Alpha6 integrin subunit mediates laminin enhancement of cisplatin-induced apoptosis in testicular tumor germ cells

Integrins as the pivotal regulators of cisplatin response in tumor cells

Cisplatin (CDDP) is a widely used first-line chemotherapeutic drug in various cancers. However, CDDP resistance is frequently observed in cancer patients. Therefore, it is required to evaluate the molecular mechanisms associated with CDDP resistance to improve prognosis among cancer patients. Integrins are critical factors involved in tumor metastasis that regulate cell-matrix and cell-cell interactions. They modulate several cellular mechanisms including proliferation, invasion, angiogenesis, polarity, and chemo resistance. Modification of integrin expression levels can be associated with both tumor progression and inhibition. Integrins are also involved in drug resistance of various solid tumors through modulation of the tumor cell interactions with interstitial matrix and extracellular matrix (ECM). Therefore, in the present review we discussed the role of integrin protein family in regulation of CDDP response in tumor cells. It has been reported that integrins mainly promoted the CDDP resistance through interaction with PI3K/AKT, MAPK, and WNT signaling pathways. They also regulated the CDDP mediated apoptosis in tumor cells. This review paves the way to suggest the integrins as the reliable therapeutic targets to improve CDDP response in tumor cells.

Comparison of Engineered Liver 3D Models and the Role of Oxygenation for Patient-Derived Tumor Cells and Immortalized Cell Lines Cocultured with Tumor Stroma in the Detection of Hepatotoxins

In metabolically active tumors, responses of cells to drugs are heavily influenced by oxygen availability via the surrounding vasculature alongside the extracellular matrix signaling. The objective of this study is to investigate hepatotoxicity by replicating critical features of hepatocellular carcinoma (HCC). This includes replicating 3D structures, metabolic activities, and tumor-specific markers. The internal environment of spheroids comprised of cancerous human patient-derived hepatocytes using microparticles is modulated to enhance the oxygenation state and recreate cell-extracellular matrix interactions. Furthermore, the role of hepatic stellate cells in maintaining hepatocyte survival and function is explored and hepatocytes from two cellular sources (immortalized and patient-derived) to create four formulations with and without microparticles are utilized. To investigate drug-induced changes in metabolism and apoptosis in liver cells, coculture spheroids with and without microparticles are exposed to three hepatotoxic drugs. The use of microparticles increases levels of apoptotic markers in both liver models under drug treatments. This coincides with reduced levels of anti-apoptotic proteins and increased levels of pro-apoptotic proteins. Moreover, cells from different origins undergo apoptosis through distinct apoptotic pathways in response to identical drugs. This 3D microphysiological system offers a viable tool for liver cancer research to investigate mechanisms of apoptosis under different microenvironmental conditions.

Focal adhesion signaling and therapy resistance in cancer

Interlocking gene mutations, epigenetic alterations and microenvironmental features perpetuate tumor development, growth, infiltration and spread. Consequently, intrinsic and acquired therapy resistance arises and presents one of the major goals to solve in oncologic research today. Among the myriad of microenvironmental factors impacting on cancer cell resistance, cell adhesion to the extracellular matrix (ECM) has recently been identified as key determinant. Despite the differentiation between cell adhesion-mediated drug resistance (CAMDR) and cell adhesion-mediated radioresistance (CAMRR), the underlying mechanisms share great overlap in integrin and focal adhesion hub signaling and differ further downstream in the complexity of signaling networks between tumor entities. Intriguingly, cell adhesion to ECM is per se also essential for cancer cells similar to their normal counterparts. However, based on the overexpression of focal adhesion hub signaling receptors and proteins and a distinct addiction to particular integrin receptors, targeting of focal adhesion proteins has been shown to potently sensitize cancer cells to different treatment regimes including radiotherapy, chemotherapy and novel molecular therapeutics. In this review, we will give insight into the role of integrins in carcinogenesis, tumor progression and metastasis. Additionally, literature and data about the function of focal adhesion molecules including integrins, integrin-associated proteins and growth factor receptors in tumor cell resistance to radio- and chemotherapy will be elucidated and discussed.

Systems biology of cisplatin resistance: past, present and future

The platinum derivative cis-diamminedichloroplatinum(II), best known as cisplatin, is currently employed for the clinical management of patients affected by testicular, ovarian, head and neck, colorectal, bladder and lung cancers. For a long time, the antineoplastic effects of cisplatin have been fully ascribed to its ability to generate unrepairable DNA lesions, hence inducing either a permanent proliferative arrest known as cellular senescence or the mitochondrial pathway of apoptosis. Accumulating evidence now suggests that the cytostatic and cytotoxic activity of cisplatin involves both a nuclear and a cytoplasmic component. Despite the unresolved issues regarding its mechanism of action, the administration of cisplatin is generally associated with high rates of clinical responses. However, in the vast majority of cases, malignant cells exposed to cisplatin activate a multipronged adaptive response that renders them less susceptible to the antiproliferative and cytotoxic effects of the drug, and eventually resume proliferation. Thus, a large fraction of cisplatin-treated patients is destined to experience therapeutic failure and tumor recurrence. Throughout the last four decades great efforts have been devoted to the characterization of the molecular mechanisms whereby neoplastic cells progressively lose their sensitivity to cisplatin. The advent of high-content and high-throughput screening technologies has accelerated the discovery of cell-intrinsic and cell-extrinsic pathways that may be targeted to prevent or reverse cisplatin resistance in cancer patients. Still, the multifactorial and redundant nature of this phenomenon poses a significant barrier against the identification of effective chemosensitization strategies. Here, we discuss recent systems biology studies aimed at deconvoluting the complex circuitries that underpin cisplatin resistance, and how their findings might drive the development of rational approaches to tackle this clinically relevant problem.

Inhibition of mammary tumor growth by estrogens: is there a specific role for estrogen receptors alpha and beta?

To evaluate the extent to which each estrogen receptor (ER) subtype contributes to the stimulation or to the inhibition of mammary tumor growth, we evaluated the effects of specific agonists in MC4-L2 cells, which are stimulated by 17β-estradiol (E(2)), and in mammary carcinomas of the MPA mouse breast cancer model, which are inhibited by E(2). Both express ERα and ERβ. In MC4-L2 cells, 4,4',4"-(4-propyl-(1H)-pyrazole-1,3,5-triyl)trisphenol (PPT; ERα agonist) and (4-hydroxy-phenyl)-propionitrile (DPN; ERβ agonist) stimulated cell proliferation, whereas the opposite occurred in C4-HI primary cultures. The inhibitory effect was associated with a decrease in ERα and cyclin D1 expression and an increase in progesterone receptor (PR) expression as well as in the Bax/Bcl-xl ratio. In vivo, mice carrying C4-HI or 32-2-HI tumors were treated with E(2), PPT or DPN (3 mg/kg/day) or with vehicle. PPT and DPN inhibited tumor size, as did E(2), during the first 72 h. After a few days, DPN-treated tumors started to grow again, while PPT-treated tumors remained quiescent for a longer period of time. A pronounced decrease in the mitotic index and an increase in the apoptotic index was associated with tumor regression. All treated tumors showed: (a) an increase in integrin α6 and Bax expression, (b) an increased stromal laminin redistribution, and (c) a decrease in ERα, Bcl-xl and Bcl-2 expression (P < 0.001). Apoptosis-inducing factor (Aif) expression was increased in DPN-treated tumors, while active caspase 9 was up-regulated in PPT-treated mice, demonstrating the involvement of the intrinsic apoptotic pathway in estrogen-induced regression in this model. In conclusion, our data indicate that although there may be some preferences for activation pathways by the different agonists, the stimulatory or inhibitory effects triggered by estrogens are cell-context dependent rather than ER isoform dependent.

T-lymphocyte-induced, Fas-mediated apoptosis is associated with early keratinocyte differentiation

The development of eczematous lesions is thought to be due in part to a breakdown in skin barrier function as a result of T lymphocytes (T cells) invading the skin causing epidermal keratinocyte apoptosis. In this study, we investigated the interaction of T cells and keratinocytes on apoptosis and terminal differentiation using an in vitro co-culture system. Experiments were performed using the HaCaT keratinocyte cell line or normal human epidermal keratinocytes. Activated human peripheral blood-derived T cells were found to induce Fas-dependent keratinocyte apoptosis by up to sixfold. Increased Fas was associated with increased IFN-gamma. The T-cell apoptotic signal was found to target preferentially keratinocytes in the very early stages of terminal differentiation, such as those with low levels of alpha 6-integrin expression, and result in subsequent increased caspase 3 activity. This observation was accompanied by a marked increase in keratinocyte ICAM-1 expression and its ligand LFA-1 on T cells. Our data suggest that T cells may initiate the onset of keratinocyte terminal differentiation making them more susceptible to Fas-dependent cell death signals delivered by the T cells.

In vitro and in vivo sensitization of SW620 metastatic colon cancer cells to CDDP-induced apoptosis by the nitric oxide donor DETANONOate: Involvement of AIF

Tumor cells develop mechanisms that dysregulate apoptotic pathways resulting in resistance to cytotoxic stimuli. Primary SW480 and metastatic SW620 colon cancer cells are resistant to CDDP-induced apoptosis. Apoptosis-inducing factor (AIF) was significantly downregulated in SW620 compared to SW480 cells; while apoptotic mediators such as Bax, Bcl-2, and Bcl(XL) were not altered in these cell lines. Examination of tumor tissues from patients with colon cancer demonstrated a significant downregulation of AIF in patients with advanced disease. The role of AIF expression in resistance was examined. Several lines of evidence suggest the involvement of AIF expression level in the sensitivity of SW620 to CDDP-induced apoptosis: (1) sensitization of SW620 by the NO donor DETANONOate to CDDP-induced apoptosis correlated with the induction of AIF as assessed by RT-PCR and Western blot analysis, (2) treatment of SW620 cells with siRNA AIF, but not with control siRNAs, inhibited DETANONOate-induced sensitization to CDDP apoptosis, (3) sensitization by DETANONOate observed in vitro was corroborated in vivo in nude mice bearing SW620 tumor xenografts and treated with the combination of DETANONOate and CDDP, and (4) tumor tissues derived from the SW620 xenografts revealed significant upregulation of AIF and increased apoptosis by DETANONOate and CDDP combination treatment. Altogether, these findings underscore the potential therapeutic application of NO donors and subtoxic chemotherapeutic drugs in the treatment of advanced colon cancer resistant to conventional chemotherapeutic agents.

Integrin-mediated cell–matrix interactions for prosurvival and antiapoptotic signaling after genotoxic injury

Interactions of cells with their microenvironment modify the cellular sensitivity of normal and tumor cells for radiation- and drug-induced genotoxic injury. The preexistent or acquired cellular resistance against such agents aggravates anticancer therapies and, therefore, complicates the recovery of patients. Recently, integrin-mediated adhesion was shown to improve cell survival of both normal and cancer cells following DNA damage. Here, I will discuss the role of integrins and integrin-mediated signaling cascades in the survival or death response upon genotoxic stress. Detailed knowledge of the responsible molecular processes might provide implications for putative therapies targeting integrins or integrin-associated molecules to achieve an optimization of anticancer treatments.