Targeted panel sequencing in the routine diagnosis of mature T- and NK-cell lymphomas: report of 128 cases from two German reference centers.

Diagnosing any of the more than 30 types of T-cell lymphomas is considered a challenging task for many pathologists and currently requires morphological expertise as well as the integration of clinical data, immunophenotype, flow cytometry and clonality analyses. Even considering all available information, some margin of doubt might remain using the current diagnostic procedures. In recent times, the genetic landscape of most T-cell lymphomas has been elucidated, showing a number of diagnostically relevant mutations. In addition, recent data indicate that some of these genetic alterations might bear prognostic and predictive value. Extensive genetic analyses, such as whole exome or large panel sequencing are still expensive and time consuming, therefore limiting their application in routine diagnostic. We therefore devoted our effort to develop a lean approach for genetic analysis of T-cell lymphomas, focusing on maximum efficiency rather than exhaustively covering all possible targets. Here we report the results generated with our small amplicon-based panel that could be used routinely on paraffin-embedded and even decalcified samples, on a single sample basis in parallel with other NGS-panels used in our routine diagnostic lab, in a relatively short time and with limited costs. We tested 128 available samples from two German reference centers as part of our routine work up (among which 116 T-cell lymphomas), which is the largest routine diagnostic series reported to date. Our results showed that this assay had a very high rate of technical success (97%) and could detect mutations in the majority (79%) of tested T-cell lymphoma samples.

Protein-Based Oncopanel as Addition to Target Sequencing in Head and Neck Squamous Cell Carcinoma to Individualize Treatment Decisions.

Head and neck squamous cell carcinoma (HNSCC) is a heterogeneous group of cancers and patients have limited therapy options if primary treatment fails. Therefore, additional information about the biology of the tumor is essential. Here we performed a feasibility study of concurrently applying two precision diagnostic tools in a consecutive series of HNSCC patients. We analyzed tumor samples of 31 patients using a genomic (oncomine) and a proteomic, immunohistochemical approach (oncopanel) and compared the result, also in the focus on their overlapping therapeutical targets. We found no strong correlation between the two approaches and observed a higher proportion of marker expression for the immunohistochemical panel. However, both panels show in our HNSCC cohort distinct patterns with druggable targets. The data suggest that both approaches complement one another and can be applied side-by-side to identify the best targets for the development of individual treatment options for HNSCC patients.

Identification of Disparities in Personalized Cancer Care-A Joint Approach of the German WERA Consortium.

(1) Background: molecular tumor boards (MTBs) are crucial instruments for discussing and allocating targeted therapies to suitable cancer patients based on genetic findings. Currently, limited evidence is available regarding the regional impact and the outreach component of MTBs; (2) Methods: we analyzed MTB patient data from four neighboring Bavarian tertiary care oncology centers in Würzburg, Erlangen, Regensburg, and Augsburg, together constituting the WERA Alliance. Absolute patient numbers and regional distribution across the WERA-wide catchment area were weighted with local population densities; (3) Results: the highest MTB patient numbers were found close to the four cancer centers. However, peaks in absolute patient numbers were also detected in more distant and rural areas. Moreover, weighting absolute numbers with local population density allowed for identifying so-called white spots-regions within our catchment that were relatively underrepresented in WERA MTBs; (4) Conclusions: investigating patient data from four neighboring cancer centers, we comprehensively assessed the regional impact of our MTBs. The results confirmed the success of existing collaborative structures with our regional partners. Additionally, our results help identifying potential white spots in providing precision oncology and help establishing a joint WERA-wide outreach strategy.

Recurrent Oncogenic JAK and STAT Alterations in Cutaneous CD30-Positive Lymphoproliferative Disorders.

The group of cutaneous CD30-positive lymphoproliferative disorders (LPD) comprises two different entities, namely lymphomatoid papulosis (LyP) and cutaneous anaplastic large T-cell lymphoma (cALCL). LyP constitutes a benign lymphoproliferation with spontaneously regressing papules, whereas cALCL presents with solitary or multiple skin tumors with a low propensity to disseminate. To elucidate the hitherto largely unknown molecular pathogenesis of these entities, we performed comprehensive next-generation sequencing in a well-characterized cohort of 12 patients. Considering the low tumor cell content of LyP, we applied targeted sequencing technologies with a hybrid capture-based DNA library preparation approach and for the identification of fusion transcripts an anchored multiplex PCR enrichment kit. As the major finding, we detected, in 50% of LPD, genetic events that implied a constitutively activated Janus kinase-signal transducer and activator of transcription signaling (JAK-STAT) pathway in these entities. The identified molecular aberrations comprised either pathogenic STAT mutations or oncogenic fusion transcripts comprising effector domains of JAK. With respect to LyP, we report to our knowledge such previously unreported genetic aberrations in this specific entity. The detection of these convergent aberrations within the JAK-STAT signaling pathway deciphers common potential driving mechanisms of lymphomagenesis within LPD being shared between LyP and cALCL. Moreover, the presence of these oncogenic alterations paves the way to develop novel personalized treatment strategies.

Establishing Pure Cancer Organoid Cultures: Identification, Selection and Verification of Cancer Phenotypes and Genotypes.

Precision medicine requires in vitro models which will both faithfully recapitulate the features of an individual's disease and enable drug testing on a wide variety of samples covering the greatest range of phenotypes possible for a particular disease. Organoid technology has immense potential to fulfill this demand, but it will be necessary to develop robust protocols that enable the generation of organoids in a dependable manner from nearly every patient. Here we provide a user's guide, including detailed step-by-step protocols, to the establishment, isolation and verification of gastric cancer organoids. Selection strategies include omission of growth factors, addition of drugs, isolation of distinct phenotypes and generation of monoclonal lines. For confirmation of cancer identity, we use sequencing, drug selection, karyotyping and histology. While we specify these protocols for human gastric cancer organoids here, the methods described are applicable to organoids derived from other tissues as well.

Prognostic Value of O-(2-[18F]Fluoroethyl)-L-Tyrosine PET/CT in Newly Diagnosed WHO 2016 Grade II and III Glioma.

PURPOSE: The use of [18F]fluoroethyl)-L-tyrosine ([18F]FET) positron emission tomography/computed tomography (PET/CT) has proven valuable in brain tumor management. This study aimed to investigate the prognostic value of radiotracer uptake in newly diagnosed grade II or III gliomas according to the current 2016 World Health Organization (WHO) classification. PROCEDURES: A total of 35 treatment-naive patients (mean age, 48 ± 17 years) with histologically proven WHO grade II or III gliomas as defined by the current 2016 WHO classification were included. Static PET/CT imaging was performed 20 min after intravenous [18F]FET injection. Images were assessed visually and semi-quantitatively using regions of interest for both tumor (SUVmax, SUVmean) and background (BKGmean) to calculate tumor-to-background (TBR) ratios. The association among histological results, molecular markers (including isocitrate dehydrogenase enzyme and methylguanine-DNA methyltransferase status), clinical features (age), and PET findings was tested and compared with outcome (progression-free [PFS] and overall survival [OS]). RESULTS: Fourteen patients presented with grade II (diffuse astrocytoma n = 10, oligodendroglioma n = 4) and 21 patients with grade III glioma (anaplastic astrocytoma n = 15, anaplastic oligodendroglioma n = 6). Twenty-seven out of the 35 patients were PET-positive (grade II n = 8/14, grade III n = 19/21), with grade III tumors exhibiting significantly higher amino acid uptake (TBRmean and TBRmax; p = 0.03 and p = 0.02, respectively). PET-negative lesions demonstrated significantly prolonged PFS (p = 0.003) as compared to PET-positive gliomas. PET-positive disease had a complementary value in prognostication in addition to patient age, glioma grade, and molecular markers. CONCLUSIONS: Amino acid uptake as assessed by [18F]FET-PET/CT imaging is useful as non-invasive read-out for tumor biology and prognosis in newly diagnosed, treatment-naive gliomas according to the 2016 WHO classification.

A GRP78-Directed Monoclonal Antibody Recaptures Response in Refractory Multiple Myeloma with Extramedullary Involvement.

PURPOSE: Glucose-regulated protein (GRP) 78 is overexpressed in multiple myeloma, and both its surface expression and its biologic significance as key sensor of the unfolded protein response make GRP78 an ideal candidate for immunotherapeutic intervention. The monoclonal antibody PAT-SM6 targets surface GRP78 and leads to disease stabilization when used as single agent in a clinical trial. In this article, we evaluated expression of GRP78 in relapsed-refractory disease and explored PAT-SM6 therapy in combination regimens. EXPERIMENTAL DESIGN: GRP78 expression was immunohistochemically analyzed during disease progression and development of drug resistance throughout different stages of multiple myeloma. Activity of PAT-SM6 was evaluated in combination with anti-multiple myeloma agents lenalidomide, bortezomib, and dexamethasone in vitro Finally, we report on a multiple myeloma patient with relapsed-refractory disease treated with PAT-SM6 in combination with bortezomib and lenalidomide. RESULTS: Although sGRP78 expression was present at all stages, it increased with disease progression and was even strongly elevated in patients with drug-resistant and extramedullary disease. Pretreatment with dexamethasone as well as dual combination of PAT-SM6/lenalidomide further increased sGRP78 expression and consecutively showed synergistic anti-multiple myeloma effects with PAT-SM6 in proliferation assays. As proof of concept, a 62-year-old male with triple resistant multiple myeloma treated with PAT-SM6, bortezomib, and lenalidomide experienced partial remission of both intra- and extramedullary lesions. CONCLUSIONS: PAT-SM6 therapy in combination regimens showed efficacy in relapsed-refractory multiple myeloma. Clin Cancer Res; 22(17); 4341-9. ©2016 AACR.

GRP78-directed immunotherapy in relapsed or refractory multiple myeloma - results from a phase 1 trial with the monoclonal immunoglobulin M antibody PAT-SM6.

UNLABELLED: The primary objective of this phase 1 study was to evaluate the safety and tolerability of the anti-glucose regulated protein 78 monoclonal immunoglobulin M antibody PAT-SM6 in subjects with relapsed or refractory multiple myeloma. Twelve heavily pretreated patients received four intravenous infusions of PAT-SM6 at doses of 0.3, 1, 3, and 6 mg/kg within 2 weeks. Efficacy, pharmacokinetics and immunogenicity were followed up until the end of the trial (day 36). In addition, immune cell patterns in peripheral blood were assessed by flow cytometry and glucose regulated protein 78 expression status was evaluated in bone marrow specimens by immunohistochemistry and flow cytometry at screening. All doses administered were found to be safe and well tolerated; the maximum tolerated dose was not reached. The most common treatment emergent adverse event was leukopenia (grades 1 and 2) in eight out of the 12 multiple myeloma patients. Pharmacokinetic analysis demonstrated dose-proportional increases in drug serum concentration. The terminal half-life ranged from 5.86 to 8.41 h, the apparent volume of distribution ranged from 101 to 150 mL/kg, and clearance ranged from 8.11 to 16.1 mL/h/kg. All patients showed glucose regulated protein 78 surface expression on multiple myeloma cells. Four out of the 12 patients (33.3 %) had stable disease, according to the International Myeloma Working Group criteria, after PAT-SM6 treatment across the doses 1, 3 and 6 mg/kg. In summary, single-agent PAT-SM6 was well tolerated with modest clinical activity in relapsed or refractory multiple myeloma. Further trials exploring the combination of PAT-SM6 with existing myeloma therapies are planned. TRIAL REGISTRATION: clinicaltrials.gov identifier: NCT01727778.

Ten-year follow-up of a prospective trial for the targeted therapy of gastric cancer with the human monoclonal antibody PAT-SC1.

The fully human monoclonal antibody PAT-SC1 is specific for an isoform of CD55 (decay-accelerating factor) designated CD55PAT-SC1. This antigen is expressed in the majority (80%) of gastric cancers (GCs), and the antibody induces tumour cell-specific apoptosis in vitro as well as in vivo. PAT-SC1, therefore, has been deemed promising as a therapeutic agent. Here, we describe the results of an academic clinical study performed in a neoadjuvant setting with resectable GC patients. Patients undergoing treatment for GC between 1997 and 2001 were tested for CD55PAT-SC1 expression. Fifty-one resectable patients that tested positively received a single administration of 20 mg PAT-SC1 48 h prior to surgery. They underwent standard surgery with either subtotal or total gastrectomy with bursectomy, omentectomy and a modified D2-lymphadenectomy, aimed at R0 resection. Primary endpoints of the present study were to evaluate side-effects of the PAT-SC1 antibody treatment and to evaluate histopathological effects such as tumour regression and induction of apoptosis. Long-term survival was a secondary endpoint. Administration of PAT-SC1 appeared safe with only reversible side-effects according to WHO grade I and II. Despite the low­dose of the antibody, 81.6% of the patients showed signs of increased apoptosis within the primary tumour and 60% showed signs of tumour cell regression. Comparison of the 10-year survival rates of the R0-resected CD55PAT-SC1-positive patients treated with the PAT-SC1 antibody with a historical collective of R0-resected CD55PAT-SC1-positive patients not treated with PAT-SC1 indicated a survival benefit in the treated patients. Furthermore, comparison of the patient survival of CD55PAT­SC1-positive vs. CD55PAT-SC1-negative groups suggested that CD55PAT-SC1 antigen expression is an independent predictor of poor survival in a Cox regression analysis. Antibody PAT-SC1 may be a useful additive therapeutic agent in the treatment of patients with CD55PAT-SC1-expressing GCs. In combination with radical standard surgery, PAT-SC1 given as an adjuvant or neoadjuvant immunotherapeutic agent induces apoptosis in tumour cells which may improve survival of these patients. Because of the human origin and its specific binding to the CD55PAT-SC1 antigen, PAT-SC1 was well tolerated in this trial.

Noninvasive visualization of tumor growth in a human colorectal liver metastases xenograft model using bioluminescence in vivo imaging.

BACKGROUND: Bioluminescence imaging (BLI) is an ideal tool for noninvasive, quantitative monitoring of tumor progression/regression in animal models. The effectiveness of different treatment strategies is displayed by an altered intensity of bioluminescence, demonstrating a change of the tumor burden. The aim of this study was to establish a reliable, reproducible colorectal hepatic metastases cancer animal model. METHODS: Cells of the human colon carcinoma cell line HCT-116 Luc(pos) expressing the firefly luciferase enzyme gene were used. HCT-116 Luc(pos) cells (2.5 × 10(6)) were injected through the portal vein into the liver of immunoincompetent nude mice. BLI was used to analyze intrahepatic tumor burden and growth kinetic. RESULTS: HCT-116 Luc(pos) cells demonstrated a progressive and reproducible growth in the liver after intraportal injection. Four days after injection, the animals were analyzed for tumor growth by BLI, and mice without or too low bioluminescence signals were excluded (between 10% and 20% animals). HCT-116 Luc(pos) intrahepatic tumors responded successfully to different dosages (5 and 10 mg/kg) of 5-fluorouracil. CONCLUSIONS: BLI is an important tool with many potential advantages for investigators. The measurement of intrahepatic tumor growth by imaging luciferase activity noninvasively provides valuable information on tumor burden and effectiveness of therapy. Thus, the presented intrahepatic metastases model based on the growth of HCT-116 Luc(pos) cells is suitable for in vivo testing of different cancer therapy strategies.

Early development of PAT-SM6 for the treatment of melanoma.

Despite the recent development of novel therapies for patients with metastatic melanoma, this disease remains fatal in the majority of those who develop a relapse. Here, we report the preclinical and early clinical development of a novel IgM antibody PAT-SM6 that specifically binds to a cancer-specific isoform of glucose-regulated protein 78 (GRP78) and low-density lipoprotein. Finding a GRP78 cancer-specific form on the surface of cancer cells, but not normal cells in vivo, presents an opportunity for cancer-specific targeting. PAT-SM6 binding to the cell surface induces apoptosis in a variety of tumors, including melanoma. Recent studies show the specificity of PAT-SM6 binding to the surface of melanoma cells and primary tissue but not to normal tissue. They also confirm, for the first time, cell proliferation inhibition and apoptosis through classical apoptotic pathways as well as induction of lipid accumulation in melanoma cells. These in-vitro data are supported by positive in-vivo data using PAT-SM6 in a xenograft C8161 model. Furthermore, PAT-SM6 was well tolerated in pharmacokinetic/toxicology studies in monkeys. On the basis of these preclinical observations, a clinical study of PAT-SM6 was carried out in patients with 'in-transit' melanoma. Even with microdosing, histological analyses of tumor biopsies detected the presence of PAT-SM6 as well as apoptosis. Although there are many small molecules and monoclonal antibodies currently in clinical development for patients with melanoma, PAT-SM6 is the only therapeutic targeting the cancer-specific isoform of GRP78. These PAT-SM6 preclinical data and positive findings from the phase 1 safety study provide strong support for the further development of this novel antibody.

The natural human IgM antibody PAT-SM6 induces apoptosis in primary human multiple myeloma cells by targeting heat shock protein GRP78.

In contrast to other haematological malignancies, targeted immunotherapy has not entered standard treatment regimens for de novo or relapsed multiple myeloma (MM) yet. While a number of IgG-formatted monoclonal antibodies are currently being evaluated in clinical trials in MM, our study aimed to investigate whether the fully human IgM monoclonal antibody PAT-SM6 that targets a tumour-specific variant of the heat shock protein GRP78 might be an attractive candidate for future immunotherapeutic approaches. We here show that GRP78 is stably and consistently expressed on the surface on tumour cells from patients with de novo, but also relapsed MM and that binding of PAT-SM6 to MM cells can specifically exert cytotoxic effects on malignant plasma cells, whereas non-malignant cells are not targeted. We demonstrate that the induction of apoptosis and, to a lesser extent, complement dependent cytotoxicity is the main mode of action of PAT-SM6, whereas antibody dependent cellular cytotoxicity does not appear to contribute to the cytotoxic properties of this antibody. Given the favourable safety profile of PAT-SM6 in monkeys, but also in a recent phase I trial in patients with malignant melanoma, our results form the basis for a planned phase I study in patients with relapsed MM.

Diagnostic and therapeutic potential of a human antibody cloned from a cancer patient that binds to a tumor-specific variant of transcription factor TAF15.

Human hybridoma technologies permit the cloning of patient antibodies that may have desirable qualities. In this study, we report the isolation of a natural IgG antibody from a stomach cancer patient that illustrates novel diagnostic and therapeutic uses. Human antibody PAT-BA4 recognizes a tumor-specific variant of the transcription factor TATA-binding protein-associated factor 15 (TAF15) that is expressed on the plasma membrane of stomach cancer and melanoma cells but not healthy tissues. TAF15 is a member of the multifunctional TET protein family involved in mRNA transcription, splicing, and transport that is normally expressed only in the cytoplasm and nucleus of fetal or adult tissue cells. However, in malignant cells, TET family members including TAF15 seem to be involved in cell adhesion and spreading. In support of this likelihood, we found that PAT-BA4 inhibited tumor cell motility and tumor cell adhesion. Our findings define a role for a tumor-specific TAF15 antigen in malignant processes.

Natural antibodies and cancer.

The innate or natural immunity is the basis and key for all immune processes. Specific receptors on macrophages, dendrites, NK cells and natural antibodies producing B cells act as a first line defense and remove all 'foreign' and potentially harmful substances, that is, bacteria, viruses, cellular waste, modified molecules and, most importantly, cancer cells. Recognition and removal of transformed cells is a lifelong task of immune surveillance processes. Antibodies are hallmark components of this anti-cancer activity. To investigate their nature, specificity, and function, we used the human hybridoma technology for isolating antibodies from cancer patients. These were then tested with a panel of assays against cancer cell lines in vitro and in vivo. Interestingly, all the tumor-specific antibodies we found were germ-line coded and belonged nearly exclusively to the IgM class. Furthermore, they all bound to new carbohydrates on post-translationally modified cell surface receptors on malignant cells. So far no affinity maturated immunoglobulins detecting tumor-specific peptides were found. However, only the presentation of peptide motifs can create an immunological memory. In general malignant cells are detected at very early precursor stages and manifest tumors can be considered as exceptional events. In addition, malignant cells are neither infectious nor hide intracellularly like viruses and some bacteria. Therefore, it makes sense that anti-tumor immunity seems to be solely a part of the natural immunity and a memory is not needed and therefore not induced. This indicates that the tumor immunity seems to be restricted to innate immune mechanisms and the instruments used by nature, like natural antibodies, are obviously excellent therapeutics.

High level expression of functional human IgMs in human PER.C6 cells.

Natural IgM antibodies play an important role in the body's defense mechanisms against transformed cells in the human body and are currently being exploited both in prognoses of malignant lesions and in the therapy of cancer patients. However, despite growing interest and clinical promise, thus far the IgM class of antibodies has failed to gain widespread commercial interest as these are considered to be difficult to produce recombinantly. IgMs are polymeric and have a relatively large mass. In addition, IgM molecules are heavily glycosylated and, when produced in non-human cell lines, they may contain non-human glycan structures which may be potentially immunogenic. Clearly, production systems capable of expressing human recombinant IgM antibodies are needed. We have successfully used PER.C6 cells-a human cell line-to generate three separate human recombinant monoclonal IgMs in suspension cultures in protein-free medium. All three of the IgMs were constructed with joining (J) chain and were expressed in the pentameric form. One of the IgMs was also expressed as a hexamer without J chain. Clones with cell specific productivities greater than 20 pg/cell/day were generated, which led to yields of 0.5 g/L to 2g/L in fed-batch production. All the IgMs expressed were biologically active as shown in binding and cytotoxicity assays. These studies demonstrate the potential of PER.C6 cells for the production of high levels of functional recombinant IgM and other polymeric molecules, using a straightforward and rapid stable cell line generation method.

Natural human immunoglobulins in cancer immunotherapy.

The natural or innate immunity is the first-line defense against transformed cells. It guarantees the recognition and removal of malignant cells at an early stage and makes manifest cancers an exceptional event. Natural antibodies, which are predominantly IgM molecules, play a major role in these defense mechanisms and they have some typical features in common. They are coded by specific germline families and equipped mainly with lambda-chains, in contrast to the majority of circulating antibodies. The targets that are recognized by these antibodies are not newly synthesized proteins, but instead post-translationally modified carbohydrate structures on membrane-bound glycoproteins and glycolipids. Another typical feature of these natural IgM antibodies is their ability to induce apoptosis in vitro and in vivo in a death domain-independent manner. These results show that natural IgM antibodies represent a huge reservoir of therapeutic antibodies.

Natural monoclonal antibodies and cancer.

Immunity is responsible for recognition and elimination of infectious particles and for removal of cellular waste, modified self structures and transformed cells. Innate or natural immunity acts as a first line defense and is also the link to acquired immunity and memory. By using the human hybridoma technology, a series of monoclonal antibodies and several new tumor-specific targets could be identified. A striking phenomenon of immunity against malignant cells is that all so far isolated tumor-specific antibodies were germ-line coded natural IgM antibodies. And neither in animals nor in humans affinity-maturated tumor-specific IgG antibodies have been detected so far. These IgM's preferentially bind to carbohydrate epitopes on post-transcriptionally modified surface receptors, which are recently patented and preferentially remove malignant cells by inducing apoptosis to avoid inflammatory processes. Our "biology-" or "function-driven" method represents a unique yet powerful approach compared to the typical approaches on screening compounds or antibodies against non-validated targets (mostly differentially expressed). Moreover, the approach creates a competitive patenting strategy of creating proprietary antibodies and validated targets at the same time, which has the potential of further streamlining the discovery of new cancer therapies.

A new tumor-specific variant of GRP78 as target for antibody-based therapy.

The chaperone GRP78 is a member of the heat-shock protein 70 (HSP70) family and is responsible for cellular homeostasis by preventing stress-induced apoptosis. GRP78 is expressed in all cells of the body. In malignant cells, which are permanently exposed to environmental stress, GRP78 is overexpressed and increased levels can be found in the cytoplasm and on the cell membrane. Thus, GRP78 promotes tumor proliferation, survival, metastases and resistance to a wide variety of therapies. Like other tumor-specific membrane molecules, GRP78 can also be present on cancer cells in a variant form. This modification qualifies it as a target for immune surveillance and antibody responses. The fully human monoclonal IgM antibody, SAM-6, was isolated from a gastric cancer patient and it binds to a new variant of GRP78 with a molecular weight of 82 kDa. The epitope is an O-linked carbohydrate moiety and is specific for malignant cells. These data show that cancer-specific modifications of cell-surface protection molecules are (a) subject of an immune response and (b) ideal targets for new therapeutical approaches.

Tumors: too sweet to remember?

Immunity, based on a natural and an educated system, is responsible for recognition and elimination of infectious particles, cellular waste, modified self and transformed cells. This dual system guarantees that dangerous particles are removed immediately after appearance and that a memory with maturated weapons exists, if the organism is re-infected by the same particle. For malignant cells, however, the immune response seems to be restricted to innate immunity, because at least for the humoral response, all so far detected tumor-specific antibodies belong to the natural immunity. In this review we try to explain why malignant cells might be "too sweet" to induce a memory.

Natural antibodies and cancer.

Immunity is not only responsible for recognition and elimination of infectious particles, but also for removal of cellular waste, modified self structures and transformed cells. Innate or natural immunity acts as a first line defense and is also the link to acquired immunity and memory. A striking phenomenon of immunity against malignant cells is that neither in animals nor in humans affinity-maturated tumor-specific IgG antibodies have been detected so far. All tumor-specific isolated antibodies were germ-line coded natural IgM antibodies. It's also a fact that these IgM's preferentially bind to carbohydrate epitopes on post-transcriptionally modified surface receptors and that they all induce a cancer-specific apoptosis, by triggering the intrinsic apoptotic pathway. From an evolutionary point of view, this makes sense because cancer cells are not infectious, so there is no need for memory. Natural IgMs bind to conservative structures because they are coded by a limited set of genes and they use apoptosis, the "clean" way of killing, to avoid inflammatory processes.