Rapid activation of FAK/mTOR/p70S6K/PAK1-signaling controls the early testosterone-induced actin reorganization in colon cancer cells

Actin cytoskeleton reorganization initiated by testosterone conjugates through activation of membrane androgen receptors (mAR) has recently been reported in colon tumor cells. This mAR-induced actin reorganization was recognized as a critical initial event, controlling apoptosis and inhibiting cell migration. The present study addressed the molecular signaling regulating the rapid actin remodeling initiated upon testosterone-induced mAR activation in Caco2 colon tumor cells. We report early phosphorylation of the Focal Adhesion Kinase (FAK), followed by substantial early phosphorylation of mammalian target of rapamycin (mTOR), S6 kinase (p70S6K) and the actin regulating p21-activated kinase (PAK1). Pharmacological inhibition of FAK-sensitive phosphatidylinositide-3-kinase (PI-3K), a known element of mAR-signaling, fully abrogated the testosterone-induced actin reorganization and the activation of mTOR, p70S6K and PAK1. Similarly, inhibition of mTOR blocked p70S6K and PAK1 phosphorylation and actin remodeling. Pretreatment of the cells with the intracellular androgen receptor (iAR) antagonist flutamide or silencing iAR through siRNA did not influence mTOR phosphorylation and actin reorganization, indicating specific mAR-induced testosterone effects that are independent of iAR signaling. In conclusion, we demonstrate for the first time a new mAR-governed pathway involving FAK/PI-3K and mTOR/p70S6K/PAK1-cascade that regulates early actin reorganization in colon cancer cells.     

Serum- and glucocorticoid-dependent kinase-1-induced cell migration is dependent on vinculin and regulated by the membrane androgen receptor

The serum- and glucocorticoid-dependent kinases 1-3 (SGK1-3) are downstream effectors of phosphatidylinositol 3-kinases, implicated in various cell responses including colon cancer tumorigenesis in mice. Here, we investigated the role of SGK1 in the regulation of cell motility. Using Caco-2 colon tumor and HEK293 embryonic kidney cells, we report that transfection with the constitutively active SGK1 mutant (SGK1-SD) significantly enhanced cell motility. The cell-adhesion protein vinculin was effectively dephosphorylated in SGK1-SD-transfected cells. Treatment of the cells with phosphatase inhibitors restored vinculin phosphorylation and inhibited cell migration, indicating a significant role for vinculin phosphorylation in SGK1-induced motility. SGK1-SD-enhanced cell motility was inhibited by activation of membrane androgen-binding sites (mAR) via testosterone-conjugates in both cell lines, whereas intracellular androgen receptor (iAR)-silencing and flutamide treatment revealed that these effects were clearly independent of the interaction of SGK1 with the classical androgen receptors (iAR). More importantly, mAR activation restored vinculin phosphorylation in SGK1-SD-transfected cells, whereas silencing of vinculin fully reversed the mAR-induced inhibition of the migratory capacity, implying that this protein is directly involved in cell motility regulation by SGK1 and mAR. This study indicates for the first time that SGK1 regulates cell migration via vinculin dephosphorylation, a mechanism that is controlled by mAR function.     

Activation of FAK/PI3K/Rac1 signaling controls actin reorganization and inhibits cell motility in human cancer cells.

We have recently identified a specific signaling pathway that regulates actin reorganization in malignant human breast and prostate epithelial cells associated with FAK, PI-3K and Rac1 activation. Here we report that this pathway operates in MCF7 cells upon activation of membrane androgen receptors (mAR). Stimulation of mAR by the non-permeable testosterone-BSA conjugate resulted in early actin reorganization documented by quantitative measurements of actin dynamics and morphological analysis of microfilament organization. This effect was regulated by early phosphorylation of FAK and subsequent PI-3K and Rac1 activation. The functional role of this pathway was further shown in A375 melanoma cells. Treatment with the opioid antagonist alpha(s1) casomorphin resulted in rapid and potent actin remodeling in A375 cells, regulated by rapid activation of the FAK/PI-3K/Rac1 signaling. Pretreatment of both cell lines with the specific PI-3K inhibitor wortmannin blocked actin reorganization. Interestingly, wound healing assays revealed that testosterone-BSA and alpha (s1) casomorphin significantly inhibited MCF7 and A375 cell motility respectively. These effects were abrogated through blockade of PI-3K signaling by wortmannin. The results presented here indicate that actin reorganization through FAK/PI3-K/Rac-1 activation operates in various human cancer cell systems supporting a functional role for FAK/PI-3K/Rac1/actin signaling in controlling cell motility.     

Distinct signaling pathways regulate differential opioid effects on actin cytoskeleton in malignant MCF7 and nonmalignant MCF12A human breast epithelial cells

The mechanisms through which opioids regulate the activity of malignant breast epithelial cells are currently unknown. In the present study we report the differential actin cytoskeleton reorganization induced by opioids in malignant (MCF7) and nonmalignant (MCF12A) breast epithelial cells expressing functional opioid receptors. Exposure of MCF7 cells to the opioid agonist alpha(s1) casomorphin induced important actin assembly and reorganization, including the formation of filopodia and lamellipodia. In contrast, incubation of MCF12A cells with alpha(s1) casomorphin revealed a partial but transient disassembly of actin microfilaments. Immunoprecipitation and immunoblot analyses showed rapid phosphorylation of focal adhesion kinase (FAK) and vinculin in opioid-treated MCF7 cells. Moreover, FAK associates with phosphatidylinositol-3 (PI-3 kinase), the latter being subsequently phosphorylated and activated. In addition, a substantial activation of the small GTPase Rac1 was observed. Pretreatment of MCF7 cells with the specific PI-3 kinase inhibitor wortmannin abolished both the activation of Rac1 and actin reorganization, while the opioid-induced phosphorylation of FAK and vinculin remained unaffected. Interestingly, in opioid-treated MCF12A cells this signaling cascade remained inactive, while we identified rapid phosphorylation of actin regulating the protein villin. Finally, opioids differentially inhibited cell motility in each cell line. Our data suggest a distinct, opioid-induced, signaling pathway activated in malignant breast epithelial cells, leading to important actin reorganization. These findings may indicate a potential antineoplastic role of opiates, based on the activation of differential signaling mechanisms.     

PI3K induced actin filament remodeling through Akt and p70S6K1: implication of essential role in cell migration

This study was designed to identify the molecular mechanisms of phosphatidylinositol 3-kinase (PI3K)-induced actin filament remodeling and cell migration. Expression of active forms of PI3K, v-P3k or Myr-P3k, was sufficient to induce actin filament remodeling to lead to an increase in cell migration, as well as the activation of Akt in chicken embryo fibroblast (CEF) cells. Either the inhibition of PI3K activity using a PI3K-specific inhibitor, LY-294002, or the disruption of Akt activity restored the integrity of actin filaments in CEF cells and inhibited PI3K-induced cell migration. We also found that expression of an activated form of Akt (Myr-Akt) was sufficient to remodel actin filaments to lead to an increase in cell migration, which was unable to be inhibited by the presence of LY-294002. Furthermore, we found that p70S6K1 kinase was a downstream molecule that can mediate the effects of both PI3K and Akt on actin filaments and cell migration. Overexpression of an active form of p70S6K1 was sufficient to induce actin filament remodeling and cell migration in CEF cells, which requires Rac activity. These results demonstrate that activation of PI3K activity alone is sufficient to remodel actin filaments to increase cell migration through the activation of Akt and p70S6K1 in CEF cells. phosphatidylinositol 3-kinase; Rac; actin filaments     

IL-8 promotes cell proliferation and migration through metalloproteinase-cleavage proHB-EGF in human colon carcinoma cells

Interleukin-8 (IL-8) has been reported to promote tumor cell growth in colon cancer cells after binding to its receptors, which are members of the G-protein coupled receptor (GPCR) family. Recent studies demonstrated that stimulation of GPCR can induce shedding of epidermal growth factor (EGF) ligands via activation of a disintegrin and metalloprotease (ADAM), with subsequent transactivation of the EGF receptor (EGFR). In this study, we investigated mechanisms of cell proliferation and migration stimulated by IL-8 in a human colon carcinoma cell line (Caco2). IL-8 increased DNA synthesis of Caco2 in a dose dependent manner and this was inhibited by ADAM, EGFR kinase, and MEK inhibitors. IL-8 transiently induced EGFR tyrosine phosphorylation after 5-90 min and this was completely inhibited by ADAM inhibitor. Neutralizing antibody against HB-EGF as a key ligand for EGFR also blocked transactivation of EGFR and cell proliferation by IL-8. Since IL-8-induced cell migration was further suppressed by the ADAM inhibitor and the HB-EGF neutralizing antibody, our data indicate that IL-8 induces cell proliferation and migration by an ADAM-dependent pathway, and that HB-EGF plays an important role as the major ligand for this pathway.     

Akt mediates Rac/Cdc42-regulated cell motility in growth factor-stimulated cells and in invasive PTEN knockout cells

Growth factors promote cell survival and cell motility, presumably through the activation of Akt and the Rac and Cdc42 GTPases, respectively. Because Akt is dispensable for Rac/Cdc42 regulation of actin reorganization, it has been assumed that Rac and Cdc42 stimulate cell motility independent of Akt in mammalian cells. However, in this study we demonstrate that Akt is essential for Rac/Cdc42-regulated cell motility in mammalian fibroblasts. A dominant-negative Akt inhibits cell motility stimulated by Rac/Cdc42 or by PDGF treatment, without affecting ruffling membrane-type actin reorganization. We have confirmed a previous report that Akt is activated by expression of Rac and Cdc42 and also observed colocalization of endogenous phosphorylated Akt with Rac and Cdc42 at the leading edge of fibroblasts. Importantly, expression of active Akt but not the closely related kinase SGK is sufficient for increasing cell motility. This effect of Akt is cell autonomous and not mediated by inhibition of GSK3. Finally, we found that dominant-negative Akt but not SGK reverses the increased cell motility phenotype of fibroblasts lacking the PTEN tumor suppressor gene. Taken together, these results suggest that Akt promotes cell motility downstream of Rac/Cdc42 in growth factor-stimulated cells and in invasive PTEN-deficient cells.     

Serum bioactive lysophospholipids prevent TRAIL-induced apoptosis via PI3K/Akt-dependent cFLIP expression and Bad phosphorylation

Serum contains a variety of biomolecules, which play an important role in cell proliferation and survival. We sought to identify the serum factor responsible for mitigating tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis and to investigate its molecular mechanism. TRAIL induced effective apoptosis without serum, whereas bovine serum decreased apoptosis by suppressing cytochrome c release and caspase activation. Indeed, albumin-bound lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) inhibited TRAIL-induced apoptosis by suppressing caspase activation and cytochrome c release. LPA increased phosphatidylinositol 3-kinase (PI3K)-dependent Akt activation, cellular FLICE-inhibitory protein (cFLIP) expression, and Bad phosphorylation, resulting in inhibition of caspase-8 activation and Bad translocation to mitochondria. The antiapoptotic effect of LPA was abrogated by PI3K inhibitor, transfection with dominant-negative Akt, and specific downregulation of cFLIP expression using siRNA and further increased by siRNA-mediated suppression of Bad expression. Moreover, sera from ovarian cancer patients showed more protective effect against TRAIL-induced apoptosis than those from healthy donors, and this protection was suppressed by PI3K inhibitor. Our results indicate that albumin-bound LPA and S1P prevent TRAIL-induced apoptosis by upregulation of cFLIP expression and in part by Bad phosphorylation, through the activation of PI3K/Akt pathway.     

The EphB4 receptor-tyrosine kinase promotes the migration of melanoma cells through Rho-mediated actin cytoskeleton reorganization

Several studies have reported the up-regulation of EphB receptor-tyrosine kinases and ephrin-B ligands in a variety of tumors, suggesting a functional relation between EphB/ephrin-B signaling and tumor progression. The ability of the EphB receptors to regulate cell migration and promote angiogenesis likely contributes to tumor progression and metastasis. Here we show that EphB receptors, and especially EphB4, regulate the migration of murine melanoma cells. Highly malignant melanoma cells express the highest levels of EphB4 receptor and migrate faster than less malignant melanoma cells. Furthermore, inhibition of EphB receptor forward signaling by overexpression of a form of EphB4 lacking the cytoplasmic portion or by treatment with competitively acting soluble EphB2-Fc results in slower melanoma cell migration. In contrast, overexpression of active EphB4 significantly enhances cell migration. The effects of EphB4 receptor on cell migration and cell morphology require its kinase activity because the inhibition of EphB4 kinase activity by overexpression of kinase dead EphB4 inhibits cell migration and affects the organization of actin cytoskeleton. Activation of EphB4 receptor with its ligand ephrin-B2-Fc enhances the migratory ability of melanoma cells and increases RhoA activity, whereas inhibiting EphB receptor forward signaling decreases RhoA activity. Moreover, expression of dominant negative RhoA blocks the effects of active EphB4 on cell migration and actin organization. These data suggest that EphB4 forward signaling contributes to the high migratory ability of invasive melanoma cells by influencing RhoA-mediated actin cytoskeleton reorganization.     

CD40-dependent activation of phosphatidylinositol 3-kinase/Akt pathway mediates endothelial cell survival and in vitro angiogenesis

CD40 has been involved in tumor and inflammatory neoangiogenesis. In this study we determined that stimulation of endothelial CD40 with sCD154 induced resistance to apoptosis and in vitro vessel-like formation by human microvascular endothelial cells (HMEC). These effects were determined to be mediated by CD40-dependent signaling because they were inhibited by a soluble CD40-muIg fusion protein. Moreover, apoptosis of HMEC was associated with an impairment of Akt phosphorylation, which was restored by stimulation with sCD154. The anti-apoptotic effect as well as in vitro vessel-like formation and Akt phosphorylation were inhibited by treatment of HMEC with two unrelated pharmacological inhibitors of phosphatidylinositol 3-kinase (PI3K), wortmannin and LY294002. CD40 stimulation induced a rapid increase in Akt enzymatic activity that was not prevented by cycloheximide, an inhibitor of protein synthesis. The enhanced Akt activity induced by stimulation of endothelial CD40 was temporarily correlated with the association of CD40 with TRAF6, c-Cbl, and the p85 subunit of PI3K. Expression of negative-dominant Akt inhibited the activation of endogenous Akt through CD40 stimulation, despite the observation that association of CD40 with TRAF6, c-Cbl, and PI3K was intact. The defective activation of Akt abrogated not only the anti-apoptotic effect of CD40 stimulation but also the proliferative response, the enhanced motility, and the in vitro formation of vessel-like tubular structures by CD40-stimulated HMEC. In conclusion, these results suggest that endothelial CD40, through activation of the PI3K/Akt signaling pathway, regulates cell survival, proliferation, migration, and vessel-like structure formation, all steps considered critical for angiogenesis.     

Three-dimensional structure of vinculin bound to actin filaments

Vinculin plays a pivotal role in cell adhesion and migration by providing the link between the actin cytoskeleton and the transmembrane receptors, integrin and cadherin. We used a combination of electron microscopy, computational docking, and biochemistry to provide an atomic model of how the vinculin tail binds actin filaments. The vinculin tail actin binding site comprises two distinct regions. One of these regions is exposed in the full-length autoinhibited conformation of vinculin, whereas the second site is sterically occluded by vinculin's N-terminal domain. The partial accessibility of the F-actin binding site in the autoinhibited full-length vinculin structure suggests that F-actin can act as part of a combinatorial input framework with other binding partners such as alpha-catenin or talin to induce vinculin head-tail dissociation, thus promoting vinculin activation. Furthermore, binding to F-actin potentiates a local rearrangement in the vinculin tail that in turn promotes vinculin dimerization and, hence, formation of actin bundles.     

Sparc localizes to the blebs of hobit cells and human primary osteoblasts

Secreted protein acidic and rich in cystein (SPARC) is a secreted glycoprotein involved in several biological processes such as tissue remodeling, embryonic development, cell/extracellular matrix interactions, and cell migration. In particular, SPARC affects bone remodeling through the regulation of both differentiation/survival of osteoblasts and bone extracellular matrix synthesis/turnover. Here, we investigated SPARC subcellular localization in the human osteoblastic HOBIT cell line by immunocytochemistry and western blot analysis. We show that, under normal exponential cell growth conditions, SPARC localized both to cell nucleus and to cytoplasm, with no co-localization on actin stress fibers. However, in colchicine-treated HOBIT cells and human primary osteoblasts undergoing blebs formation, SPARC showed a different cellular distribution, with an additional marked compartmentalization inside the blebs, where it co-localized with globular actin and actin-binding proteins such as alpha-actinin, cortactin, and vinculin. Moreover, we demonstrate by an in vitro assay that the addition of SPARC to actin and alpha-actinin inhibited the formation of cross-linked actin filaments and disrupted newly formed filaments, most likely due to a direct interaction between SPARC and alpha-actinin, as indicated by immunoprecipitation assay. The specific silencing of SPARC RNA expression markedly decreased the ability of colchicine-treated HOBIT cells to undergo blebbing, suggesting a direct role for SPARC in cell morphology dynamics during cytoskeletal reorganization.     

E-selectin modulates the malignant properties of T84 colon carcinoma cells

The extravasation of metastatic cells is regulated by molecular events involving the initial adhesion of tumor cells to the endothelium and subsequently the migration of cells in the host connective tissue. E-selectin on endothelial cells and sialyl Lewis X carbohydrate component on tumor cells are mainly involved in the adhesion of colon carcinoma cells to the endothelium of target organ. Interaction of T84 colon cancer cells to purified E-selectin in vitro caused an increase in the tyrosine phosphorylation of a number of proteins as well as the modulation of cellular properties correlated to the metastatic phenotype. Specifically, E-selectin-stimulated actin reorganization, increased collagenase secretion, and induced cell migration. Treatment of T84 cells with herbimycin A inhibited cell adhesion as well as selectin-induced increase of cell migration, and cytoskeleton assembly. Our data demonstrate that binding of cancer cells to E-selectin starts signal transduction pathways which may affect the tumor metastatic abilities.     

Ectopic expression of L-plastin in human tumor cells: Diagnostic and therapeutic implications

Modulation of the actin cytoskeleton is critical for tumor cell migration and invasion. Therefore, actin-binding proteins which regulate this modulation may be valuable targets to inhibit the metastatic properties of tumor cells. Changes in the actin cytoskeleton are accomplished by a variety of actin-binding proteins such as cofilin, α-actinin, filamin, fascin and the plastins. Interestingly, the hematopoetic isoform of the plastins, L-plastin, is not only expressed by hematopoetic cells, but also by most human cancer cell lines. Yet, data regarding the functional importance of L-plastin expression in tumor tissues are controversial: in colon carcinomas, the expression level of L-plastin correlated with tumor progression, whereas no such correlation could be seen in breast carcinomas. We therefore systematically investigated whether expression of L-plastin influences the adhesiveness, the motility and invasiveness of human tumor cells. An siRNA mediated knock-down of L-plastin in an L-plastin positive melanoma cell line inhibited migration of these cells. Accordingly, expression of L-plastin in L-plastin negative melanoma cells led to enhanced cell migration towards extracellular matrix components. However, mere expression of L-plastin did not promote tumor cell invasion into basement membranes. Only, if L-plastin was phosphorylated, tumor cell invasion was promoted. Therefore, in clinical studies, not only the expression of L-plastin but also the phosphorylation status of L-plastin should be compared with regard to tumor progression.Besides the potential prognostic relevance of L-plastin expression and phosphorylation in human cancer cells, L-plastin may represent a novel target for cancer therapy. Moreover, the constitutive activity of the L-plastin promotor in non-hematopoetic tumors opens up novel perspectives for gene therapy of cancer using L-plastin-promotor driven viral vectors.     

Opposing effects of Bad phosphorylation at two distinct sites by Akt1 and JNK1/2 on ischemic brain injury

Increasing evidence suggests that the Bcl-2 family proteins play pivotal roles in regulation of the mitochondria cell-death pathway on transient cerebral ischemia. Bad, a BH3-only proapoptotic Bcl-2 family protein, has been shown to be phosphorylated extensively on serine by kinds of kinases. However, the exact mechanisms of the upstream kinases in regulation of Bad signaling pathway remain unknown. Here, we reported that Bad could be phosphorylated not only by Akt1 but also by JNK1/2 after transient global ischemia in rat hippocampal CA1 region. Our data demonstrated that Akt1 mediated the phosphorylation of Bad at serine 136, which increased the interaction of serine 136-phosphorylated Bad with 14-3-3 proteins and prevented the dimerization of Bad with Bcl-Xl, inhibited the release of cytochrome c to the cytosol and the death effector caspase-3 activation, leading to the survival of neuron. In contrast, JNK1/2 induced the phosphorylation of Bad at a novel site of serine 128 after brain ischemia/reperfusion, which inhibited the interaction of PI3K/Akt-induced serine 136-phosphorylated Bad with 14-3-3 proteins, thereby promoted the apoptotic effect of Bad. In addition, activated Akt1 inhibited the activation of Bad(S128) through downregulating JNK1/2 activation, thus inhibiting JNK-mediated Bad apoptosis pathway. Furthermore, the fate of cell to survive or to die was determined by a balance between prosurvival and proapoptotic signals. Taken together, our studies reveal that Bad phosphorylation at two distinct sites induced by Akt1 and JNK1/2 have opposing effects on ischemic brain injury, and present the possibility of Bad as a potential therapeutic target for stroke treatment.     

TGFbeta1 -mediated epithelial to mesenchymal transition is accompanied by invasion in the SiHa cell line

It has recently been suggested by several investigators that the epithelial-mesenchymal transition-inducing capacity of TGFbetas contributes to invasive transition of tumors at later stages of carcinogenesis. In the present study, we examined the possibility of TGFbeta1-stimulated epithelial-mesenchymal transition in SiHa cell line, detailed molecular events in the process, and its possible contribution to the invasive transition of tumors. TGFbeta1-induced epithelial-mesenchymal transition of SiHa cells was based on morphological and biochemical criteria; actin stress fiber formation, focal translocalization of integrin alphav, talin, and vinculin, fibronectin-based matrix assembly at the cell periphery, and translocalization and down-regulation of E-cadherin. TGFbeta1 also stimulated surface expression of integrin alphavbeta3 and FAK activation. Focal translocalization of integrin alphav preceded actin reorganization and fibronectin matrix assembly, and functional blocking of the integrin suppressed actin stress fiber formation. Furthermore, induction of actin reorganization and fibronectin matrix assembly by TGFbeta1 were shown to be mutually independent events. These changes were irreversible because 5 minutes pulse exposure to TGFbeta1 was sufficient to stimulate progress of actin reorganization and fibronectin matrix assembly. In further studies with raft culture, TGFbeta1 was found to stimulate invasion of SiHa cells into a type I collagen gel matrix. In conclusion, TGFbeta1 stimulated epithelial-mesenchymal transition of SiHa cells, indicating a positive role in the invasive transition of tumors.     

Overexpression of lumican affects the migration of human colon cancer cells through up-regulation of gelsolin and filamentous actin reorganization

Cell migration is a multistep process initiated by extracellular matrix components that leads to cytoskeletal changes and formation of different protrusive structures at the cell periphery. Lumican, a small extracellular matrix leucine-rich proteoglycan, has been shown to inhibit human melanoma cell migration by binding to α2β1 integrin and affecting actin cytoskeleton organization. The aim of this study was to determine the effect of lumican overexpression on the migration ability of human colon adenocarcinoma LS180 cells. The cells stably transfected with plasmid containing lumican cDNA were characterized by the increased chemotactic migration measured on Transwell filters. Lumican-overexpressing cells presented the elevated filamentous to monomeric actin ratio and gelsolin up-regulation. This was accompanied by a distinct cytoskeletal actin rearrangement and gelsolin subcellular relocation, as observed under laser scaning confocal microscope. Moreover, LS180 cells overexpressing lumican tend to form podosome-like structures as indicated by vinculin redistribution and its colocalization with gelsolin and actin at the submembrane region of the cells. In conclusion, the elevated level of lumican secretion to extracellular space leads to actin cytoskeletal remodeling followed by an increase in migration capacity of human colon LS180 cells. These data suggest that lumican expression and its presence in ECM has an impact on colon cancer cells motility and may modulate invasiveness of colon cancer.     

Conditioned media from adipocytes promote proliferation,migration, and invasion in melanoma and colorectal cancer cells

Epidemiological evidence suggests that obesity can significantly increase the risk of various cancers, although the mechanisms underlying this link are completely unknown. Here, we analyzed the effect of adipocytes on melanoma and colon cancer cells proliferation, migration, and invasion. The potential effects of conditioned media (CM) obtained from differentiated mouse 3T3-L1 cells and human adipose tissue-derived mesenchymal stem cells (hAMSC) on the proliferation, migration, and invasion of B16BL6 melanoma and colon 26-L5 cancer cells were investigated. The 3T3-L1 and hAMSC CM increased cell proliferation, migration, and invasion in both the cell lines. In addition, adipocytes CM increased matrix metalloproteinase 9 (MMP-9) and MMP-2 activity in both B16BL6 and colon 26-L5 cells. These effects were found to be associated with an increased expression of various oncogenic proteins in B16BL6 and colon 26-L5 cells. Also, adipocyte CM induced Akt and mTOR activation in both tumor cell lines, and the pharmacological inhibition of Akt and mTOR blocked the CM induced Akt as well as mTOR activation and CM-stimulated melanoma and colon cancer cell proliferation, migration, and invasion. These data suggest that adipocyte promotes melanoma and colon cancer progression through modulating the expression of diverse proteins associated with cancer growth and metastasis as well as modulation of the Akt/mTOR signaling.