Panoply™ Human AKT2 Knockdown Stable Cell Line

Despite recent therapeutic advances, melanoma remains the deadliest form of skin cancer due to its highly metastatic nature. Melanomas harboring the oncogenic BRAF V600E mutation and PTEN loss exhibit unrestrained PI3K/AKT signaling and enhanced aggressiveness. However, the specific roles of distinct AKT isoforms in melanoma initiation, progression, and metastasis have not been fully elucidated, and it remains unclear whether these isoforms perform unique functions or exhibit functional redundancy during these stages. Here, researchers utilized a novel mouse model enabling isoform-specific AKT deletion to investigate the impact of individual AKT isoforms on melanoma initiation; simultaneously, they examined tumor progression, maintenance, and metastasis through isoform-specific knockdown experiments in a panel of human metastatic melanoma cell lines. The results demonstrate that while AKT2 is dispensable for primary tumor formation, it promotes cell migration and invasion in vitro as well as metastatic lesion formation in vivo; in contrast, AKT1 is critical for melanoma initiation and cell proliferation. The researchers proposed a mechanism wherein AKT2 inhibition in PTEN-deficient, BRAF-mutant human melanoma cells impedes glycolysis and downregulates gene expression signatures associated with epithelial-mesenchymal transition (EMT), thereby limiting metastatic spread. These findings suggest that therapies specifically targeting AKT2 and AKT1 could serve as novel treatment strategies for patients with melanoma at different stages of the disease.

Anchorage-independent growth is essential for the proliferation of metastatic cells; therefore, researchers investigated the role of AKT2 in this process. The results showed that AKT2 knockdown reduced the number of WM1799 cell colonies (Figure 1A, B), while colony size showed only a slight trend toward reduction (Figure 1C), indicating that AKT2 knockdown limits the cells' ability to grow in a three-dimensional culture environment. Subsequently, the researchers evaluated the effect of AKT2 knockdown on subcutaneous tumor growth in vivo, as the early stages of tumorigenesis also rely on anchorage-independent growth. They subcutaneously injected AKT2-knockdown WM1799 cells into immunodeficient NOD/SCID mice (to eliminate the influence of adaptive immune responses on melanoma cell growth); once palpable tumors formed, a subset of the mice was switched to a doxycycline-containing diet (Figure 1D). Compared with control mice fed a standard diet, AKT2 knockdown significantly slowed tumor growth (Figure 1E); however, despite sustained AKT2 knockdown in most tumors (Figure 1F), tumors eventually grew in both groups of mice. Furthermore, the researchers observed no change in total AKT phosphorylation levels in AKT2-knockdown tumors, suggesting that AKT1 or AKT3 activity might exert a compensatory effect over time, thereby promoting tumor growth.

Figure 1. AKT2 depletion restricts anchorage-independent growth. (McRee S K, et al., 2023)