Expression of beta 1 integrins (very late antigens-4 and -5) on myeloma cells and clinical correlates in patients with multiple myeloma

IMMUNOTAR - Integrative prioritization of cell surface targets for cancer immunotherapy

Cancer remains a leading cause of mortality globally. Recent improvements in survival have been facilitated by the development of less toxic immunotherapies; however, identifying targets for immunotherapies remains a challenge in the field. To address this challenge, we developed IMMUNOTAR, a computational tool that systematically prioritizes and identifies candidate immunotherapeutic targets. IMMUNOTAR integrates user-provided RNA-sequencing or proteomics data with quantitative features extracted from publicly available databases based on predefined optimal immunotherapeutic target criteria and quantitatively prioritizes potential surface protein targets. We demonstrate the utility and flexibility of IMMUNOTAR using three distinct datasets, validating its effectiveness in identifying both known and new potential immunotherapeutic targets within the analyzed cancer phenotypes. Overall, IMMUNOTAR enables the compilation of data from multiple sources into a unified platform, allowing users to simultaneously evaluate surface proteins across diverse criteria. By streamlining target identification, IMMUNOTAR empowers researchers to efficiently allocate resources and accelerate immunotherapy development.

Evidence for Cell Adhesion-Mediated Drug Resistance of Multiple Myeloma Cells in Vivo

Background/Aims

Multiple myeloma is an incurable disease and patients eventually die of disease progression due to drug resistance. VLA-4 (very late antigen 4), VCAM (vascular adhesion molecule), LFA-1 (leukocyte function-associated antigen 1), and ICAM-1 (intercellular adhesion molecule 1)-mediated adhesion of myeloma cells to bone marrow stromal cells induces primary multidrug resistance in vitro. Based on these preclinical data we hypothesized that myeloma cells with strong adhesion - due to strong expression of adhesion molecules on the cell surface - are selected by chemotherapy in patients. To prove this hypothesis we determined the expression levels of adhesion molecules in 31 multiple myeloma patients by flow cytometry.

Methods

A 3-color stain with CD38, CD138 and antibodies against VLA-4, ICAM-1, LFA-1, and VCAM was performed. The patients were either at diagnosis (chemo-naive; n=17) or at relapse (pre-treated; n=15). Furthermore, the response to the next chemotherapy of chemo-naive patients was correlated with the expression levels of adhesion molecules.

Results

ICAM-1, VLA-4, and VCAM expression was higher in pre-treated patients than in chemo-naive patients and the expression levels increased with the number of chemotherapy regimens. Primarily multidrug-resistant patients had significantly higher expression levels of VLA-4 and ICAM-1 than responders.

Conclusion

This study suggests that multiple myeloma cells expressing high levels of VLA-4 and ICAM-1 are drug resistant and that such a subpopulation of cells is selected by chemotherapy.

Ex Vivo and In Vivo Evaluation of Overexpressed VLA-4 in Multiple Myeloma Using LLP2A Imaging Agents

Very-late-antigen-4 (VLA-4, α4β1 integrin, CD49d/CD29) is a transmembrane adhesion receptor that plays an important role in cancer and immune responses. Enhanced VLA-4 expression has been observed in multiple myeloma (MM) cells and surrounding stroma. VLA-4 conformational activation has been associated with MM pathogenesis. VLA-4 is a promising MM imaging and therapeutic biomarker.

METHODS

Specificity of (64)Cu-LLP2A ((64)Cu-CB-TE1A1P-PEG4-LLP2A), a high-affinity VLA-4 peptidomimetic-based radiopharmaceutical, was evaluated in α4 knock-out mice and by competitive blocking in wild-type tumor-bearing mice. (64)Cu-LLP2A PET/CT (static and dynamic) imaging was conducted in C57BL6/KaLwRij mice bearing murine 5TGM1-GFP syngeneic tumors generated after intravenous injection via the tail. Blood samples were collected for serum protein electrophoresis. Bone marrow and splenic cells extracted from tumor-bearing and control mice (n= 3/group) were coincubated with the optical analog LLP2A-Cy5 and mouse B220, CD4, Gr1, and Mac1 antibodies and analyzed by fluorescence-activated cell sorting. Human radiation dose estimates for (64)Cu-LLP2A were extrapolated from mouse biodistribution data (6 time points, 0.78 MBq/animal, n= 4/group). Ten formalin-fixed paraffin-embedded bone marrow samples from deceased MM patients were stained with LLP2A-Cy5.

RESULTS

(64)Cu-LLP2A and LLP2A-Cy5 demonstrated high specificity for VLA-4-positive mouse 5TGM1-GFP myeloma and nonmalignant inflammatory host cells such as T cells and myeloid/monocytic cells. Ex vivo flow cytometric analysis supported a direct effect of myeloma on increased VLA-4 expression in host hematopoietic microenvironmental elements. SUVs and the number of medullar lesions detected by (64)Cu-LLP2A PET corresponded with increased monoclonal (M) protein (g/dL) in tumor-bearing mice over time (3.29 ± 0.58 at week 0 and 9.97 ± 1.52 at week 3). Dynamic PET with (64)Cu-LLP2A and (18)F-FDG demonstrated comparable SUV in the prominent lesions in the femur. Human radiation dose estimates indicated urinary bladder wall as the dose-limiting organ (0.200 mGy/MBq), whereas the dose to the red marrow was 0.006 mGy/MBq. The effective dose was estimated to be 0.017 mSv/MBq. Seven of the ten human samples displayed a high proportion of cells intensely labeled with LLP2A-Cy5 probe.

CONCLUSION

(64)Cu-LLP2A and LLP2A-Cy5 demonstrated binding specificity for VLA-4 in an immune-competent murine MM model. (64)Cu-LLP2A displayed favorable dosimetry for human studies and is a potential imaging candidate for overexpressed VLA-4.