"Charting cellular attraction-based interactome with Multivalent Adhesive Probe AFM (MAPA)" - Adhesion of cells defined by physicochemical composition of the interacting cell surfaces is the key factor determining organism development, tissue integrity, immune response, and cancer metastasis. Enormous progress in this field achieved in recent years has been hampered by limited biophysical tools capable to simultaneously measure adhesive properties of live cells, to qualitatively determine chemistry governing cell bonding and to analyze distinct types of adhesion. Atomic force microscopy (AFM) based force spectrometry can provide data on viscoelastic properties and limited receptor-targeted surface composition. Here we propose to develop and validate technology that can deliver adhesion maps and physicochemical surface composition maps of live cells. Our technology uniquely analyzes dispersive adhesion based on van der Waals interactions not accessible by other methods, AFM based and beyond, focused on viscoelastic properties of cells. Dispersive adhesion is especially relevant for invasive cells devoid of tumor microenvironment and searching for interactions, such as circulating tumor cells (CTCs). We determined that properties of frequency spectra of an AFM probe momentarily engaged in oscillation mode, based van der Waals interactions with an object, strongly depend on physicochemistry of the tested material. In our pilot experiments we used frequency spectra to fast and unambiguously identify distinct bio-relevant surfaces, cultured cancer cells of controlled invasiveness, and cancer cells isolated from patients, which are mostly left unresolved with viscoelastic adhesion. Therefore, we hypothesize that specific qualitative and quantitative data on dispersive cell adhesion (no cell indentation, no elastic component) can be extracted from broad-range frequency spectra of an AFM probe vibrating within the van der Waals distance above the cell surface. We plan to test our hypothesis and develop the corresponding technology: Multivalent Adhesive Probe AFM (MAPA), in the following steps. (I) First, we will determine technical benchmarks to measure adhesiveness of bio-relevant model surfaces. After optimization of spectra collection, we will establish procedures for spectral analysis and derive biomaterial- specific spectral signatures. (II) Next, we will extend the MAPA technology to test attractiveness of human cultured prostate cancer cells subjected to invasion-promoting conditions: circulation-simulating fluid shear stress, induction of epithelial to mesenchymal transition or fusion with tumor-associated macrophages to produce aggressive tumor-macrophage hybrids (TMHs). (III) Finally, we will validate the MAPA technology with CTCs and TMHs isolated from the blood of a small cohort of prostate cancer patients. We will aim at fast and reliable discerning of fusion-prone CTCs and early-stage TMHs not detectible with AFM force spectrometry and other single cell methods. The successful qualitative and quantitative interrogation of cell attractiveness holds the promise not only to better understand the fundamental biological processes but also adds capability to follow disease progression and response to therapies for improved diagnosis and prognosis.
