New insights into the formation and the function of lamellipodia and ruffles in mesenchymal cell migration

ABSTRACT

Lamellipodia and ruffles are veil-shaped cell protrusions composed of a highly branched actin filament meshwork assembled by the Arp2/3 complex. These structures not only hallmark the leading edge of cells adopting the adhesion-based mesenchymal mode of migration but are also thought to drive cell movement.

Although regarded as textbook knowledge, the mechanism of formation of lamellipodia and ruffles has been revisited in the last years leveraging new technologies. Furthermore, recent observations have also challenged our current view of the function of lamellipodia and ruffles in mesenchymal cell migration.

Here, I review this literature and compare it with older studies to highlight the controversies and the outstanding open issues in the field. Moreover, I outline simple and plausible explanations to reconcile conflicting results and conclusions. Finally, I integrate the mechanisms regulating actin-based protrusion in a unifying model that accounts for random and ballistic mesenchymal cell migration.     

Differential roles of WAVE1 and WAVE2 in dorsal and peripheral ruffle formation for fibroblast cell migration

Cell migration is driven by actin polymerization at the leading edge of lamellipodia, where WASP family verprolin-homologous proteins (WAVEs) activate Arp2/3 complex. When fibroblasts are stimulated with PDGF, formation of peripheral ruffles precedes that of dorsal ruffles in lamellipodia. Here, we show that WAVE2 deficiency impairs peripheral ruffle formation and WAVE1 deficiency impairs dorsal ruffle formation. During directed cell migration in the absence of extracellular matrix (ECM), cells migrate with peripheral ruffles at the leading edge and WAVE2, but not WAVE1, is essential. In contrast, both WAVE1 and WAVE2 are essential for invading migration into ECM, suggesting that the leading edge in ECM has characteristics of both ruffles. WAVE1 is colocalized with ECM-degrading enzyme MMP-2 in dorsal ruffles, and WAVE1-, but not WAVE2-, dependent migration requires MMP activity. Thus, WAVE2 is essential for leading edge extension for directed migration in general and WAVE1 is essential in MMP-dependent migration in ECM.     

Quantifying lamella dynamics of cultured cells by SACED, a new computer-assisted motion analysis.

Formation of lamellipodia and the retraction of ruffles are essential activities during motility and migration of eukaryotic cells. We have developed a computer-assisted stroboscopic method for the continuous observation of cell dynamics (stroboscopic analysis of cell dynamics, SACED) that allows one to analyze changes in lamellipodia protrusion and ruffle retraction with high resolution in space and time. To demonstrate the potential of this method we analyzed keratinocytes in culture, unstimulated or stimulated with epidermal growth factor (EGF), which is known to induce cell motility and migration. Keratinocytes stimulated with EGF exhibited a 2.6-fold increase in their migration velocity, which coincided with enhanced ruffle retraction velocity (144%) and increased ruffle frequency (135%) compared to control cells. We also recorded an enhanced frequency of lamellipodia (135%), whereas the velocity of lamellipodia protrusion remained unchanged. These results on ruffle and lamellipodia dynamics in epidermal cells show that SACED is at least equal to established methods in terms of accuracy. SACED is, however, advantageous concerning resolution in time and therefore allows one to analyze the activity of lamellipodia and ruffles in as yet unknown detail. Moreover, SACED offers two opportunities that render this technique superior to established methods: First, several parameters relevant to cell motility can be analyzed simultaneously. Second, a large number of cells can conveniently be examined, which facilitates the compilation of statistically significant data.     

Paxillin mediates sensing of physical cues and regulates directional cell motility by controlling lamellipodia positioning

Physical interactions between cells and the extracellular matrix (ECM) guide directional migration by spatially controlling where cells form focal adhesions (FAs), which in turn regulate the extension of motile processes. Here we show that physical control of directional migration requires the FA scaffold protein paxillin. Using single-cell sized ECM islands to constrain cell shape, we found that fibroblasts cultured on square islands preferentially activated Rac and extended lamellipodia from corner, rather than side regions after 30 min stimulation with PDGF, but that cells lacking paxillin failed to restrict Rac activity to corners and formed small lamellipodia along their entire peripheries. This spatial preference was preceded by non-spatially constrained formation of both dorsal and lateral membrane ruffles from 5-10 min. Expression of paxillin N-terminal (paxN) or C-terminal (paxC) truncation mutants produced opposite, but complementary, effects on lamellipodia formation. Surprisingly, pax-/- and paxN cells also formed more circular dorsal ruffles (CDRs) than pax+ cells, while paxC cells formed fewer CDRs and extended larger lamellipodia even in the absence of PDGF. In a two-dimensional (2D) wound assay, pax-/- cells migrated at similar speeds to controls but lost directional persistence. Directional motility was rescued by expressing full-length paxillin or the N-terminus alone, but paxN cells migrated more slowly. In contrast, pax-/- and paxN cells exhibited increased migration in a three-dimensional (3D) invasion assay, with paxN cells invading Matrigel even in the absence of PDGF. These studies indicate that paxillin integrates physical and chemical motility signals by spatially constraining where cells will form motile processes, and thereby regulates directional migration both in 2D and 3D. These findings also suggest that CDRs may correspond to invasive protrusions that drive cell migration through 3D extracellular matrices.     

Modulation of Rac localization and function by dynamin

The GTPase dynamin controls a variety of endocytic pathways, participates in the formation of phagosomes, podosomal adhesions, and invadopodia, and in regulation of the cytoskeleton and apoptosis. Rac, a member of the Rho family of small GTPases, controls formation of lamellipodia and focal complexes, which are critical in cell migration and phagocytosis. We now show that disruption of dynamin(-2) function alters Rac localization and inhibits cell spreading and lamellipodia formation even though Rac is activated. Dominant-negative K44A dynamin(-2) inhibited cell spreading and lamellipodia formation on fibronectin without blocking cell adhesion; dynamin(-2) depletion by specific small interfering RNA inhibited lamellipodia in a similar manner. Dyn2(K44A) induced Rac mislocalization away from cell edges, into abnormal dorsal ruffles, and led to increased total Rac activity. Fluorescence resonance energy transfer imaging of Rac activity confirmed its predominant localization to aberrant dorsal ruffles in the presence of dominant-negative dyn2(K44A). Dyn2(K44A) induced the accumulation of tubulated structures bearing membrane-bound Rac-GFP. Constitutively active but not wild-type GFP-Rac was found on macropinosomes and Rac-dependent, platelet-derived growth factor-induced macropinocytosis was abolished by Dyn2(K44A) expression. These data suggest an indispensable role of dynamin in Rac trafficking to allow for lamellipodia formation and cell spreading.     

Effects of bacterial physiological states and bacterial species on host–microbe interactions

Abstract

This study investigated how the physiological states of Aggregatibacter actinomycetemcomitans (Aa) and Streptococcus mitis affect their intracellular invasion capabilities and the resulting host cell responses. The physiological states included two forms of planktonic states, floating or sedimented (by centrifugation) and the biofilm state (with centrifugation). Confluent epithelial Ca9-22 cells were challenged with floating or sedimented planktonic cultures, or with 24-h biofilms for 3?h. The results show that intracellular invasion efficiencies were clearly affected by the bacterial physiological states. For both bacterial species, the sedimented-cells displayed 2–10 times higher invasion efficiency than the floating-cells (p?<?0.05). The invasion efficiency of Aa biofilms was three fold lower than sedimented cells, whereas those of S. mitis biofilms were similar to sedimented cells. Unlike invasion, the metabolic activities of Ca9-22 were unaffected by different bacterial physiological states. However, Aa biofilms induced higher IL-1β expression than planktonic cultures. In conclusion, different bacterial physiological states can affect the outcomes of (in vitro) host–microbe interaction in different ways.     

Membrane ruffles in cell migration: indicators of inefficient lamellipodia adhesion and compartments of actin filament reorganization

During epithelial cell migration, membrane ruffles can be visualized by phase contrast microscopy as dark waves arising at the leading edge of lamellipodia that move centripetally toward the main cell body. Despite the common use of the term membrane ruffles, their structure, molecular composition, and the mechanisms leading to their formation remained largely unknown. We show here that membrane ruffles differ from the underlying cell lamella by more densely packed bundles of actin filaments that are enriched in the actin cross-linkers filamin and ezrin, pointing to a specific bundling process based on these cross-linkers. The accumulation of phosphorylated, that is, inactivated, cofilin in membrane ruffles suggests that they are compartments of inhibited actin filament turnover. High Rac1 and low RhoA activities were found under conditions of suboptimal integrin-ligand interaction correlating with low lamellipodia persistence, inefficient migration, and high ruffling rates. Based on these findings, we define membrane ruffles as distinct compartments of specific composition that form as a consequence of inefficient lamellipodia adhesion.     

14-3-3beta-Rac1-p21 activated kinase signaling regulates Akt1-mediated cytoskeletal organization, lamellipodia formation and fibronectin matrix assembly

Akt1 belongs to the three-gene Akt family and functions as a serine-threonine kinase regulating phosphorylation of an array of substrates and mediating cellular processes such as cell migration, proliferation, survival, and cell cycle. Our previous studies have established the importance of Akt1 in angiogenesis and absence of Akt1 resulted in impaired integrin activation, adhesion, migration, and extracellular matrix assembly by endothelial cells and fibroblasts. In this study, we identify the downstream signaling pathways activated by Akt1 in the regulation of these cellular events. We demonstrate here that Akt1 is necessary for the growth factor stimulated activation of 14-3-3beta-Rac1-p21 activated kinase (Pak) pathway in endothelial cells and fibroblasts. While activation of Akt1 resulted in translocation of Rac1 to membrane ruffles, enhanced Rac1 activity, Pak1 phosphorylation, and lamellipodia formation, resulting in enhanced adhesion and assembly of fibronectin, inhibition of Akt1 resulted in inhibition of these processes due to impaired Rac1-Pak signaling. Formation of lamellipodia, adhesion, and fibronectin assembly by myristoylated Akt1 expression in NIH 3T3 fibroblasts was inhibited by co-expression with either dominant negative Rac1 or dominant negative Pak1. In contrast, impaired lamellipodia formation, adhesion, and fibronectin assembly by dominant negative-Akt1 expression was rescued by co-expression with either constitutively active-Rac1 or -Pak1. Moreover, previously reported defects in adhesion and extracellular matrix assembly by Akt1(-/-) fibroblasts could be rescued by expression with either active-Rac1 or -Pak1, implying the importance of Rac1-Pak signaling in growth factor stimulated cytoskeletal assembly, lamellipodia formation and cell migration in endothelial cells and fibroblasts downstream of Akt1 activation.     

Regulation of Macrophage Motility by the Water Channel Aquaporin-1: Crucial Role of M0/M2 Phenotype Switch

The water channel aquaporin-1 (AQP1) promotes migration of many cell types. Although AQP1 is expressed in macrophages, its potential role in macrophage motility, particularly in relation with phenotype polarization, remains unknown. We here addressed these issues in peritoneal macrophages isolated from AQP1-deficient mice, either undifferentiated (M0) or stimulated with LPS to orientate towards pro-inflammatory phenotype (classical macrophage activation; M1). In non-stimulated macrophages, ablation of AQP1 (like inhibition by HgCl₂) increased by 2–3 fold spontaneous migration in a Src/PI3K/Rac-dependent manner. This correlated with cell elongation and formation of lamellipodia/ruffles, resulting in membrane lipid and F4/80 recruitment to the leading edge. This indicated that AQP1 normally suppresses migration of resting macrophages, as opposed to other cell types. Resting Aqp1^-/- macrophages exhibited CD206 redistribution into ruffles and increased arginase activity like IL4/IL13 (alternative macrophage activation; M2), indicating a M0-M2 shift. In contrast, upon M1 orientation by LPS in vitro or peritoneal inflammation in vivo, migration of Aqp1^-/- macrophages was reduced. Taken together, these data indicate that AQP1 oppositely regulates macrophage migration, depending on stimulation or not by LPS, and that macrophage phenotypic and migratory changes may be regulated independently of external cues.     

Chlamydia trachomatis and Chlamydophila abortus induce the expression of secretory leukocyte protease inhibitor in cells of the human female reproductive tract

C. trachomatis and C. abortus are related Gram‐negative intracellular bacteria that cause reproductive failure due to infertility (C. trachomatis) or abortion (C. abortus). These organisms target epithelial cells in the reproductive tract and/or placenta, but the innate immune mechanisms that lead to protection or pathology and disease are poorly understood. SLPI is an innate immune molecule which protects mucosal surfaces from infection and injury. C. trachomatis and C. abortus were found to induce SLPI mRNA and peptide expression in HeLa (cervical epithelium) and JEG‐3 cells (trophoblast) respectively. Both cell lines constitutively expressed SLPI and, although infection enhanced this expression, killed organisms did not. These data demonstrate that Chlamydia/Chlamydophila grow in cells that express SLPI, suggesting that SLPI does not exert antimicrobial effects against these organisms. However, SLPI has multiple functions, and we speculate that it may play a role in controlling tissue inflammation and pathology.     

Synthesis of some acrylophenones with N-methylpiperazine and evaluation of their cytotoxicities

In this study, the compounds having acrylophenone structure, 1-aryl-2-(N-methylpiperazinomethyl)-2-propen-1-one dihydrochlorides, were synthesized and their chemical structures were identified with ¹H NMR, ¹³C NMR and HRMS spectra. The cytotoxicities of the compounds were tested towards Ca9-22 (human gingival carcinoma), HSC-2 (human oral squamous carcinoma), HSC-3 (human oral squamous carcinoma) and HSC-4 (human oral squamous carcinoma) cell lines as tumor cell lines and HGF (gingival fibroblasts), HPLF (periodontal ligament fibroblasts) and HPC (pulp cells) cell lines as non-tumor cell lines. PSE of the compound TA2, which has a methyl substituent on phenyl ring, pointed out the compound TA2 as a leader compound to be considered.     

Filamin A links sphingosine kinase 1 and sphingosine-1-phosphate receptor 1 at lamellipodia to orchestrate cell migration

Sphingosine kinase 1 (SphK1) catalyzes the phosphorylation of sphingosine to produce the potent lipid mediator sphingosine-1-phosphate (S1P), which plays a critical role in cell motility via its cell surface receptors. Here, we have identified filamin A (FLNa), an actin-cross-linking protein involved in cell movement, as a bona fide SphK1-interacting protein. Heregulin stimulated SphK1 activity only in FLNa-expressing A7 melanoma cells but not in FLNa-deficient cells and induced its translocation and colocalization with FLNa at lamellipodia. SphK1 was required for heregulin-induced migration, lamellipodia formation, activation of PAK1, and subsequent FLNa phosphorylation. S1P directly stimulated PAK1 kinase, suggesting that it may be a target of intracellularly generated S1P. Heregulin also induced colocalization of S1P₁ (promotility S1P receptor) but not S1P₂, with SphK1 and FLNa at membrane ruffles. Moreover, an S1P₁ antagonist inhibited the lamellipodia formation induced by heregulin. Hence, FLNa links SphK1 and S1P₁ to locally influence the dynamics of actin cytoskeletal structures by orchestrating the concerted actions of the triumvirate of SphK1, FLNa, and PAK1, each of which requires and/or regulates the actions of the others, at lamellipodia to promote cell movement.     

Involvement of microtubule-associated protein 2 (MAP2) in oral cancer cell motility: a novel biological function of MAP2 in non-neuronal cells

Microtubule-associated protein 2 (MAP2) has been better known for its well-defined role primarily in neurite outgrowth during neuronal development. However, the biological functions of MAP2 in non-neuronal cells, such as epithelial cells, remain largely unknown. In the present study, we sought to investigate the cellular functions of MAP2 by separately establishing stable expression of two MAP2 isoforms, MAP2A and MAP2C, in oral squamous cell carcinoma, Ca9-22. Ectopic expression of MAP2A or MAP2C results in microtubule bundling predominantly at the cell periphery. Remarkably, overexpression of MAP2A but not MAP2C significantly promotes migration of Ca9-22 cells, whereas knockdown of MAP2A expression by specific siRNA oligos dramatically decreases cell migration of HaCaT, an immortalized keratinocyte cell line with abundant endogenous MAP2A. Furthermore, by immunohistochemical studies, MAP2A was shown to highly and selectively express in invasive oral cancer tissues, consistent with its motility-promoting cellular function revealed through in vitro assays. Thus, our findings have not only identified a novel role of MAP2 in non-neuronal cells, but also provided the first implication of MAP2 in malignant oral cancer tissues.     

VEGFR-2 inhibitors and apoptosis inducers: synthesis and molecular design of new benzo[g]quinazolin bearing benzenesulfonamide moiety

Two series of novel 4-(2-(2-(2-(substituted) hydrazinyl)-2-oxoethylthio)-4-oxobenzo[g]quinazolin-3(4H)-yl) benzenesulfonamide 5–17 and 4-(2-(2-(substituted-1H-pyrazol-1-yl)-2-oxoethylthio)-4-oxobenzo[g]quinazolin-3(4H)-yl) benzenesulfonamide 18–24 were synthesised from the starting material 4-(2-(2-hydrazinyl-2-oxoethylthio)-4-oxobenzo[g]quinazolin-3(4H)-yl) benzenesulfonamide 5, to be evaluated for their inhibitory activity towards VEGFR-2. The target compounds 5–24, were screened for their cytotoxic activity against MCF-7 breast cancer cell line and the percentage inhibition against VEGFR-2. Compounds 9, 20, 22 and 23, showed excellent VEGFR-2 inhibitory activity with IC₅₀ ranging from 0.64 to 1.04?µm. Being the most potent, compound 9 was evaluated for its apoptotic inducer effect by studying the effect on caspase-3, it was found to increase its level. Compound 9 boosted the level of Bax and reduced the level of BCl2, compared to the control. Cell cycle analysis was conducted, compound 9 showed cell cycle arrest at G2/M phase. Moreover, mild cytotoxic effect (IC₅₀?=?29.41?µm, respectively) in normal breast cells MCF-12?A, was observed when treated with the same compound. Finally, a molecular docking study was performed to investigate the possible binding interaction inside the active site of the VEGFR-2 enzyme.     

Pointed-end capping by tropomodulin3 negatively regulates endothelial cell motility

Actin filament pointed-end dynamics are thought to play a critical role in cell motility, yet regulation of this process remains poorly understood. We describe here a previously uncharacterized tropomodulin (Tmod) isoform, Tmod3, which is widely expressed in human tissues and is present in human microvascular endothelial cells (HMEC-1). Tmod3 is present in sufficient quantity to cap pointed ends of actin filaments, localizes to actin filament structures in HMEC-1 cells, and appears enriched in leading edge ruffles and lamellipodia. Transient overexpression of GFP-Tmod3 leads to a depolarized cell morphology and decreased cell motility. A fivefold increase in Tmod3 results in an equivalent decrease in free pointed ends in the cells. Unexpectedly, a decrease in the relative amounts of F-actin, free barbed ends, and actin-related protein 2/3 (Arp2/3) complex in lamellipodia are also observed. Conversely, decreased expression of Tmod3 by RNA interference leads to faster average cell migration, along with increases in free pointed and barbed ends in lamellipodial actin filaments. These data collectively demonstrate that capping of actin filament pointed ends by Tmod3 inhibits cell migration and reveal a novel control mechanism for regulation of actin filaments in lamellipodia.     

Electrolytically generated acid functional water inhibits NF-κB activity by attenuating nuclear-cytoplasmic shuttling of p65 and p50 subunits

Background: Human β-defensin 2 (hBD2) gene expression is dependent on nuclear factor kappa B (NF-κB) activity. We have previously demonstrated that electrolytically generated acid functional water (FW) induces the expression of hBD2 in the human oral squamous cell carcinoma (OSCC) cell line Ca9-22. However, the induction was not dependent on NF-κB activity; in fact, FW inhibited NF-κB activity. Therefore, we hypothesized that FW might reduce spontaneous interleukin 8 (IL-8) secretion by Ca9-22 cells, which is heavily dependent on NF-κB activity. This study aimed at demonstrating the inhibitory effect of FW on NF-κB activity. Methods: Ca9-22 cells were incubated with FW, and spontaneous IL-8 secretion was observed by enzyme-linked immunosorbent assay. Luciferase assay was performed using the 5′-untranslated region of the IL-8 gene. The steps of NF-κB activation blocked by FW were evaluated by localization of the NF-κB subunits p65 and p50 by immunofluorescence staining. Western blotting was further performed to confirm the changes in NF-κB subunit localization. Results: The Ca9-22 cells spontaneously secreted IL-8, which was rapidly and drastically inhibited by FW treatment. The luciferase assay demonstrated the inhibitory action of FW, which was diminished by deletion of the NF-κB binding site from this construct. FW treatment altered the distribution of both the p65 and p50 subunits. P65, which was localized in the nucleus during the resting state, moved to the cytoplasm after FW treatment, whereas, p50, localized in the cytoplasm during the resting state, moved to the nucleus subsequent to FW treatment. Conclusions: The results from this study indicate that FW might inhibit spontaneous IL-8 secretion by redistribution of the NF-κB subunits within the cells.     

shRNA抑制活化诱导的胞苷脱氨酶（AID）对前列腺癌细胞C4-2表型的影响

目的:探讨AID在前列腺癌中的表达情况,AID对前列腺癌细胞C4-2的侵袭、迁移、增殖以及凋亡方面的影响。方法:应用靶向敲减AID的慢病毒对前列腺癌细胞C4-2进行干扰,运用Western-blot、免疫组化、平板克隆形成、流式、Transwell实验对前列腺癌组织和前列腺癌细胞C4-2表型的变化情况进行研究。结果:临床前列腺癌样本中AID高表达,良性前列腺增生组织中AID低表达,正常前列腺组织不表达(*P0.05);shRNA干扰以后的shAICDA-C4-2单克隆细胞株中AID的表达量显著降低,其增殖、迁移和侵袭能力阳性对照组(Monoclonal6)与阴性对照组(NC)相比分别降低49%、80%、63%,凋亡率阳性对照组(Monoclonal6)为阴性对照组(NC)的3.2倍。结论:前列腺癌组织中AID高表达,AID在促进前列腺癌细胞的增殖、迁移、侵袭,抑制前列腺自细胞的凋亡中具有极其重要的作用。AID表达极可能与前列腺癌的进展、预后明显相关。     

Differential susceptibility to hydrogen sulfide-induced apoptosis between PHLDA1-overexpressing oral cancer cell lines and oral keratinocytes: Role of PHLDA1 as an apoptosis suppressor

Hydrogen sulfide (H₂S) is a novel gasotransmitter that plays multiple biological roles in various body systems. In addition to its endogenous production, H₂S is produced by bacteria colonizing digestive organs, including the oral cavity. H₂S was previously shown to enhance pro-apoptotic effects in cancer cell lines, although the mechanisms involved remain unclear. To properly assess the anti-cancer effects of H₂S, however, investigations of apoptotic effects in normal cells are also necessary. The aims of this study were (1) to compare the susceptibility to H₂S-induced apoptosis between the oral cancer cell line Ca9-22 and oral keratinocytes that were derived from healthy gingiva, and (2) to identify candidate genes involved in the induction of apoptosis by H₂S. The susceptibility to H₂S-induced apoptosis in Ca9-22 cells was significantly higher than that in keratinocytes. H₂S exposure in Ca9-22 cells, but not keratinocytes, enhanced the expression of pleckstrin homology-like domain, family A, member 1 (PHLDA1), which was identified through a differential display method. In addition, PHLDA1 expression increased during actinomycin D-induced apoptosis in Ca9-22 cells. Knockdown of PHLDA1 expression by small interfering RNA in Ca9-22 cells led to expression of active caspase 3, thus indicating apoptosis induction. The tongue cancer cell line SCC-25, which expresses PHLDA1 at a high level, showed similar effects. Our data indicate that H₂S is an anti-cancer compound that may contribute to the low incidence of oral cancer. Furthermore, we demonstrated the role of PHLDA1 as an apoptosis suppressor.     

Apo-10’-lycopenoic acid inhibits cancer cell migration and angiogenesis and induces peroxisome proliferator-activated receptor γ

ScopeWe have previously shown that apo-10’-lycopenoic acid (ALA), a derivative of lycopene through cleavage by carotene-9’,10’-oxygenase, inhibits tumor progression and metastasis in both liver and lung cancer animal models. The underlying mechanism remains unknown. We hypothesized that ALA inhibits cancer cell motility and angiogenesis by up-regulating peroxisome proliferator-activated receptor γ (PPARγ) which is involved in controlling angiogenesis, tumor progression and metastasis.Methods and resultsALA treatment, in dose-dependent manner, was effective at inhibiting migration and invasion of liver and lung cancer cells (HuH7 and A549) in both Transwell and wound-healing models, as well as suppressing actin remodeling and ruffling/lamellipodia formation in HuH7 and immortalized lung BEAS-2B cells. ALA treatment resulted in suppression of angiogenesis in both tube formation and aortic ring assays and inhibition of matrix metalloproteinase-2 expression and activation in both HuH7 and A549 cells. Additionally, ALA dose-dependently increased the mRNA expression and protein levels of PPARγ in human THLE-2 liver cells.ConclusionALA inhibits cancer cell motility and angiogenesis and induces PPARγ expression, which could be one of the potential mechanisms for ALA protecting against tumor progression.