Panoply™ Human NTSR2 Over-expressing Stable Cell Line

1. cell chronic lymphocytic leukemia (B-CLL) cells are resistant to apoptosis and therefore accumulate in large numbers, impairing normal B-cell function and the patient's immune system. Since current therapies cannot eradicate these apoptosis-resistant cells, there is an urgent need to identify new survival pathways as novel targets for anti-cancer treatment. Overexpression of cell surface G protein-coupled receptors drives cell transformation and thus plays a crucial role in the development and progression of malignant tumors. Here, researchers discovered that neurotensin receptor 2 (NTSR2) is a key driver of apoptosis resistance in B-CLL cells. NTSR2 is highly expressed in B-CLL cells, while its natural ligand, neurotensin (NTS), is expressed at very low levels in both B-CLL cells and patient plasma. Surprisingly, NTSR2 is constitutively activated and phosphorylated, not due to gain-of-function mutations, but rather as a result of its interaction with the oncogenic tyrosine kinase receptor TrkB. Functional and biochemical analyses indicate that the NTSR2-TrkB interaction is a conditional oncogenic driver, requiring the involvement of TrkB's ligand, brain-derived neurotrophic factor (BDNF), which, unlike NTS, is highly expressed in B-CLL cells.

Here, researchers used two human B lymphocyte cell lines, one derived from lymphoma (BL-41) and the other from B-cell chronic lymphocytic leukemia (B-CLL) (MEC-1). Although the endogenous expression of NTSR2 in BL-41 and MEC-1 cells was higher than in normal B cells, it was lower than in B-CLL cells. Therefore, to equalize expression levels between different models, researchers constructed NTSR2-overexpressing BL-41 and MEC-1 cells. The results showed that in NTSR2-overexpressing cells, the phosphorylation levels of several proteins involved in cell survival pathways (including Src, JNK, p38, and Akt) increased 2-3 times (Figure 1a and b). Furthermore, in NTSR2-overexpressing cells, the number of cytoplasmic nucleosomes decreased, reflecting changes in the level of apoptosis (Figure 1c), while the expression of anti-apoptotic proteins Bcl-xL and Bcl-2 increased (Figure 1d and e). Similar results were obtained when the cells were cultured in serum-free medium for 24 hours, ruling out the possibility that NTSR2 was activated by ligands present in calf serum (Figure 1f-i). In summary, these results indicate that NTSR2 overexpression acts as an oncogene by stimulating Src and MAP kinases and upregulating the expression of anti-apoptotic proteins, thereby promoting cell survival and enhancing resistance to apoptosis, respectively.

Figure 1. NTSR2 overexpression induces cell survival signaling pathways. (Abbaci A, et al., 2018)