multiple carcinomas. A significant improvement in tumor prevention was sought by administering allogeneic mammary carcinoma cells expressing HER-2/neu combined with systemic IL-12. This treatment reduced tumor incidence by 90% and more than doubled mouse lifetime. For the maximum prevention p185(neu) antigen must be expressed by allogeneic cells. IL-12 treatment strongly increased the cell vaccine efficacy. The mammary glands of mice receiving the combined treatment displayed a markedly reduced epithelial cell proliferation, angiogenesis, and HER-2/neu expression, while the few hyperplastic foci were heavily infiltrated by granulocytes, macrophages, and CD8(+) lymphocytes. Specific anti-HER-2/neu antibodies were produced and a nonpolarized activation of CD4(+) and CD8(+) cells secreting IL-4 and interferon (IFN)-gamma were evident. A central role for IFN-gamma in the preventive effect was proven by the lack of efficacy of vaccination in IFN-gamma gene knockout HER-2/neu transgenic Balb/c mice. A possible requirement for IFN-gamma is related to its effect on antibody production, in particular on IgG2a and IgG2b subclasses, that were not induced in IFN-gamma knockout HER-2/neu mice. In conclusion, our data show that an allogeneic HER-2/neu-expressing cell vaccine combined with IL-12 systemic treatment can prevent the onset of genetically determined tumors.

Prevention of spontaneous neu-expressing mammary tumor development in mice transgenic for rat proto-neu by DNA vaccination

The HER-2/neu proto-oncogene is overexpressed in 20-30% of human breast cancers and is associated with high recurrence risk. The oncogenic potential of HER-2/neu, together with its elevated expression in tumors, cell surface localization, and immunogenicity in some patients, make this oncoprotein an ideal target for immunotherapeutic approaches. To test the efficacy of immune-based strategies in eliciting an antitumor response, we used the N#202 transgenic mouse model engineered to overexpress the rat neu proto-oncogene under the control of the mouse mammary tumor virus promoter; females of this line develop spontaneous focal mammary tumors by 6 months of age. Transgenic mice immunized intramuscularly with a HER-2 cDNA ligated into the VR1012 (VICAL) expression vector under the control of the cytomegalovirus promoter developed significantly fewer spontaneous tumors as compared with mice injected with the empty vector (P < 0.0001) or not injected (P = 0.0006). However, this protection was observed only when immunization was started in 3-month-old but not in 6-month-old mice. These data suggest that the xenogeneic HER-2 DNA sequence can break immune tolerance to rat neu in transgenic N#202 mice and induce protective immunity that impairs the neu oncogene-driven progression of mammary carcinogenesis. The preventive effect achieved by our immunological approach appeared not to be based on anti-neu specific B and T cell immune attacks but was more possibly based on different mechanisms including aspecific and inflammatory immunological responses.

p185(neu) protein is required for tumor and anchorage-independent growth, not for cell proliferation of transgenic mammary carcinoma

Transgenic FVB-NeuN mice (N202) bearing the rat neu protooncogene driven by the mouse mammary tumor virus promoter/enhancer develop focal mammary carcinomas overexpressing the neu-encoded p185(neu) protein. In vitro expression of p185(neu) among mammary carcinoma cultures was heterogeneous, and we could establish some cell lines and clones displaying a complete loss of p185(neu) expression, along with others with very high p185(neu) protein level. Upon in vivo injection, p185(neu)-positive cells gave rise to fast-growing tumors with a short latency, while p185(neu)-negative cells required a very long latency time, and the resulting tumors were invariably p185(neu)-positive. The lower growth ability of p185(neu)-negative cells in vivo was also confirmed in athymic nude mice. In vitro, analysis of anchorage-independent growth in soft agar revealed colony formation from p185(neu)-positive but not p185(neu)-negative cells. The direct involvement of p185(neu) in clonogenicity was demonstrated by the inhibition of p185(neu)-positive colony growth in soft agar in the presence of an anti-p185(neu) monoclonal antibody. By contrast, a higher level of anchorage-dependent clonogenic growth and proliferation was observed in p185(neu)-negative cells as compared to p185(neu)-positive cells, thus explaining the relative ease with which p185(neu)-negative cell lines and clones were established in vitro. Together, the results indicate that p185(neu) expression can lead to tumor formation and metastasis through the modification of intrinsic properties of cells related to anchorage-independent growth ability rather than to proliferation or host-dependent mechanisms.

Role of HER2 gene overexpression in breast carcinoma

The HER2 proto-oncogene encodes a transmembrane glycoprotein of 185 kDa (p185(HER2)) with intrinsic tyrosine kinase activity. Amplification of the HER2 gene and overexpression of its product induce cell transformation. Numerous studies have demonstrated the prognostic relevance of p185(HER2), which is overexpressed in 10% to 40% of human breast tumors. Recent data suggest that p185(HER2) is a ligand orphan receptor that amplifies the signal provided by other receptors of the HER family by heterodimerizing with them. Ligand-dependent activation of HER1, HER3, and HER4 by EGF or heregulin results in heterodimerization and, thereby, HER2 activation. HER2 overexpression is associated with breast cancer patient responsiveness to doxorubicin, to cyclophosphamide, methotrexate, and fluorouracil (CMF), and to paclitaxel, whereas tamoxifen was found to be ineffective and even detrimental in patients with HER2-positive tumors. In vitro analyses have shown that the role of HER2 overexpression in determining the sensitivity of cancer cells to drugs is complex, and molecules involved in its signaling pathway are probably the actual protagonists of the sensitivity to drugs. The association of HER2 overexpression with human tumors, its extracellular accessibility, as well as its involvement in tumor aggressiveness are all factors that make this receptor an appropriate target for tumor-specific therapies. A number of approaches are being investigated as possible therapeutic strategies that target HER2: (1) growth inhibitory antibodies, which can be used alone or in combination with standard chemotherapeutics; (2) tyrosine kinase inhibitors (TKI), which have been developed in an effort to block receptor activity because phosphorylation is the key event leading to activation and initiation of the signaling pathway; and (3) active immunotherapy, because the HER2 oncoprotein is immunogenic in some breast carcinoma patients.

Ectopic expression of pRb2/p130 suppresses the tumorigenicity of the c-erbB-2-overexpressing SKOV3 tumor cell line

We investigated the in vitro and in vivo effects of the ectopic expression of the pRb2/p130 cell cycle regulator on c-erbB-2-associated tumorigenicity. SKOV3 ovarian cancer cells, which display c-erbB-2 gene amplification and oncoprotein (p185HER2) overexpression, were stably transfected with a plasmid containing the coding sequence for human wild-type pRb2/p130 (wtRb2), or with pcDNA3 empty vector. Three wtRb2-transfected clones (cl. 24, ci. 49, cl. 100) and one empty vector-transfected clone (cl. mock) were randomly picked and further analysed. Western blot analysis revealed high levels of pRb2/p130 in the three clones compared to mock cells. Levels of p185HER2 and the extent of its tyrosine phosphorylation were similar in all transfectant clones, as were levels of pRb1 and p107. In anchorage-independent growth assays, the number of colonies from wtRb2 clone-transfectants was about 90% less than that arising from mock cells (P<0.001). Tumor take rates of the three wtRb2-transfected clones xenografted in nu/nu mice were much lower than those of mock cells, and tumor volume was decreased by 80% (P<0.001). A mutant version of pRb2/p130 deleted of the pocket region (mut-Rb2) was also transfected into SKOV3 cells and studied in parallel with the wtRb2-transfected and pcDNA empty vector-transfected bulk populations. mut-Rb2 transfected cells showed no inhibition of in vitro colony formation and were fully tumorigenic. Together, these findings indicate that Rb2 acts as a tumor suppressor gene in vivo and in vitro in SKOV3 cells and that the intact pocket region is required for the suppressor activity.

Increased expression of c-erbB-2 in hormone-dependent breast cancer cells inhibits cell growth and induces differentiation

c-erbB-2, a member of the tyrosine kinase oncogene family, is overexpressed in about 30% of human breast tumors where it correlates with poor prognosis. In vitro studies have suggested that increased expression of the receptor plays an important role in malignant progression. To better understand the direct effects of p185HER2 overexpression, a human c-erbB-2 expression vector was transfected into the hormone-dependent MCF-7 human breast carcinoma cell line and cell growth was analysed. Unexpectedly, colony formation assay revealed a reduction in the number and size of colonies as compared with mock-transfected cells. In hormone-deprived medium, c-erbB-2 transfected cells acquired growth capability, consistent with previous reports. By contrast, two c-erbB-2-transfected clones grown in complete medium showed a reduced proliferation rate despite the activation of a fully functional oncoprotein capable of autophosphorylation and induction of the MAPK pathway. The number of c-erbB-2-overexpressing cells in the S phase of the cell cycle was about one-half the number of control and mock-transfected cells. Also, overexpression of c-erbB-2 induced overexpression of p21WAF1, pRB hypophosphorylation and a mature differentiated cell phenotype with production of lipid droplets. Functional inactivation of p185HER2 by means of a specific single chain antibody indicated the c-erbB-2-dependence of the observed alterations. These data show that the exogenous overexpression of the c-erbB-2 gene in hormone-dependent breast cancer cells inhibits proliferation and induces differentiation.

High-titer HER-2/neu protein-specific antibody can be detected in patients with early-stage breast cancer

PURPOSE

To evaluate HER-2/neu-specific antibody immunity in patients with breast cancer, to determine the rate of occurrence of serum antibodies to HER-2/neu in patients with breast cancer, and to relate the presence of specific immunity to overexpression of HER-2/neu protein in primary tumor.

METHODS

The antibody response to HER-2/neu protein was analyzed in 107 newly diagnosed breast cancer patients. Sera was analyzed for the presence of HER-2/neu-specific antibodies with a capture enzyme-linked immunosorbent assay (ELISA) and verified by Western blot. Sera from 200 volunteer blood donors was used as a control population.

RESULTS

The presence of antibodies to HER-2/neu correlated with the presence of breast cancer. HER-2/neu antibodies at titers of > or = 1:100 were detected in 12 of 107 (11%) breast cancer patients versus none of 200 (0%) normal controls (P < .01). The presence of antibodies to HER-2/neu also correlated to overexpression of HER-2/neu protein in the patient's primary tumor. Nine of 44 (20%) patients with HER-2/neu-positive tumors had HER-2/neu-specific antibodies, whereas three of 63 (5%) patients with HER-2/neu-negative tumors had antibodies (P = .03). The antibody responses could be substantial. Titers of greater than 1:5,000 were detected in five of 107 (5%).

CONCLUSION

The presence of HER-2/neu antibodies in breast cancer patients and the correlation with HER-2/neu-positive cancer implies that immunity to HER-2/neu develops as a result of exposure of patients to HER-2/neu protein expressed by their own cancer. These findings should stimulate further studies to develop the detection of immunity to oncogenic proteins as tumor markers, as well as the development and testing of vaccine strategies to induce and augment immunity to HER-2/neu for the treatment of breast cancer or prevention of recurrent disease.

Killing of laminin receptor-positive human lung cancers by tumor infiltrating lymphocytes bearing gammadelta(+) t-cell receptors

BACKGROUND

The monomeric laminin receptor, a 67-kd high-affinity laminin-binding protein, is expressed by a variety of normal cell types. Overexpression and abnormal surface distribution of this receptor have been demonstrated in tumor cells where it appears to promote tumor invasion and metastasis. Previously, we reported the existence of an association between laminin receptor overexpression by lung cancer cells and the presence of tumor-infiltrating lymphocytes (TILs) bearing gammadelta T-cell receptors. Gammadelta(+) lymphocytes represents a sizable fraction of the TILs in approximately one fourth of lung cancers analyzed thus far.

PURPOSE

The aim of this study was to determine whether gammadelta(+) TILs might participate in the immune response against lung cancer through recognition of monomeric laminin receptors expressed by tumor cells.

METHODS

Tumor cells from 11 lung cancer specimens exhibiting sizable gammadelta(+) T-cell infiltrates and from 11 other specimens infiltrated predominantly by lymphocytes bearing alphabeta(+) T-cell receptors were analyzed for expression of the monomeric laminin receptor by use of the monoclonal antibody (MAb) MLuC5. Gammadalta TILs and chibeta+ TILs derived from four tumors were each examined for cytotoxic activity toward lung cancer target cells by use of a standard 51Cr-release assay and lung tumor cell lines expressing different levels of surface monomeric laminin receptor. The ability of MAbs directed against the laminin receptor (i.e., MLuC5) or against gammadelta T-cell receptors (i.e., TigammaA and A13) as well as laminin peptides known to bind to the laminin receptor to inhibit TIL-mediated target cells lysis was also determined.

RESULTS

We confirmed that the association between overexpression of the monomeric laminin receptor by lung tumor cells and the presence of gammadeltadelta+ TILs is statistically significant (two sided P = .003; Fisher's exact test). We also observed a relationship between the levels of laminin receptor expression on cultured lung cancer cells and their susceptibility to specific lysis by gammadelta(+), but not alphabeta+, TILs. This specific cell killing was not T-cell receptor mediated, but it was inhibited by addition of the anti-monomeric laminin receptor MAb MLuC5 and by a synthetic peptide corresponding to amino acids 2091-2108 of the laminin A chain.

CONCLUSION AND IMPLICATIONS

Our results indicate gammadelta(+) TILs localized at human lung cancer sites can kill tumor cells in a process that involves interaction with the monomeric laminin receptor. The infiltration of gammadelta(+) TILs at lung tumor sites may represent a first line of defense against cells undergoing malignant transformation.

1975-1995 revised anti-cancer serological response: biological significance and clinical implications

In the 1970s a considerable amount of work was carried out in an attempt to identify an anti-tumor serological response in cancer patients. These analyses have not been very informative due to the complexity and heterogeneity of the response. More recently, the availability of recombinant molecules, synthetic peptides and analytic and semi-quantitative assays has enabled a better dissection of humoral immunity. Antibodies against intracellular antigens (c-myb, c-myc, p53 and p21 ras) have been found in a significant, albeit varying, proportion of patients bearing various tumors. Association with a poor prognosis is documented for anti-p53 antibodies in breast carcinoma patients. A number of cell surface antigens, including mucins, oncoproteins and carbohydrate antigens have been found to elicit a humoral immune response and, in some instances, circulating immune complexes were observed. A protective role for or, on the other hand, masking effects of such antibodies is still controversial. An indication that a serological response can be beneficial comes from vaccination studies. A significant association between the development of an anti-tumor antigen antibody response and prolonged survival was observed following vaccination of melanoma patients with GM2 or anti-idiotypic antibodies which molecularly mimic tumor-associated antigens. It is to be hoped that in the near future the numerous ongoing immunization trials and prognostic studies demonstrate whether antibody response can exert a protective role in vivo.

Macrophage infiltrate and prognosis in c-erbB-2-overexpressing breast carcinomas

PURPOSE

Experiments were designed to investigate the association between tumor leukocytic infiltrates with other pathologic and biologic variables in primary tumors and with prognosis, and to define the phenotype of the infiltrating leukocytes.

PATIENTS AND METHODS

A retrospective series of 1,207 primary breast carcinomas was studied according to different prognostic variables, including the presence of lymphoplasmacytic infiltrate (LPI). LPI was analyzed in association with other variables and survival. Additionally, a small prospective series of surgical specimens from 75 primary breast carcinomas with infiltrating leukocytes was tested by immunohistochemistry on frozen sections to phenotypically characterize the infiltrate, using anti-CD reagents, and the tumor, using anti-c-erbB-2 oncoprotein monoclonal antibody.

RESULTS

In the retrospective series, menopausal status, nodal status, tumor size, stage, grade, and p185HER2 overexpression but not LPI were found to be associated with prognosis and maintained their prognostic significance in a multivariate analysis. LPI was significantly associated with some of these independent prognostic factors, such as tumor size (P = .03), stage (P = .004), grade III carcinomas (P < .000001), and overexpression of the p185HER2 (P < .000001). In some subgroups of patients in whom LPI was found more frequently, such as grade III cases or N- and c-erbB-2-positive cases, LPI was found to be indicative of a good prognosis (P = .008 and P = .03, respectively). Phenotypic analysis of the infiltrating leukocytes revealed a preponderance of macrophages in high-grade (P = .05) or c-erbB-2-positive (P = .008) tumors, whereas T cells constituted most of the infiltrate in the other tumors.

CONCLUSION

Our data demonstrate different leukocytic types in the infiltrate of breast tumors with different prognostic significance.

An in vivo model to compare human leukocyte infiltration in carcinoma xenografts producing different chemokines

In this study we tested whether the pattern of cytokines expressed by human carcinomas could account for a different in vivo recruitment of leukocyte subpopulations as a part of the anti-tumor immune response. Two carcinoma cell lines, SK-OV-3 ovary carcinoma and CALU-3 lung carcinoma, were analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR), immunofluorescence and ELISA for the expression and in vitro production of cytokines with chemotactic, proinflammatory and growth-stimulating activity. Although both cell lines displayed a constitutive expression of granulocyte colony-stimulating factor (G-CSF), granulocyte macrophage-CSF (GM-CSF), M-CSF, interleukin (IL-) 1 alpha and IL-8, only CALU-3 cell line expressed IL-10, RANTES (Regulated upon Activation, Normal T Expressed and Secreted) and monocyte-activating protein (MCP)-1. MCP-1 and IL-8 were detected by immunohistochemistry on sections from tumors xenografted in nude mice. To analyze whether the tumor-released cytokines modulate leukocytes in tumor infiltration, we studied the distribution of human peripheral blood leukocytes injected in the proximity of SK-OV-3 and of CALU-3 tumor xenografts. While SK-OV-3 was unable to recruit human leukocytes and appeared to be barely infiltrated by murine CD45+ cells, CALU-3 appeared to be rapidly and heavily infiltrated by human leukocytes which induced tumor necrosis within 18-24 hr.

Distinct pattern of HSP72 and monomeric laminin receptor expression in human lung cancers infiltrated by gamma/delta T lymphocytes

We have previously demonstrated that gamma/delta T lymphocytes may participate in the host immune response against lung adenocarcinomas. Here we show that, in about one-fourth of human lung cancers, gamma/delta T cells represented a significant proportion of freshly isolated tumor-infiltrating lymphocytes. Moreover, these cells selectively expand in vitro upon culture in the presence of IL-2, thus suggesting a prior activation in vivo. Finally, when we evaluated the expression of heat shock proteins and of a panel of tumor-associated antigens in lung cancers infiltrated by gamma/delta vs. alpha/beta T cells, we found that the former displayed a distinct antigenic pattern, characterized by over-expression of HSP72 and of the 67-kDa high-affinity laminin receptor, which might account for gamma/delta T-cell recognition.

Antibody response against the c-erbB-2 oncoprotein in breast carcinoma patients

Indirect immunofluorescence analysis of sera from breast carcinoma patients whose tumors were characterized for overexpression of the c-erbB-2 oncoprotein (p185HER2) and for lympho-plasma cell infiltration, revealed no circulating antibodies specifically directed against the p185HER2 molecule in the 20 samples tested, whereas supernatants of B-cell clones, derived from Epstein-Barr virus-transformed peripheral blood lymphocytes from 10 of these patients, contained such antibodies in 6 of the 7 c-erbB-2- and lympho-plasma cell infiltration-positive cases. The antibodies contained in two of the positive supernatants immunoprecipitated a M(r) 185,000 molecule from oncoprotein-positive cell extracts that was identified as the oncoprotein in sequential immunoprecipitation experiments with anti-p185HER2 monoclonal antibodies. No cells producing antibodies with a similar reactivity were obtained from Epstein-Barr virus-transformed peripheral blood lymphocytes from breast carcinoma patients with p185HER2-negative tumors or from healthy donors. These data prove the existence of an antibody response specifically directed against the p185HER2 oncoprotein in breast carcinoma patients that may represent an important effector mechanism in the control of c-erbB-2-overexpressing tumors.

The extracellular domain of the c-erbB-2 oncoprotein is released from tumor cells by proteolytic cleavage

A molecule that is immunologically related to the c-erbB-2 oncogene product (p185HER2/neu) was detected in the conditioned culture medium from neu-overexpressing tumor cell lines and in sera of advanced-stage breast carcinoma patients. Using a sensitive (in the range of 0.5 ng ml-1) double-determinant radioimmunoassay (DDIRMA) with two monoclonal antibodies (MAbs) directed against the neu extracellular domain (ECD), soluble oncoproteins were detected in supernatants from several neu-positive tumor cell lines, independent of the levels of membrane p185HER2 expression. The molecule detected did not react with a MAb directed against an intracytoplasmic epitope of the p185HER2. Western blot analysis of the concentrated supernatant revealed a protein of approximately 110 kDa molecular mass, which closely matches the predicted size of the glycosylated p185HER2 ECD. Immunoprecipitation of culture supernatant from cell surface-radioiodinated cells confirmed the 110 kDa molecular mass of the glycosylated shed protein, which migrated to 86 kDa after deglycosylation. Proteolytic cleavage of the p185HER2 molecule was demonstrated in release assays carried out with protease inhibitors. The combined use of leupeptin and EDTA completely inhibited release of the molecule. Analysis of sera from breast carcinoma patients and healthy donors by DDIRMA revealed the presence of soluble neu in 15% of pathologic sera but none of the normal sera. A good correlation was found between neu-overexpression in the primary tumor and the soluble marker in serum of patients with advanced disease; sera of early-stage patients were always negative, independent of neu-overexpression in the tumor. These results suggest the usefulness of soluble neu as an indicator of tumor aggressiveness but not as a diagnostic marker of breast cancer.

Network of idiotypic and anti-idiotypic antibodies related to the ovarian carcinoma-associated folate binding protein

The present paper describes the generation and characterization of anti-idiotypic monoclonal antibodies (Ab2 MAbs) produced against the MOv19 MAb (Ab1 MAb), which shows a restricted reactivity with human ovarian carcinoma. The Ab2 MAbs were produced by immunizing mice with MOv19 conjugated to syngeneic mouse red blood cells (MRBC). After the somatic hybridization, five Ab2 MAbs, designated Id19.1, Id19.2, Id19.3, Id19.4 and Id19.5, were selected by a sandwich assay on the basis of their specific reactivity to the MOv19 MAb, but not to the isotype-matched MAb used as a control. A complete cross-inhibition between these 5 MAbs was observed, indicating that they recognize overlapping idiotopes on MOv19. The Ab2/antigen relationship of two Ab2 MAbs (Id19.1 and Id19.2) was investigated by competition experiments on a relevant tumor target cell line. We showed that both Ab2 MAbs were able to interfere with the antigen binding capacity of 125I-MOv19. Moreover, Id19.1 was able partially to inhibit the binding of the purified radiolabelled antigen recognized by the MOv19 MAb (125I-CaMOv19) on insolubilized MOv19. To investigate further whether the Ab2 MAb is the "internal image" of CaMOv19, Id19.1 was used as immunogen with the aim to induce an anti-CaMOv19 response. The antisera tested by indirect solid-phase radioimmunoassay (RIA) on the Ab2 MAb and the irrelevant isotype-matched control MAb revealed an anti-anti-idiotypic response (Ab3). However, no Ab3 antibodies with Ab1-like specificity (Ab1') were found in the immune sera, as assessed by testing the antisera both in indirect immunofluorescence (IF) and solid-phase RIA on CaMOv19-positive target cell lines.

Evaluation of the immunoreactive fraction of an anti-tumour monoclonal antibody

Over a period of approximately 1 year, the immunoreactivity of the anti-ovary carcinoma MAb MOv18 was evaluated after radiolabelling with 125I on two different ovarian carcinoma cell lines, OvCa432 and IGROV1. A high variability of the immunoreactive values was observed by analysing different preparations of radiolabelled MOv18 (from 12 to 21% on OvCa432 and from 22 to 56% on IGROV1) and by using the same radiolabelled preparation (12% on OvCa432 and 51% on IGROV1). Since the variability could be due to the target cells, we set up an alternative binding assay using the anti-idiotypic MAb anti-Id18.1 directed against a private idiotype closely associated with the MOv18 paratope. Three different experiments carried out with the anti-idiotypic MAb gave reproducible results with an immunoreactive range from 71 to 83%. A direct comparison between the reactivity of the same 125I-MOv18 preparation on anti-Id18.1 and on IGROV1 confirmed the higher value of the immunoreactive fraction estimated on the more homogeneous anti-idiotypic reagent (71%), rather than on the tumour cells (56%). These data suggest that anti-idiotypic MAbs could represent suitable reagents for the evaluation of the immunoreactivity of an antibody preparation after radiolabelling and before in vivo administration.

Activation of mononuclear cells to be used for hybrid monoclonal antibody-induced lysis of human ovarian carcinoma cells

Recently we reported that cytotoxic T-cell clones can be retargeted to unrelated tumor cells by bispecific monoclonal antibodies (MAbs), anti-CD3 and anti-ovarian carcinoma (alpha OC/TR) (Mezzanzanica et al., 1988). In the perspective of in vivo tumor immunotherapy, as an alternative to cytotoxic T lymphocytes (CTL) from T-cell clones, since human peripheral blood mononuclear cells (PBMCs) without stimulation were quite ineffective, a suitable in vitro activation method was developed to render PBMCs lytic for relevant targets in the presence of the bispecific hybrid MAb alpha OC/TR. This activation protocol was applied to PBMCs from 9 healthy donors (HD) and 6 ovarian carcinoma patients (P) and to tumor-associated lymphocytes (TAL) from 4 ovarian carcinoma P. The method consisted of in vitro stimulation with phytohemagglutinin (PHA) for 2 days, followed by culture with a low dose of recombinant human interleukin-2 (rIL-2) for 6 to 10 days. The antibody-mediated lysis of CTL from HD PBMCs was found to be specifically directed against cells expressing the relevant ovarian tumor antigen when different tumor cell lines and short-term cultures of tumor and normal cells were tested. The antibody-mediated lysis of CTL from P PBMCs or TAL was efficient both on autologous and allogeneic ovarian tumor cells, whereas no reactivity with autologous normal cells was observed and LAK activity was only evident in 1 out of 4 cases. The hybrid antibody induced cytotoxic activity of CTL from P was, however, lower than that of CTL from HD.

Human ovarian carcinoma lysis by cytotoxic T cells targeted by bispecific monoclonal antibodies: analysis of the antibody components

In the perspective of in vivo therapeutic applications, the monoclonal antibody (MAb) MOv18 was selected for its restricted reactivity with human ovarian carcinoma. Using the pH 2.8 desorption assay, we found that the antigen recognized by MOv18 had a high stability on the cell membrane and poor internalization. Therefore, a therapeutic approach which does not require internalization, i.e., the re-targeting of cytotoxic T lymphocytes (CTL) by bispecific MAbs, was investigated. MOv18 and anti-CD3 MAbs were used to produce bispecific reagents, obtained either by chemical cross-linkage (hetero-conjugates) or by somatic hybridization techniques (hybrid MAbs). The maintenance of the binding reactivity and specificity of the bispecific MAbs was analyzed by solid-phase radioimmunoassay, immunofluorescence and cross-competition tests on the relevant target cells (ovarian carcinoma cell line OVCA 432 for MOv18 and PHA-stimulated peripheral blood mononuclear cells for anti-CD3 MAbs), and on 2 irrelevant tumor cell lines. Bv a 51Cr-release assay the bispecific MAbs were found to efficiently promote, at picomolar concentration, cell lysis by CTL clones, but the specificity pattern was wider than that predicted by the binding studies. The F(ab')2 fragment of one hybrid MAb mediated a lysis which was just as efficient as the entire MAb on the relevant target cells and allowed specific lysis to be distinguished from Fc-receptor-mediated lysis. Human immunoglobulins were unable to compete with the Fc receptor binding of the hybrid MAbs and therefore, in the perspective of in vivo applications, Fc fragment removal seems to be an essential step. Analysis of the bispecific reagents indicated that hybrid MAbs are superior to the heteroconjugate as far as storage stability is concerned.

Anti-ovarian carcinoma anti-T3 heteroconjugates or hybrid antibodies induce tumor cell lysis by cytotoxic T-cells

In the perspective of therapeutic in vivo targeting for T-cell attack, the monoclonal antibody (MAb) MOv18, selected for its restricted reactivity with human ovarian carcinoma, and an anti-T3 MAb were used to produce heteroconjugate or hybrid antibodies derived by fusion of relevant hybridomas. Specificity and activity of bispecific MAbs were analyzed by solid-phase RIA, immunofluorescence and a 51Cr-release assay on the ovarian carcinoma cell line OVCA 432, which expresses the relevant tumor-associated antigen, and on several irrelevant tumor cell lines. Both reagents efficiently promoted, at picomolar concentration, target cell lysis by cytotoxic T-cell (CTL) clones. Although the pattern of tumor cell lines which were lysed was wider than that predicted by binding studies, further studies using a double-determinant immunoradiometric assay confirmed the specificity of MAb targeting. Analysis of reagents indicated that the hybrid MAb was superior to the heteroaggregate as far as purification recovery and storage stability were concerned. Besides CTL clones, peripheral blood lymphocytes could also be used as cytolytic effectors, provided that a suitable in vitro activation scheme was used.

Characterization of human ovarian carcinoma-associated antigens defined by novel monoclonal antibodies with tumor-restricted specificity

Three new monoclonal antibodies (MAbs) (MOv16, MOv18 and MOv19) were raised against human ovarian carcinoma. To obtain more specific reagents than those produced so far, we adopted the following experimental approach which consisted of: the selection of a poorly differentiated ovarian carcinoma which was unreactive with all the MAb previously selected in our laboratory; and the application of a particular immunization protocol. The reactivity of the selected MAbs was studied by solid-phase RIA on live and fixed cells from tumor cell lines and by immunofluorescence on frozen sections from surgical specimens. The MAb MOv16 reacted with 60% of ovarian carcinomas as well as with a high percentage of other carcinomas and with some normal tissues. In contrast, MOv18 and MOv19 appeared to have restricted specificities for ovarian carcinomas and cystadenomas. Reactivity on other carcinomas was only observed in a few cases and no reactivity was found on non-epithelial tumors or normal tissues. Immunoprecipitation experiments indicated that MOv16 recognizes a 48-50-kDA protein, whereas MOv18 and MOv19 both identify a 38-40 kDA glycoprotein band. Cross-competition experiments, together with a double-determinant immunoradiometric assay which uses MOv18 as catcher and MOv19 as tracer, suggested that they recognize different epitopes carried by the same molecule. The affinity constants of MOv18 and MOv19 were estimated to be in the range of 10(8)-10(9) M-1. Taken together, the properties of these antibodies, their restricted ovarian tumor specificities and relative high affinity constants, suggest that they could represent promising tools for in vivo applications.