Pathways driving the endocytosis of mutant and wild-type EGFR in cancer

Combination of monensin and erlotinib synergistically inhibited the growth and cancer stem cell properties of triple-negative breast cancer by simultaneously inhibiting EGFR and PI3K signaling pathways

BACKGROUND

Cancer stem cells (CSCs) in triple-negative breast cancer (TNBC) are recognized as a highly challenging subset of cells, renowned for their heightened propensity for relapse and unfavorable prognosis. Monensin, an ionophoric antibiotic, has been reported to exhibit significant therapeutic efficacy against various cancers, especially CSCs. Erlotinib is classified as one of the EGFR-TKIs and has been previously identified as a promising therapeutic target for TNBC. Our research aims to assess the effectiveness of combination of monensin and erlotinib as a potential treatment strategy for TNBC.

METHODS

The combination of monensin and erlotinib was assessed for its potential anticancer activity through various in vitro assays, including cytotoxicity assay, colony formation assay, wound healing assay, transwell assay, mammosphere formation assay, and proportion of CSCs assay. Additionally, an in vivo study using tumor-bearing nude mice was conducted to evaluate the inhibitory effect of the monensin and erlotinib combination on tumor growth.

RESULTS

The results indicated that combination of monensin with erlotinib synergistically inhibited cell proliferation, the migration rate, the invasion ability and decreased the CSCs proportion, and CSC markers SOX2 and CD133 in vivo and in vitro. Furthermore, the primary proteins involved in the signaling pathways of the EGFR/ERK and PI3K/AKT are simultaneously inhibited by the combination treatment of monensin and erlotinib in vivo and in vitro.

CONCLUSIONS

The simultaneous inhibition of the EGFR/ERK and PI3K/AKT/mTOR signaling pathways by the combination of monensin and erlotinib exhibited a synergistic effect on suppressing tumor proliferation and cancer cell stemness in TNBC.

Preparation and evaluation of the PD0721‑DOX antibody‑drug conjugate targeting EGFRvIII to inhibit glioblastoma

Epidermal growth factor receptor variant III (EGFRvIII) is prominently expressed in various epithelial tumors. PD0721, a single-chain antibody (scFv), has been developed to specifically target EGFRvIII. Although doxorubicin (DOX) is an essential treatment approach for glioblastoma (GBM), its toxic effects and limited targeting capabilities are a challenge. To overcome the above limitations, antibody-drug conjugates (ADCs) have been developed to exploit the specificity of monoclonal antibodies in directing potent cytotoxic drugs to tumor cells expressing the target antigens. The present study aimed to conjugate DOX with PD0721 scFv to construct a PD0721-DOX ADC targeting EGFRvIII and examine its targeting effect and in vitro anti-GBM activity. PD0721-DOX ADC was generated by combining PD0721 scFv with DOX, using dextran T-10 as a linker. The drug-to-antibody ratio (DAR) was measured by ultraviolet and visible spectrophotometry (UV-Vis). A series of techniques, including cytotoxicity assays, immunofluorescence, cell internalization and flow cytometry assays were employed to evaluate the targeting efficacy and anti-GBM activity of the PD0721-DOX ADC. Following the conjugation of PD0721 scFv with DOX, the UV-Vis results showed a noticeable red shift in the maximum absorbance. The DAR of PD0721 scFv and DOX was 9.23:1. Cytotoxicity assays demonstrated that DK-MG cells treatment with PD0721-DOX ADC at 10 and 20 µg/ml significantly increased cytotoxicity compared with U-87MG ATCC cells (all P<0.01). Confocal microscopy revealed distinct green and red fluorescence in EGFRvIII-expressing DK-MG cells, while no fluorescence was observed in EGFRvIII negative U-87MG ATCC cells. Furthermore, compared with U-87MG ATCC cells, DK-MG cells showed effective internalization of the PD0721-DOX ADC (P<0.001). Finally, flow cytometric analyses indicated that the PD0721-DOX ADC significantly promoted the apoptosis of DK-MG cells compared with U-87MG ATCC cells (P<0.01). In summary, the current study suggested that the PD0721-DOX ADC could exhibit a notable targeting efficacy and potent anti-GBM activity.

Deguelin Restores Paclitaxel Sensitivity in Paclitaxel-Resistant Ovarian Cancer Cells via Inhibition of the EGFR Signaling Pathway

Background

Ovarian cancer is one of women's malignancies with the highest mortality among gynecological cancers. Paclitaxel is used in first-line ovarian cancer chemotherapy. Research on paclitaxel-resistant ovarian cancer holds significant clinical importance.

Methods

Cell viability and flow cytometric assays were conducted at different time and concentration points of deguelin and paclitaxel treatment. Immunoblotting was performed to assess the activation status of key signaling molecules important for cell survival and proliferation following treatment with deguelin and paclitaxel. The fluo-3 acetoxymethyl assay for P-glycoprotein transport activity assay and cell viability assay in the presence of N-acetyl-L-cysteine were also conducted.

Results

Cell viability and flow cytometric assays demonstrated that deguelin resensitized paclitaxel in a dose- and time-dependent manner. Cotreatment with deguelin and paclitaxel inhibited EGFR and its downstream signaling molecules, including AKT, ERK, STAT3, and p38 MAPK, in SKOV3-TR cells. Interestingly, cotreatment with deguelin and paclitaxel suppressed the expression level of EGFR via the lysosomal degradation pathway. Cotreatment did not affect the expression and function of P-glycoprotein. N-acetyl-L-cysteine failed to restore cell cytotoxicity when used in combination with deguelin and paclitaxel in SKOV3-TR cells. The expression of BCL-2, MCL-1, and the phosphorylation of the S155 residue of BAD were downregulated. Moreover, inhibition of paclitaxel resistance by deguelin was also observed in HeyA8-MDR cells.

Conclusion

Our research showed that deguelin effectively suppresses paclitaxel resistance in SKOV3-TR ovarian cancer cells by downregulating the EGFR and its downstream signaling pathway and modulating the BCL-2 family proteins. Furthermore, deguelin exhibits inhibitory effects on paclitaxel resistance in HeyA8-MDR ovarian cancer cells, suggesting a potential mechanism for paclitaxel resensitization that may not be cell-specific. These findings suggest that deguelin holds promise as an anticancer therapeutic agent for overcoming chemoresistance in ovarian cancer.

EGF receptor modulates HEV entry in human hepatocytes

BACKGROUND AND AIMS

Being the most common cause of acute viral hepatitis with >20 million cases per year and 70,000 deaths annually, HEV presents a long-neglected and underinvestigated health burden. Although the entry process of viral particles is an attractive target for pharmacological intervention, druggable host factors to restrict HEV entry have not been identified so far.

APPROACH AND RESULTS

Here we identify the EGF receptor (EGFR) as a novel host factor for HEV and reveal the significance of EGFR for the HEV entry process. By utilizing RNAi, chemical modulation with Food and Drug Administration-approved drugs, and ectopic expression of EGFR, we revealed that EGFR is critical for HEV infection without affecting HEV RNA replication or assembly of progeny virus. We further unveiled that EGFR itself and its ligand-binding domain, rather than its signaling function, is responsible for the proviral effect. Modulation of EGF expression in HepaRG cells and primary human hepatocytes affected HEV infection.

CONCLUSIONS

Taken together, our study provides novel insights into the life cycle of HEV and identified EGFR as a possible target for future antiviral strategies against HEV.

The role of progesterone receptor membrane component (PGRMC) in the endometrium

PGRMC is a non-classical receptor that mediates the non-genomic responses to progesterone and is distributed in different subcellular compartments. PGRMC belongs to the membrane-associated progesterone receptor (MAPR) family. Two PGRMC subtypes (PGRMC1 and PGRMC2) have been characterized, and both are expressed in the human endometrium. PGRMC expression is differentially regulated during the menstrual cycle in the human endometrium. Although PGRMC1 is predominantly expressed in the proliferative phase and PGRMC2 in the secretory phase, this expression changes in pathologies such as endometriosis, in which PGRMC2 expression considerably decreases, promoting progesterone resistance. In endometrial cancer, PGRMC1 is overexpressed, its activation induces tumors growth, and confers chemoresistance in the presence of progesterone. Thus, PGRMCs play a key role in progesterone actions in the endometrium.

Pleiotropic Actions of PGRMC Proteins in Cancer

Progesterone receptor membrane component (PGRMC) proteins play important roles in tumor growth, progression, and chemoresistance, of which PGRMC1 is the best characterized. The ancestral member predates the evolution of metazoans, so it is perhaps not surprising that many of the purported actions of PGRMC proteins are rooted in fundamental metabolic processes such as proliferation, apoptosis, and DNA damage responses. Despite mediating some of the actions of progesterone (P4) and being fundamentally required for female fertility, PGRMC1 and PGRMC2 are broadly expressed in most tissues. As such, these proteins likely have both progesterone-dependent and progesterone-independent functions. It has been proposed that PGRMC1 acquired the ability to mediate P4 actions over evolutionary time through acquisition of its cytochrome b5-like heme/sterol-binding domain. Diverse reproductive and nonreproductive diseases associate with altered PGRMC1 expression, epigenetic regulation, or gene silencing mechanisms, some of which include polycystic ovarian disease, premature ovarian insufficiency, endometriosis, Alzheimer disease, and cancer. Although many studies have been completed using transformed cell lines in culture or in xenograft tumor approaches, recently developed transgenic model organisms are offering new insights in the physiological actions of PGRMC proteins, as well as pathophysiological and oncogenic consequences when PGRMC expression is altered. The purpose of this mini-review is to provide an overview of PGRMC proteins in cancer and to offer discussion of where this field must go to solidify PGRMC proteins as central contributors to the oncogenic process.

Glycyrrhizin Derivatives Suppress Cancer Chemoresistance by Inhibiting Progesterone Receptor Membrane Component 1

Progesterone receptor membrane component 1 (PGRMC1) is highly expressed in various cancer cells and contributes to tumor progression. We have previously shown that PGRMC1 forms a unique heme-stacking functional dimer to enhance EGF receptor (EGFR) activity required for cancer proliferation and chemoresistance, and the dimer dissociates by carbon monoxide to attenuate its biological actions. Here, we determined that glycyrrhizin (GL), which is conventionally used to ameliorate inflammation, specifically binds to heme-dimerized PGRMC1. Binding analyses using isothermal titration calorimetry revealed that some GL derivatives, including its glucoside-derivative (GlucoGL), bind to PGRMC1 potently, whereas its aglycone, glycyrrhetinic acid (GA), does not bind. GL and GlucoGL inhibit the interaction between PGRMC1 and EGFR, thereby suppressing EGFR-mediated signaling required for cancer progression. GL and GlucoGL significantly enhanced EGFR inhibitor erlotinib- or cisplatin (CDDP)-induced cell death in human colon cancer HCT116 cells. In addition, GL derivatives suppressed the intracellular uptake of low-density lipoprotein (LDL) by inhibiting the interaction between PGRMC1 and the LDL receptor (LDLR). Effects on other pathways cannot be excluded. Treatment with GlucoGL and CDDP significantly suppressed tumor growth following xenograft transplantation in mice. Collectively, this study indicates that GL derivatives are novel inhibitors of PGRMC1 that suppress cancer progression, and our findings provide new insights for cancer treatment.

Loss of CPAP causes sustained EGFR signaling and epithelial-mesenchymal transition in oral cancer

Higher epidermal growth factor receptor (EGFR) signaling can contribute to tumor metastasis and resistance to therapies in oral squamous cell carcinoma (OSCC). EGFR signaling can promote epithelial-mesenchymal transition (EMT) in OSCC. EMT is a process by which epithelial cells acquire invasive properties and it can contribute to tumor metastasis. Not only do the abnormal functions of microtubule and microtubule-organizing centers (MTOC) such as centrosomes lead to cancers, but also the malignant tissues are characterized by aberrant centriolar features and amplified centrosomes. Microtubule inhibition therapies increase the sensitivity to EGFR targeting drugs in various cancers. In this study, we show that the loss of expression of a microtubule/tubulin binding protein, centrosomal protein 4.1-associated protein (CPAP), which is critical for centriole biogenesis and normal functioning of the centrosome, caused an increase in the EGFR levels and its signaling and, enhanced the EMT features and invasiveness of OSCC cells. Further, depletion of CPAP enhanced the tumorigenicity of these cells in a xeno-transplant model. Importantly, CPAP loss-associated EMT features and invasiveness of multiple OSCC cells were attenuated upon depletion of EGFR in them. On the other hand, we found that CPAP protein levels were higher in EGF treated OSCC cells as well as in oral cancer tissues, suggesting that the frequently reported aberrant centriolar features of tumors are potentially a consequence, but not the cause, of tumor progression. Overall, our novel observations show that, in addition to its known indispensable role in centrosome biogenesis, CPAP also plays a vital role in suppressing tumorigenesis in OSCC by facilitating EGFR homeostasis.

Cooperation and Interplay between EGFR Signalling and Extracellular Vesicle Biogenesis in Cancer

Epidermal growth factor receptor (EGFR) takes centre stage in carcinogenesis throughout its entire cellular trafficking odyssey. When loaded in extracellular vesicles (EVs), EGFR is one of the key proteins involved in the transfer of information between parental cancer and bystander cells in the tumour microenvironment. To hijack EVs, EGFR needs to play multiple signalling roles in the life cycle of EVs. The receptor is involved in the biogenesis of specific EV subpopulations, it signals as an active cargo, and it can influence the uptake of EVs by recipient cells. EGFR regulates its own inclusion in EVs through feedback loops during disease progression and in response to challenges such as hypoxia, epithelial-to-mesenchymal transition and drugs. Here, we highlight how the spatiotemporal rules that regulate EGFR intracellular function intersect with and influence different EV biogenesis pathways and discuss key regulatory features and interactions of this interplay. We also elaborate on outstanding questions relating to EGFR-driven EV biogenesis and available methods to explore them. This mechanistic understanding will be key to unravelling the functional consequences of direct anti-EGFR targeted and indirect EGFR-impacting cancer therapies on the secretion of pro-tumoural EVs and on their effects on drug resistance and microenvironment subversion.

SGCE Promotes Breast Cancer Stem Cells by Stabilizing EGFR

Breast cancer stem cells (BCSCs) are responsible for resistance to chemotherapy, high degree of metastasis, and poor prognosis, especially in triple-negative breast cancer (TNBC). The CD24lowCD44high and high aldehyde dehydrogenase 1 (ALDH1) cell subpopulation (CD24lowCD44high ALDH1+) exhibit very high tumor initiating capacity. In the current study, the upregulated genes are analyzed in both CD24lowCD44high and ALDH1+ cell populations at single-cell resolution, and a highly expressed membrane protein, SGCE, is identified in both BCSC populations. Further results show that SGCE depletion reduces BCSC self-renewal, chemoresistance, and metastasis both in vitro and in vivo, partially through affecting the accumulation of extracellular matrix (ECM). For the underlying mechanism, SGCE functions as a sponge molecule for the interaction between epidermal growth factor receptor (EGFR) and its E3 ubiquitination ligase (c-Cbl), and thus inhibits EGFR lysosomal degradation to stabilize the EGFR protein. SGCE knockdown promotes sensitivity to EGFR tyrosine kinase inhibitors (TKIs), providing new clues for deciphering the current failure of targeting EGFR in clinical trials and highlighting a novel candidate for BCSC stemness regulation.

The exon 19-deleted EGFR undergoes ubiquitylation-mediated endocytic degradation via dynamin activity-dependent and -independent mechanisms

Background

The epidermal growth factor receptor (EGFR) is closely implicated in cancer, and sequencing analyses have revealed a high mutation rate of EGFR in lung cancer. Recent advances have provided novel insights into the endocytic regulation of wild-type EGFR, but that of mutated EGFR remains elusive. In the present study, we aim to investigate the endocytic degradation of a frequently occurred exon 19-deleted mutant in lung cancer.

Methods

The EGF-induced endocytic degradation of EGFR was examined in a panel of lung cancer cells using immunoblotting. The subcellular distribution of internalized EGFR was investigated using immunofluorescence and confocal microscopy. The effects of dynamin were assessed using its small molecule inhibitors, while the influence of RTN3 was tested using shRNA-mediated knockdown. Finally the ubiquitylation status of EGFR mutant was studied using immunoprecipitation under steady state and tyrosine kinase inhibitor-treated conditions.

Results

EGF induced various rates of EGFR endocytic degradation in lung cancer cells. Interestingly, the exon 19 deletion mutant is constantly internalized and sorted to lysosome for degradation, and this process is independent of dynamin activity. EGF stimulation and HSP90 inhibition further enhance the endocytic degradation of the exon 19 deletion mutant, in a dynamin activity-dependent and -independent manner, respectively. Albeit with different modes of internalization, the uptake of the exon 19-deleted EGFR is mediated through receptor ubiquitylation.

Conclusions

The internalized EGFR mutant is constantly routed through endosome to lysosome for degradation. The endocytosis of EGFR mutant occurs through both dynamin activity-dependent and -independent mechanisms. Our findings gain novel insights into the endocytic regulation of mutated EGFR and may have potential clinical implications.

Role of long non-coding RNA in drug resistance in non-small cell lung cancer

Lung cancer is the leading cause of cancer-associated death, and non-small cell lung cancer (NSCLC) accounts for 85% of all lung cancer cases. Many drugs have been used to treat NSCLC in order to improve patient prognosis. Platinum-based chemotherapy is the first-line treatment for locally advanced or metastatic patients. For patients with activating EGFR mutations, tyrosine kinase inhibitors are the best treatment choice. NSCLC initially exhibits an excellent response to treatment; however, acquired resistance has been observed in many patients, leading to ineffective treatment. Clinical resistance is an impediment in the treatment of patients with advanced NSCLC. Many sequencing technologies have shown that long non-coding RNA (lncRNA) is expressed differently between drug-resistant and drug-sensitive lung cancer cells. We review the literature on lncRNA in drug resistance of NSCLC. The aim of this review is to gain insight into the molecular mechanisms of drug resistance, mainly focusing on the role of lncRNA in NSCLC.

Overexpression of the long noncoding RNA CCAT1 promotes metastasis via epithelial-to-mesenchymal transition in lung adenocarcinoma

The long noncoding RNA (lncRNA) colon cancer-associated transcript 1 (CCAT1) has been identified as an oncogene in multiple types of human malignancy, and the aberrant expression of CCAT1 has been associated with the tumorigenesis and progression of cancer. However, the underlying mechanism of how CCAT1 affects malignant behaviors in lung adenocarcinoma cells remains unknown. In the current study, the expression of CCAT1 was identified to be increased in lung adenocarcinoma tissues (n=96) by reverse transcription-quantitative polymerase chain reaction (RT-qPCR), and its expression level was associated with epidermal growth factor receptor (EGFR) expression (P=0.011), lymphatic metastasis (P=0.003) and tumor node metastasis (TNM) stage (P=0.003). In vitro, by using Transwell assays, the overexpression of CCAT1 was demonstrated to promote the migration and invasion of H358 lung adenocarcinoma cells; while downregulation of CCAT1 expression inhibited H1650 cell migration and invasion. Furthermore, western blot analysis indicated that aberrant CCAT1 expression may induce epithelial-to-mesenchymal transition (EMT) by regulating the expression levels of EMT markers (E-cadherin, N-cadherin and vimentin). In conclusion, these results indicate that CCAT1 is able to promote the metastasis of lung adenocarcinoma cells by inducing EMT.

Epidermal growth factor receptor (EGFR): A rising star in the era of precision medicine of lung cancer

Lung cancer is a leading cause of cancer mortality worldwide. In tumors, the important role of noncoding RNA regulatory networks has been more and more reveal. EGFR has been identified as an oncogenic driver of NSCLC, especially activating mutations EGFR and its inhibition with specific TKIs can generate dramatic tumor responses. Studies have shown that EGFR plays significant roles in the progression of NSCLC. Subset analysis of the small proportion of patients with EGFR-mutant lung cancer showed a disease-free survival benefit, but was underpowered to detect a survival advantage. Herein, we highlight the progression of EGFR, noncoding RNA, and their roles in carcinogenesis. We also focus on anti-lung cancer drug development and EGFR-related drug resistance.

Insulin Receptor Plasma Membrane Levels Increased by the Progesterone Receptor Membrane Component 1

The insulin receptor (IR) is a ligand-activated receptor tyrosine kinase that has a key role in metabolism, cellular survival, and proliferation. Progesterone receptor membrane component 1 (PGRMC1) promotes cellular signaling via receptor trafficking and is essential for some elements of tumor growth and metastasis. In the present study, we demonstrate that PGRMC1 coprecipitates with IR. Furthermore, we show that PGRMC1 increases plasma membrane IR levels in multiple cell lines and decreases insulin binding at the cell surface. The findings have therapeutic applications because a small-molecule PGRMC1 ligand, AG205, also decreases plasma membrane IR levels. However, PGRMC1 knockdown via short hairpin RNA expression and AG205 treatment potentiated insulin-mediated phosphorylation of the IR signaling mediator AKT. Finally, PGRMC1 also increased plasma membrane levels of two key glucose transporters, GLUT-4 and GLUT-1. Our data support a role for PGRMC1 maintaining plasma membrane pools of the receptor, modulating IR signaling and function.

Long non-coding RNA BC087858 induces non-T790M mutation acquired resistance to EGFR-TKIs by activating PI3K/AKT and MEK/ERK pathways and EMT in non-small-cell lung cancer

Our previous study demonstrated that long non-coding RNA (lncRNA) BC087858 could stimulate acquired resistance to EGFR-TKIs in non-small cell lung (NSCLC) but the specific regulatory mechanism remained unknown. We aimed to explore the role and mechanism of lncRNA BC087858 on EGFR-TKIs acquired resistance. LncRNA BC087858 mRNA expression was detected by reverse transcription polymerase chain reaction in different NSCLC cell lines and tissues. The relationship between BC087858 expression and clinicopathological factors was performed by Cox multivariate regression analysis. Small-interfering RNA, flow cytometry and trans-well assay were conducted to explore the biological functions of BC087858. Western blotting was used to analyze the target proteins expression. Over-expression was observed in NSCLC cells and patients with acquired resistance to EGFR-TKIs and significantly associated with a shorter progression-free survival (PFS) (12.0 vs. 17.0 months, P = 0.0217) in tumors with respond to EGFR-TKIs. The significant relationship was not observed in patients with T790M mutation (median PFS 17.6 vs. 12.5 months, P = 0.522) but in patients with non-T790M (median PFS 8.0 vs. 18.25 months,P = 0.0427). Down-regulation of BC087858 could significantly promote PC9/R and PC9/G2 cells invasion (P < 0.05; respectively). BC087858 knockdown restored gefitinib sensitivity in acquired resistant cells with non-T790M and inhibited the activation of the PI3K/AKT and MEK/ERK pathways and epithelial-mesenchymal transition (EMT) via up- regulating ZEB1 and Snail. In conclusion, LncRNA BC087858 could promote cells invasion and induce non-T790M mutation acquired resistance to EGFR-TKIs by activating PI3K/AKT and MEK/ERK pathways and EMT via up- regulating ZEB1 and Snail in NSCLC.

PGRMC1 regulation by phosphorylation: potential new insights in controlling biological activity

Progesterone receptor membrane component 1 (PGRMC1) is a multifunctional protein implicated in multiple pathologies, including cancer and Alzheimer's disease. The recently published structure of PGRMC1 revealed heme-mediated dimerization that directed the PGRMC1-dependent cytochrome P450-mediated detoxification of doxorubicin. We describe here how the PGRMC1 structure also enables important new insights into the possible regulation of PGRMC1 function by phosphorylation. Predicted regulatory interaction sites for SH2- and SH3-domain proteins are in non-structured regions that could be available to cytoplasmic enzymes. Further to the published interpretation, we suggest that phosphorylation of PGRMC1 at position Y113 may promote the attested membrane trafficking function of PGRMC1. To stimulate further experimentation, we also discuss that heme-mediated dimerization of PGRMC1 and membrane trafficking may be mutually exclusive functions. These roles could potentially be reciprocally regulated by phosphorylation/dephosphorylation at Y113. It follows that the phosphorylation status of PGRMC1 should be further explored in order to better understand many of its proposed biological functions.

Advances in the Development of Molecularly Targeted Agents in Non-Small-Cell Lung Cancer

Non-small-cell lung cancer (NSCLC) remains a significant global health challenge and the leading cause of cancer-related mortality. The traditional 'one-size-fits-all' treatment approach has now evolved into one that involves personalized strategies based on histological and molecular subtypes. The molecular era has revolutionized the treatment of patients harboring epidermal growth factor receptor (EGFR), anaplastic lymphoma kinase (ALK) and ROS1 gene aberrations. In the appropriately selected population, anti-tumor agents against these molecular targets can significantly improve progression-free survival. However, the emergence of acquired resistance is inevitable. Novel potent compounds with much improved and rational selectivity profiles, such as third-generation EGFR T790M resistance mutation-specific inhibitors, have been developed and added to the NSCLC armamentarium. To date, attempts to overcome resistance bypass pathways through downstream signaling blockade has had limited success. Furthermore, the majority of patients still do not harbor known driver genetic or epigenetic alterations and/or have no new available treatment options, with chemotherapy remaining their standard of care. Several potentially actionable driver aberrations have recently been identified, with the early clinical development of multiple inhibitors against these promising targets currently in progress. The advent of immune checkpoint inhibitors has led to significant benefit for advanced NSCLC patients with durable responses observed. Further interrogation of the underlying biology of NSCLC, coupled with modern clinical trial designs, is now required to develop novel targeted therapeutics rationally matched with predictive biomarkers of response, so as to further advance NSCLC therapeutics through the next decade.

Conditional Ablation of Progesterone Receptor Membrane Component 2 Causes Female Premature Reproductive Senescence

The nonclassical progesterone receptors progesterone receptor membrane component (PGRMC) 1 and PGRMC2 have been implicated in regulating cell survival of endometrial and ovarian cells in vitro and are abundantly expressed in these cell types. The objective of this study was to determine if Pgrmc1 and Pgrmc2 are essential for normal female reproduction. To accomplish this objective, Pgrmc1 and/or Pgrmc2 floxed mice (Pgrmc2fl/fl and Pgrmc1/2fl/fl) were crossed with Pgr-cre mice, which resulted in the conditional ablation of Pgrmc1 and/or Pgrmc2 from female reproductive tissues (i.e.,Pgrmc2d/d and Pgrmc1/2d/d mice). A breeding trial revealed that conditional ablation of Pgrmc2 initially led to subfertility, with Pgrmc2d/d female mice producing 47% fewer pups/litter than Pgrmc2fl/fl mice (P = 0.001). Pgrmc2d/d mice subsequently underwent premature reproductive senescence by parities 2 to 5, producing 37.8% fewer litters overall during the trial compared with Pgrmc2fl/fl mice (P = 0.020). Similar results were observed with Pgrmc1/2d/d mice. Based on ovarian morphology and serum P4, the subfertility/infertility was not due to faulty ovulation or luteal insufficiency. Rather an analysis of midgestation implantation sites revealed that postimplantation embryonic death was the major cause of the subfertility/infertility. As with our previous report of Pgrmc1d/d mice, Pgrmc2d/d and Pgrmc1/2d/d mice developed endometrial cysts consistent with accelerated aging of this tissue. Given the timing of postimplantation embryonic demise, uterine decidualization may be disrupted in mice deficient in PGRMC2 or PGRMC1/2. Overall, this study revealed that Pgrmc1 and/or Pgrmc2 are required for the maintenance of uterine histoarchitecture and normal female reproductive lifespan.

A Novel Role for Progesterone Receptor Membrane Component 1 (PGRMC1): A Partner and Regulator of Ferrochelatase

Heme is an iron-containing cofactor essential for multiple cellular processes and fundamental activities such as oxygen transport. To better understand the means by which heme synthesis is regulated during erythropoiesis, affinity purification coupled with mass spectrometry (MS) was performed to identify putative protein partners interacting with ferrochelatase (FECH), the terminal enzyme in the heme biosynthetic pathway. Both progesterone receptor membrane component 1 (PGRMC1) and progesterone receptor membrane component 2 (PGRMC2) were identified in these experiments. These interactions were validated by reciprocal affinity purification followed by MS analysis and immunoblotting. The interaction between PGRMC1 and FECH was confirmed in vitro and in HEK 293T cells, a non-erythroid cell line. When cells that are recognized models for erythroid differentiation were treated with a small molecule inhibitor of PGRMC1, AG-205, there was an observed decrease in the level of hemoglobinization relative to that of untreated cells. In vitro heme transfer experiments showed that purified PGRMC1 was able to donate heme to apo-cytochrome b5. In the presence of PGRMC1, in vitro measured FECH activity decreased in a dose-dependent manner. Interactions between FECH and PGRMC1 were strongest for the conformation of FECH associated with product release, suggesting that PGRMC1 may regulate FECH activity by controlling heme release. Overall, the data illustrate a role for PGRMC1 in regulating heme synthesis via interactions with FECH and suggest that PGRMC1 may be a heme chaperone or sensor.

Conditional Ablation of Progesterone Receptor Membrane Component 1 Results in Subfertility in the Female and Development of Endometrial Cysts

Progesterone (P4) is essential for female fertility. The objective of this study was to evaluate the functional requirement of the nonclassical P4 receptor (PGR), PGR membrane component 1, in regulating female fertility. To achieve this goal, the Pgrmc1 gene was floxed by insertion of loxP sites on each side of exon 2. Pgrmc1 floxed (Pgrmc1(fl/fl)) mice were crossed with Pgr(cre) or Amhr2(cre) mice to delete Pgrmc1 (Pgrmc1(d/d)) from the female reproductive tract. A 6-month breeding trial revealed that conditional ablation of Pgrmc1 with Pgr(cre/+) mice resulted in a 40% reduction (P = .0002) in the number of pups/litter. Neither the capacity to ovulate in response to gonadotropin treatment nor the expression of PGR and the estrogen receptor was altered in the uteri of Pgrmc1(d/d) mice compared with Pgrmc1(fl/fl) control mice. Although conditional ablation of Pgrmc1 from mesenchymal tissue using Amhr2(cre/+) mice did not reduce the number of pups/litter, the total number of litters born in the 6-month breeding trial was significantly decreased (P = .041). In addition to subfertility, conditional ablation of Pgrmc1 using either Amhr2(cre/+) or Pgr(cre/+) mice resulted in the development of endometrial cysts starting around 4 months of age. Interestingly, pregnancy attenuated the formation of these uterine cysts. These new findings demonstrate that PGR membrane component 1 plays an important role in female fertility and uterine tissue homeostasis.

A decade of EGFR inhibition in EGFR-mutated non small cell lung cancer (NSCLC): Old successes and future perspectives

The discovery of Epidermal Growth Factor Receptor (EGFR) mutations in Non Small Cell Lung Cancer (NSCLC) launched the era of personalized medicine in advanced NSCLC, leading to a dramatic shift in the therapeutic landscape of this disease. After ten years from the individuation of activating mutations in the tyrosine kinase domain of the EGFR in NSCLC patients responding to the EGFR tyrosine kinase inhibitor (TKI) Gefitinib, several progresses have been done and first line treatment with EGFR TKIs is a firmly established option in advanced EGFR-mutated NSCLC patients. During the last decade, different EGFR TKIs have been developed and three inhibitors have been approved so far in these selected patients. However, despite great breakthroughs have been made, treatment of these molecularly selected patients poses novel therapeutic challenges, such as emerging of acquired resistance, brain metastases development or the need to translate these treatments in earlier clinical settings, such as adjuvant therapy.

The aim of this paper is to provide a comprehensive review of the major progresses reported so far in the EGFR inhibition in this molecularly-selected subgroup of NSCLC patients, from the early successes with first generation EGFR TKIs, Erlotinib and Gefitinib, to the novel irreversible and mutant-selective inhibitors and ultimately the emerging challenges that we, in the next future, are called to deal with.

Long non-coding RNA UCA1 induces non-T790M acquired resistance to EGFR-TKIs by activating the AKT/mTOR pathway in EGFR-mutant non-small cell lung cancer

The aim of this study was to explore the role of long non-coding RNA UCA1 (urothelial cancer-associated 1) in acquired resistance to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) in EGFR-mutant non-small cell lung cancer (NSCLC). In our study, UCA1 expression was significantly increased in lung cancer cells and patients with acquired resistance to EGFR-TKIs. Over-expression of UCA1 was significantly associated with a shorter progression-free survival (PFS) [13.0 vs. 8.5 months, P < 0.01] in tumors with respond to EGFR-TKIs. The significant relationship was not observed in patients with T790M mutation (10.5 vs. 12.0 months, P = 0.778), but in patients with non-T790M (19.0 vs. 9.0 months, P = 0.023). UCA1 knockdown restored gefitinib sensitivity in acquired resistant cells with non-T790M and inhibited the activation of the AKT/mTOR pathway and epithelial-mesenchymal transition (EMT). The mTOR inhibitor was effective in UCA1-expressing cell PC9/R. Inhibiting mTOR could change the expression of UCA1, although there was no significant difference. In conclusion, the influence of over-expression of UCA1 on PFS for patients with acquired resistance to EGFR-TKIs was from the subgroup with non-T790M mutation. UCA1 may induce non-T790M acquired resistance to EGFR-TKIs by activating the AKT/mTOR pathway and EMT.

The emerging role of progesterone receptor membrane component 1 (PGRMC1) in cancer biology

Progesterone receptor membrane component 1 (PGRMC1) is a multi-functional protein with a heme-binding moiety related to that of cytochrome b₅, which is a putative progesterone receptor. The recently solved PGRMC1 structure revealed that heme-binding involves coordination by a tyrosinate ion at Y113, and induces dimerization which is stabilized by hydrophobic stacking of heme on adjacent monomers. Dimerization is required for association with cytochrome P450 (cyP450) enzymes, which mediates chemoresistance to doxorubicin and may be responsible for PGRMC1's anti-apoptotic activity. Here we review the multiple attested involvement of PGRMC1 in diverse functions, including regulation of cytochrome P450, steroidogenesis, vesicle trafficking, progesterone signaling and mitotic spindle and cell cycle regulation. Its wide range of biological functions is attested to particularly by its emerging association with cancer and progesterone-responsive female reproductive tissues. PGRMC1 exhibits all the hallmarks of a higher order nexus signal integration hub protein. It appears capable of acting as a detector that integrates information from kinase/phosphatase pathways with heme and CO levels and probably redox status.

Constitutive asymmetric dimerization drives oncogenic activation of epidermal growth factor receptor carboxyl-terminal deletion mutants

Genomic alterations targeting the Epidermal Growth Factor Receptor (EGFR) gene have been strongly associated with cancer pathogenesis. The clinical effectiveness of EGFR targeted therapies, including small molecules directed against the kinase domain such as gefitinib, erlotinib and afatinib, have been proven successful in treating non-small cell lung cancer patients with tumors harboring EGFR kinase domain mutations. Recent large-scale genomic studies in glioblastoma and lung cancer have identified an additional class of oncogenic mutations caused by the intragenic deletion of carboxy-terminal coding regions. Here, we report that combinations of exonic deletions of exon 25 to 28 lead to the oncogenic activation of EGF receptor in the absence of ligand and consequent cellular transformation, indicating a significant role of C-terminal domain in modulating EGFR activation. Furthermore, we show that the oncogenic activity of the resulting C-terminal deletion mutants are efficiently inhibited by EGFR-targeted drugs including erlotinib, afatinib, dacomitinib as well as cetuximab, expanding the therapeutic rationale of cancer genome-based EGFR targeted approaches. Finally, in vivo and in vitro preclinical studies demonstrate that constitutive asymmetric dimerization in mutant EGFR is a key mechanism for oncogenic activation and tumorigenesis by C-terminal deletion mutants. Therefore, our data provide compelling evidence for oncogenic activation of C-terminal deletion mutants at the molecular level and we propose that C-terminal deletion status of EGFR can be considered as a potential genomic marker for EGFR-targeted therapy.

Integrin α5 Suppresses the Phosphorylation of Epidermal Growth Factor Receptor and Its Cellular Signaling of Cell Proliferation via N-Glycosylation

Integrin α5β1-mediated cell adhesion regulates a multitude of cellular responses, including cell proliferation, survival, and cross-talk between different cellular signaling pathways. Integrin α5β1 is known to convey permissive signals enabling anchorage-dependent receptor tyrosine kinase signaling. However, the effects of integrin α5β1 on cell proliferation are controversial, and the molecular mechanisms involved in the regulation between integrin α5β1 and receptor tyrosine kinase remain largely unclear. Here we show that integrin α5 functions as a negative regulator of epidermal growth factor receptor (EGFR) signaling through its N-glycosylation. Expression of WT integrin α5 suppresses the EGFR phosphorylation and internalization upon EGF stimulation. However, expression of the N-glycosylation mutant integrin α5, S3-5, which contains fewer N-glycans, reversed the suppression of the EGFR-mediated signaling and cell proliferation. In a mechanistic manner, WT but not S3-5 integrin α5 forms a complex with EGFR and glycolipids in the low density lipid rafts, and the complex formation is disrupted upon EGF stimulation, suggesting that the N-glycosylation of integrin α5 suppresses the EGFR activation through promotion of the integrin α5-glycolipids-EGFR complex formation. Furthermore, consistent restoration of those N-glycans on the Calf-1,2 domain of integrin α5 reinstated the inhibitory effects as well as the complex formation with EGFR. Taken together, these data are the first to demonstrate that EGFR activation can be regulated by the N-glycosylation of integrin α5, which is a novel molecular paradigm for the cross-talk between integrins and growth factor receptors.

Novel roles of androgen receptor, epidermal growth factor receptor, TP53, regulatory RNAs, NF-kappa-B, chromosomal translocations, neutrophil associated gelatinase, and matrix metalloproteinase-9 in prostate cancer and prostate cancer stem cells

Approximately one in six men will be diagnosed with some form of prostate cancer in their lifetime. Over 250,000 men worldwide die annually due to complications from prostate cancer. While advancements in prostate cancer screening and therapies have helped in lowering this statistic, better tests and more effective therapies are still needed. This review will summarize the novel roles of the androgen receptor (AR), epidermal growth factor receptor (EGFR), the EGFRvIII variant, TP53, long-non-coding RNAs (lncRNAs), microRNAs (miRs), NF-kappa-B, chromosomal translocations, neutrophil associated gelatinase, (NGAL), matrix metalloproteinase-9 (MMP-9), the tumor microenvironment and cancer stem cells (CSC) have on the diagnosis, development and treatment of prostate cancer.