Panoply™ Human APLNR Over-expressing Stable Cell Line

Apelin is a known mediator of survival and mitogenic signaling through the apelin receptor (Aplnr) and has been implicated in various cancers. However, less is known about Elabela (ELA/APELA) signaling, also mediated by Aplnr, and its role, as well as the conversion of its precursor, proELA, to mature ELA, in cancer remains unclear. Here, researchers identified mTORC1 signaling as a key mediator of ELA, which inhibits the growth, migration, and survival of renal tumor cells. Furthermore, sunitinib and ELA exhibited synergistic effects in inhibiting tumor growth and angiogenesis in mice. Site-directed mutagenesis and pharmacological experiments provided evidence that altering the proELA cleavage site by furin induces enhanced ELA antitumor activity. Aplnr is expressed in various renal cell types, whereas ELA is typically expressed by epithelial cells. Together, these results reveal a tumor-suppressive role for ELA-mediated mTORC1 signaling and establish the potential use of ELA or its derivatives in the treatment of renal cancer.

To confirm the autocrine effects of ELA on cell proliferation, the researchers generated HEK293 cells stably overexpressing APLNR (HEK-APLNR). Stable expression of ELA or mutant ELA in APLNR-overexpressing HEK293 cells inhibited their confluence compared to controls (Figure 1D). Mice were then subcutaneously inoculated with control cells and the same cells stably expressing ELA. As shown in Figure 1E, expression of ELA in Renca cells reduced their ability to induce tumor growth. Injection of Renca cells into the subcapsular space of mouse kidneys resulted in reduced tumor growth in mice bearing ELA tumors. Similarly, using the human renal cancer cell line ACHN as a second model, the researchers found that stably expressing mutated ELA in ACHN cells using a lentiviral vector inhibited their ability to mediate tumor growth in nude mice (Figure 1F). Next, they assessed cell migration in a wound healing assay and observed that Renca and APLNR-overexpressing HEK293 control cells healed wounds within 24 hours, while cells expressing ELA and mut ELA showed inefficient wound healing over the same timeframe (Figure 1G and H). Furthermore, cells stably expressing ELA or mut ELA exhibited elevated levels of apoptosis compared to controls (Figure 1I and J). Further experiments demonstrated that expression of ELA and mut ELA in Renca cells increased levels of cleaved caspase-3 and PARP (Figure 1K), suggesting that these apoptotic molecules are involved in ELA- and mut ELA-induced cell death.

Figure 1. Repression of the malignant phenotype and increased activation of mTORC1 signaling by ELA. (Soulet F, et al., 2020)