Behind the paper
The discovery of effective novel molecular targets for cancer and their development into bedside therapies remains the central goal of cancer research worldwide. However, to combat this rebellious group of cells that cause cancer is far from straightforward. Cancer is driven by complex, multi-regulatory pathways that cannot be stalled or terminated by shutting down just one route as it is prone to find another way to sustain its growth and proliferation, making targeted intervention a significant challenge. If we can identify these resistance mechanisms of the cell and find ways to encounter them, we can improvise the existing therapeutic approaches.
Previous work from the lab has identified a novel molecular target called TIP1. It is a 124 amino acid containing protein with a single PDZ domain via which it interacts with different molecules to carry out various biological processes. TIP1 is found to be elevated in different cancers and its expression could be co-related with the prognosis of the disease. We found that blocking the functional domain of this molecule has cytotoxic and anti-proliferative effects in NSCLC and glioblastoma cells. Also, TIP1 is radiation inducible, which makes it a better druggable target. Blocking TIP1 by antibodies sensitized cancer cells to radiation [1].
However, it was noticed that the commencement of cell death is evident only after 72 to 96h of incubation with the anti-TIP1 antibody. A quantitative mass spectrometry analysis was performed to investigate the underlying mechanisms that might diminish or offset the anticancer effects of TIP1 blockade. That is when we discovered that there is a significant, 10-fold upregulation of Midkine (MDK) following treatment with the anti-TIP1 antibody. There was a time dependent increase in intracellular as well as secreted MDK upon blocking TIP1 in both NSCLC as well as glioblastoma cells. MDK has been reported to play a major role in therapy resistance in different cancers so we hypothesized that induction of MDK might be a cell response to counteract the antiproliferative effects of the anti-TIP1 antibody. This marked the initiation for embracing and advancing the work that has been published in Cancer Gene Therapy[2].
It was interesting to investigate the mechanism underlying the upregulation of MDK following TIP1 blockade. The Wnt/β-catenin pathway is an important mediator of NSCLC therapy resistance. We found by Fluorescence Resonance Energy transfer (FRET) and co-immunoprecipitation experiments that TIP1 interacts with β-catenin. Western blot and TOP/FOP luciferase reporter assay revealed blocking TIP1 resulted in increase in nuclear translocation and transcriptional activity of β-catenin while knockdown of β-catenin abrogates upregulation of MDK following blockade of the functional domain of TIP1. This highlighted the role of β-catenin/Wnt signaling in MDK induction.
Several studies have reported inhibition of MDK using a small molecule inhibitor called iMDK has profound anticancer benefits in different cancer. In our study we found that dual targeting of TIP1 and MDK had enhanced anticancer effects than targeting either of these protein alone in NSCLC.
Overall, our data has two major findings. Firstly, MDK plays a role in modulating the response to TIP1 blockade in cancer cells via the β-catenin/Wnt signaling, and next that dual targeting of TIP1 and MDK exerts enhanced anti-proliferative effects in NSCLC cells. This study provides the first evidence supporting the therapeutic potential of co-targeting TIP1 and MDK as a novel strategy for NSCLC treatment.
Read the full paper here: https://rdcu.be/ervCQ
1 Singh AK, Dadey DY, Rau MJ, Fitzpatrick J, Shah HK, Saikia M et al. Blocking the functional domain of TIP1 by antibodies sensitizes cancer to radiation therapy. Biomed Pharmacother 2023; 166: 115341.
2 Saikia M, Shah HK, Hallahan DE, Singh AK, Kapoor V. Blocking the functional domain of cancer cell surface TIP1 upregulates Midkine via the beta-catenin/Wnt signaling pathway. Cancer Gene Ther 2025.