Monoclonal antibodies for diagnosis and potential therapy of small cell lung cancer--the ganglioside antigen fucosyl-GM1

Stimulation of osteoblastic differentiation and mineralization in MC3T3-E1 cells by antler and fermented antler using Cordyceps militaris

ETHNOPHARMACOLOGICAL RELEVANCE

For thousands of years antlers have been used in Asian countries to promote rapid healing, treat weight loss, slow growth in children, strengthen weak bones, and alleviate cold hands and feet.

AIM OF THE STUDY

The present study was performed to examine the effect of fermentation on the ability of antler to act as a stimulator of bone growth.

MATERIALS AND METHODS

This study used pre-osteoblast MC3T3-E1 cells to examine factors related to bone growth, such as cell proliferation, production of alkaline phosphatase (ALP), and deposition of extracellular matrix proteins (e.g., collagens, osteonectin, bone sialoprotein (BSP)), via the treatment of non-fermented and fermented antler.

RESULTS

Antler fermentation using Cordyceps militaris was carried out at 25°C for seven days. The total content of sugar, sialic acid, and protein increased with fermentation time. Cell proliferation was greater in the fermented antler- (FA-) treated groups than in the NFA- (non-fermented antler-) treated groups, in which proliferation increased significantly up to 137% of the basal value. Significant increases in mRNA expression and ALP activity were found at FA concentrations of 50-100 μg/ml; at 100 μg/ml the activity had increased 119% compared to the control activity. For NFA and FA the expression levels of type I collagen mRNA significantly increased in a dose-dependent manner at all treatment doses. However, significant differences between the antler groups were not observed. Mineralization significantly increased by NFA and FA treatment to 183% and 241%, respectively, when compared to colostrum, as a positive control (165%).

CONCLUSIONS

Antler treatment increased the proliferation of osteoblasts and bone matrix proteins, such as type I collagen and BSP. Antler fermented with Cordyceps militaris showed enhanced activity, and its stimulatory effects on cell proliferation and ALP production were greater than those of NFA. We surmise that these increases in activity were related to increased sialic acid content. Therefore, the results of this study suggest that the physiological effects of antler, including bone growth, may be increased through the fermentation process.

A new small cell lung cancer (SCLC)-specific marker discovered through antigenic subtraction of neuroblastoma cells

Small cell lung cancer (SCLC) is an aggressive form of lung cancer associated with cigarette smoking and presently accounts for approximately 20% of all lung cancer cases. SCLC cells derive from a neuroendocrine origin and therefore their antigenic profile coincides, to a great extent, with that of neuroendocrine cells. Multiple attempts to generate SCLC-specific MoAbs during the past decade have failed because all SCLC-specific MoAbs isolated also react against neuroendocrine tissues or normal immune cells. Cross-reactivity with normal antigens raises safety concerns due to the inevitable toxicity of such interactions and the dreaded effects. The concept of DIAAD trade mark ( Differential Immunization for Antigen and Antibody Discovery) provides for an immune response that can be effectively focused on cancer antigens. The object is to overcome obstacles resulting from an antigenic hierarchical pattern biased towards a response to dominant antigens in order to induce a robust immune response to cancer antigens. Cancer antigens are weak or nonimmunogenic molecules. Due to the fact that the immune system responds more strongly to immunodominant antigens than to weak immunogenic antigens, cancer cell proliferation is unencumbered. DIAAD employs protocols of induction of tolerance and immunity, conducted in sequential order to "biologically subtract" the immune response of dominant antigens expressed by normal cells. This biological subtraction is achieved in a laboratory animal by first eliminating the immune response to the normal cells or closely related cancer cells, followed by immunization of the same laboratory animal with diseased cells. This procedure directs the immune response exclusively towards antigens expressed by the diseased and not the normal cells. Our objective was to use DIAAD to generate monoclonal antibodies specific to SCLC antigens that are not shared by neuroendocrine cells by contrasting a pool of human SCLC cell lines with a pool of human neuroendocrine cancer cell lines. Four monoclonal antibodies reacted strongly and exclusively with SCLC cells and identified a membrane molecule comprising a single chain glycoprotein. Two of four antibodies were selected for a detailed analysis that revealed a narrow tissue specificity of antigen expressed by colon, lung, and pancreatic cancers (less than 20% staining was found on breast, ovarian and prostate cancer). These antibodies did not bind to various other cancers such as kidney, carcinoid, lymphoma, sarcoma, adrenal, liver, melanoma, seminoma, leiomyoma, basal cell cancer, or undifferentiated cancer. The epitope recognized by the selected MoAbs was destroyed with the removal of carbohydrates from SCLC cells. This result does not exclude the possibility of protein-carbohydrate cooperation in epitope recognition. However, it strongly suggests the pivotal role of carbohydrates in antibody binding to this molecule. Upon binding to the extracellular molecule on SCLC cells, the antibodies were shown to internalize. A low or insignificant level of internalization was recorded following incubation of the antibodies with neuroendocrine-derived tumors. The capacity of these antibodies to internalize upon binding the extracellular receptors renders them potential candidates for prodrug or immunotoxin-targeted therapeutics. In a qualitative experiment involving immunoaffinity purification, the SCLC antigen was shown to be differentially detected in sera of SCLC patients. Plans are being generated to explore the possible utility of this novel SCLC-specific antigen recognized by the above MoAbs as a new biomarker for early diagnosis of the disease, as well as for therapeutic intervention for SCLC.

Pretargeting with the affinity enhancement system for radioimmunotherapy

The pretargeting technique referred to as the Affinity Enhancement System (AES) uses bispecific antibodies and radiolabeled bivalent haptens that bind cooperatively to target cells in vivo. Experimental and clinical data demonstrate that AES can deliver large radiation doses to tumor cells with high tumor to normal tissue contrast ratios and long activity residence time in tumors. Preliminary clinical results of radioimmunotherapy of medullary thyroid carcinomas and lung cancers look promising.

Anti-ganglioside GM2 monoclonal antibody-dependent killing of human lung cancer cells by lymphocytes and monocytes

Ganglioside GM2 (GM2) frequently appears on the cell surface of human cancers of neuroendocrine origin. A mouse-human chimeric monoclonal antibody (mAb), KM966, against GM2 was previously found to promote the lysis of various cancer cells by human blood mononuclear cells (MNC). In this study, we analyzed the effector cells responsible for the chimeric mAb-dependent cell-mediated cytotoxicity (ADCC) against small cell lung cancer (SCLC) cells and examined the enhancing effect of various cytokines on the ADCC activity. The ADCC activity was assessed by 4-h 51Cr release assay. Highly purified lymphocytes (> 99%) and monocytes (> 90%) were separated by centrifugal elutriation from peripheral blood MNC of the same healthy donor. KM966 induced lysis of SCLC cells mediated by both lymphocytes and monocytes to similar extents, in a dose-dependent manner. Pretreatment of lymphocytes with various cytokines [interleukin (IL)-2, IL-12 and interferon-gamma] and that of monocytes with macrophage-colony-stimulating factor significantly augmented the killer activity against SCLC cells in the presence of KM966 mAb. KM966 was also effective for the lysis of non-small cell lung cancer cells in direct proportion to the GM2 expression levels. These findings suggest that combined treatment of KM966 mAb with cytokines may be therapeutically useful for in vivo killing of lung cancer cells expressing GM2 through the ADCC reaction.

Metabolism of the anticancer peptide H-Arg-D-Trp-NmePhe-D-Trp-Leu-Met-NH2

H-Arg-D-Trp-NmePhe-D-Trp-Leu-Met-NH2 (Antagonist G) will be the first broad-spectrum neuropeptide antagonist to enter a phase I clinical trial. Its in vitro and in vivo metabolism has been extensively characterized. The major metabolites were identified and their structures elucidated by mass spectroscopy and amino acid analysis. Metabolism occurred almost exclusively at the C-terminus and was arrested by phenylmethylsulfonylfluoride, a known serine-protease inhibitor. Biological characterization of the metabolites demonstrated that the degradation of Antagonist G produces metabolites that retain neuropeptide antagonist properties.

Fucosyl-GM1 in small-cell lung cancer. A comparison with the tumour marker neuron-specific enolase

BACKGROUND

Recently, the ganglioside Fucosyl-GM1 (FucGM1) has been described as a possible new tumour marker for small-cell lung cancer (SCLC). FucGM1 has been detected in 75% to 90% of SCLC tumours by immunohistochemical analysis and in about 50% of sera from SCLC patients. Neuron-specific enolase (NSE) is a glycolytic enzyme which is expressed in the majority of SCLC tumours and patient sera.

PATIENTS AND METHODS

Sera from 156 patients with SCLC were analyzed for FucGM1 with a scintillation proximity assay (SPA), which is a simple and sensitive analysis. Sera were analyzed before the initiation of chemotherapy, and twenty patients were monitored during and after treatment. The concentration of FucGM1 was compared to the tumour marker NSE and related to clinical data and survival.

RESULTS

Sixty-three per cent of the patients were positive for FucGM1. The concentrations did not correlate with NSE or clinical data including stage of disease, organ site of metastases or ABO blood group status. Nor did the expression of FucGM1 correlate with survival. As a monitor of clinical response, a correlation was found in 8 out of 20 patients. Eighty-four per cent of the patients were positive for NSE; and 97% were positive for either FucGM1 or NSE.

CONCLUSION

We conclude that FucGM1 does not have a clinical role as a tumour marker for patients with SCLC at diagnosis or during treatment.

Serological tumor markers for small cell lung cancer and their therapeutic implications

Serological tumor markers may become widely used as inexpensive and non-invasive methods of cancer detection. Markers of current interest for small cell lung cancer (SCLC) comprise enzymes, peptides, proteins, and carbohydrates. None of the serological markers for SCLC have yet proven to be of diagnostic value and at present their use is limited to monitoring disease and indicating prognosis. However, whilst serological markers related to the metabolic state of SCLC cells, such as neuron-specific enolase, serum thymidine kinase and tissue polypeptide antigen, may only be used for monitoring patients and for estimating prognosis, the other serological markers under current investigation may be used to indicate new treatment forms. Several novel approaches, including interference in the autocrine growth-regulating loop of SCLC by either peptides or antibodies, have been tried, SCLC is a highly heterogeneous tumor with respect to antigen expression, regulation of growth, and differentiation state. It is therefore important that new interventions are directed against both antigen-positive and antigen-negative tumor cells. For instance, radioisotopes or enzymes coupled to antibodies may be effective by exerting toxicity at some distance from the target. Antigens expressed on SCLC cells, such as peptide receptors involved in growth regulation, carbohydrate antigens like Lewis antigens, carcinoembryonic antigen and the ganglioside fucosylGM1, provide potential targets for antibody-conjugated therapy.