Essential role of Pyk2 and Src kinase activation in neuropeptide-induced proliferation of small cell lung cancer cells

Advancing Src kinase inhibition: From structural design to therapeutic innovation - A comprehensive review

Src kinase, a non-receptor tyrosine kinase implicated in cellular signaling networks, plays a pivotal role in tumor progression and therapeutic resistance. Despite intensive research efforts spanning decades, no Src-selective kinase inhibitors have yet entered clinical use, highlighting the challenges in developing targeted therapeutics. Here we review recent advances in small-molecule Src inhibitor development, focusing on structural design strategies, binding mechanisms, and therapeutic applications. We analyze emerging approaches including fragment-based drug design, allosteric targeting, and substrate-competitive inhibition that have yielded promising new scaffold classes. Special attention is given to innovations in achieving isozyme selectivity, particularly through exploitation of non-ATP binding pockets and covalent inhibition strategies. Integration of artificial intelligence, living organoid platforms, and targeted protein degradation technologies is accelerating inhibitor optimization. We discuss key challenges in Src inhibitor development, including the need for enhanced selectivity, reduced off-target effects, and improved resistance profiles. Our analysis reveals promising directions for future therapeutic development, emphasizing the importance of rational design principles guided by structural insights and emerging technologies. These findings provide a framework for developing next-generation Src inhibitors with improved clinical potential.

Adaptor protein CEMIP reduces the chemosensitivity of small cell lung cancer via activation of an SRC-YAP oncogenic module

Small cell lung cancer (SCLC) is a recalcitrant malignancy with dismal prognosis due to rapid relapse after an initial treatment response. More effective treatments for SCLC are desperately needed. Our previous studies showed that cell migration-inducing hyaluronan binding protein (CEMIP) functionally promotes SCLC cell proliferation and metastasis. In this study, we investigated whether and how CEMIP regulates the chemosensitivity of SCLC. Through the GDSC database, we found that CEMIP expression levels were positively correlated with the IC50 values of several commonly used chemotherapeutic drugs in SCLC cells (cisplatin, gemcitabine, 5-fluorouracil and cyclophosphamide). We demonstrated that overexpression or knockdown of CEMIP in SCLC cells resulted in a notable increase or reduction in the IC50 value of cisplatin or etoposide, respectively. We further revealed that CEMIP functions as an adaptor protein in SCLC cells to interact with SRC and YAP through the 1-177 aa domain and 820-1361 aa domain, respectively, allowing the autophosphorylation of Y416 and activation of SRC, thus facilitating the interaction between YAP and activated SRC, and resulting in increased phosphorylation of Y357, protein stability, nuclear accumulation and transcriptional activation of YAP. Overexpressing SRC or YAP counteracted the CEMIP knockdown-mediated increase in the sensitivity of SCLC cells to cisplatin and etoposide. The combination of the SRC inhibitor dasatinib or the YAP inhibitor verteporfin and cisplatin/etoposide (EP regimen) displayed excellent synergistic antitumor effects on SCLC both in vitro and in vivo. This study demonstrated that targeted therapy against the CEMIP/SRC/YAP complex is a potential strategy for SCLC and provides a rationale for the development of future clinical trials with translational prospects.

High expression of PYK2 is associated with poor prognosis and cancer progression in early-stage cervical carcinoma

Proline-rich tyrosine kinase-2 (PYK2), also known as calcium dependent tyrosine kinase, regulates different signal transduction cascades that control cell proliferation, migration, and invasion. However, the role of PYK2 in cervical cancer remains to be elucidated. The current study retrospectively included 134 patients with cervical cancer from December 2007 to September 2014. PYK2 expression was detected in tissue microarray and cervical cancer cell lines. Statistical analysis was performed to evaluate its clinicopathological significance. Small interfering RNA (siRNA) was employed to suppress endogenous PYK2 expression in cervical cancer cells to observe the biological function. PYK2 expression was up-regulated in cervical cancer specimens compared with paired adjacent normal cervical tissue samples. Statistical analyses indicated that PYK2 expression might be an independent prognostic indicator for patients with early-stage cervical cancer. A nomogram model was constructed based on PYK2 expression and other clinicopathological risk factors, and it performed well in predicting patients survival. In cellular studies, down-regulation of PYK2 remarkably inhibited cellular proliferation, migration and invasion. PYK2 expression possessed the potential to serve as a novel prognostic marker in cervical cancer patients.

An overview of kinin mediated events in cancer progression and therapeutic applications

Kinins are bioactive peptides generated in the inflammatory milieu of the tissue microenvironment, which is involved in cancer progression and inflammatory response. Kinins signals through activation of two G-protein coupled receptors; inducible Bradykinin Receptor B1 (B1R) and constitutive receptor B2 (B2R). Activation of kinin receptors and its cross-talk with receptor tyrosine kinases activates multiple signaling pathways, including ERK/MAPK, PI3K, PKC, and p38 pathways regulating cancer hallmarks. Perturbations of the kinin-mediated events are implicated in various aspects of cancer invasion, matrix remodeling, and metastasis. In the tumor microenvironment, kinins initiate fibroblast activation, mesenchymal stem cell interactions, and recruitment of immune cells. Albeit the precise nature of kinin function in the metastasis and tumor microenvironment are not completely clear yet, several kinin receptor antagonists show anti-metastatic potential. Here, we showcase an overview of the complex biology of kinins and their role in cancer pathogenesis and therapeutic aspects.

KC-180-2 Exerts Anti-SCLC Effects via Dual Inhibition of Tubulin Polymerization and Src Signaling

In this study, a series of N-benzyl-2-(5-phenylpyridin-2-yl) acetamide-based derivatives were successfully designed and synthesized as anti-cancer agents. KC-180-2 was screened as a potentially leading compound with dual mechanisms of action: Src signaling and tubulin polymerization inhibition. It efficiently suppressed the proliferation of five cancer cell lines (MDA-MB-231, H446, SKOV-3, HepG2, and HT29), with IC₅₀ values ranging from 5 to 188 nM, especially small-cell lung cancer (SCLC) cells (IC₅₀, 5 nM). Correspondingly, it exerted a significant therapeutic effect on the H446 small-cell lung cancer xenograft model, significantly reducing the volume of tumors without obvious toxicity. Mechanistically, this compound significantly inhibited the polymerization of purified tubulin in vitro, inducing G2/M cell cycle arrest and binding to the kinase catalytic domain of the Src protein, which reduced the phosphorylation of Src. Thus, KC-180-2 is a potential lead compound for the further development of a new anti-tumor drug against SCLC.

The Galaninergic System: A Target for Cancer Treatment

The aim of this review is to show the involvement of the galaninergic system in neuroendocrine (phaeochromocytomas, insulinomas, neuroblastic tumors, pituitary tumors, small-cell lung cancer) and non-neuroendocrine (gastric cancer, colorectal cancer, head and neck squamous cell carcinoma, glioma) tumors. The galaninergic system is involved in tumorigenesis, invasion/migration of tumor cells and angiogenesis, and this system has been correlated with tumor size/stage/subtypes, metastasis and recurrence rate. In the galaninergic system, epigenetic mechanisms have been related with carcinogenesis and recurrence rate. Galanin (GAL) exerts both proliferative and antiproliferative actions in tumor cells. GAL receptors (GALRs) mediate different signal transduction pathways and actions, depending on the particular G protein involved and the tumor cell type. In general, the activation of GAL1R promoted an antiproliferative effect, whereas the activation of GAL2R induced antiproliferative or proliferative actions. GALRs could be used in certain tumors as therapeutic targets and diagnostic markers for treatment, prognosis and surgical outcome. The current data show the importance of the galaninergic system in the development of certain tumors and suggest future potential clinical antitumor applications using GAL agonists or antagonists.

Expression of claudin-8 is induced by aldosterone in renal collecting duct principal cells

Fine tuning of Na⁺ reabsorption takes place along the aldosterone-sensitive distal nephron, which includes the collecting duct (CD), where it is mainly regulated by aldosterone. In the CD, Na⁺ reabsorption is mediated by the epithelial Na⁺ channel and Na⁺ pump (Na⁺-K⁺-ATPase). Paracellular ion permeability is mainly dependent on tight junction permeability. Claudin-8 is one of the main tight junction proteins expressed along the aldosterone-sensitive distal nephron. We have previously shown a coupling between transcellular Na⁺ reabsorption and paracellular Na⁺ barrier. We hypothesized that aldosterone controls the expression levels of both transcellular Na⁺ transporters and paracellular claudin-8 in a coordinated manner. Here, we show that aldosterone increased mRNA and protein levels as well as lateral membrane localization of claudin-8 in cultured CD principal cells. The increase in claudin-8 mRNA levels in response to aldosterone was prevented by preincubation with 17-hydroxyprogesterone, a mineralocorticoid receptor antagonist, and by inhibition of transcription with actinomycin D. We also showed that a low-salt diet, which stimulated aldosterone secretion, was associated with increased claudin-8 abundance in the mouse kidney. Reciprocally, mice subjected to a high-salt diet, which inhibits aldosterone secretion, or treated with spironolactone, a mineralocorticoid receptor antagonist, displayed decreased claudin-8 expression. Inhibition of glycogen synthase kinase-3, Lyn, and Abl signaling pathways prevented the effect of aldosterone on claudin-8 mRNA and protein abundance, suggesting that signaling of protein kinases plays a permissive role on the transcriptional activity of the mineralocorticoid receptor. This study shows that signaling via multiple protein kinases working in concert mediates aldosterone-induced claudin-8 expression in the CD.NEW & NOTEWORTHY In this study, we showed that aldosterone modulates claudin-8 expression in cultured collecting duct principal cells and in the mouse kidney. The upregulation of claudin-8 expression in response to aldosterone is dependent on at least glycogen synthase kinase-3, Lyn, and Abl signaling pathways, indicating the participation of multiple protein kinases to the effect of aldosterone.

Discovery of a Brigatinib Degrader SIAIS164018 with Destroying Metastasis-Related Oncoproteins and a Reshuffling Kinome Profile

Proteolysis-targeting chimera (PROTAC) is an attractive technology in drug discovery. Canonically, targets act as a basic starting point in the most previous PROTAC design. Here, we designed degraders considering from the view of clinical benefits. With this novel design, Brigatinib was turned into a degrader SIAIS164018 and endowed with unique features. First, SIAIS164018 could degrade not only ALK fusion proteins in activating or G1202R-mutated form but also mutant EGFR with L858R + T790M, which are two most important targets in non-small-cell lung cancer. Second, SIAIS164018 strongly inhibited cell migration and invasion of Calu-1 and MDA-MB-231. Third and surprisingly, SIAIS164018 degrades several important oncoproteins involved in metastasis such as FAK, PYK2, and PTK6. Interestingly, SIAIS164018 reshuffled the kinome ranking profile when compared to Brigatinib. Finally, SIAIS164018 is orally bioavailable and well tolerated in vivo. SIAIS164018 is an enlightening degrader for us to excavate the charm of protein degradation.

Galanin System in Human Glioma and Pituitary Adenoma

Expression of neuropeptides and their corresponding receptors has been demonstrated in different cancer types, where they can play a role in tumor cell growth, invasion, and migration. Human galanin (GAL) is a 30-amino-acid regulatory neuropeptide which acts through three G protein-coupled receptors, GAL₁-R, GAL₂-R, and GAL₃-R that differ in their signal transduction pathways. GAL and galanin receptors (GALRs) are expressed by different tumors, and direct involvement of GAL in tumorigenesis has been shown. Despite its strong expression in the central nervous system (CNS), the role of GAL in CNS tumors has not been extensively studied. To date, GAL peptide expression, GAL receptor binding and mRNA expression have been reported in glioma, meningioma, and pituitary adenoma. However, data on the cellular distribution of GALRs are sparse. The aim of the present study was to examine the expression of GAL and GALRs in different brain tumors by immunohistochemistry. Anterior pituitary gland (n = 7), pituitary adenoma (n = 9) and glioma of different WHO grades I-IV (n = 55) were analyzed for the expression of GAL and the three GALRs with antibodies recently extensively validated for specificity. While high focal GAL immunoreactivity was detected in up to 40% of cells in the anterior pituitary gland samples, only one pituitary adenoma showed focal GAL expression, at a low level. In the anterior pituitary, GAL₁-R and GAL₃-R protein expression was observed in up to 15% of cells, whereas receptor expression was not detected in pituitary adenoma. In glioma, diffuse and focal GAL staining was noticed in the majority of cases. GAL₁-R was observed in eight out of nine glioma subtypes. GAL₂-R immunoreactivity was not detected in glioma and pituitary adenoma, while GAL₃-R expression was significantly associated to high-grade glioma (WHO grade IV). Most interestingly, expression of GAL and GALRs was observed in tumor-infiltrating immune cells, including neutrophils and glioma-associated macrophages/microglia. The presence of GALRs on tumor-associated immune cells, especially macrophages, indicates that GAL signaling contributes to homeostasis of the tumor microenvironment. Thus, our data indicate that GAL signaling in tumor-supportive myeloid cells could be a novel therapeutic target.

EGFR signaling pathway occupies an important position in cancer-related downstream signaling pathways of Pyk2

Proline-rich tyrosine kinase 2 (Pyk2) is a member of focal adhesion kinase (FAK) non-receptor tyrosine kinase family and has been found to promote cancer cell survival, proliferation, migration, invasion, and metastasis. Pyk2 takes part in different carcinogenic signaling pathways to promote cancer progression, including epidermal growth factor receptor (EGFR) signaling pathway. EGFR signaling pathway is a traditional carcinogenic signaling pathway, which plays a critical role in tumorigenesis and tumor progression. FAK inhibitors have been reported to fail to get the ideal anti-cancer outcomes because of activation of EGFR signaling pathway. Better understanding of Pyk2 downstream targets and interconnectivity between Pyk2 and carcinogenic EGFR signaling pathway will help finding more effective targets for clinical anti-cancer combination therapies. Thus, the interconnectivity between Pyk2 and EGFR signaling pathway, which regulates tumor development and metastasis, needs to be elucidated. In this review, we summarized the downstream targets of Pyk2 in cancers, focused on the connection between Pyk2 and EGFR signaling pathway in different cancer types, and provided a new overview of the roles of Pyk2 in EGFR signaling pathway and cancer development.

Trpm2 enhances physiological bioenergetics and protects against pathological oxidative cardiac injury: Role of Pyk2 phosphorylation

The mechanisms by which Trpm2 channels enhance mitochondrial bioenergetics and protect against oxidative stress-induced cardiac injury remain unclear. Here, the role of proline-rich tyrosine kinase 2 (Pyk2) in Trpm2 signaling is explored. Activation of Trpm2 in adult myocytes with H₂ O₂ resulted in 10- to 21-fold increases in Pyk2 phosphorylation in wild-type (WT) myocytes which was significantly lower (~40%) in Trpm2 knockout (KO) myocytes. Pyk2 phosphorylation was inhibited (~54%) by the Trpm2 blocker clotrimazole. Buffering Trpm2-mediated Ca²⁺ increase with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) resulted in significantly reduced pPyk2 in WT but not in KO myocytes, indicating Ca²⁺ influx through activated Trpm2 channels phosphorylated Pyk2. Part of phosphorylated Pyk2 translocated from cytosol to mitochondria which has been previously shown to augment mitochondrial Ca²⁺ uptake and enhance adenosine triphosphate generation. Although Trpm2-mediated Ca²⁺ influx phosphorylated Ca²⁺ -calmodulin kinase II (CaMKII), the CaMKII inhibitor KN93 did not significantly affect Pyk2 phosphorylation in H₂ O₂ -treated WT myocytes. After ischemia/reperfusion (I/R), Pyk2 phosphorylation and its downstream prosurvival signaling molecules (pERK1/2 and pAkt) were significantly lower in KO-I/R when compared with WT-I/R hearts. After hypoxia/reoxygenation, mitochondrial membrane potential was lower and superoxide level was higher in KO myocytes, and were restored to WT values by the mitochondria-targeted superoxide scavenger MitoTempo. Our results suggested that Ca²⁺ influx via tonically activated Trpm2 phosphorylated Pyk2, part of which translocated to mitochondria, resulting in better mitochondrial bioenergetics to maintain cardiac health. After I/R, Pyk2 activated prosurvival signaling molecules and prevented excessive increases in reactive oxygen species, thereby affording protection from I/R injury.

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.

Significance of PYK2 level as a prognosis predictor in patients with colon adenocarcinoma after surgical resection

Background

Proline-rich/Ca²⁺-activated tyrosine kinase 2 (PYK2) belongs to the non-receptor tyrosine kinase family, regulates downstream signaling via catalyzing protein phosphorylation. We aimed to investigate clinical significance and mechanisms of PYK2 in colon adenocarcinoma (CAC).

Methods

Real time quantitative PCR and immunohistochemistry staining was used to evaluate the expression of PYK2 in clinical CAC tissues. Its association with clinicopathologic characteristics was analyzed by Chi-square test. Kaplan-Meier univariate survival analysis and multivariate Cox regression analysis were used to identify clinical significance of PYK2 in the overall survival of CAC patients. Transfection of PYK2 were conducted to reveal the underlying mechanism in regulating CAC progression.

Results

We found that PYK2 was upregulated in CAC tissues compared with normal colon tissues on both RNA and protein levels. Higher tissue PYK2 expression level was closely associated with lymph node metastasis. Statistical analyses indicated PYK2 as an independent prognostic biomarker for CAC. Cellular studies demonstrated that PYK2 enhanced the capacities of tumor proliferation and invasion. Moreover, the phosphorylation level of AKT was positively correlated with PYK2 expression, subsequently modulate expression of c-Myc and Cyclin D1, suggesting that PYK2 may promote tumor progression through activating AKT signaling.

Conclusion

High PYK2 in CAC tissues indicate poor prognosis.

The human ion channel TRPM2 modulates neuroblastoma cell survival and mitochondrial function through Pyk2, CREB, and MCU activation

Transient receptor potential melastatin channel subfamily member 2 (TRPM2) has an essential function in cell survival and is highly expressed in many cancers. Inhibition of TRPM2 in neuroblastoma by depletion with CRISPR technology or expression of dominant negative TRPM2-S has been shown to significantly reduce cell viability. Here, the role of proline-rich tyrosine kinase 2 (Pyk2) in TRPM2 modulation of neuroblastoma viability was explored. In TRPM2-depleted cells, phosphorylation and expression of Pyk2 and cAMP-responsive element-binding protein (CREB), a downstream target, were significantly reduced after application of the chemotherapeutic agent doxorubicin. Overexpression of wild-type Pyk2 rescued cell viability. Reduction of Pyk2 expression with shRNA decreased cell viability and CREB phosphorylation and expression, demonstrating Pyk2 modulates CREB activation. TRPM2 depletion impaired phosphorylation of Src, an activator of Pyk2, and this may be a mechanism to reduce Pyk2 phosphorylation. TRPM2 inhibition was previously demonstrated to decrease mitochondrial function. Here, CREB, Pyk2, and phosphorylated Src were reduced in mitochondria of TRPM2-depleted cells, consistent with their role in modulating expression and activation of mitochondrial proteins. Phosphorylated Src and phosphorylated and total CREB were reduced in TRPM2-depleted nuclei. Expression and function of mitochondrial calcium uniporter (MCU), a target of phosphorylated Pyk2 and CREB, were significantly reduced. Wild-type TRPM2 but not Ca²⁺-impermeable mutant E960D reconstituted phosphorylation and expression of Pyk2 and CREB in TRPM2-depleted cells exposed to doxorubicin. Results demonstrate that TRPM2 expression protects the viability of neuroblastoma through Src, Pyk2, CREB, and MCU activation, which play key roles in maintaining mitochondrial function and cellular bioenergetics.

Proline-Rich Protein Tyrosine Kinase 2 in Inflammation and Cancer

Focal adhesion kinase (FAK) and its homologous FAK-related proline-rich tyrosine kinase 2 (Pyk2) contain the same domain, exhibit high sequence homology and are defined as a distinct family of non-receptor tyrosine kinases. This group of kinases plays critical roles in cytoskeletal dynamics and cell adhesion by regulating survival and growth signaling. This review summarizes the physiological and pathological functions of Pyk2 in inflammation and cancers. In particular, overexpression of Pyk2 in cancerous tissues is correlated with poor outcomes. Pyk2 stimulates multiple oncogenic signaling pathways, such as Wnt/β-catenin, PI3K/Akt, MAPK/ERK, and TGF-β/EGFR/VEGF, and facilitates carcinogenesis, migration, invasion, epithelial⁻mesenchymal transition and metastasis. Therefore, Pyk2 is a high-value therapeutic target and has clinical significance.

Expression of the serotonin receptor 2B in uveal melanoma and effects of an antagonist on cell lines

Uveal melanoma (UM) is the most common primary tumor in the adult, and disseminates to the liver in half of patients. A 15-gene expression profile prognostic assay allows to determine the likelihood of metastasis in patients using their ocular tumor DNA, but a cure still remains to be discovered. The serotonin receptor 2B represents the discriminant gene of this molecular signature with the greatest impact on the prognosis of UM. However, its contribution to the metastatic potential of UM remains unexplored. The purpose of this study was to investigate the effects of a selective serotonin receptor 2B antagonist on cellular and molecular behaviours of UM cells. UM cell lines expressing high level of serotonin receptor 2B proteins were selected by Western blotting. The selective serotonin receptor 2B antagonist PRX-08066 was evaluated for its impact on UM cells using viability assays, phosphorylated histone H3 immunostainings, clonogenic assays, migration assays, invasion assays and membrane-based protein kinase phosphorylation antibody arrays. The pharmacological inhibition of the serotonin receptor 2B reduced the viability of UM cells and the population in mitosis, and impaired their clonogenicity and potential of migration. It also decreased the phosphorylation of kinases from signaling pathways classically activated by the serotonin receptor 2B, as well as kinases β-catenin, Proline-rich tyrosine kinase 2, and Signal transducer and activator of transcription 5. Our findings support a role for the serotonin receptor 2B in the proliferation and migration of UM cells, through activation of many signaling pathways such as WNT, Focal adhesion kinase and Janus kinase/STAT.

Lemongrass essential oil and citral inhibit Src/Stat3 activity and suppress the proliferation/survival of small-cell lung cancer cells, alone or in combination with chemotherapeutic agents

Small-cell lung cancer (SCLC) is intractable due to its high propensity for relapse. Novel agents are thus needed for SCLC treatment. Lemongrass essential oil (LG-EO) and its major constituent, citral, have been reported to inhibit the proliferation and survival of several types of cancer cells. However, the precise mechanisms through which LG-EO and citral exert their effects on SCLC cells have not been fully elucidated. SCLC cells express Src and have high levels of Src-tyrosine kinase (Src-TK) activity. In most SCLC cell lines, constitutive phosphorylation of Stat3(Y705), which is essential for its activation, has been detected. Src-TK can phosphorylate Stat3(Y705), and activated Stat3 promotes the expression of the anti-apoptotic factors Bcl-xL and Mcl-1. In the present study, LG-EO and citral prevented Src-TK from phosphorylating Stat3(Y705), resulting in decreased Bcl-xL and Mcl-1 expression, in turn suppressing the proliferation/survival of SCLC cells. To confirm these findings, the wild-type-src gene was transfected into the LU135 SCLC cell line (LU135‑wt-src), in which Src and activated phospho-Stat3(Y705) were overexpressed. The suppression of cell proliferation and the induction of apoptosis by treatment with LG-EO or citral were significantly attenuated in the LU135-wt-src cells compared with the control LU135-mock cells. The signal transducer and activator of transcription 3 (Stat3) signaling pathway is also associated with intrinsic drug resistance. LU135-wt-src cells were significantly resistant to conventional chemotherapeutic agents compared with LU135-mock cells. The combined effects of citral and each conventional chemotherapeutic agent on SCLC cells were also evaluated. The combination treatment exerted additive or more prominent effects on LU135-wt-src, LU165 and MN1112 cells, which are relatively chemoresistant SCLC cells. These findings suggest that either LG-EO or citral, alone or in combination with chemotherapeutic agents, may be a novel therapeutic option for SCLC patients.

Exploiting cancer's phenotypic guise against itself: targeting ectopically expressed peptide G-protein coupled receptors for lung cancer therapy

Lung cancer, claiming millions of lives annually, has the highest mortality rate worldwide. This advocates the development of novel cancer therapies that are highly toxic for cancer cells but negligibly toxic for healthy cells. One of the effective treatments is targeting overexpressed surface receptors of cancer cells with receptor-specific drugs. The receptors-in-focus in the current review are the G-protein coupled receptors (GPCRs), which are often overexpressed in various types of tumors. The peptide subfamily of GPCRs is the pivot of the current article owing to the high affinity and specificity to and of their cognate peptide ligands, and the proven efficacy of peptide-based therapeutics. The article summarizes various ectopically expressed peptide GPCRs in lung cancer, namely, Cholecystokinin-B/Gastrin receptor, the Bombesin receptor family, Bradykinin B1 and B2 receptors, Arginine vasopressin receptors 1a, 1b and 2, and the Somatostatin receptor type 2. The autocrine growth and pro-proliferative pathways they mediate, and the distinct tumor-inhibitory effects of somatostatin receptors are then discussed. The next section covers how these pathways may be influenced or 'corrected' through therapeutics (involving agonists and antagonists) targeting the overexpressed peptide GPCRs. The review proceeds on to Nano-scaled delivery platforms, which enclose chemotherapeutic agents and are decorated with peptide ligands on their external surface, as an effective means of targeting cancer cells. We conclude that targeting these overexpressed peptide GPCRs is potentially evolving as a highly promising form of lung cancer therapy.

PYK2 integrates growth factor and cytokine receptors signaling and potentiates breast cancer invasion via a positive feedback loop

The involvement of ErbB family members in breast cancer progression and metastasis has been demonstrated by many studies. However, the downstream effectors that mediate their migratory and invasive responses have not been fully explored. In this study, we show that the non-receptor tyrosine kinase PYK2 is a key effector of EGFR and HER2 signaling in human breast carcinoma. We found that PYK2 is activated by both EGF and heregulin (HRG) in breast cancer cells, and positively regulates EGF/HRG-induced cell spreading, migration and invasion. PYK2 depletion markedly affects ERK1/2 and STAT3 phosphorylation in response to EGF/HRG as well as to IL8 treatment. Importantly, PYK2 depletion also reduced EGF/HRG-induced MMP9 and IL8 transcription, while IL8 inhibition abrogated EGF-induced MMP9 transcription and attenuated cell invasion. IL8, which is transcriptionally regulated by STAT3 and induces PYK2 activation, prolonged EGF-induced PYK2, STAT3 and ERK1/2 phosphorylation suggesting that IL8 acts through an autocrine loop to reinforce EGF-induced signals. Collectively our studies suggest that PYK2 is a common downstream effector of ErbB and IL8 receptors, and that PYK2 integrates their signaling pathways through a positive feedback loop to potentiate breast cancer invasion. Hence, PYK2 could be a potential therapeutic target for a subset of breast cancer patients.

Physiology, signaling, and pharmacology of galanin peptides and receptors: three decades of emerging diversity

Galanin was first identified 30 years ago as a "classic neuropeptide," with actions primarily as a modulator of neurotransmission in the brain and peripheral nervous system. Other structurally-related peptides-galanin-like peptide and alarin-with diverse biologic actions in brain and other tissues have since been identified, although, unlike galanin, their cognate receptors are currently unknown. Over the last two decades, in addition to many neuronal actions, a number of nonneuronal actions of galanin and other galanin family peptides have been described. These include actions associated with neural stem cells, nonneuronal cells in the brain such as glia, endocrine functions, effects on metabolism, energy homeostasis, and paracrine effects in bone. Substantial new data also indicate an emerging role for galanin in innate immunity, inflammation, and cancer. Galanin has been shown to regulate its numerous physiologic and pathophysiological processes through interactions with three G protein-coupled receptors, GAL1, GAL2, and GAL3, and signaling via multiple transduction pathways, including inhibition of cAMP/PKA (GAL1, GAL3) and stimulation of phospholipase C (GAL2). In this review, we emphasize the importance of novel galanin receptor-specific agonists and antagonists. Also, other approaches, including new transgenic mouse lines (such as a recently characterized GAL3 knockout mouse) represent, in combination with viral-based techniques, critical tools required to better evaluate galanin system physiology. These in turn will help identify potential targets of the galanin/galanin-receptor systems in a diverse range of human diseases, including pain, mood disorders, epilepsy, neurodegenerative conditions, diabetes, and cancer.

Noncanonical G-protein-dependent modulation of osteoclast differentiation and bone resorption mediated by Pasteurella multocida toxin

Pasteurella multocida toxin (PMT) induces atrophic rhinitis in animals, which is characterized by a degradation of nasal turbinate bones, indicating an effect of the toxin on bone cells such as osteoblasts and osteoclasts. The underlying molecular mechanism of PMT was defined as a persistent activation of heterotrimeric G proteins by deamidation of a specific glutamine residue. Here, we show that PMT acts directly on osteoclast precursor cells such as bone marrow-derived CD14⁺ monocytes and RAW246.7 cells to induce osteoclastogenesis as measured by expression of osteoclast-specific markers such as tartrate-resistant acid phosphatase and bone resorption activity. Treatment performed solely with PMT stimulates osteoclast differentiation, showing a receptor activator of nuclear factor-κB ligand (RANKL)-independent action of the toxin. The underlying signal transduction pathway was defined as activation of the heterotrimeric G proteins Gα_q/11 leading to the transactivation of Ras and the mitogen-activated protein kinase pathway. Gα_q/11 transactivates Ras via its effector phospholipase Cβ-protein kinase C (PKC) involving proline-rich tyrosine kinase 2 (Pyk2). PMT-induced activation of the mitogen-activated protein kinase pathway results in stimulation of the osteoclastogenic transcription factors AP-1, NF-κB, and NFATc1. In addition, Ca²⁺-dependent calcineurin activation of NFAT is crucial for PMT-induced osteoclastogenesis. The data not only elucidate a rationale for PMT-dependent bone loss during atrophic rhinitis but also highlight a noncanonical, G-protein-dependent pathway toward bone resorption that is distinct from the RANKL-RANK pathway but mimics it. We define heterotrimeric G proteins as as-yet-underestimated entities/players in the maturation of osteoclasts which might be of pharmacological relevance.

Pasteurella multocida toxin (PMT) induces degradation of nasal turbinate bones, leading to the syndrome of atrophic rhinitis. Recently, the molecular mechanism and substrate specificity of PMT were identified. The toxin activates heterotrimeric G proteins by a covalent modification. However, the mechanism by which PMT induces bone degradation is poorly understood. Our report demonstrates a direct effect of PMT on osteoclast precursor cells, leading to maturation of bone-degrading osteoclasts. Interestingly, PMT stimulates osteoclastogenesis independently of the cytokine RANKL, which is a key factor in induction of osteoclast differentiation. This implicates a noncanonical osteoclastogenic signaling pathway induced by PMT. The elucidated Gα_q/11-dependent osteoclastogenic signal transduction pathway ends in osteoclastogenic NFAT signaling. The noncanonical, heterotrimeric G protein-dependent osteoclast differentiation process may be of pharmacological relevance, as members of this pathway are highly druggable. In particular, modulation of G protein-coupled receptor activity in osteoclast progenitors by small molecules might be of specific interest.

SOCS3 expression is inversely correlated with Pyk2 in non-small cell lung cancer and exogenous SOCS3 inhibits proliferation and invasion of A549 cells

AIMS

We have confirmed that suppressor of cytokine signalling 3 (SOCS3) is silenced and proline-rich tyrosine kinase 2 (Pyk2) is over-expressed in non-small cell lung cancer (NSCLC). The aim of this study was to investigate the correlation of SOCS3 and Pyk2 expression in NSCLC, and the effects of SOCS3 up-regulation on A549 cells.

METHODS

One hundred cases of NSCLC were detected for the expression of SOCS3 and Pyk2 by immunohistochemistry. The expression of SOCS3 and Pyk2 were also examined in human bronchial epithelial cells (HBE) and six lung cancer cell lines using Western blot and immunofluorescence staining. Then plasmid containing full-length SOCS3 was transfected into A549 cells to further investigate the effects of SOCS3 over-expression on proliferation, apoptosis and invasion of transfected cells, which were examined using MTT, flow cytometry and Transwell assays.

RESULTS

Our results showed a significant negative correlation between SOCS3 and Pyk2 in both NSCLC tissues and cell lines. Up-regulation of SOCS3 increased the apoptotic rates of transfected cells, while the numbers of proliferative and invasive cells were decreased.

CONCLUSIONS

Our data indicate that SOCS3 definitely plays roles in regulating Pyk2 expression, and up-regulation of SOCS3 could be an effective way to prevent the progression of NSCLC.

A phase II trial of the Src-kinase inhibitor saracatinib after four cycles of chemotherapy for patients with extensive stage small cell lung cancer: NCCTG trial N-0621

INTRODUCTION

To assess the efficacy and the Src-kinase inhibitor saracatinib (AZD-0530) after four cycles of platinum-based chemotherapy for extensive stage small cell lung cancer (SCLC).

METHODS

Patients with at least stable disease received saracatinib at a dose of 175 mg/day by mouth until disease progression, unacceptable toxicity, or patient refusal. The primary endpoint was the 12-week progression-free survival (PFS) rate from initiation of saracatinib treatment. Planned interim analysis in first 20 patients, where 13 or more patients alive and progression-free at 12-weeks would allow continued enrollment to 40 total patients.

RESULTS

All 23 evaluable patients received platinum based standard chemotherapy. Median age was 58 years (range: 48-82). 96% of patients had a performance status of 0/1. Median of two cycles given (range: 1-34). All 23 (100%) patients have ended treatment, most for disease progression (19/23). The 12-week PFS rate was 26% (6/23; 95% CI: 10-48%). From start of standard chemotherapy, median PFS was 4.7 months (95% CI: 4.5-5.1) and median OS was 11.2 months (95% CI: 9.9-13.8). Eight (35%) and three (13%) patients experienced at least one grade 3/4 or grade 4 AE, respectively. Commonly occurring grade 3/4 adverse events were thrombocytopenia (13%), fatigue (9%), nausea (9%), and vomiting (9%).

CONCLUSIONS

Saracatinib at a dose of 175 mg/day by mouth is well tolerated. However, the PFS rate observed at the pre-planned interim analysis did not meet the criteria for additional enrollment.

Focal adhesion protein expression in human diffuse large B-cell lymphoma

AIMS

Focal adhesions have been associated with poor prognosis in multiple cancer types, but their prognostic value in diffuse large B-cell lymphoma (DLBCL) has not been evaluated. The aim of this study was to investigate the expression patterns and the prognostic value of the focal adhesion proteins FAK, Pyk2, p130Cas and HEF1 in DLBCL.

METHODS AND RESULTS

Focal adhesion protein expression was examined using immunohistochemistry in normal lymphoid tissues and in 60 DLBCL patient samples. Kaplan-Meier survival and Cox regression analysis were performed to evaluate the correlation of focal adhesion protein expression with patient prognosis. FAK, Pyk2, p130Cas and HEF1 expression was mostly found in the germinal centres of normal human lymphoid tissues. When assessed in DLBCL samples, FAK, Pyk2, p130Cas and HEF1 were highly expressed in 45%, 34%, 42% and 45% of the samples, respectively. Multivariate Cox analysis revealed that decreased FAK expression was a significant independent predictor of poorer disease outcome.

CONCLUSIONS

FAK expression is an independent prognostic factor in DLBCL. Our results suggest that the addition of FAK immunostaining to the current immunohistochemical algorithms may facilitate risk stratification of DLBCL patients.

Small-cell lung cancer: an update on targeted therapies

Lung cancer is the leading cause of cancer-related deaths world-wide and small-cell lung cancer (SCLC) accounts for up to 25% of lung cancer deaths. There has been a considerable amount of research in the understanding of the depth of biology of SCLC and utilizing this knowledge to develop targeted approaches. The treatment of SCLC remains a challenge, despite remarkable initial efficacy to combination chemotherapy and radiation therapy. The response is usually short-lived and the prognosis of SCLC has not changed over the past few decades, necessitating the critical need for evaluating novel agents/therapies. Several signaling pathways have been found to be activated in SCLC tumor cells, forming a rationale for blocking some of the drugable targets. Molecular changes and biological markers have been identified but remain to be validated. Novel and targeted agents have been evaluated but without much success. Increasing understanding of the biology and potential clinical evaluation of biomarkers will pave the way for more effective treatments.

PYK-2 is tyrosine phosphorylated after activation of pituitary adenylate cyclase activating polypeptide receptors in lung cancer cells

The signal transduction mechanisms of pituitary adenylate cyclase activating polypeptide (PACAP) were investigated in lung cancer cells. Previously, PACAP-27 addition to NCI-H838 cells increased phosphatidylinositol turnover and intracellular cAMP leading to proliferation of lung cancer cells. Also, PACAP receptors (PAC1) regulated the tyrosine phosphorylation of ERK, focal adhesion kinase, and paxillin. In this communication, the effects of PACAP on cytosolic Ca(2+) and PYK-2 tyrosine phosphorylation were investigated. PACAP-27 increased cytosolic Ca(2+) within seconds after addition to FURA-2 AM loaded NCI-H838 cells. The increase in cytosolic Ca(2+) caused by PACAP was inhibited by PACAP(6-38) (PAC1 antagonist), U73122 (phospholipase C inhibitor), or BAPTA (calcium chelator), but not H89 (PKA inhibitor). PACAP-38, but not vasoactive intestinal peptide (VIP), addition to NCI-H838 or H1299 cells significantly increased the tyrosine phosphorylation of PYK-2 after 2 min. The increase in PYK-2 tyrosine phosphorylation caused by PACAP was inhibited by PACAP(6-38), U73122, or BAPTA, but not H89. The results suggest that PAC1 regulates PYK-2 tyrosine phosphorylation in a calcium-dependent manner.

Focal adhesion kinases in adhesion structures and disease

Cell adhesion to the extracellular matrix (ECM) is essential for cell migration, proliferation, and embryonic development. Cells can contact the ECM through a wide range of matrix contact structures such as focal adhesions, podosomes, and invadopodia. Although they are different in structural design and basic function, they share common remodeling proteins such as integrins, talin, paxillin, and the tyrosine kinases FAK, Pyk2, and Src. In this paper, we compare and contrast the basic organization and role of focal adhesions, podosomes, and invadopodia in different cells. In addition, we discuss the role of the tyrosine kinases, FAK, Pyk2, and Src, which are critical for the function of the different adhesion structures. Finally, we discuss the essential role of these tyrosine kinases from the perspective of human diseases.

TGFBI expression reduces in vitro and in vivo metastatic potential of lung and breast tumor cells

Controversy has arisen as to the role of transforming growth factor-β-induced protein (TGFBI) in the regulation of tumor metastasis. Using lung and breast cancer cell lines (H522 and MCF-7, respectively), we established that TGFBI induced cell adhesion to extracellular matrix proteins by activating adhesion-associated signaling and subsequent structure reformation, ultimately leading to cells less motile; whereas TGFBI reduced abilities of colony formation in soft agar, penetration through matrix gel, and activation of matrix metalloproteinases 2 and 9. Furthermore, injection of TGFBI-expressing cells into immuno-deficient mice resulted in a significant reduction in tumor metastasis in vivo. Taken together, these data suggest that TGFBI moderates the metastatic potential of cancer cells.

HCMV pUS28 initiates pro-migratory signaling via activation of Pyk2 kinase

Background

Human Cytomegalovirus (HCMV) has been implicated in the acceleration of vascular disease and chronic allograft rejection. Recently, the virus has been associated with glioblastoma and other tumors. We have previously shown that the HCMV-encoded chemokine receptor pUS28 mediates smooth muscle cell (SMC) and macrophage motility and this activity has been implicated in the acceleration of vascular disease. pUS28 induced SMC migration involves the activation of the protein tyrosine kinases (PTKs) Src and Focal adhesion kinase as well as the small GTPase RhoA. The PTK Pyk2 has been shown to play a role in cellular migration and formation of cancer, especially glioblastoma. The role of Pyk2 in pUS28 signaling and migration are unknown.

Methods

In the current study, we examined the involvement of the PTK Pyk2 in pUS28-induced cellular motility. We utilized in vitro migration of SMC to determine the requirements for Pyk2 in pUS28 pro-migratory signaling. We performed biochemical analysis of Pyk2 signaling in response to pUS28 activation to determine the mechanisms involved in pUS28 migration. We performed mass spectrometric analysis of Pyk2 complexes to identify novel Pyk2 binding partners.

Results

Expression of a mutant form of Pyk2 lacking the autophosphorylation site (Tyr-402) blocks pUS28-mediated SMC migration in response to CCL5, while the kinase-inactive Pyk2 mutant failed to elicit the same negative effect on migration. pUS28 stimulation with CCL5 results in ligand-dependent and calcium-dependent phosphorylation of Pyk2 Tyr-402 and induced the formation of an active Pyk2 kinase complex containing several novel Pyk2 binding proteins. Expression of the autophosphorylation null mutant Pyk2 F402Y did not abrogate the formation of an active Pyk2 kinase complex, but instead prevented pUS28-mediated activation of RhoA. Additionally, pUS28 activated RhoA via Pyk2 in the U373 glioblastoma cells. Interestingly, the Pyk2 kinase complex in U373 contained several proteins known to participate in glioma tumorigenesis.

Conclusions

These findings represent the first demonstration that pUS28 signals through Pyk2 and that this PTK participates in pUS28-mediated cellular motility via activation of RhoA. Furthermore, these results provide a potential mechanistic link between HCMV-pUS28 and glioblastoma cell activation.

In vitro modulation of Bcl-2 levels in small cell lung cancer cells: effects on cell viability

Small cell lung cancer (SCLC) is an aggressive disease, representing 15% of all cases of lung cancer, has high metastatic potential and low prognosis that urgently demands the development of novel therapeutic approaches. One of the proposed approaches has been the down-regulation of BCL2, with poorly clarified and controversial therapeutic value regarding SCLC. The use of anti-BCL2 small interfering RNA (siRNA) in SCLC has never been reported. The aim of the present study was to select and test the in vitro efficacy of anti-BCL2 siRNA sequences against the protein and mRNA levels of SCLC cells, and their effects on cytotoxicity and chemosensitization. Two anti-BCL2 siRNAs and the anti-BCL2 G3139 oligodeoxynucleotide (ODN) were evaluated in SCLC cells by the simultaneous determination of Bcl-2 and viability using a flow cytometry method recently developed by us in addition to Western blot, real-time reverse-transcription PCR, and cell growth after single and combined treatment with cisplatin. In contrast to previous reports about the use of ODN, a heterogeneous and up to 80% sequence-specific Bcl-2 protein knockdown was observed in the SW2, H2171 and H69 SCLC cell lines, although without significant sequence-specific reduction of cell viability, cell growth, or sensitization to cisplatin. Our results question previous data generated with antisense ODN and supporting the present concept of the therapeutic interest in BCL2 silencing per se in SCLC, and support the growing notion of the necessity of a multitargeting molecular approach for the treatment of cancer.

[Molecular targeted therapies in small-cell lung cancer]

Small-cell lung cancers (SCLC) are aggressive malignancies, however, characterized by high primary chemosensitivity. Unfortunately, for the vast majority of patients, relapse is the rule with emergence of secondary resistance mechanisms. In the era of molecular targeted therapies, characterization of a number of molecular abnormalities has encouraged implementation of several clinical trials. This literature review summarizes the various pharmacological approaches used in SCLC to improve survival in localized and extensive forms of the disease. Initial trials with molecular targeted therapies have not been able to improve clinical outcome compared to the standard etoposide-cisplatin chemotherapy regimen in extensive forms. However, new targets continue to be identified and many treatments are currently being assessed, including blockade of angiogenesis, signal transduction, cell cycle or induction of apoptosis.

A phase II study of dasatinib in patients with chemosensitive relapsed small cell lung cancer (Cancer and Leukemia Group B 30602)

INTRODUCTION

SRC is an oncogene with an essential role in the invasiveness and metastasis of solid tumors including small cell lung cancer. Dasatinib is a potent inhibitor of SRC as well as other tyrosine kinases. The primary objective of this study was to determine the efficacy of second-line dasatinib in patients with chemosensitive (relapse or progression > or =90 days after completing first-line therapy) small cell lung cancer.

METHODS

Patients with measurable disease; performance status 0 to 1; no more than one prior platinum-based chemotherapy regimen; and adequate hematologic, hepatic, and renal function were eligible. Dasatinib was administered orally at 70 mg twice daily continuously (1 cycle = 21 days) until disease progression or unacceptable toxicity. Response was determined after every two cycles. Patients were followed until disease progression or death. The study was prospectively designed to simultaneously discriminate between complete plus partial response rates of 5% versus 20% and progression-free survival (PFS) rates at 6 weeks of 50% versus 70.7% in 53 evaluable patients with at least 92% power. The study was to be terminated early and declared negative if 1 or less objective response and 14 or fewer instances of PFS > or =6 weeks were observed among the initial 27 patients; however, patient accrual continued while the initial 27 patients were evaluated.

RESULTS

Between April 2007 and December 2008, 45 patients were enrolled, but one patient never received any protocol therapy and one patient was ineligible: male/female, 17/26; white/black/unknown, 40/2/1; median age, 64 years (range, 35-84 years); and performance status 0/1, 12/31. No objective response was recorded among the 43 eligible and treated patients. Among the initial 27 patients, only 13 instances of PFS > or =6 weeks were observed. With a median follow-up time of 7.1 months, median estimated overall survival and PFS times for the 43 eligible and treated patients were 17.0 and 5.9 weeks, respectively. Common reasons for removal of patients from protocol treatment were progressive disease (65%) and adverse events (26%). Toxicity was generally mild to moderate: grade 3 events of >5% frequency included fatigue and pleural and pericardial effusions; and no grade 4 or 5 events were encountered.

CONCLUSIONS

Dasatinib did not reach our specified efficacy criteria in this clinical setting, and the study was terminated.

Construction of shRNA expression plasmids targeting the Pyk2 gene and their expression in Lovo cells

AIM: To construct the recombinant small hairpin RNA (shRNA) plasmids targeting the proline-rich tyrosine kinase 2 (Pyk2) gene (pGCsi-Pyk2 shRNA) and detect their expression in Lovo cells.

METHODS: Three pairs of Pyk2 shRNA sequences were designed and ligated to the pGCsi vector that contains U6 promoter and hygromycin B to obtain shRNA expression plasmids targeting the Pyk2. The recombinant pGCsi-Pyk2 shRNA plasmids were introduced into Lovo cells by liposome-mediated transfection and selected with hygromycin B. The expression of Pyk2 mRNA and protein was detected by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot, respectively.

RESULTS: Restriction enzyme digestion and sequence analysis showed that recombinant pGCsi-Pyk2 shRNA plasmids were successfully constructed. The expression levels of Pyk2 mRNA and protein in Lovo cells transfected with pGCsi-Pyk2 shRNA plasmids were significantly lower than those in Lovo cells transfected with empty or negative plamsids.

CONCLUSION: Recombinant pGCsi-Pyk2 shRNA plasmids are successfully constructed. Their transfection can silence the expression of Pyk2 gene in Lovo cells. The pGCsi-Pyk2 shRNA plasmids obtained lay a foundation for further study of the role of the Pyk2 gene in the pathogenesis of colorectal cancer.

Pyk2 activation triggers epidermal growth factor receptor signaling and cell motility after wounding sheets of epithelial cells

Activation of the epidermal growth factor receptor (EGFR) is a key signaling event that promotes cells to move and cover wounds in many epithelia. We have previously shown that wounding activates the EGFR through activation of the Src family kinases (SFKs), which induce proteolytic shedding of epidermal growth factor-like ligands from the cell surface. A major goal in wound healing research is to identify early signals that promote motility, and here we examined the hypothesis that members of the focal adhesion kinase family are upstream activators of the SFKs after wounding. We found that focal adhesion kinase is not activated by wounding but that a different family member, Pyk2 (PTK2B/RAFTK/CAKbeta), is activated rapidly and potently. Pyk2 interaction with c-Src is increased after wounding, as determined by co-immunoprecipitation experiments. Disruption of Pyk2 signaling either by small interfering RNA or by expression of a dominant negative mutant led to inhibition of wound-induced activation of the SFKs and the EGFR, and conversely, overexpression of wild-type Pyk2 stimulated SFK and EGFR kinase activities in cells. In wound healing studies, Pyk2 small interfering RNA or dominant negative inhibited cell migration. These results show that activation of Pyk2 is an early signal that promotes wound healing by stimulating the SFK/EGFR signaling pathway.

Critical role of G(alpha)12 and G(alpha)13 for human small cell lung cancer cell proliferation in vitro and tumor growth in vivo

PURPOSE

In small cell lung cancer cells (SCLC), various autocrine stimuli lead to the parallel activation of G(q/11) and G(12/13) proteins. Although the contribution of the G(q/11)-phospholipase C-beta cascade to mitogenic effects in SCLC cells is well established, the relevance of G(12/13) signaling is still elusive. In other tumor entities, G(12/13) activation promotes invasiveness without affecting cellular proliferation. Here, we investigate the role of G(12/13)-dependent signaling in SCLC.

EXPERIMENTAL DESIGN

We used small hairpin RNA-mediated targeting of G(alpha)(12), G(alpha)(13), or both in H69 and H209 cells and analyzed the effects of G(alpha)(12) and/or G(alpha)(13) knockdown on tumor cells in vitro, tumor growth in vivo, and mitogen-activated protein kinase (MAPK) activation.

RESULTS

Lentiviral expression of small hairpin RNAs resulted in robust and specific G(alpha)(12) and G(alpha)(13) knockdown as well as markedly inhibited proliferation, colony formation, and bradykinin-promoted stimulation of cell growth. Analyzing the activation status of all three major MAPK families revealed nonredundant functions of G(alpha)(12) and G(alpha)(13) in SCLC and a marked p42/p44 activation upon G(alpha)(12)/G(alpha)(13) knockdown. In a s.c. tumor xenograft mouse model, G(alpha)(12) or G(alpha)(13) downregulation led to decreased tumor growth due to reduced tumor cell proliferation. More importantly, G(alpha)(12)/G(alpha)(13) double knockdown completely abolished H69 tumorigenicity in mice.

CONCLUSIONS

G(alpha)(12) and G(alpha)13) exert a complex pattern of nonredundant effects in SCLC, and in contrast to other tumor types, SCLC cell proliferation in vitro and tumorigenicity in vivo critically depend on G(12/13) signaling. Due to the complete abolishment of tumorgenicity in our study, RNAi-mediated double knockdown may provide a promising new avenue in SCLC treatment.

Small cell lung cancer: are we making progress?

Although the incidence of small cell lung cancer (SCLC) has declined during the past 30 years, it remains a significant cause of cancer mortality in the United States and across the world. With appropriate treatment, about 20% of patients who present with limited stage SCLC can be cured of their disease. Unfortunately, the outcome for the remainder of patients is extremely poor. The only significant advance in extensive stage SCLC in the past 2 decades is the recent discovery that prophylactic cranial irradiation improves survival in those patients whose disease has responded to initial chemotherapy. Numerous attempts to enhance the antitumor effects of traditional chemotherapy for SCLC have not been successful. As the understanding of the biology of SCLC increased, a number of rational molecular targets for therapy have been identified. Although initial attempts at "targeted therapy" in SCLC have been unsuccessful, several newly identified targets hold promise and give hope that significant improvements in therapy for this challenging disease are not far away.

Targeting Pyk2 for therapeutic intervention

IMPORTANCE OF THE FIELD

The focal adhesion tyrosine kinases FAK and Pyk2 are uniquely situated to act as critical mediators for the activation of signaling pathways that regulate cell migration, proliferation and survival. By coordinating adhesion and cytoskeletal dynamics with survival and growth signaling, FAK and Pyk2 represent molecular therapeutic targets in cancer as malignant cells often exhibit defects in these processes.

AREAS COVERED IN THIS REVIEW

This review examines the structure and function of the focal adhesion kinase Pyk2 and intends to provide a rationale for the employment of modulating strategies that include both catalytic and extra-catalytic approaches that have been developed in the last 3 - 5 years.

WHAT THE READER WILL GAIN

Targeting tyrosine kinases in oncology has focused on the ATP binding pocket as means to inhibit catalytic activity and downregulate pathways involved in tumor invasion. This review discusses the available catalytic inhibitors and compares them to the alternative approach of targeting protein-protein interactions that regulate kinase activity.

TAKE HOME MESSAGE

Development of specific catalytic inhibitors of the focal adhesion kinases has improved but significant challenges remain. Thus, approaches that inhibit the effector function of Pyk2 by targeting regulatory modules can increase specificity and will be a welcome asset to the therapeutic arena.

The galanin system in cancer

Many tumours of neuroendocrine origin, and also an increasing number of non-neuroendocrine cancers, have been shown to express neuropeptides and/or their corresponding receptors. These peptides and receptors represent the molecular basis for in vivo diagnostic or therapeutic targeting of cancer with radiolabelled or cytotoxic peptide analogues. Galanin is a classical neuropeptide that functions in diverse physiological processes such as food intake, nociception, and blood pressure regulation, and it can also act as a growth factor for neurons. Expression of galanin peptide has been detected in pheochromocytoma, pituitary adenoma, neuroblastic tumours, gastrointestinal cancer, squamous cell carcinoma, brain tumours, melanoma, breast cancer and embryonal carcinoma. In several cancers and tumour cell lines expression of galanin receptors--three are known (GalR1, 2 and 3)--has been shown as well. Expression of peptide or receptors has been correlated with tumour stage or subtypes of pituitary adenoma, neuroblastic tumours, colon carcinoma and squamous cell carcinoma. Galanin treatment has tumour-reducing effects in murine models of gastrointestinal cancer, whereas in animal experiments on adenoma formation, galanin seems to act as a growth factor, promoting both proliferation and tumour formation. In cell culture experiments on tumour cell lines, galanin has shown growth promoting or inhibiting effects. Activation of GalR1 is generally anti-proliferative, whereas activation of GalR2 can have pro- or anti-proliferative effects. Therefore, galanin and its receptors are promising targets for diagnosis and treatment of several types of tumours.

Design of peptide-targeted liposomes containing nucleic acids

Anticancer systemic gene silencing therapy has been so far limited by the inexistence of adequate carrier systems that ultimately provide an efficient intracellular delivery into target tumor cells. In this respect, one promising strategy involves the covalent attachment of internalizing-targeting ligands at the extremity of PEG chains grafted onto liposomes. Therefore, the present work aims at designing targeted liposomes containing nucleic acids, with small size, high encapsulation efficiency and able to be actively internalized by SCLC cells, using a hexapeptide (antagonist G) as a targeting ligand. For this purpose, the effect of the liposomal preparation method, loading material (ODN versus siRNA) and peptide-coupling procedure (direct coupling versus post-insertion) on each of the above-mentioned parameters was assessed. Post-insertion of DSPE-PEG-antagonist G conjugates into preformed liposomes herein named as stabilized lipid particles, resulted in targeted vesicles with a mean size of about 130 nm, encapsulation efficiency close to 100%, and a loading capacity of approximately 5 nmol siRNA/mumol of total lipid. In addition, the developed targeted vesicles showed increased internalization in SCLC cells, as well as in other tumor cells and HMEC-1 microvascular endothelial cells. The improved cellular association, however, did not correlate with enhanced downregulation of the target protein (Bcl-2) in SCLC cells. These results indicate that additional improvements need to be performed in the future, namely by ameliorating the access of the nucleic acids to the cytoplasm of the tumor cells following receptor-mediated endocytosis.

Identification of 4 new HLA-DR–restricted minor histocompatibility antigens as hematopoietic targets in antitumor immunity

Potent graft-versus-leukemia (GVL) effects can be mediated by donor-derived T cells recognizing minor histocompatibility antigens (mHags) in patients treated with donor lymphocyte infusion (DLI) for relapsed hematologic malignancies after HLA-matched allogeneic stem cell transplantation (alloSCT). Donor-derived T cells, however, may not only induce GVL, but also mediate detrimental graft-versus-host disease (GVHD). Because HLA-class II is under noninflammatory conditions predominantly expressed on hematopoietic cells, CD4+ T cells administered late after alloSCT may selectively confer GVL without GVHD. Although a broad range of different HLA-class I–restricted mHags have been identified, the first 2 autosomal HLA-class II–restricted mHags have only recently been characterized. By screening a recombinant bacteria cDNA expression library, we identified 4 new HLA-class II–restricted mHags recognized by CD4+ T cells induced in a patient with relapsed chronic myeloid leukemia who achieved long-term complete remission and experienced only mild GVHD of the skin after DLI. All CD4+ T cells were capable of recognizing the mHags presented by HLA-DR surface molecules on primary hematopoietic cells, but not on skin-derived (cytokine-treated) fibroblasts. The selective recognition of hematopoietic cells as well as the balanced population frequencies and common HLA-DR restriction elements make the novel mHags possible targets for development of immunotherapeutic strategies.

Up-regulation of proline-rich tyrosine kinase 2 in non-small cell lung cancer

Proline-rich tyrosine kinase 2 (PYK2) is a non-receptor tyrosine kinase, plays different roles in intracellular signaling pathways, that regulates a number of biological processes, such as cell proliferation, differentiation, adhesion and migration, which have been shown to correlate with tumor development and aggression. However, the involvement of PYK2 in human non-small cell lung cancer (NSCLC) has not yet been determined. In the present study, 90 patients with NSCLC (represented by adenocarcinoma and squamous cell carcinoma) were included retrospectively. NSCLC tissues were detected for the expression of PYK2 by immunohistochemistry. Correlation between the expression of PYK2 with the clinicopathological characteristics was analyzed. There were 64% (58 out of 90) of NSCLC patients with higher level of PYK2. Higher expression of PYK2 was significantly correlated with lymph node metastasis (node positive versus node negative, p=0.007). Patients with higher expression of PYK2 had advanced stage of NSCLCs (I+II versus III+IV, p=0.012). Protein level of PYK2 was also examined in 30 of these tumorous samples and matched non-tumorous counterparts by western blotting. PYK2 was apparently up-regulated in NSCLC tissues (tumor versus non-tumor, p=0.000). In the cell studies, extensive expression and activation of PYK2 were both found in higher metastatic BE1 cells. The activity of ERK1/2 in BE1 cells appeared extremely high as well. In conclusion, our results demonstrated that PYK2 is up-regulated in NSCLCs, and the higher expression and activation of PYK2 may play a role in modulating the activity of ERK1/2, and lead to the progression of NSCLC.