Identifying the structure-activity relationship of leelamine necessary for inhibiting intracellular cholesterol transport

Abstract

Leelamine is an anticancer chemotherapeutic agent inhibiting intracellular cholesterol transport. Cell death mediated by leelamine occurs due to the lysosomotropic property of the compound, its accumulation in the lysosome, and inhibition of cholesterol transport leading to lack of availability for key processes required for functioning of cancer cells. The present study dissects the structure-activity-relationship of leelamine using synthesized derivatives of leelamine and abietic acid, a structurally similar compound, to identify the moiety responsible for anti-cancer activity. Similar to leelamine, all active derivatives had an amino group or a similar moiety that confers a lysosomotropic property to the compound enabling its accumulation in the lysosome. Active derivatives inhibited intracellular cholesterol transport and hindered xenografted melanoma tumor development without obvious systemic toxicity. In silico studies suggested that active derivatives accumulating in lysosomes bound to NPC1, a protein responsible for cholesterol export from the lysosome, to inhibit its activity that then caused accumulation, and lack of cholesterol availability for other key cellular activities. Thus, active derivatives of leelamine or abietic acid maintained lysosomotropic properties, bound to NPC1, and disrupted cellular cholesterol transport as well as availability to retard tumor development.

Targeting cholesterol transport in circulating melanoma cells to inhibit metastasis

“…Nanolipolee‐007 significantly induced intracellular cholesterol levels in both circulating and adherent C8161.Cl9‐vGFP (Figure c) and UACC 903M‐GFP (Figure d) cell lines compared to controls, while cotreatment with β‐cyclodextrin reversed the effect. This result suggested that cholesterol transport was inhibited in CTCs following Nanolipolee‐007 treatment and that it could be reversed using β‐cyclodextrin as reported in the literature (Gowda et al., ; Kuzu et al., , , ).…”

“…β‐Cyclodextrin was premixed with melanoma cells to counteract Nanolipolee‐007, thereby demonstrating the involvement of cholesterol transport inhibition in mediating this process. Thus, leelamine killed circulating melanoma cells through a process that could be reversed using β‐cyclodextrin, which based on the literature, could be due to inhibition of cholesterol transport (Gowda et al., ; Kuzu, Toprak, Noory, & Robertson, ; Kuzu et al., , ).…”

“…Inhibition of cholesterol transport makes cholesterol unavailable to cancer cells causing shut down of cellular signaling pathways on which the cancer cell is reliant for cell survival (Gowda et al., ; Kuzu et al., , , ). Two major signaling cascades promoting melanoma development, AKT and STAT3, were inhibited by leelamine in adherent UACC 903 cells after 3–24 hr of treatment (Gowda, Madhunapantula, Kuzu, et al., ; Gowda, Madhunapantula, Sharma, et al., ; Kuzu et al., ).…”

“…Cell death mediated by leelamine was associated with disruption of intracellular cholesterol transport caused by accumulation in the lysosome and disrupting cholesterol transport out of the lysosome by NPC1 (Gowda et al., ; Kuzu et al., ). Lack of available cholesterol then disrupts important cellular process needed for cell survival (Gowda, Madhunapantula, Kuzu, et al., ; Gowda, Madhunapantula, Sharma, et al., ; Kuzu et al., ).…”

Assessing human B cell repertoire diversity and convergence

“…Often, structure modeling tools are also used to design antibodies that target a specific epitope or to improve antigen binding of known antibodies . Moreover, several studies combined computational structure modeling and crystallographic approaches . Over the last years, antibody structure modeling has been developed to a level where it can also be used to gain information on antibody‐antigen interactions.…”