In Search of Effective Anticancer Agents-Novel Sugar Esters Based on Polyhydroxyalkanoate Monomers

Abstract

Cancer is one of the deadliest illness globally. Searching for new solutions in cancer treatments is essential because commonly used mixed, targeted and personalized therapies are sometimes not sufficient or are too expensive for common patients. Sugar fatty acid esters (SFAEs) are already well-known as promising candidates for an alternative medical tool. The manuscript brings the reader closer to methods of obtaining various SFAEs using combined biological, chemical and enzymatic methods. It presents how modification of SFAE's hydrophobic chains can influence their cytotoxicity against human skin melanoma and prostate cancer cell lines. The compound's cytotoxicity was determined by an MTT assay, which followed an assessment of SFAEs' potential metastatic properties in concentrations below IC₅₀ values. Despite relatively high IC₅₀ values (63.3-1737.6 μM) of the newly synthesized SFAE, they can compete with other sugar esters already described in the literature. The chosen bioactives caused low polymerization of microtubules and the depolymerization of actin filaments in nontoxic levels, which suggest an apoptotic rather than metastatic process. Altogether, cancer cells showed no propensity for metastasis after treating them with SFAE. They confirmed that lactose-based compounds seem the most promising surfactants among tested sugar esters. This manuscript creates a benchmark for creation of novel anticancer agents based on 3-hydroxylated fatty acids of bacterial origin.

Keywords: anticancer agents; chemical modifications; fluorination; melanoma; polyhydroxyalkanoates; prostate cancer; sugar esters.

Figure 1

Scheme of sugar fatty acid esters enzymatic synthesis with glucose as an example. The remaining sugar-based SFAEs (galactose and lactose) and all structures of the obtained compounds are presented in Supplementary Figure S1. Where: R₁: -OH group or nonanoic acid—structure shown in blue rectangle; R₂: modified or not modified (mPHN or F-mPHN) PHN monomeric residues—their structures are shown in red rectangle; R₃: -OH group or one of residues which structures are shown in red rectangle.

Figure 2

Changes in cytoskeleton of cancer cells visualized with confocal microscopy. Microtubular network—green channel (488 nm); Actin-cytokinoskeleton—red channel (546 nm); intermediate filaments (vimentin)—white channel (excitation—far red 647 nm). Brighter areas (greater density) that can be observed in green channels indicate greater polymerization of microtubules. An increased presence of biodiverse pickling inside the cytoplasm can be seen in red channels suggests an elevated content of depolymerized actin: (a) DU145 after 48 h of incubation; (b) High resolution images of DU145 after 48 h of incubation; (c) High resolution images of HTB140 after 48 h of incubation.

Figure 2

Changes in cytoskeleton of cancer cells visualized with confocal microscopy. Microtubular network—green channel (488 nm); Actin-cytokinoskeleton—red channel (546 nm); intermediate filaments (vimentin)—white channel (excitation—far red 647 nm). Brighter areas (greater density) that can be observed in green channels indicate greater polymerization of microtubules. An increased presence of biodiverse pickling inside the cytoplasm can be seen in red channels suggests an elevated content of depolymerized actin: (a) DU145 after 48 h of incubation; (b) High resolution images of DU145 after 48 h of incubation; (c) High resolution images of HTB140 after 48 h of incubation.

Figure 2

Changes in cytoskeleton of cancer cells visualized with confocal microscopy. Microtubular network—green channel (488 nm); Actin-cytokinoskeleton—red channel (546 nm); intermediate filaments (vimentin)—white channel (excitation—far red 647 nm). Brighter areas (greater density) that can be observed in green channels indicate greater polymerization of microtubules. An increased presence of biodiverse pickling inside the cytoplasm can be seen in red channels suggests an elevated content of depolymerized actin: (a) DU145 after 48 h of incubation; (b) High resolution images of DU145 after 48 h of incubation; (c) High resolution images of HTB140 after 48 h of incubation.

Figure 3

Changes of nuclei roundness based on image analysis algorithms. These small changes may indicate some reorganizations of cytoskeleton but are not typical for metastatic transition: (a) DU145; (b) HTB140.

Figure 4

Number of adhesion points formed by DU145 cells during incubation with the investigated compounds (with concentrations below IC₅₀). Adhesion points defined as dot forms placed in the focal plane located between the cell body and glass surface. Their greater number may suggest intensification of migration process caused by investigated compounds. In case of HTB140 cells, no vimentin analysis was performed due to its almost complete depolymerization which indicates strong impact of SFAE on cytoskeleton.

Figure 5

Transmigration assay of cancer cells in a presence of the investigated SFAE measured after 96 h. An increase in the ratio of proliferated cells after passing through the inserts, caused by the SFAE, may indicate that tested compounds could promote metastasis (at concentrations below the IC₅₀). A decrease in this ratio may indicate lack of such effect. (a) DU145; (b) HTB140.