Selective targeting of FAK–Pyk2 axis by alpha-naphthoflavone abrogates doxorubicin resistance in breast cancer cells

A new class of CYP1B1 inhibitors derived from bentranil

Cytochrome P450 1B1 (CYP1B1) is highly expressed in a variety of tumors and implicated to drug resistance. More and more researches have suggested that CYP1B1 is a new target for cancer prevention and therapy. Various CYP1B1 inhibitors with a rigid polycyclic skeleton have been developed, such as flavonoids, trans-stilbenes, and quinazolines. To obtain a new class of CYP1B1 inhibitors, we designed and synthesized a series of bentranil analogues, moreover, IC₅₀ determinations were performed for CYP1B1 inhibition of five of these compounds and found that 6o and 6q were the best inhibitors, with IC₅₀ values in the nM range. The selectivity index (SI) of CYP1B1 over CYP1A1 and CYP1A2 was 30-fold higher than that of α-naphthoflavone (ANF). The molecular docking results showed that compound 6q fitted better into the CYP1B1 binding site than other compounds, which was consistent with our experimental results. On the basis of 6o and 6q, it is expected to develop CYP1B1 inhibitors with stronger affinity, higher selectivity and better solubility.

Activated PyK2 and Its Associated Molecules Transduce Cellular Signaling from the Cancerous Milieu for Cancer Metastasis

PyK2 is a member of the proline-rich tyrosine kinase and focal adhesion kinase families and is ubiquitously expressed. PyK2 is mainly activated by stimuli, such as activated Src kinases and intracellular acidic pH. The mechanism of PyK2 activation in cancer cells has been addressed extensively. The up-regulation of PyK2 through overexpression and enhanced phosphorylation is a key feature of tumorigenesis and cancer migration. In this review, we summarized the cancer milieu, including acidification and cancer-associated molecules, such as chemical reagents, interactive proteins, chemokine-related molecules, calcium channels/transporters, and oxidative molecules that affect the fate of PyK2. The inhibition of PyK2 leads to a beneficial strategy to attenuate cancer cell development, including metastasis. Thus, we highlighted the effect of PyK2 on various cancer cell types and the distribution of molecules that affect PyK2 activation. In particular, we underlined the relationship between PyK2 and cancer metastasis and its potential to treat cancer cells.

Pharmacological blockage of the AHR-CYP1A1 axis: a call for in vivo evidence

The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that can be activated by structurally diverse compounds arising from the environment and the microbiota and host metabolism. Expanding evidence has been shown that the modulation of the canonical pathway of AHR occurs during several chronic diseases and that its abrogation might be of clinical interest for metabolic and inflammatory pathological processes. However, most of the evidence on the pharmacological abrogation of the AHR-CYP1A1 axis has been reported in vitro, and therefore, guidance for in vivo studies is needed. In this review, we cover the state-of-the-art of the pharmacodynamic and pharmacokinetic properties of AHR antagonists and CYP1A1 inhibitors in different in vivo rodent (mouse or rat) models of disease. This review will serve as a road map for those researchers embracing this emerging therapeutic area targeting the AHR. Moreover, it is a timely opportunity as the first AHR antagonists have recently entered the clinical stage of drug development.

Eriocitrin, a dietary flavonoid suppressed cell proliferation, induced apoptosis through modulation of JAK2/STAT3 and JNK/p38 MAPKs signaling pathway in MCF-7 cells

Eriocitrin, a lemons flavanone, exhibits several biological properties, antiproliferative, and proapoptotic effects. However, its molecular mechanical action is not entirely clarified. Oxidative stress causes abnormal stimulation of signal transducer and activator of transcription 3 (STAT3) and c-Jun NH2-terminal kinase (JNK), p38 mitogen-activated protein kinases (MAPKs) signaling has been strongly connected with the ruling of cell survival and apoptosis of cancer cells. Herein, we investigated an antiproliferative and proapoptotic effect that Eriocitrin modulates STAT3/MAPKs signaling activation in MCF-7 cells. We noticed that Eriocitrin strongly enhances reactive oxygen species (ROS) generation, alteration of mitochondrial outer membrane potential, and enhances apoptotic morphological changes. Furthermore, Eriocitrin suppressed STAT3 phosphorylation via inhibiting an upstream molecule of JAK2 and Src kinase activation, thereby blocking STAT3 nuclear translocation. Similarly, Eriocitrin causes oxidative stress-mediated JNK/p38 MAPK signaling activation. We confirmed that Eriocitrin induced ROS-mediated apoptosis inhibited by the antioxidant substance of N-acetylcysteine. Eriocitrin induced apoptosis via suppression of STAT3 signaling regulated proteins, activating proapoptotic factors Bax, caspase 7, 8, 9 and suppressing Bcl-2, Bcl-x expression in MCF-7 cells. Overall, these results evidenced that Eriocitrin can affect multiple signaling events associated with tumorigenesis. From this evidence, Eriocitrin, a novel chemotherapeutic agent, can be used to treat breast cancer.

Anticancer effects of asiatic acid against doxorubicin-resistant breast cancer cells via an AMPK-dependent pathway in vitro

BACKGROUND AND PURPOSE

Asiatic acid is one of the active compounds isolated from Centella asiatica and has been used to treat many diseases, including hypertension, pulmonary fibrosis, and cancer. It exhibits anticancer effects in many cancers, such as ovarian, lung and colon cancer; however, its anticancer effects in breast cancer and the underlying mechanism are not fully understood. Chemoresistance is often induced after the use of chemotherapy, and it is a challenging problem in cancer therapy. The effects of asiatic acid on chemoresistance in breast cancer have never been studied. Therefore, the aim of the present study was to examine the anticancer effects of asiatic acid in doxorubicin-resistant breast cancer MCF-7 cells.

METHODS

The cells were incubated with asiatic acid at 0-160 μM for 2-24 h. Cell viability and cytotoxicity were evaluated by 3-[4, 5-dimethyl-2-thiazolyl]-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays. Florescent images were taken using a confocal microscope. P-gp function and apoptosis assays were performed using flow cytometry. Caspase activity was measured with the Caspase-Glo™ Assay System. The phosphorylation and expression of relevant proteins were assessed by western blots. Molecular docking was performed and scored by AutoDock. Cellular thermal shift assay (CETSA) was applied for experimental valuation.

RESULTS

Our data demonstrated that asiatic acid induced cell death in multiple ways, including reactive oxygen species production, adenosine triphosphate (ATP) content reduction, and adaptive immunity balance via intrinsic apoptosis, AMP-activated protein kinase (AMPK), programmed death-ligand 1 (PD-L1), and indirect nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) transcriptional pathways, using experimental validation and in silico analysis. Moreover, asiatic acid also enhanced the sensitivity of doxorubicin-resistant MCF-7 cells to doxorubicin by improving P-glycoprotein (P-gp) function.

CONCLUSIONS

This study provides evidence that asiatic acid has strong anticancer effects to reverse multidrug resistance and could be developed as a promising adjuvant drug for the treatment of chemoresistant cancer.

Discovery of heterocycle-containing α-naphthoflavone derivatives as water-soluble, highly potent and selective CYP1B1 inhibitors

Cytochrome P450 1B1 (CYP1B1) has been well validated as an attractive target for cancer prevention and drug resistance reversal. In continuation of our interest in this area, herein, a set of forty-six 6,7,10-trimethoxy-α-naphthoflavone derivatives varying in B ring was synthesized and screened against CYP1 enzymes, leading to the identification of fluorine-containing compound 15i as the most potent and selective CYP1B1 inhibitor (IC₅₀ value of 0.07 nM), being 84-fold more potent than that of the template molecule ANF. Alternatively, the amino-substituted derivative 13h not only possessed a potent inhibitory effect on CYP1B1 (IC₅₀ value of 0.98 nM), but also had a substantially increased water solubility as compared with the lead ANF (311 μg/mL for 13h and <5 μg/mL for ANF). The current study expanded the structural diversity of CYP1B1 inhibitors, and compound 13h could be considered as a promising starting point with great potential for further studies.

Tackling drug resistance with efflux pump inhibitors: from bacteria to cancerous cells

Drug resistance is a serious concern in a clinical setting jeopardizing treatment for both infectious agents and cancers alike. The wide-spread emergence of multi-drug resistant (MDR) phenotypes from bacteria to cancerous cells necessitates the need to target resistance mechanisms and prevent the emergence of resistant mutants. Drug efflux seems to be one of the preferred approaches embraced by both microbial and mammalian cells alike, to thwart the action of chemotherapeutic agents thereby leading to a drug resistant phenotype. Relative to microbes, which predominantly employs proton motive force (PMF) powered, Major Facilitator Superfamily (MFS)/Resistance Nodulation and Division (RND) classes of efflux pumps to efflux drugs, cancerous cells preferentially use ATP fuelled ATP binding cassette (ABC) transporters to extrude chemotherapeutic agents. The prevalence, evolutionary characteristics and overlapping functions of ABC transporters have been highlighted in this review. Additionally, we outline the role of ABC pumps in conferring MDR phenotype to both bacteria and cancerous cells and underscore the importance of efflux pump inhibitors (EPI) to mitigate drug resistance. Based on the literature reports and analysis, we reason out feasibility of employing bacteria as a tool to screen for EPI's targeting ABC pumps of cancerous cells.

Mechanisms of Matrix-Induced Chemoresistance of Breast Cancer Cells-Deciphering Novel Potential Targets for a Cell Sensitization

Tumor cell binding to microenvironment components such as collagen type 1 (COL1) attenuates the sensitivity to cytotoxic drugs like cisplatin (CDDP) or mitoxantrone (MX), referred to as cell adhesion mediated drug resistance (CAM-DR). CAM-DR is considered as the onset for resistance mutations, but underlying mechanisms remain elusive. To evaluate CAM-DR as target for sensitization strategies, we analyzed signaling pathways in human estrogen-positive MCF-7 and triple-negative MDA-MB-231 breast cancer cells by western blot, proteome profiler array and TOP-flash assay in presence of COL1. β1-Integrins, known to bind COL1, appear as key for mediating COL1-related resistance in both cell lines that primarily follows FAK/PI3K/AKT pathway in MCF-7, and MAPK pathway in MDA-MB-231 cells. Notably, pCREB is highly elevated in both cell lines. Consequently, blocking these pathways sensitizes the cells evidently to CDDP and MX treatment. Wnt signaling is not relevant in this context. A β1-integrin knockdown of MCF-7 cells (MCF-7-β1-kd) reveals a signaling shift from FAK/PI3K/AKT to MAPK pathway, thus CREB emerges as a promising primary target for sensitization in MDA-MB-231, and secondary target in MCF-7 cells. Concluding, we provide evidence for importance of CAM-DR in breast cancer cells and identify intracellular signaling pathways as targets to sensitize cells for cytotoxicity treatment regimes.

Alpha-naphthoflavone induces apoptosis through endoplasmic reticulum stress via c-Src-, ROS-, MAPKs-, and arylhydrocarbon receptor-dependent pathways in HT22 hippocampal neuronal cells

α-Naphthoflavone (αNF) is a prototype flavone, also known as a modulator of aryl hydrocarbon receptor (AhR). In the present study, we investigated the molecular mechanisms of αNF-induced cytotoxic effects in HT22 mouse hippocampal neuronal cells. αNF induced apoptotic cell death via activation of caspase-12 and -3 and increased expression of endoplasmic reticulum (ER) stress-associated proteins, including C/EBP homologous protein (CHOP). Inhibition of ER stress by treatment with the ER stress inhibitor, salubrinal, or by CHOP siRNA transfection reduced αNF-induced cell death. αNF activated mitogen-activated protein kinases (MAPKs), such as p38, JNK, and ERK, and inhibition of MAPKs reduced αNF-induced CHOP expression and cell death. αNF also induced accumulation of reactive oxygen species (ROS) and an antioxidant, N-acetylcysteine, reduced αNF-induced MAPK phosphorylation, CHOP expression, and cell death. Furthermore, αNF activated c-Src kinase, and inhibition of c-Src by a kinase inhibitor, SU6656, or siRNA transfection reduced αNF-induced ROS accumulation, MAPK activation, CHOP expression, and cell death. Inhibition of AhR by an AhR antagonist, CH223191, and siRNA transfection of AhR and AhR nuclear translocator reduced αNF-induced AhR-responsive luciferase activity, CHOP expression, and cell death. Finally, we found that inhibition of c-Src and MAPKs reduced αNF-induced transcriptional activity of AhR. Taken together, these findings suggest that αNF induces apoptosis through ER stress via c-Src-, ROS-, MAPKs-, and AhR-dependent pathways in HT22 cells.

Role of Pyk2 in Human Cancers

Proline-rich tyrosine kinase 2 (Pyk2) plays essential roles in tumorigenesis and tumor progression. Pyk2 serves as a non-receptor tyrosine kinase regulating tumor cell survival, proliferation, migration, invasion, metastasis, and chemo-resistance, and is associated with poor prognosis and shortened survival in various cancer types. Thus, Pyk2 has been traditionally regarded as an oncogene and potential therapeutic target for cancers. However, a few studies have also demonstrated that Pyk2 exerts tumor-suppressive effects in some cancers, and anti-cancer treatment of Pyk2 inhibitors may only achieve marginal benefits in these cancers. Therefore, more detailed knowledge of the contradictory functions of Pyk2 is needed. In this review, we summarized the tissue distribution, expression, interactive molecules of Pyk2 in the signaling pathway, and roles of Pyk2 in cancers, and focused on regulation of the interconnectivity between Pyk2 and its downstream targets. The potential use of inhibitors of Pyk2 and its related pathways in cancer therapy is also discussed.

Structural-based design, synthesis, and antitumor activity of novel alloxazine analogues with potential selective kinase inhibition

Protein kinases are promising therapeutic targets for cancer therapy. Here, we applied multiple approaches to optimize the potency and selectivity of our reported alloxazine scaffold. Flexible moieties at position 2 of the hetero-tricyclic system were incorporated to fit into the ATP binding site and extend to the adjacent allosteric site and selectively inhibit protein kinases. This design led to potential selective inhibition of ABL1, CDK1/Cyclin A1, FAK, and SRC kinase by 30-59%. Cytotoxicity was improved by ∼50 times for the optimized lead (10b; IC₅₀ = 40 nM) against breast cancer (MCF-7) cells. Many compounds revealed potential cytotoxicity against ovarian (A2780) and colon carcinoma (HCT116) cells of ∼10-30 time improvement (IC₅₀ 5-17 nM). The results of the Annexin-V/PI apoptotic assay demonstrated that many compounds induced significantly early (89-146%) and a dramatically late (556-1180%) cell death in comparison to the vehicle control of MCF-7 cells. SAR indicated that 5-deazaalloxazines have a higher selectivity for Abl-1 and FAK kinases than alloxazines. The correlations between GoldScore fitness into FAK and SRC kinases and IC₅₀ against MCF-7 and A2780 cells were considerable (R²: 0.86-0.98).

Development of 2-arylbenzo[h]quinolone analogs as selective CYP1B1 inhibitors

The CYP1B1 enzyme is regarded as a potential target for cancer prevention and therapy. Based on the structure of α-naphthoflavone (ANF), diverse 2-arylbenzo[h]quinolone derivatives were designed, synthesized and evaluated as selective CYP1B1 inhibitors. Compared with ANF, although few of the title compounds possessed comparable or slightly higher CYP1B1 inhibitory activity, these compounds displayed a significantly increased selectivity toward CYP1B1 over CYP1A2. Among them compounds 5e, 5g and 5h potently inhibited the activity of CYP1B1 with IC₅₀ values of 3.6, 3.9 and 4.1 nM respectively, paralleled by an excellent selectivity profile. On the basis of predicted clog P values, these target compounds may exhibit improved water-solubility compared to ANF. In particular, 5h showed a great superiority in the reversal of CYP1B1-mediated docetaxel resistance in vitro. The current study may serve as a good starting point for the further development of more potent as well as specific CYP1B1 inhibitors capable of reversing CYP1B1-mediated anticancer-drug resistance.

2-arylbenzo[h]quinolin-4(1H)-ones are developed as selective CYP1B1 inhibitors.

Manumycin A suppresses exosome biogenesis and secretion via targeted inhibition of Ras/Raf/ERK1/2 signaling and hnRNP H1 in castration-resistant prostate cancer cells

Emerging evidence links exosomes to cancer progression by the trafficking of oncogenic factors and neoplastic reprogramming of stem cells. This necessitates identification and integration of functionally validated exosome-targeting therapeutics into current cancer management regimens. We employed quantitative high throughput screen on two libraries to identify exosome-targeting drugs; a commercially available collection of 1280 pharmacologically active compounds and a collection of 3300 clinically approved compounds. Manumycin-A (MA), a natural microbial metabolite, was identified as an inhibitor of exosome biogenesis and secretion by castration-resistant prostate cancer (CRPC) C4-2B, but not the normal RWPE-1, cells. While no effect was observed on cell growth, MA attenuated ESCRT-0 proteins Hrs, ALIX and Rab27a and exosome biogenesis and secretion by CRPC cells. The MA inhibitory effect is primarily mediated via targeted inhibition of the Ras/Raf/ERK1/2 signaling. The Ras-dependent MA suppression of exosome biogenesis and secretion is partly mediated by ERK-dependent inhibition of the oncogenic splicing factor hnRNP H1. Our findings suggest that MA is a potential drug candidate to suppress exosome biogenesis and secretion by CRPC cells.

Identification of NCK1 as a novel downstream effector of STAT3 in colorectal cancer metastasis and angiogenesis

Signal transducer and activator of transcription 3 (STAT3) is known to activate targets associated with invasion, proliferation, and angiogenesis in a wide variety of cancers. The adaptor protein NCK1 is involved in cytoskeletal movement and was identified as a STAT3-associated target in human tumors. However, the underlying molecular mechanism associated with colorectal cancer (CRC) metastasis is not yet completely understood. In this study, we report a novel STAT3 to NCK1 signaling pathway in colorectal cancer (CRC). We investigated the expression of NCK1 and its potential clinical and biological significance in CRC. NCK1 was noticeably up-regulated in human CRC tissues. NCK1 was also significantly associated with serosal invasion, lymph metastasis, and tumor-node-metastasis classification but was inversely correlated with differentiation. Gain-of-function and loss-of-function studies have shown that ectopic expression of NCK1 enhanced metastasis and angiogenesis in CRC cells. By gene expression analyses, we revealed a high co-overexpression of STAT3 and NCK1 in CRC tissues. Ectopic overexpression of STAT3 in CRC cells induced the expression of NCK1, whereas STAT3 knockdown decreased the expression of NCK1. Promoter activation and binding analyses demonstrated that STAT3 promoted the expression of NCK1 via direct action on the NCK1 promoter. The knock down of NCK1 partially reduced the CRC cell metastasis and angiogenesis promoted by STAT3. Additionally, by co-immunoprecipitation assays, we verified that NCK1 interacted with PAK1, which resulted in the activation of the PAK1/ERK pathway. STAT3 induced the transcription of NCK1 and triggered a PAK1/ERK cascade in CRC. These findings suggest a novel STAT3 to NCK1 to PAK1/ERK signaling mechanism that is potentially critical for CRC metastasis and angiogenesis.

Exercise during pregnancy decreases doxorubicin-induced cardiotoxic effects on neonatal hearts

Cancer treatment with Doxorubicin (DOX) is limited due its dose-dependent cardiotoxicity, mainly related to the oxidative stress production. In experimental models of DOX treatment exercise can be used as a beneficial adjuvant therapy. This work aimed to investigate the effects of exercise during pregnancy on DOX-induced cardiotoxicity in cardiomyocytes of progeny, examining the possible intergenerational cardioprotective effects of maternal exercise. For this purpose pregnant rats were divided in control and exercise groups and pre-treated during gestational days. Hearts of newborns were used to obtain a culture of cardiomyocytes to be treated with DOX for analyses of cell viability, apoptosis and necrosis; ROS production; DNA damage; SOD and CAT activities; and Sirt6 protein expression. The results showed that exercise during pregnancy induced an increase in the viability of neonatal cardiomyocytes and a decrease in DOX-induced apoptotic and necrotic death which were correlated to the decrease in ROS production and an increase in antioxidant defenses. Exercise also protected neonatal cardiomyocytes from DOX-induced DNA damage, demonstrating a reduction in the oxidative DNA breaks. Likewise, exercise induced an increase in expression of Sirt6 in neonatal cardiomyocytes. Therefore, these results demonstrate for the first time that exercise performed by mothers protects the neonatal heart against DOX-induced toxicity. Our data demonstrate the intergenerational effect of exercise in cardiomyocytes of progeny, where the modulation of oxidative stress through antioxidant enzymes, and DNA integrity via Sirt6, were induced due to exercise in mothers, increasing the resistance of the neonatal heart against DOX toxicity.

Nelfinavir targets multiple drug resistance mechanisms to increase the efficacy of doxorubicin in MCF-7/Dox breast cancer cells

Development of multidrug resistance (MDR) remains a significant problem in cancer chemotherapy and underscores the importance of using chemosensitizers. Well known MDR mechanisms include: (i) upregulation of drug-efflux; (ii) increased signaling via AKT; and (iii) decreased apoptosis. Therefore, chemosensitizers should target multiple resistance mechanisms. We investigated the efficacy of nelfinavir (NFV), a clinically approved anti-HIV drug, in increasing doxorubicin (DOX) toxicity in a MDR breast cancer cell line, MCF-7/Dox. As compared to parental MCF-7 cells, the MCF-7/Dox were 15-20 fold more resistant to DOX-induced cytotoxicity at 48 h post-exposure (DOX IC50 = 1.8 μM vs. 32.4 μM). Coexposures to NFV could significantly (p < 0.05) decrease DOX-IC50 in MCF-7/Dox cells. Multiple exposures to physiologic concentrations of NFV (2.25 μM or 6.75 μM) decreased DOX-IC50 by 21-fold and 50-fold, respectively. Interestingly, although single exposure to NFV transiently induced P-glycoprotein (P-gp) levels, multiple treatments with NFV inhibited both P-gp expression and efflux function, which increased intracellular DOX concentrations. Single exposure to NFV augmented the markers of cell-survival (AKT) and autophagy (LC3-II), whereas multiple exposures enabled suppression of both total AKT (t-AKT) and insulin like growth factor-1 (IGF-1)-induced phosphorylated AKT (p-AKT) levels. Multiple exposures to NFV also resulted in increased unfolded protein response (UPR) transducers, e.g. Grp78, p-PERK, p-eIF2α, and ATF-4; and endoplasmic reticulum (ER) stress induced death sensors, e.g. CHOP & TRIB-3. Multiple exposures to NFV also abrogated the mitogenic effects of IGF-1. In mice carrying MCF-7/Dox tumor xenografts, intraperitoneal (i.p.) injection of NFV (20 mg/kg/day) and DOX (2 mg/kg/twice/wk) decreased tumor growth more significantly (p < 0.01) than either agent alone. Immunohistochemical (IHC) analysis revealed decreased p-AKT and Ki-67 levels. Thus, NFV overcomes MDR in breast cancer cells and should be tested as an adjunct to chemotherapy.

Colorimetric Detection of Some Highly Hydrophobic Flavonoids Using Polydiacetylene Liposomes Containing Pentacosa-10,12-diynoyl Succinoglycan Monomers

Flavonoids are a group of plant secondary metabolites including polyphenolic molecules, and they are well known for antioxidant, anti-allergic, anti-inflammatory and anti-viral propertied. In general, flavonoids are detected with various non-colorimetric detection methods such as column liquid chromatography, thin-layer chromatography, and electrochemical analysis. For the first time, we developed a straightforward colorimetric detection system allowing recognition of some highly hydrophobic flavonoids such as alpha-naphthoflavone and beta-naphthoflavone, visually using 10,12-pentacosadiynoic acid (PCDA) derivatized with succinoglycan monomers isolated from Sinorhizobium meliloti. Besides changes in visible spectrum, we also demonstrate fluorescence changes using our detection system in the presence of those flavonoids. The succinoglycan monomers attached to PCDA molecules may function as an unstructured molecular capturer for some highly hydrophobic flavonoids by hydrophobic interactions, and transmit their molecular interactions as a color change throughout the PCDA liposome.

A novel injectable phospholipid gel co-loaded with doxorubicin and bromotetrandrine for resistant breast cancer treatment by intratumoral injection

Systemically administered anticancer treatments were greatly limited by extensive side effects mainly due to nonspecific distributions in vivo, and multidrug resistance in various tumors. A phospholipids-based in situ-forming gel platform has been developed for the concurrent delivery of doxorubicin (DOX) and bromotetrandrin (W198). Phospholipid gel containing DOX and W198 remained in a solution (sol) state before injection and underwent rapid gelation after injection in vivo. The release of DOX and W198 from phospholipid gel (PG) was sustained in vitro for over 20 days (d). DOX and W198 from PG achieved prolonged release for over two weeks in rats via subcutaneous injection. Compared with repeated injections of free drug, eliminated cardiac toxicity and less bone marrow inhibition were observed for DOX and W198-loaded PG (DOX/W198-PG) in normal rats via subcutaneous injection. Also, a single intratumoral injection of DOX/W198-PG in the resistant MCF-7/Adr xenograft-bearing mice showed much better antitumor efficacy compared to other treatment groups. In sum, DOX/W198-PG was well demonstrated to achieve sustained drug release both in vitro and in vivo with eliminated toxicity and improved antitumor efficacy by reversing the multidrug resistance in breast cancers.

The role of Pyk2 in the CCR7-mediated regulation of metastasis and viability in squamous cell carcinoma of the head and neck cells in vivo and in vitro

In the present study, we aimed to demonstrate whether praline-rich tyrosine kinase-2 (Pyk2) participates in the chemokine receptor 7 (CCR7) downstream signaling network, and to determine the role of this molecule and the related mechanism in the CCR7-mediated regulation of viability and metastasis in vivo and in vitro of squamous cell carcinoma of the head and neck (SCCHN). We constructed the stable Pyk2 related non-kinase (PRNK)-expressing SCCHN cell line, and examined the viability, apoptosis, migration, invasion and adhesion ability in the transfected and untransfected SCCHN cells. An SCCHN tumor model in nude mice was designed and the tumor growth rate was assayed. E-cadherin and vimentin expression was assessed when Pyk2 was inactivated. We found that the stable PRNK-expressing SCCHN cells exhibited low viability, a high rate of apoptosis, low migratory ability, low invasive ability and low adhesion capacity. In the nude mouse body, the tumors formed by these cells grew slowly when compared to the tumor growth in the control group. When Pyk2 was inactivated, CCR7-induced E-cadherin and vimentin expression levels were altered. Thus, Pyk2 is a key downstream signaling molecules of CCR7 in SCCHN, which promotes SCCHN tumorigenesis and progression.

Membrane microparticles: shedding new light into cancer cell communication

BACKGROUND

Microparticles (MPs) or ectosomes are small enclosed fragments (from 0.2 to 2 μm in diameter) released from the cellular plasma membrane. Several oncogenic molecules have been identified inside MPs, including soluble proteins XIAP, survivin, metalloproteinases, CX3CL1, PYK2 and other microRNA-related proteins; membrane proteins EGFR, HER-2, integrins and efflux pumps; and messenger RNAs and microRNAs miR-21, miR-27a, let-7, miR-451, among others. Studies have shown that MPs transfer their cargo to neoplastic or non-malignant cells and thus contribute to activation of oncogenic pathways, resulting in cell survival, drug resistance and cancer dissemination.

DISCUSSION AND CONCLUSION

This review summarizes recent findings on MP biogenesis and the role of the MPs cargo in cancer and discusses some of the RNAs and proteins involved. In addition, the discussion covers evidence of (1) how and which signaling pathways can be activated by MPs in recipient cells; (2) recipient cell-type selectivity in incorporation of proteins and RNAs transported by MPs; and (3) how upon stimulation, stromal cells release MPs, promoting resistance to chemotherapeutics and invasiveness in cancer cells.