The 5T4 oncofetal glycoprotein does not act as a general organizer of the CXCL12 system in cancer cells

Abstract

The chemokine, CXCL12, promotes cancer growth and metastasis through interaction with either CXCR4 and/or CXCR7. This tumor-specific organization of the CXCL12 system obscures current therapeutic approaches, aiming at the selective inactivation of CXCL12 receptors. Since it has been previously suggested that the cellular use of CXCR4 or CXCR7 is dictated by the 5T4 oncofetal glycoprotein, we have now tested whether 5T4 would represent a general and reliable marker for the organization of the CXCL12 system in cancer cells. The CXCR4 antagonist, AMD3100, as well as the CXCR7 antagonist, CCX771, demonstrated that the cancer cell lines A549, C33A, DLD-1, MDA-231, and PC-3 use either CXCR7 and/or CXCR4 for mediating CXCL12-induced chemotaxis and cell proliferation. The use of CXCL12 receptors as well as their subcellular localization remained unchanged in most cell lines following siRNA-mediated depletion of 5T4. In distinct cell lines, inhibition of 5T4 expression, however, modulated tumor cell migration and proliferation per se. Collectively our analyses fail to demonstrate general organizational influences of 5T4 of the CXCL12 system in different cancer cell lines, and, hence, dismiss its future use as a diagnostic marker.

Functions of the CXCL12 Receptor ACKR3/CXCR7—What Has Been Perceived and What Has Been Overlooked

“…Importantly, in addition to stem and progenitor cells, distinct links between CXCL12 receptors and affected cell functions seem to be also realized at least in some cancer cells. As previously shown (Puchert et al, 2018),…”

“…In this respect it is noteworthy that combined fluorescence labeling of CXCR4 and ACKR3 in various tumor cell lines which require both CXCR4 and ACKR3 to respond to CXCL12 produced rather inconclusive results. Specifically, these experiments showed overlapping CXCR4 and ACKR3 staining in distinct cellular domains while other domains only showed staining for either CXCR4 or ACKR3 (Puchert et al, 2018). Finally, it has to be kept in mind that the 1D).…”

“…As both a proof of principle and a hint to the complexity of these interactions, previous work demonstrated that CXCL11 attenuates CXCL12-dependent chemotaxis of CT26.WT tumor cells (Rupertus et al, 2014) whereas pretreating HeLa cells with CXCL11 was found to facilitate CXCL12induced chemotaxis (Miekus et al, 2010). Further work on this issue and subsequent insights into the therapeutic implications of these interactions is urgently needed, especially, as revealed by ongoing work in our lab, numerous cancer cells co-express for example ACKR3, CXCR4, and CXCR3 (Puchert et al, 2018(Puchert et al, , 2020.…”

Identification of CXCL11 as part of chemokine network controlling skeletal muscle development

“…Due to unknown reasons, the size of the confirmed CXCL11 protein band (approximately 40 kD) is distinctly higher than predicted. Specificity of the CXCR7 and CXCR4 antibodies was successfully established by previous work, using cells with deleted or inhibited chemokine receptor expression (Puchert et al 2018 ; Hunger et al 2012 ).

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Cancer stem cell mobilization and therapeutic targeting of the 5T4 oncofetal antigen

“…However, the generality of surface expression of 5T4 as a marker for preferential CXCR4 rather than the CXCR7 receptor usage has not been verified generally using various other cell lines. 77 Nevertheless, in a tissue/tumor context, it is plausible that surface 5T4 expression at the tumor periphery directs spread towards a local vasculature generated CXCL12 gradient while in the center 5T4 negative tumor cells response to the chemokine is proliferation or anti-apoptosis. 62 This is consistent with patterns of 5T4 tumor expression previously described using immunohistochemistry where both cytoplasmic and membrane positive focal areas are detected, particularly in colorectal cancer 78 5T4 and Wnt signaling.…”