Akt and RhoA inhibition promotes anoikis of aggregated B16F10 melanoma cells

Therapeutic targeting of anoikis resistance in cutaneous melanoma metastasis

The acquisition of resistance to anoikis, the cell death induced by loss of adhesion to the extracellular matrix, is an absolute requirement for the survival of disseminating and circulating tumour cells (CTCs), and for the seeding of metastatic lesions. In melanoma, a range of intracellular signalling cascades have been identified as potential drivers of anoikis resistance, however a full understanding of the process is yet to be attained. Mechanisms of anoikis resistance pose an attractive target for the therapeutic treatment of disseminating and circulating melanoma cells. This review explores the range of small molecule, peptide and antibody inhibitors targeting molecules involved in anoikis resistance in melanoma, and may be repurposed to prevent metastatic melanoma prior to its initiation, potentially improving the prognosis for patients.

Chemoprevention of 4NQO-Induced Mouse Tongue Carcinogenesis by AKT Inhibitor through the MMP-9/RhoC Signaling Pathway and Autophagy

Oral cancer (OC), the most common cancer in the head and neck, which has a poor prognosis, histopathologically follows a stepwise pattern of hyperplasia, dysplasia, and cancer. Blocking the progression of OC in the precancer stage could greatly improve the survival and cure rates. AKT protein plays a critical role in the signal transduction of cancer cells, and we found that AKT was overexpressed in human OC samples through analysis of TCGA database. Therefore, this study is aimed at investigating the chemopreventive effect of an AKT inhibitor (MK2206 2HCl) on OC. In vivo, we established a 4-nitroquinoline-1-oxide- (4NQO-) induced mouse tongue carcinogenesis model to investigate the potential chemopreventive effect of MK2206 2HCl on mouse OC resulting from 4NQO. The results showed that MK2206 2HCl could significantly reduce the incidence rate and growth of OC, inhibit the transformation of dysplasia to cancer in the 4NQO-induced mouse tongue carcinogenesis model, and simultaneously markedly suppress cell proliferation, angiogenesis, and mast cell (MC) infiltration in 4NQO-induced mouse tongue cancers. In vitro, our results revealed that MK2206 2HCl could also inhibit oral squamous cell carcinoma (OSCC) cell malignant biological behaviors, including cell proliferation, colony formation, cell invasion, and migration, while promoting apoptosis. Mechanistic studies revealed that MK2206 2HCl suppressed matrix metalloproteinase 9 (MMP-9) and RhoC expression and promoted autophagy gene LC3 II expression. In summary, our findings demonstrated the chemopreventive effect of MK2206 2HCl on the 4NQO-induced mouse tongue carcinogenesis model, which likely has an underlying mechanism mediated by the MMP-9/RhoC signaling pathway and autophagy.

Skin Cancers and the Contribution of Rho GTPase Signaling Networks to Their Progression

Skin cancers are the most common cancers worldwide. Among them, melanoma, basal cell carcinoma of the skin and cutaneous squamous cell carcinoma are the three major subtypes. These cancers are characterized by different genetic perturbations even though they are similarly caused by a lifelong exposure to the sun. The main oncogenic drivers of skin cancer initiation have been known for a while, yet it remains unclear what are the molecular events that mediate their oncogenic functions and that contribute to their progression. Moreover, patients with aggressive skin cancers have been known to develop resistance to currently available treatment, which is urging us to identify new therapeutic opportunities based on a better understanding of skin cancer biology. More recently, the contribution of cytoskeletal dynamics and Rho GTPase signaling networks to the progression of skin cancers has been highlighted by several studies. In this review, we underline the various perturbations in the activity and regulation of Rho GTPase network components that contribute to skin cancer development, and we explore the emerging therapeutic opportunities that are surfacing from these studies.

DUXAP8 knockdown inhibits the development of melanoma by regulating the miR-3182/NUPR1 pathway

Double homeobox A pseudogene 8 (DUXAP8) has been reported to regulate the growth of several types of cancers, such as breast cancer and ovarian cancer. However, its role in melanoma remains unclear. In the present study, the mechanism through which DUXAP8 regulates melanoma progression was explored. The expression levels of DUXAP8 were determined in 43 samples from patients with melanoma in different stages, as well as human epidermal melanocytes cells and malignant melanoma cell lines using reverse transcription-quantitative PCR (RT-qPCR). The prognosis of patients was analyzed using the Kaplan-Meier method. The relationship between lncRNA DUXAP8 expression and microRNA (miR)-3182 or nuclear protein 1 transcriptional regulator (NUPR1) levels was analyzed using Pearson's correlation. Luciferase reporter and RNA pull-down were used to examine the interactions between these molecules. Proliferation was assessed using Cell Counting-Kit-8. Transwell assays were used to examine cell migration and invasion. lncRNA DUXAP8 was upregulated in melanoma tissue and cells compared with normal tissues and cells. The levels of DUXAP8 inversely correlated with survival time of patients with melanoma. Knockdown of lncRNA DUXAP8 inhibited proliferation, migration and invasion of melanoma cells. lncRNA DUXAP8 targeted miR-3182, while miR-3182 targeted NUPR1. The overexpression of NUPR1 reversed the effects of DUXAP8 knockdown or miR-3182 mimic on melanoma progression. In conclusion, lncRNA DUXAP8 downregulation inhibits the development of melanoma by regulating the miR-3182/NUPR1 axis.

Guaiazulene Triggers ROS-Induced Apoptosis and Protective Autophagy in Non-small Cell Lung Cancer

Non-small cell lung cancer (NSCLC) is one of the most frequent cancers worldwide, yet effective treatment remains a clinical challenge. Guaiazulene (GYZ), a cosmetic color additive, has previously been characterized as a potential antitumor agent due to observed anticancer effects. However, the efficacy of GYZ in the treatment of NSCLC and the involved molecular mechanisms remain largely unknown. Here, we indicated a role for GYZ in the suppression of NSCLC both in vitro and in vivo via triggering reactive oxygen species (ROS)-induced apoptosis. Concomitantly, GYZ induced complete autophagic flux in NSCLC cells via inhibiting the Akt/mTOR signaling pathway, which displayed cytoprotective effect against GYZ-induced growth suppression. Accompanied with autophagy inhibition obviously enhanced the effects of GYZ. Notably, GYZ acts synergistically with paclitaxel in the suppression of NSCLC in vitro. Together, our results for the first time reported that GYZ suppressed the proliferation of NSCLC and suggested a potential strategy for inhibiting NSCLC growth by combinational use of GYZ and autophagy inhibitors.

YAP activation in melanoma contributes to anoikis resistance and metastasis

Melanoma is inherently heterogeneous, providing resistance to apoptosis. Anoikis resistance is a hallmark feature of metastatic melanoma to escape apoptosis when cells lose contact with adjacent cells or extracellular matrix. The yes-associated protein transcription co-activator is the effector of Hippo pathway. Herein, we investigated the function of yes-associated protein in anoikis resistance of melanoma cells. When melanoma cells were grown under anchorage-independent condition, anoikis-resistant cells displayed higher levels of yes-associated protein activation than the cells that were attached to the basement membrane, as evidenced by downregulated phosphorylated yes-associated protein at Ser127 and higher expression of downstream genes BCL2 and MCL-1. Yes-associated protein overexpression directly enhanced the anoikis resistance and metastatic potential of melanoma cells. Conversely, yes-associated protein inhibitor CA3 exhibited Dose-dependent induction of anoikis in resistant melanoma cells and exerted great inhibition on cell migration. Knockdown of yes-associated protein expression by shRNA also rendered melanoma cells susceptible to anoikis and interrupted cell invasiveness. Yes-associated protein inhibition in anoikis-resistant cells also reduced the number of metastatic nodules in the lung sections of SCID mice. Clinically, higher yes-associated protein level in the lung metastasis tissues correlated with higher BCL2 and MCL1 expressions compared with the non-metastasis tissues. Overall, our finding suggests that the aberrant activation of yes-associated protein exerts important role on anoikis resistance and metastatic capability of melanoma cells.

Autophagy, anoikis, ferroptosis, necroptosis, and endoplasmic reticulum stress: Potential applications in melanoma therapy

Melanoma as the most major skin malignancy has attracted much attention, so far. Although a successful therapeutic strategy requires an accurate understanding of the precise mechanisms for the initiation and progression of the melanoma. Several types of cell death mechanisms have recently been identified along with conventional cell death mechanisms such as apoptosis and necrosis. Among those mechanisms, necroptosis, anoikis, ferroptosis, and autophagy may be considered to have remarkable modulatory impacts on melanoma. In the present review, we explain the mechanisms of cell death signaling pathways related to autophagy, ferroptosis, anoikis, necroptosis, and reticulum endoplasmic stress in cells and describe how those mechanisms transduce signals in melanoma cells. Meanwhile, we describe how we can modulate those mechanisms to eliminate melanoma.

Unconventional Ways to Live and Die: Cell Death and Survival in Development, Homeostasis, and Disease

Balancing cell death and survival is essential for normal development and homeostasis and for preventing diseases, especially cancer. Conventional cell death pathways include apoptosis, a form of programmed cell death controlled by a well-defined biochemical pathway, and necrosis, the lysis of acutely injured cells. New types of regulated cell death include necroptosis, pyroptosis, ferroptosis, phagoptosis, and entosis. Autophagy can promote survival or can cause death. Newly described processes of anastasis and resuscitation show that, remarkably, cells can recover from the brink of apoptosis or necroptosis. Important new work shows that epithelia achieve homeostasis by extruding excess cells, which then die by anoikis due to loss of survival signals. This mechanically regulated process both maintains barrier function as cells die and matches rates of proliferation and death. In this review, we describe these unconventional ways in which cells have evolved to die or survive, as well as the contributions that these processes make to homeostasis and cancer.

The anti-tumor NC1 domain of collagen XIX inhibits the FAK/ PI3K/Akt/mTOR signaling pathway through αvβ3 integrin interaction

Type XIX collagen is a minor collagen associated with basement membranes. It was isolated for the first time in a human cDNA library from rhabdomyosarcoma and belongs to the FACITs family (Fibril Associated Collagens with Interrupted Triple Helices). Previously, we demonstrated that the NC1 domain of collagen XIX (NC1(XIX)) exerts anti-tumor properties on melanoma cells by inhibiting their migration and invasion. In the present work, we identified for the first time the integrin αvβ3 as a receptor of NC1(XIX). Moreover, we demonstrated that NC1(XIX) inhibits the FAK/PI3K/Akt/mTOR pathway, by decreasing the phosphorylation and activity of the major proteins involved in this pathway. On the other hand, NC1(XIX) induced an increase of GSK3β activity by decreasing its degree of phosphorylation. Treatments targeting this central signaling pathway in the development of melanoma are promising and new molecules should be developed. NC1(XIX) seems to have the potential for the design of new anti-cancer drugs.

Knockdown of RHOC by shRNA suppresses invasion and migration of cholangiocellular carcinoma cells via inhibition of MMP2, MMP3, MMP9 and epithelial-mesenchymal transition

Ras homolog family member C (RHOC) is important during the progression of several types of cancer, including prostate, breast and hepatocellular carcinoma. However, the function of RHOC in cholangiocellular carcinoma (CCC), a highly recurrent and metastatic carcinoma with poor prognosis, remains unclear. The aim of the present study was to investigate the involvement of RHOC in CCC tumor progression. RHOC expression levels were examined in CCC tissues and cells, and adjacent nontumorous bile duct tissues. The effects and molecular mechanisms of RHOC expression on cell migration and invasion were also investigated. The current study demonstrated that RHOC protein was frequently overexpressed in human CCC specimens and CCC cell lines. Downregulation of RHOC inhibited CCC cell invasion and migration partially via inhibition of matrix metalloproteinase 2, 3 and 9 expression. RHOC also modulated the expression of several epithelial-mesenchymal transition (EMT)-associated proteins, including E‑cadherin, vimentin, Slug and Snail, to promote to EMT progression. The present results demonstrated that RHOC is important for the invasion and migration of CCC through simultaneous regulation of MMPs and EMT‑associated protein, suggesting that RHOC is a potential molecular target for CCC treatment.

Evaluation of MicroRNAs Regulating Anoikis Pathways and Its Therapeutic Potential

Dysregulation of microRNAs (miRNAs) has been implicated in almost every known survival mechanisms utilized by cancer cells. One of such mechanisms, anoikis resistance, plays a pivotal role in enabling metastasis by allowing cancer cells to circumvent cell death induced by lack of attachment. Understanding how miRNAs regulate the various anoikis pathways has become the research question of increasing number of studies published in the past years. Through these studies, a growing list of miRNAs has been identified to be important players in promoting either anoikis or resistance to anoikis. In this review, we will be focusing on these miRNAs and how the findings from those studies can contribute to novel therapeutic strategies against cancer progression. We will be examining miRNAs that have been found to promote anoikis sensitivity in numerous cancer types followed by miRNAs that inhibit anoikis. In addition, we will also be taking a look at major signaling pathways involved in the action of the each of these miRNAs to gain a better understanding on how miRNAs regulate anoikis.

Focal adhesion kinase phosphorylates the phosphatase and tensin homolog deleted on chromosome 10 under the control of p110δ phosphoinositide-3 kinase

The phosphatase and tensin homolog deleted on chromosome 10 (PTEN) tumor suppressor protein is regulated by various mechanisms that are not fully understood. This includes regulation by Tyr phosphorylation by a mechanism that remains elusive. Here, we show that focal adhesion kinase (FAK) phosphorylates PTEN in vitro, in cell-free systems and in cells. Furthermore, by mass spectrometry, we identified Tyr336 on PTEN as being phosphorylated by FAK. Tyr336 phosphorylation increased phosphatase activity, protein-lipid interaction, and protein stability of PTEN. In cells, including primary mouse macrophages and human cancer cell lines, FAK was found to be negatively regulated by p110δ phosphoinositide-3 kinase (PI3K), whereas the activation of FAK was positively regulated by RhoA-associated kinase (ROCK). Indeed, the phosphorylation of FAK was unexpectedly increased in macrophages derived from mice expressing kinase-dead p110δ. Pharmacologic inactivation of RhoA/ROCK reduced the phosphorylation of FAK to normal levels in cells with genetically inactivated p110δ. Likewise, pharmacologic inactivation of FAK reduced the phosphorylation of PTEN in cells expressing kinase-dead p110δ and restored the functional defects of p110δ inactivation, including Akt phosphorylation and cell proliferation. This work identifies FAK as a target of p110δ PI3K that links RhoA with PTEN and establishes for the first time that PTEN is a substrate of FAK-mediated Tyr phosphorylation.

Resistance to the mTOR inhibitor temsirolimus alters adhesion and migration behavior of renal cell carcinoma cells through an integrin α5- and integrin β3-dependent mechanism

Inhibitors of the mammalian target of rapamycin (mTOR) have improved the treatment of renal cell carcinoma (RCC). However, chronic drug exposure may trigger resistance, limiting the utility of these agents. The metastatic behavior of RCC cells, susceptible (RCC(par)) or resistant (RCC(res)) to the mTOR inhibitor temsirolimus, was investigated. Adhesion to vascular endothelium or immobilized collagen and fibronectin was quantified. Chemotactic motility was evaluated with a modified Boyden chamber assay. Integrin α and β subtype receptors were analyzed by flow cytometry and Western blot analysis. The physiological relevance of the integrins was then determined by blocking studies and small interfering RNA knockdown. Adhesion to endothelial cells and to fibronectin (not to collagen) and chemotaxis were enhanced in RCC(res) compared to RCC(par). RCC(res) detached from fibronectin and motile activity further increased under retreatment with low-dosed temsirolimus. α5 integrin was diminished inside the cell and at the cell surface, whereas the β3 subtype was reduced intracellularly but elevated at the plasma membrane. In RCC(par), blocking α5 surface receptors enhanced RCC-collagen but reduced RCC-fibronectin interaction, whereas the opposite was true for RCC(res). Chemotaxis of RCC(par) but not of RCC(res) was strongly diminished by the α5 antibody. Blocking β3 significantly lowered chemotaxis with stronger effects on RCC(res), compared to RCC(par). Importantly, β3 knockdown reduced chemotaxis of RCC(par) but upregulated the motile behavior of RCC(res). Temsirolimus resistance is characterized by quantitative alterations of integrin α5 and β3 expression, coupled to functional changes of the integrin molecules, and forces a switch from RCC adhesion to RCC migration.

Cancer cell survival during detachment from the ECM: multiple barriers to tumour progression

Epithelial cells require attachment to the extracellular matrix (ECM) for survival. However, during tumour progression and metastasis, cancerous epithelial cells must adapt to and survive in the absence of ECM. During the past 20 years, several cellular changes, including anoikis, have been shown to regulate cell viability when cells become detached from the ECM. In this Opinion article, we review in detail how cancer cells can overcome or take advantage of these specific processes. Gaining a better understanding of how cancer cells survive during detachment from the ECM will be instrumental in designing chemotherapeutic strategies that aim to eliminate ECM-detached metastatic cells.