Development and implementation of a direct detection, quantitation and validation system for class I MHC self-peptide epitopes

Jain

Caseltine

et al. 2011

Self Cite

mAbs that recognize peptides presented on the cell surface by MHC class I molecules are potential therapeutic agents for cancer therapy. We have previously demonstrated that these Abs, which we termed TCR mimic mAbs (TCRm), reduce tumor growth in models of breast carcinoma. However, mechanisms of TCRm-mediated tumor growth reduction remain largely unknown. In this study, we report that these Abs, in contrast to several mAbs used currently in the clinic, destroy tumor cells independently of immune effector mechanisms such as Ab-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC). We found that TCRm-mediated apoptosis of tumor cells was associated with selective and specific binding of these Abs to peptide/HLA class I complexes, which triggered the activation of JNK and intrinsic caspase pathways. This signaling was accompanied by the release of mitochondrial cytochrome c and apoptosis-inducing factor. TCRm-induced apoptosis in tumor cells was completely inhibited by soluble MHC tetramers loaded with relevant peptide as well as with inhibitors for JNK and caspases. Furthermore, mAbs targeting MHC class I, independent of the peptide bound by HLA, did not stimulate apoptosis, suggesting that the Ab-binding site on the MHC/peptide complex determines cytotoxicity. This study suggests the existence of mechanisms, in addition to ADCC and CDC, through which these therapeutic Abs destroy tumor cells. These mechanisms would appear to be of particular importance in severely immunocompromised patients with advanced neoplastic disease, since immune cell-mediated killing of tumor cells through ADCC and CDC is substantially limited in these individuals.

“…This treatment resulted in the significant reduction of tumor growth when compared with mice that were administrated with control IgG2a F(ab9) 2 (Fig. 1D).…”

Section: F(ab9) 2 Fragments Of Rl4b Inhibit Tumor Growthmentioning

confidence: 91%

mentioning

confidence: 99%

TCR Mimic Monoclonal Antibodies Induce Apoptosis of Tumor Cells via Immune Effector-Independent Mechanisms

Jain

Caseltine

et al. 2011

Self Cite

“…Mice were immunized with an emulsion containing 50 mg purified MIF [19][20][21][22][23][24][25][26][27] / HLA-A2 complexes and Quil-A adjuvant (Sigma-Aldrich, St. Louis, MO) to produce TCR mimic (TCRm) as previously described (29,30).…”

Section: Immunizationmentioning

confidence: 99%

An HLA-Presented Fragment of Macrophage Migration Inhibitory Factor Is a Therapeutic Target for Invasive Breast Cancer

Hawkins

Lightfoot

et al. 2011

Self Cite

This report describes a novel HLA/peptide complex with potential prognostic and therapeutic roles for invasive breast cancer. Macrophage migration inhibitory factor (MIF) mediates inflammation and immunity, and MIF overexpression is observed in breast cancer. We hypothesized that the HLA class I of cancerous breast epithelial cells would present MIF-derived peptides. Consistent with this hypothesis, the peptide FLSELTQQL (MIF19–27) was eluted from the HLA-A*0201 (HLA-A2) of breast cancer cell lines. We posited that if this MIF19–27/HLA-A2 complex was exclusively found in invasive breast cancer, it could be a useful prognostic indicator. To assess the presentation of MIF peptides by the HLA of various cells and tissues, mice were immunized with the MIF19–27/HLA-A2 complex. The resulting mAb (RL21A) stained invasive ductal carcinoma (IDC) but not ductal carcinoma in situ, fibroadenoma, or normal breast tissues. RL21A did not stain WBCs (total WBCs) or normal tissues from deceased HLA-A2 donors, substantiating the tumor-specific nature of this MIF/HLA complex. As this MIF/HLA complex appeared specific to the surface of IDC, RL21A was tested as an immunotherapeutic for breast cancer in vitro and in vivo. In vitro, RL21A killed the MDA-MB-231 cell line via complement and induction of apoptosis. In an in vivo orthotopic mouse model, administration of RL21A reduced MDA-MB-231 and BT-20 tumor burden by 5-fold and by >2-fold, respectively. In summary, HLA-presented MIF peptides show promise as prognostic cell surface indicators for IDC and as targets for immunotherapeutic intervention.

“…Recently, several groups including our own have generated Abs against specific peptide/MHC complexes (32)(33)(34)(35)(36)(37). A number of different approaches have been used.…”

mentioning

confidence: 99%

“…Our approach combines immunization with synthetic immunogen and high throughput screening techniques to generate antipeptide/MHC Abs we have dubbed TCR mimic (TCRm) Abs (40,41). The majority of the Abs generated by our laboratory using this process have shown high binding affinity and fine binding specificity, and they can be used for the detection and quantitation of peptide/MHC class I molecules (32,33).…”

mentioning

confidence: 99%

TCR Mimic Monoclonal Antibody Targets a Specific Peptide/HLA Class I Complex and Significantly Impedes Tumor Growth In Vivo Using Breast Cancer Models

Neethling²,

Caseltine³

et al. 2010

Self Cite

Our laboratory has developed a process for generating mAbs with selectivity to unique peptides in the context of MHC molecules. Recently, we reported that RL4B, an mAb that we have called a TCR mimic (TCRm) because it recognizes peptide in the context of MHC, has cytotoxic activity in vitro and prevented growth of tumor cells in a prophylactic setting. When presented in the context of HLA-A2, RL4B TCRm recognizes the peptide GVLPALPQV derived from human chorionic gonadotropin (hCG)-β. In this study, we show that RL4B TCRm has strong binding affinity for the GVLPALPQV peptide/HLA-A2 epitope and fine binding specificity for cells that express endogenous hCGβ Ag and HLA-A2. In addition, suppression of tumor growth with RL4B TCRm was observed in orthotopic models for breast cancer. Using two aggressive human tumor cell lines, MDA-MB-231 and MCF-7, we provide evidence that RL4B TCRm significantly retards tumor growth, supporting a possible role for TCRm agents in therapeutic settings. Moreover, tumors in mice responded to RL4B TCRm therapy in a dose-dependent manner, eliminating tumors at the highest dose. RL4B TCRm strongly detects the hCGβ peptide/HLA-A2 epitope in human primary breast tumor tissue, but does not react or reacts weakly with normal breast tissue from the same patient. These results further illustrate the selective nature of TCRm Abs and the clinical relevance of the GVLPALPQV peptide/HLA-A2 epitope expression in tumor cells, because they provide the first evidence that Abs that mimic the TCR can be used to markedly reduce and suppress tumor growth.