IGF-1R inhibition enhances radiosensitivity and delays double-strand break repair by both non-homologous end-joining and homologous recombination

Nutrition, GH/IGF-1 signaling, and cancer

Cancer is the second leading cause of death in the United States and among the most prevalent diseases globally, with an incidence expected to grow because of smoking, pollution, poor dietary habits, obesity, and the rise in the older population. Given their ability to reduce risk factors, albeit with varying efficacy, nutrition and fasting could help prevent cancer and other age-related disorders. Calorie restriction (CR), various forms of intermittent fasting (IF) or periodic fasting (PF), and fasting-mimicking diets (FMDs) have been shown to improve health span, increase lifespan, and prevent or postpone cancer in rodents. The effects of specific diets and fasting regimens on aging and cancer appear to be mediated in part by the reduction in the activity of the growth hormone (GH)/insulin-like-growth-factor-I (IGF-1) axis. Nevertheless, recent data indicate that the alternation of low and normal levels of these hormones and factors may be ideal for optimizing longevity and function. Here, we review the role of nutrition, CR, and fasting/FMD on cancer, focusing on the hypothesis that the modulation of GH, IGF-1, and insulin signaling partly mediates the effect of these dietary interventions on cancer prevention.

The Role of Insulin-like Growth Factor Binding Protein (IGFBP)-2 in DNA Repair and Chemoresistance in Breast Cancer Cells

The role if insulin-like growth factor binding protein-2 (IGFBP-2) in mediating chemoresistance in breast cancer cells has been demonstrated, but the mechanism of action is unclear. This study aimed to further investigate the role of IGFBP-2 in the DNA damage response induced by etoposide in MCF-7, T47D (ER+ve), and MDA-MB-231 (ER-ve) breast cancer cell lines. In the presence or absence of etoposide, IGFBP-2 was silenced using siRNA in the ER-positive cell lines, or exogenous IGFBP-2 was added to the ER-negative MDA-MB-231 cells. Cell number and death were assessed using trypan blue dye exclusion assay, changes in abundance of proteins were monitored using Western blotting of whole cell lysates, and localization and abundance were determined using immunofluorescence and cell fractionation. Results from ER-positive cell lines demonstrated that upon exposure to etoposide, loss of IGFBP-2 enhanced cell death, and this was associated with a reduction in P-DNA-PKcs and an increase in γH2AX. Conversely, with ER-negative cells, the addition of IGFBP-2 in the presence of etoposide resulted in cell survival, an increase in P-DNA-PKcs, and a reduction in γH2AX. In summary, IGFBP-2 is a survival factor for breast cancer cells that is associated with enhancement of the DNA repair mechanism.

Contrasting consequences of podocyte insulin-like growth factor 1 receptor inhibition

Insulin signaling to the glomerular podocyte via the insulin receptor (IR) is critical for kidney function. In this study we show that near-complete knockout of the closely related insulin-like growth factor 1 receptor (IGF1R) in podocytes is detrimental, resulting in albuminuria in vivo and podocyte cell death in vitro. In contrast, partial podocyte IGF1R knockdown confers protection against doxorubicin-induced podocyte injury. Proteomic analysis of cultured podocytes revealed that while near-complete loss of podocyte IGF1R results in the downregulation of mitochondrial respiratory complex I and DNA damage repair proteins, partial IGF1R inhibition promotes respiratory complex expression. This suggests that altered mitochondrial function and resistance to podocyte stress depends on the level of IGF1R suppression, the latter determining whether receptor inhibition is protective or detrimental. Our work suggests that the partial suppression of podocyte IGF1R could have therapeutic benefits in treating albuminuric kidney disease.

Exploring the Role of Hyperinsulinemia in Obesity-Associated Tumor Development

Although there has been a long-standing connection between hyperinsulinemia and cancer development, there is a lack of understanding of the role of the insulin receptor on cells that can become cancerous. In a recent issue of Cell Metabolism, Zhang and colleagues, using a diet-induced obesity mouse model, identified a direct function of insulin receptors on pancreatic acinar cells expressing a KRASG12D mutation in promoting obesity-associated pancreatic cancer. Furthermore, insulin receptor signaling from hyperinsulinemia promoted the secretion of digestive enzymes that contributed to acinar to ductal metaplasia. These findings highlight an important connection between obesity, diabetes, and pancreatic tumor development and suggest potential strategies for obesity-associated cancer prevention targeting the insulin receptor signaling pathways.

IGF-I protects porcine granulosa cells from hypoxia-induced apoptosis by promoting homologous recombination repair through the PI3K/AKT/E2F8/RAD51 pathway

Severe hypoxia induced by vascular compromise (ovarian torsion, surgery), obliteration of vessels (aging, chemotherapy, particularly platinum drugs) can cause massive follicle atresia. On the other hand, hypoxia increases the occurrence of DNA double-strand breaks (DSBs) and triggers cellular damage repair mechanisms; however, if the damage is not promptly repaired, it can also induce the apoptosis program. Insulin-like growth factor-I (IGF-I) is a polypeptide hormone that plays essential roles in stimulating mammalian follicular development. Here, we report a novel role for IGF-I in protecting hypoxic GCs from apoptosis by promoting DNA repair through the homologous recombination (HR) process. Indeed, the hypoxic environment within follicles significantly inhibited the efficiency of HR-directed DNA repair. The presence of IGF-I-induced HR pathway to alleviate hypoxia-induced DNA damage and apoptosis primarily through upregulating the expression of the RAD51 recombinase. Importantly, we identified a new transcriptional regulator of RAD51, namely E2F8, which mediates the protective effects of IGF-I on hypoxic GCs by facilitating the transcriptional activation of RAD51. Furthermore, we demonstrated that the PI3K/AKT pathway is crucial for IGF-I-induced E2F8 expression, resulting in increased RAD51 expression and enhanced HR activity, which mitigates hypoxia-induced DNA damage and thereby protects against GCs apoptosis. Together, these findings define a novel mechanism of IGF-I-mediated GCs protection by activating the HR repair through the PI3K/AKT/E2F8/RAD51 pathway under hypoxia.

Insulin Receptor Isoforms and Insulin Growth Factor-like Receptors: Implications in Cell Signaling, Carcinogenesis, and Chemoresistance

This comprehensive review thoroughly explores the intricate involvement of insulin receptor (IR) isoforms and insulin-like growth factor receptors (IGFRs) in the context of the insulin and insulin-like growth factor (IGF) signaling (IIS) pathway. This elaborate system encompasses ligands, receptors, and binding proteins, giving rise to a wide array of functions, including aspects such as carcinogenesis and chemoresistance. Detailed genetic analysis of IR and IGFR structures highlights their distinct isoforms, which arise from alternative splicing and exhibit diverse affinities for ligands. Notably, the overexpression of the IR-A isoform is linked to cancer stemness, tumor development, and resistance to targeted therapies. Similarly, elevated IGFR expression accelerates tumor progression and fosters chemoresistance. The review underscores the intricate interplay between IRs and IGFRs, contributing to resistance against anti-IGFR drugs. Consequently, the dual targeting of both receptors could present a more effective strategy for surmounting chemoresistance. To conclude, this review brings to light the pivotal roles played by IRs and IGFRs in cellular signaling, carcinogenesis, and therapy resistance. By precisely modulating these receptors and their complex signaling pathways, the potential emerges for developing enhanced anti-cancer interventions, ultimately leading to improved patient outcomes.

Emerging Role of IGF-1 in Prostate Cancer: A Promising Biomarker and Therapeutic Target

Prostate cancer (PCa) is a highly heterogeneous disease driven by gene alterations and microenvironmental influences. Not only enhanced serum IGF-1 but also the activation of IGF-1R and its downstream signaling components has been increasingly recognized to have a vital driving role in the development of PCa. A better understanding of IGF-1/IGF-1R activity and regulation has therefore emerged as an important subject of PCa research. IGF-1/IGF-1R signaling affects diverse biological processes in cancer cells, including promoting survival and renewal, inducing migration and spread, and promoting resistance to radiation and castration. Consequently, inhibitory reagents targeting IGF-1/IGF-1R have been developed to limit cancer development. Multiple agents targeting IGF-1/IGF-1R signaling have shown effects against tumor growth in tumor xenograft models, but further verification of their effectiveness in PCa patients in clinical trials is still needed. Combining androgen deprivation therapy or cytotoxic chemotherapeutics with IGF-1R antagonists based on reliable predictive biomarkers and developing and applying novel agents may provide more desirable outcomes. This review will summarize the contribution of IGF-1 signaling to the development of PCa and highlight the relevance of this signaling axis in potential strategies for cancer therapy.

From Therapy Resistance to Targeted Therapies in Prostate Cancer

Prostate cancer (PCa) is the second most common malignancy among men worldwide. Although early-stage disease is curable, advanced stage PCa is mostly incurable and eventually becomes resistant to standard therapeutic options. Different genetic and epigenetic alterations are associated with the development of therapy resistant PCa, with specific players being particularly involved in this process. Therefore, identification and targeting of these molecules with selective inhibitors might result in anti-tumoral effects. Herein, we describe the mechanisms underlying therapy resistance in PCa, focusing on the most relevant molecules, aiming to enlighten the current state of targeted therapies in PCa. We suggest that selective drug targeting, either alone or in combination with standard treatment options, might improve therapeutic sensitivity of resistant PCa. Moreover, an individualized analysis of tumor biology in each PCa patient might improve treatment selection and therapeutic response, enabling better disease management.

Drugging IGF-1R in cancer: New insights and emerging opportunities

The insulin-like growth factor (IGF) axis plays important roles in cancer development and metastasis. The type 1 IGF receptor (IGF-1R) is a key member in the IGF axis and has long been recognized for its oncogenic role in multiple cancer lineages. Here we review the occurrence of IGF-1R aberrations and activation mechanisms in cancers, which justify the development of anti-IGF-1R therapies. We describe the therapeutic agents available for IGF-1R inhibition, with focuses on the recent or ongoing pre-clinical and clinical studies. These include antisense oligonucleotide, tyrosine kinase inhibitors and monoclonal antibodies which may be conjugated with cytotoxic drug. Remarkably, simultaneous targeting of IGF-1R and several other oncogenic vulnerabilities has shown early promise, highlighting the potential benefits of combination therapy. Further, we discuss the challenges in targeting IGF-1R so far and new concepts to improve therapeutic efficacy such as blockage of the nuclear translocation of IGF-1R.

CHK1 inhibition exacerbates replication stress induced by IGF blockade

We recently reported that genetic or pharmacological inhibition of insulin-like growth factor receptor (IGF-1R) slows DNA replication and induces replication stress by downregulating the regulatory subunit RRM2 of ribonucleotide reductase, perturbing deoxynucleotide triphosphate (dNTP) supply. Aiming to exploit this effect in therapy we performed a compound screen in five breast cancer cell lines with IGF neutralising antibody xentuzumab. Inhibitor of checkpoint kinase CHK1 was identified as a top screen hit. Co-inhibition of IGF and CHK1 caused synergistic suppression of cell viability, cell survival and tumour growth in 2D cell culture, 3D spheroid cultures and in vivo. Investigating the mechanism of synthetic lethality, we reveal that CHK1 inhibition in IGF-1R depleted or inhibited cells further downregulated RRM2, reduced dNTP supply and profoundly delayed replication fork progression. These effects resulted in significant accumulation of unreplicated single-stranded DNA and increased cell death, indicative of replication catastrophe. Similar phenotypes were induced by IGF:WEE1 co-inhibition, also via exacerbation of RRM2 downregulation. Exogenous RRM2 expression rescued hallmarks of replication stress induced by co-inhibiting IGF with CHK1 or WEE1, identifying RRM2 as a critical target of the functional IGF:CHK1 and IGF:WEE1 interactions. These data identify novel therapeutic vulnerabilities and may inform future trials of IGF inhibitory drugs.

Local non-pituitary growth hormone is induced with aging and facilitates epithelial damage

Microenvironmental factors modulating age-related DNA damage are unclear. Non-pituitary growth hormone (npGH) is induced in human colon, non-transformed human colon cells, and fibroblasts, and in 3-dimensional intestinal organoids with age-associated DNA damage. Autocrine/paracrine npGH suppresses p53 and attenuates DNA damage response (DDR) by inducing TRIM29 and reducing ATM phosphorylation, leading to reduced DNA repair and DNA damage accumulation. Organoids cultured up to 4 months exhibit aging markers, p16, and SA-β-galactosidase and decreased telomere length, as well as DNA damage accumulation, with increased npGH, suppressed p53, and attenuated DDR. Suppressing GH in aged organoids increases p53 and decreases DNA damage. WT mice exhibit age-dependent colon DNA damage accumulation, while in aged mice devoid of colon GH signaling, DNA damage remains low, with elevated p53. As age-associated npGH induction enables a pro-proliferative microenvironment, abrogating npGH signaling could be targeted as anti-aging therapy by impeding DNA damage and age-related pathologies.

Chesnokova et al. show that non-pituitary growth hormone (npGH) is induced in aging DNA-damaged colon epithelium and suppresses DNA damage response by attenuating the phosphorylation of DNA repair proteins. npGH induction promotes DNA damage accumulation, resulting in age-associated colon microenvironment changes. Accordingly, disrupted GH signaling in aging mice prevents accumulated DNA damage.

DNA Damage Responses during the Cell Cycle: Insights from Model Organisms and Beyond

Genome damage is a threat to all organisms. To respond to such damage, DNA damage responses (DDRs) lead to cell cycle arrest, DNA repair, and cell death. Many DDR components are highly conserved, whereas others have adapted to specific organismal needs. Immense progress in this field has been driven by model genetic organism research. This review has two main purposes. First, we provide a survey of model organism-based efforts to study DDRs. Second, we highlight how model organism study has contributed to understanding how specific DDRs are influenced by cell cycle stage. We also look forward, with a discussion of how future study can be expanded beyond typical model genetic organisms to further illuminate how the genome is protected.

Combined metformin-salicylate treatment provides improved anti-tumor activity and enhanced radiotherapy response in prostate cancer; drug synergy at clinically relevant doses

•

Combined metformin + salicylate treatment has improved anti-tumor efficacy in prostate cancer.

•

At clinically achievable doses, it induces increased metabolic stress and sensitizes tumors to radiation.

•

Metformin + salicylate blocks pathways of de novo lipogenesis and protein synthesis.

•

In combination with radiation suppresses HIF1a and DNA replication.

•

This work supports clinical investigation of metformin + salicylate in combination with radiotherapy.

Background

There is need for well-tolerated therapies for prostate cancer (PrCa) secondary prevention and to improve response to radiotherapy (RT). The anti-diabetic agent metformin (MET) and the aspirin metabolite salicylate (SAL) are shown to activate AMP-activated protein kinase (AMPK), suppress de novo lipogenesis (DNL), the mammalian target of rapamycin (mTOR) pathway and reduce PrCa proliferation in-vitro. The purpose of this study was to examine whether combined MET+SAL treatment could provide enhanced PrCa tumor suppression and improve response to RT.

Methods

Androgen-sensitive (22RV1) and resistant (PC3, DU-145) PrCa cells and PC3 xenografts were used to examine whether combined treatment with MET+SAL can provide improved anti-tumor activity compared to each agent alone in non-irradiated and irradiated PrCa cells and tumors. Mechanisms of action were investigated with analysis of signaling events, mitochondria respiration and DNL activity assays.

Results

We observed that PrCa cells are resistant to clinically relevant doses of MET. Combined MET + SAL treatment provides synergistic anti-proliferative activity at clinically relevant doses and enhances the anti-proliferative effects of RT. This was associated with suppression of oxygen consumption rate (OCR), activation of AMPK, suppression of acetyl-CoA carboxylase (ACC)-DNL and mTOR-p70^s6k/4EBP1 and HIF1α pathways. MET + SAL reduced tumor growth in non-irradiated tumors and enhanced the effects of RT.

Conclusion

MET+SAL treatment suppresses PrCa cell proliferation and tumor growth and enhances responses to RT at clinically relevant doses. Since MET and SAL are safe, widely-used and inexpensive agents, these data support the investigation of MET+SAL in PrCa clinical trials alone and in combination with RT.

Nuclear IGF1R interacts with NuMA and regulates 53BP1‑dependent DNA double‑strand break repair in colorectal cancer

Nuclear insulin-like growth factor 1 receptor (nIGF1R) has been associated with poor overall survival and chemotherapy resistance in various types of cancer; however, the underlying mechanism remains unclear. In the present study, immunoprecipitation-coupled mass spectrometry was performed in an IGF1R-overexpressing SW480-OE colorectal cancer cell line to identify the nIGF1R interactome. Network analysis revealed 197 proteins of interest which were involved in several biological pathways, including RNA processing, DNA double-strand break (DSB) repair and SUMOylation pathways. Nuclear mitotic apparatus protein (NuMA) was identified as one of nIGF1R's colocalizing partners. Proximity ligation assay (PLA) revealed different levels of p53-binding protein 1 (53BP1)-NuMA colocalization between IGF1R-positive (R⁺) and IGF1R-negative (R⁻) mouse embryonic fibroblasts following exposure to ionizing radiation (IR). 53BP1 was retained by NuMA in the R⁻ cells during IR-induced DNA damage. By contrast, the level of NuMA-53BP1 was markedly lower in R⁺ cells compared with R⁻ cells. The present data suggested a regulatory role of nIGF1R in 53BP1-dependent DSB repair through its interaction with NuMA. Bright-field PLA analysis on a paraffin-embedded tissue microarray from patients with colorectal cancer revealed a significant association between increased nuclear colocalizing signals of NuMA-53BP1 and a shorter overall survival. These results indicate that nIGF1R plays a role in facilitating 53BP1-dependent DDR by regulating the NuMA-53BP1 interaction, which in turn might affect the clinical outcome of patients with colorectal cancer.

Dual Characters of GH-IGF1 Signaling Pathways in Radiotherapy and Post-radiotherapy Repair of Cancers

Radiotherapy remains one of the most important cancer treatment modalities. In the course of radiotherapy for tumor treatment, the incidental irradiation of adjacent tissues could not be completely avoided. DNA damage is one of the main factors of cell death caused by ionizing radiation, including single-strand (SSBs) and double-strand breaks (DSBs). The growth hormone-Insulin-like growth factor 1 (GH-IGF1) axis plays numerous roles in various systems by promoting cell proliferation and inhibiting apoptosis, supporting its effects in inducing the development of multiple cancers. Meanwhile, the GH-IGF1 signaling involved in DNA damage response (DDR) and DNA damage repair determines the radio-resistance of cancer cells subjected to radiotherapy and repair of adjacent tissues damaged by radiotherapy. In the present review, we firstly summarized the studies on GH-IGF1 signaling in the development of cancers. Then we discussed the adverse effect of GH-IGF1 signaling in radiotherapy to cancer cells and the favorable impact of GH-IGF1 signaling on radiation damage repair to adjacent tissues after irradiation. This review further summarized recent advances on research into the molecular mechanism of GH-IGF1 signaling pathway in these effects, expecting to specify the dual characters of GH-IGF1 signaling pathways in radiotherapy and post-radiotherapy repair of cancers, subsequently providing theoretical basis of their roles in increasing radiation sensitivity during cancer radiotherapy and repairing damage after radiotherapy.

IGF-1R depletion sensitizes colon cancer cell lines to radiotherapy

PURPOSE

Insulin like growth factor receptor 1 (IGF-1R) has been documented to play a key role in radiation response, thereby offering an attractive drug target to enhance tumor sensitivity to radiotherapy. Here, we investigated weather knockdown of IGF-1R can sensitize colorectal cancer (CRC) cell lines to radiation.

MATERIAL AND METHODS

Human colon carcinoma SW480 and HT-29 cells were transfected with specific small interference RNA (siRNA) to mediate IGF-1R depletion. The expression of IGF-1R mRNA and protein among transfected and untransfected cells was detected by Western blot analysis. Changes in cell proliferation and radiosensitivity were evaluated by the clonogenic survival assay. NVP-ADW742, an IGF-1R inhibitor, in combination with radiation was studied. RAD51, a measure for homologous recombination repair, and 53BP1, a maker for non-homologous end-joining (NHEJ), were determined by immunofluorescence for double-strand breaks (DSB) repair pathways. Cell cycle was also examined in the IGF-1R knockdown and IGF-1R-inhibited cells.

RESULTS

CRC cell lines were selectively sensitized to radiation after siRNA-mediated IGF-1R depletion. NVP-ADW742 efficiently increases cancer cell response to radiation. Furthermore, initial formation of RAD51 foci after IR, and 53BP1 foci were significantly reduced in IGF-1R-depleted or with IGF-1R Inhibitor CRC cell lines. Lastly, IGF-1R-depleted or with IGF-1R Inhibitor caused more G2 phase cell arrest.

CONCLUSION

Our findings demonstrate that depletion of IGF-1R lead to an increase in radiosensitivity in CRC.

EPHA2 Interacts with DNA-PKcs in Cell Nucleus and Controls Ionizing Radiation Responses in Non-Small Cell Lung Cancer Cells

Ephrin (EFN)/ Erythropoietin-producing human hepatocellular receptors (Eph) signaling has earlier been reported to regulate non-small cell lung cancer (NSCLC) cell survival and cell death as well as invasion and migration. Here, the role of Ephrin type-A receptor 2 (EphA2) on the DNA damage response (DDR) signaling and ionizing radiation (IR) cellular effect was studied in NSCLC cells. Silencing of EphA2 resulted in IR sensitization, with increased activation of caspase-3, PARP-1 cleavage and reduced clonogenic survival. Profiling of EphA2 expression in a NSCLC cell line panel showed a correlation to an IR refractory phenotype. EphA2 was found to be transiently and rapidly phosphorylated at Ser897 in response to IR, which was paralleled with the activation of ribosomal protein S6 kinase (RSK). Using cell fractionation, a transient increase in both total and pSer897 EphA2 in the nuclear fraction in response to IR was revealed. By immunoprecipitation and LC-MS/MS analysis of EphA2 complexes, nuclear localized EphA2 was found in a complex with DNA-PK_cs. Such complex formation rapidly increased after IR but returned back to basal level within an hour. Targeting EphA2 with siRNA or by treatment with EFNA1 ligand partly reduced phosphorylation of DNA-PK_cs at S2056 at early time points after IR. Thus, we report that EphA2 interacts with DNA-PK_cs in the cell nucleus suggesting a novel mechanism involving the EphA2 receptor in DDR signaling and IR responsiveness.

Targeting IGF Perturbs Global Replication through Ribonucleotide Reductase Dysfunction

Inhibition of IGF receptor (IGF1R) delays repair of radiation-induced DNA double-strand breaks (DSB), prompting us to investigate whether IGF1R influences endogenous DNA damage. Here we demonstrate that IGF1R inhibition generates endogenous DNA lesions protected by 53BP1 bodies, indicating under-replicated DNA. In cancer cells, inhibition or depletion of IGF1R delayed replication fork progression accompanied by activation of ATR-CHK1 signaling and the intra-S-phase checkpoint. This phenotype reflected unanticipated regulation of global replication by IGF1 mediated via AKT, MEK/ERK, and JUN to influence expression of ribonucleotide reductase (RNR) subunit RRM2. Consequently, inhibition or depletion of IGF1R downregulated RRM2, compromising RNR function and perturbing dNTP supply. The resulting delay in fork progression and hallmarks of replication stress were rescued by RRM2 overexpression, confirming RRM2 as the critical factor through which IGF1 regulates replication. Suspecting existence of a backup pathway protecting from toxic sequelae of replication stress, targeted compound screens in breast cancer cells identified synergy between IGF inhibition and ATM loss. Reciprocal screens of ATM-proficient/deficient fibroblasts identified an IGF1R inhibitor as the top hit. IGF inhibition selectively compromised growth of ATM-null cells and spheroids and caused regression of ATM-null xenografts. This synthetic-lethal effect reflected conversion of single-stranded lesions in IGF-inhibited cells into toxic DSBs upon ATM inhibition. Overall, these data implicate IGF1R in alleviating replication stress, and the reciprocal IGF:ATM codependence we identify provides an approach to exploit this effect in ATM-deficient cancers. SIGNIFICANCE: This study identifies regulation of ribonucleotide reductase function and dNTP supply by IGFs and demonstrates that IGF axis blockade induces replication stress and reciprocal codependence on ATM. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/81/8/2128/F1.large.jpg.

IGF-1 Receptor Signaling Regulates Type II Pneumocyte Senescence and Resulting Macrophage Polarization in Lung Fibrosis

PURPOSE

Type II pneumocyte (alveolar epithelial cells type II [AECII]) senescence has been implicated in the progression of lung fibrosis. The capacity of senescent cells to modulate pulmonary macrophages to drive fibrosis is unexplored. Insulin-like growth factor-1 receptor (IGF-1R) signaling has been implicated as a regulator of senescence and aging.

METHODS AND MATERIALS

Mice with an AECII-specific deletion of IGF-1R received thoracic irradiation (n ≥ 5 per condition), and the effect of IGF-1R deficiency on radiation-induced AECII senescence and macrophage polarization to an alternatively activated phenotype (M2) was investigated. IGF-1R signaling, macrophage polarization, and senescence were evaluated in surgically resected human lung (n = 63).

RESULTS

IGF-1R deficient mice demonstrated reduced AECII senescence (senescent AECII/field; intact: 7.25% ± 3.5% [mean ± SD], deficient: 2.75% ± 2.8%, P = .0001), reduced accumulation of M2 macrophages (intact: 24.7 ± 2.2 cells/field, deficient: 15.5 ± 1.2 cells/field, P = .0086), and fibrosis (hydroxyproline content; intact: 71.9 ± 21.7 μg/lung, deficient: 31.7 ± 7.9, P = .0485) after irradiation. Senescent AECII enhanced M2 polarization in a paracrine fashion (relative Arg1 mRNA, 0 Gy: 1.0 ± 0.4, 17.5 Gy: 7.34 ± 0.5, P < .0001). Evaluation of surgical samples from patients treated with chemoradiation demonstrated increased expression of IGF-1 (unirradiated: 10.2% ± 4.9% area, irradiated: 15.1% ± 11.5%, P = .0377), p21 (unirradiated: 0.013 ± 0.02 histoscore, irradiated: 0.084 ± 0.09 histoscore, P = .0002), IL-13 (unirradiated: 13.7% ± 2.8% area, irradiated: 21.7% ± 3.8%, P < .0001), and M2 macrophages in fibrotic regions relative to nonfibrotic regions (unirradiated: 11.4 ± 12.2 CD163 + cells/core, irradiated: 43.1 ± 40.9 cells/core, P = .0011), consistent with findings from animal models of lung fibrosis.

CONCLUSIONS

This study demonstrates that senescent AECII are necessary for the progression of pulmonary fibrosis and serve as a targetable, chronic stimuli for macrophage activation in fibrotic lung.

Relationships between DNA repair and RTK-mediated signaling pathways

Receptor Tyrosine Kinases (RTK) are an important family involved in numerous signaling pathways essential for proliferation, cell survival, transcription or cell-cycle regulation. Their role and involvement in cancer cell survival have been widely described in the literature, and are generally associated with overexpression and/or excessive activity in the cancer pathology. Because of these characteristics, RTKs are relevant targets in the fight against cancer. In the last decade, increasingly numerous works describe the role of RTK signaling in the modulation of DNA repair, thus providing evidence of the relationship between RTKs and the protein actors in the repair pathways. In this review, we propose a summary of RTKs described as potential modulators of double-stranded DNA repair pathways in order to put forward new lines of research aimed at the implementation of new therapeutic strategies targeting both DNA repair pathways and RTK-mediated signaling pathways.

Quantitative Tyrosine Phosphoproteomic Analysis of Resistance to Radiotherapy in Nasopharyngeal Carcinoma Cells

BACKGROUND

Radioresistance poses a major challenge in nasopharyngeal carcinoma (NPC) treatment. Protein tyrosine phosphorylation has emerged as a key device in the control of resistance to therapy in cancer cells.

METHODS

Using tandem mass tag (TMT) labeling and phospho-antibody affinity enrichment followed by high-resolution LC-MS/MS analysis, quantitative tyrosine phosphorylome analysis was performed in CNE2 (parental) and its radioresistant subline CNE2-IR.

RESULTS

Altogether, 233 tyrosine phosphorylation sites in 179 protein groups were identified, among which 179 sites in 140 proteins were quantified. Among the quantified proteins, 38 tyrosine phosphorylation proteins are up-regulated and 18 tyrosine phosphorylation proteins are down-regulated in CNE2-IR vs CNE2. Increased tyrosine phosphorylation in multiple receptor/protein tyrosine kinases (EPHA2, EGFR, IGF1R, ABL1 and LYN) was identified in CNE2-IR vs CNE2 cells. Intensive bioinformatic analyses revealed robust activation of multiple biological processes/pathways including E-cadherin stabilization, cell-cell adhesion, and cell junction organization in radioresistant CNE2-IR cells. Specifically, we observed that the CNE2 cells incubated with EphrinA1-Fc exhibited higher EPHA2 Y772 phosphorylation and lower E-cadherin expression, as compared with PBS control. Furthermore, an ATP-competitive EPHA2 RTK inhibitor (ALW-II-41-27, ALW) reduced EPHA2 Y772 phosphorylation and increased the expression of E-cadherin in CNE2-IR cells. Colony formation analysis showed that EFNA1 (EFNA1 is the ligand of EPHA2) treatment in CNE2 significantly promoted colony formation after 6Gy irradiation; while incubation with EPHA2 inhibitor ALW-II-41-27 in CNE2-IR cells impaired colony formation after irradiation, as compared with solvent control (DMSO).

CONCLUSION

In conclusion, phosphoproteomic approach allowed us to link tyrosine kinases signaling with radioresistance in NPC. Further studies are necessary to delineate the molecular function of EPHA2/E-cadherin signaling in radioresistant NPC and to explore rational combination therapy and its underlying mechanism.

Depletion of insulin-like growth factor 1 receptor increases radiosensitivity in colorectal cancer

Background

Although radiation therapy for advanced colorectal cancer (CRC) is very effective in some patients, treatment resistance limits its efficacy. Insulin-like growth factor 1 receptor (IGF1R) can affect tumor responsiveness and sensitivity to radiation in several cancer types. Herein, we studied the underlying function of IGF1R in the resistance of advanced CRC to radiation therapy and the possible use of drugs targeting IGF1R to overcome this resistance in patients with CRC.

Methods

Differences in the expression levels of the IGF1R were assessed in CRC samples from patients who were radiosensitive or radioresistant. Two radio-resistant colorectal cancer cell lines, SW480 and HT29, were selected for in vitro studies, and the involvement of the IGF1R in their radiation resistance was elucidated by suppressing its expression through a targeted siRNA and through the use of a specific IGF1R inhibitor, BMS-754807. We assessed radiosensitivity in these human CRC cells lines by examining their proliferation and colony formation, as well as cell cycle analysis. Activation of the Akt pathway was assessed using western blotting.

Results

Compared with tissues from radiosensitive patients, higher IGF1R expression levels were found in patients with radiation-resistant colorectal cancer, while BMS-754807 had improved radiosensitivity and reversed radiation tolerance in both colorectal cancer cell lines. Pre-treatment with BMS-754807 prior to irradiation inhibited Akt phosphorylation, induced cell cycle arrest, and increased DNA damage. Therefore, the IGF1R contributes to radiation resistance of CRC cells in vitro.

Conclusions

This study supports the notion that the radiosensitivity of radiation-resistant colorectal cancer cells can be enhanced by directly targeting IGF1R expression or activity. Ultimately, the combination of radiotherapy with IGF1R targeted inhibitors could potentially increase its effectiveness in the treatment of advanced colorectal cancer.

Nuclear IGF1R interact with PCNA to preserve DNA replication after DNA-damage in a variety of human cancers

Nuclear IGF1R has been linked to poor outcome in cancer. We recently showed that nuclear IGF1R phosphorylates PCNA and increases DNA damage tolerance. In this paper we aimed to describe this mechanism in cancer tissue as well as in cancer cell lines. In situ proximity ligation assay identified frequent IGF1R and PCNA colocalization in many cancer types. IGF1R/PCNA colocalization was more frequently increased in tumor cells than in adjacent normal, and more prominent in areas with dysplasia and invasion. However, the interaction was often lost in tumors with poor response to neoadjuvant treatment and most metastatic lesions. In two independent cohorts of serous ovarian carcinomas and oropharyngeal squamous cell carcinomas, stronger IGF1R/PCNA colocalization was significantly associated with a higher overall survival. Ex vivo irradiation of ovarian cancer tissue acutely induced IGF1R/PCNA colocalization together with γH2AX-foci formations. In vitro, RAD18 mediated mono-ubiquitination of PCNA during replication stress was dependent on IGF1R kinase activity. DNA fiber analysis revealed that IGF1R activation could rescue stalled DNA replication forks, but only in cancer cells with baseline IGF1R/PCNA interaction. We believe that the IGF1R/PCNA interaction is a basic cellular mechanism to increase DNA stress tolerance during proliferation, but that this mechanism is lost with tumor progression in conjunction with accumulated DNA damage and aberrant strategies to tolerate genomic instability. To exploit this mechanism in IGF1R targeted therapy, IGF1R inhibitors should be explored in the context of concomitant induction of DNA replication stress as well as in earlier clinical stages than previously tried.

The role of insulin-like growth factors in the development of prostate cancer

INTRODUCTION

Preclinical, clinical, and population studies have provided robust evidence for an important role for the insulin-like growth factor (IGF) system in the development of prostate cancer.

AREAS COVERED

An overview of the IGF system is provided. The evidence implicating the IGF system in the development of prostate cancer is summarized. The compelling evidence culminated in a number of clinical trials of agents targeting the system; the reasons for the failure of these trials are discussed.

EXPERT OPINION

Clinical trials of agents targeting the IGF system in prostate cancer were terminated due to limited objective clinical responses and are unlikely to be resumed unless a convincing predictive biomarker is identified that would enable the selection of likely responders. The aging population and increased screening will lead to greater diagnosis of prostate cancer. Although the vast majority will be indolent disease, the epidemics of obesity and diabetes will increase the proportion that progress to clinical disease. The increased population of worried men will result in more trials aimed to reduce the risk of disease progression; actual clinical endpoints will be challenging and the IGFs remain the best intermediate biomarkers to indicate a response that could alter the course of disease.

Peptide Hormone Regulation of DNA Damage Responses

DNA damage response (DDR) and DNA repair pathways determine neoplastic cell transformation and therapeutic responses, as well as the aging process. Altered DDR functioning results in accumulation of unrepaired DNA damage, increased frequency of tumorigenic mutations, and premature aging. Recent evidence suggests that polypeptide hormones play a role in modulating DDR and DNA damage repair, while DNA damage accumulation may also affect hormonal status. We review the available reports elucidating involvement of insulin-like growth factor 1 (IGF1), growth hormone (GH), α-melanocyte stimulating hormone (αMSH), and gonadotropin-releasing hormone (GnRH)/gonadotropins in DDR and DNA repair as well as the current understanding of pathways enabling these actions. We discuss effects of DNA damage pathway mutations, including Fanconi anemia, on endocrine function and consider mechanisms underlying these phenotypes. (Endocrine Reviews 41: 1 - 19, 2020).

Manipulation of Metabolic Pathways and Its Consequences for Anti-Tumor Immunity: A Clinical Perspective

In the relatively short history of anti-tumor treatment, numerous medications have been developed against a variety of targets. Intriguingly, although many anti-tumor strategies have failed in their clinical trials, metformin, an anti-diabetic medication, demonstrated anti-tumor effects in observational studies and even showed its synergistic potential with immune checkpoint inhibitors (ICIs) in subsequent clinical studies. Looking back from bedside-to-bench, it may not be surprising that the anti-tumor effect of metformin derives largely from its ability to rewire aberrant metabolic pathways within the tumor microenvironment. As one of the most promising breakthroughs in oncology, ICIs were also found to exert their immune-stimulatory effects at least partly via rewiring metabolic pathways. These findings underscore the importance of correcting metabolic pathways to achieve sufficient anti-tumor immunity. Herein, we start by introducing the tumor microenvironment, and then we review the implications of metabolic syndrome and treatments for targeting metabolic pathways in anti-tumor therapies. We further summarize the close associations of certain aberrant metabolic pathways with impaired anti-tumor immunity and introduce the therapeutic effects of targeting these routes. Lastly, we go through the metabolic effects of ICIs and conclude an overall direction to manipulate metabolic pathways in favor of anti-tumor responses.

Insulin-like growth factor receptor signaling in tumorigenesis and drug resistance: a challenge for cancer therapy

Insulin-like growth factors (IGFs) play important roles in mammalian growth, development, aging, and diseases. Aberrant IGFs signaling may lead to malignant transformation and tumor progression, thus providing the rationale for targeting IGF axis in cancer. However, clinical trials of the type I IGF receptor (IGF-IR)-targeted agents have been largely disappointing. Accumulating evidence demonstrates that the IGF axis not only promotes tumorigenesis, but also confers resistance to standard treatments. Furthermore, there are diverse pathways leading to the resistance to IGF-IR-targeted therapy. Recent studies characterizing the complex IGFs signaling in cancer have raised hope to refine the strategies for targeting the IGF axis. This review highlights the biological activities of IGF-IR signaling in cancer and the contribution of IGF-IR to cytotoxic, endocrine, and molecular targeted therapies resistance. Moreover, we update the diverse mechanisms underlying resistance to IGF-IR-targeted agents and discuss the strategies for future development of the IGF axis-targeted agents.

Inhibition of FGFR2-Signaling Attenuates a Homology-Mediated DNA Repair in GIST and Sensitizes Them to DNA-Topoisomerase II Inhibitors

Deregulation of receptor tyrosine kinase (RTK)-signaling is frequently observed in many human malignancies, making activated RTKs the promising therapeutic targets. In particular, activated RTK-signaling has a strong impact on tumor resistance to various DNA damaging agents, e.g., ionizing radiation and chemotherapeutic drugs. We showed recently that fibroblast growth factor receptor (FGFR)-signaling might be hyperactivated in imatinib (IM)-resistant gastrointestinal stromal tumors (GIST) and inhibition of this pathway sensitized tumor cells to the low doses of chemotherapeutic agents, such as topoisomerase II inhibitors. Here, we report that inhibition of FGFR-signaling in GISTs attenuates the repair of DNA double-strand breaks (DSBs), which was evidenced by the delay in γ-H2AX decline after doxorubicin (Dox)-induced DNA damage. A single-cell gel electrophoresis (Comet assay) data showed an increase of tail moment in Dox-treated GIST cells cultured in presence of BGJ398, a selective FGFR1-4 inhibitor, thereby revealing the attenuated DNA repair. By utilizing GFP-based reporter constructs to assess the efficiency of DSBs repair via homologous recombination (HR) and non-homologous end-joining (NHEJ), we found for the first time that FGFR inhibition in GISTs attenuated the homology-mediated DNA repair. Of note, FGFR inhibition/depletion did not reduce the number of BrdU and phospho-RPA foci in Dox-treated cells, suggesting that inhibition of FGFR-signaling has no impact on the processing of DSBs. In contrast, the number of Dox-induced Rad51 foci were decreased when FGFR2-mediated signaling was interrupted/inhibited by siRNA FGFR2 or BGJ398. Moreover, Rad51 and -H2AX foci were mislocalized in FGFR-inhibited GIST and the amount of Rad51 was substantially decreased in -H2AX-immunoprecipitated complexes, thereby illustrating the defect of Rad51 recombinase loading to the Dox-induced DSBs. Finally, as a result of the impaired homology-mediated DNA repair, the increased numbers of hypodiploid (i.e., apoptotic) cells were observed in FGFR2-inhibited GISTs after Dox treatment. Collectively, our data illustrates for the first time that inhibition of FGF-signaling in IM-resistant GIST interferes with the efficiency of DDR signaling and attenuates the homology-mediated DNA repair, thus providing the molecular mechanism of GIST’s sensitization to DNA damaging agents, e.g., DNA-topoisomerase II inhibitors.

Type 1 IGF receptor associates with adverse outcome and cellular radioresistance in paediatric high-grade glioma

High-grade glioma (HGG) is highly resistant to therapy, prompting us to investigate the contribution of insulin-like growth factor receptor (IGF-1R), linked with radioresistance in other cancers. IGF-1R immunohistochemistry in 305 adult HGG (aHGG) and 103 paediatric/young adult HGG (pHGG) cases revealed significant association with adverse survival in pHGG, with median survival of 13.5 vs 29 months for pHGGs with moderate/strong vs negative/weak IGF-1R (p = 0.011). Secondly, we tested IGF-1R inhibitor BMS-754807 in HGG cells, finding minimal radiosensitisation of 2/3 aHGG cell lines (dose enhancement ratios DERs < 1.60 at 2–8 Gy), and greater radiosensitisation of 2/2 pHGG cell lines (DERs ≤ 4.16). BMS-754807 did not influence radiation-induced apoptosis but perturbed the DNA damage response with altered induction/resolution of γH2AX, 53BP1 and RAD51 foci. These data indicate that IGF-1R promotes radioresistance in pHGG, potentially contributing to the association of IGF-1R with adverse outcome and suggesting IGF-1R as a candidate treatment target in pHGG.

Dual-specificity protein phosphatase DUSP4 regulates response to MEK inhibition in BRAF wild-type melanoma

Background

Aiming to improve treatment options for BRAF wild-type melanoma, we previously conducted the DOC-MEK study of docetaxel with MEK inhibitor (MEKi) selumetinib or placebo, revealing trends to prolongation of progression-free survival (hazard ratio 0.75, P = 0.130), and improved response rates (32% vs 14%, P = 0.059) with docetaxel plus selumetinib. NRAS status did not associate with outcome. Here, the aim was to identify novel biomarkers of response to MEKi.

Methods

A MEK 6 gene signature was quantified using NanoString and correlated with clinical outcomes. Two components of the gene signature were investigated by gene silencing in BRAF/NRAS wild-type melanoma cells.

Results

In melanomas of patients on the selumetinib but not the placebo arm, two gene signature components, dual-specificity protein phosphatase 4 (DUSP4) and ETS translocation variant 4 (ETV4), were expressed more highly in responders than non-responders. In vitro, ETV4 depletion inhibited cell survival but did not influence sensitivity to MEKi selumetinib or trametinib. In contrast, DUSP4-depleted cells showed enhanced cell survival and increased resistance to both selumetinib and trametinib.

Conclusions

ETV4 and DUSP4 associated with clinical response to docetaxel plus selumetinib. DUSP4 depletion induced MEKi resistance, suggesting that DUSP4 is not only a biomarker but also a mediator of MEKi sensitivity.

Clinical Trial Registration

DOC-MEK (EudraCT no: 2009-018153-23).

Radioresistant laryngeal cancers upregulate type 1 IGF receptor and exhibit increased cellular dependence on IGF and EGF signalling

OBJECTIVES

Patients failing radiotherapy for laryngeal squamous cell carcinoma (LSCC) often require salvage total laryngectomy which has major functional consequences, highlighting a need for biomarkers of radiotherapy resistance. In other tumour types, radioresistance has been linked to epidermal growth factor receptor (EGFR) and type 1 insulin-like growth factor receptor (IGF-1R). Here, we evaluated IGF-1R and EGFR as predictors and mediators of LSCC radioresistance.

DESIGN

We compared IGF-1R and EGFR immunohistochemical scores in patients with LSCC achieving long-term remission post-radiotherapy (n = 23), patients treated with primary laryngectomy (n = 22) or salvage laryngectomy following radiotherapy recurrence (n = 18). To model radioresistance in vitro, two LSCC cell lines underwent clinically relevant irradiation to 55 Gy in 2.75 Gy fractions.

RESULTS

Type 1 insulin-like growth factor receptor expression was higher in pre-treatment biopsies of radiotherapy failures compared with those in long-term remission and was upregulated post-radiotherapy. Patients undergoing primary laryngectomy had more advanced T/N stage and greater tumour IGF-1R content than those achieving long-term remission. Pre-treatment EGFR did not associate with radiotherapy outcomes but showed a trend to upregulation post-irradiation. In vitro, radiosensitivity was enhanced by inhibition of EGFR but not IGF. Repeated irradiation upregulated IGF-1R in BICR18 and SQ20B cells and EGFR in SQ20B, and enhanced SQ20B radioresistance. Repeatedly irradiated SQ20B_55 cells were not radiosensitised by inhibition of IGF and/or EGFR, but IGF-1R:EGFR co-inhibition suppressed baseline cell survival more effectively than blockade of either pathway alone, and more effectively than in parental cells.

CONCLUSIONS

Radiation upregulates IGF-1R and may enhance IGF/EGFR dependence, suggesting that IGF/EGFR blockade may have activity in LSCCs that recur post-radiotherapy.

Therapeutic Targeting of the IGF Axis

The insulin like growth factor (IGF) axis plays a fundamental role in normal growth and development, and when deregulated makes an important contribution to disease. Here, we review the functions mediated by ligand-induced IGF axis activation, and discuss the evidence for the involvement of IGF signaling in the pathogenesis of cancer, endocrine disorders including acromegaly, diabetes and thyroid eye disease, skin diseases such as acne and psoriasis, and the frailty that accompanies aging. We discuss the use of IGF axis inhibitors, focusing on the different approaches that have been taken to develop effective and tolerable ways to block this important signaling pathway. We outline the advantages and disadvantages of each approach, and discuss progress in evaluating these agents, including factors that contributed to the failure of many of these novel therapeutics in early phase cancer trials. Finally, we summarize grounds for cautious optimism for ongoing and future studies of IGF blockade in cancer and non-malignant disorders including thyroid eye disease and aging.

IGF-1R Inhibition Suppresses Cell Proliferation and Increases Radiosensitivity in Nasopharyngeal Carcinoma Cells

Although ionizing radiation (IR) has provided considerable improvements in nasopharyngeal carcinoma (NPC) treatment, radioresistance is still a major threat for some subsets of patients. The insulin-like growth factor-1 receptor (IGF-1R) signaling pathway is tightly regulated and plays critical roles in mediating cell proliferation, growth, and survival. Thus, IGF-1R may be a potential therapeutic target for patients with different malignancies. However, its mechanism in NPC is not fully investigated. Linsitinib is an oral small molecule and is a tyrosine kinase inhibitor (TKI) of IGF-1R, which has been known for antitumor effects used widely. Here, we evaluated the proliferation and radiosensitivity of NPC cell lines (CNE-2 and SUNE-1) after linsitinib treatment. We found that linsitinib suppresses IGF-1-induced cell proliferation through inhibiting Akt and ERK phosphorylation. Moreover, linsitinib further boosted IR-induced DNA damage, G2-M cell cycle delay, and apoptosis in NPC cells. Finally, linsitinib reversed radioresistant NPC cells by decreasing the phosphorylation of IGF-1R. Our data indicated that the combination of linsitinib and IR and targeting IGF-1R by linsitinib could be a promising therapeutic strategy for NPC.

Activation of the IGF Axis in Thyroid Cancer: Implications for Tumorigenesis and Treatment

The Insulin-like growth factor (IGF) axis is one of the best-established drivers of thyroid transformation, as thyroid cancer cells overexpress both IGF ligands and their receptors. Thyroid neoplasms encompass distinct clinical and biological entities as differentiated thyroid carcinomas (DTC)-comprising papillary (PTC) and follicular (FTC) tumors-respond to radioiodine therapy, while undifferentiated tumors-including poorly-differentiated (PDTC) or anaplastic thyroid carcinomas (ATCs)-are refractory to radioactive iodine and exhibit limited responses to chemotherapy. Thus, safe and effective treatments for the latter aggressive thyroid tumors are urgently needed. Despite a strong preclinical rationale for targeting the IGF axis in thyroid cancer, the results of the available clinical studies have been disappointing, possibly because of the crosstalk between IGF signaling and other pathways that may result in resistance to targeted agents aimed against individual components of these complex signaling networks. Based on these observations, the combinations between IGF-signaling inhibitors and other anti-tumor drugs, such as DNA damaging agents or kinase inhibitors, may represent a promising therapeutic strategy for undifferentiated thyroid carcinomas. In this review, we discuss the role of the IGF axis in thyroid tumorigenesis and also provide an update on the current knowledge of IGF-targeted combination therapies for thyroid cancer.

IGF signalling in germ cells and testicular germ cell tumours: roles and therapeutic approaches

The insulin-like growth factor (IGF) axis plays key roles in normal tissue growth and development as well as in the progression of several tumour types and their subsequent growth and progression to a metastatic phenotype. This review explores the role of IGF system in normal germ cell development and function in addition to examining the evidence for deregulation of IGF signalling in cancer, with particular relevance to evidence supporting a role in testicular germ cell tumours (TGCTs). Despite the clear preclinical rationale for targeting the IGF axis in cancer, there has been a lack of progress in identifying which patients may benefit from such therapy. Future employment of agents targeting the IGF pathway is expected to concentrate on their use in combination with other treatments to prevent resistance and exploit their potential as chemo- and radiosensitizers.

Growth Hormone Induces Colon DNA Damage Independent of IGF-1

DNA damage occurs as a result of environmental insults and aging and, if unrepaired, may lead to chromosomal instability and tumorigenesis. Because GH suppresses ataxia-telangiectasia mutated kinase phosphorylation, decreases DNA repair, and increases DNA damage accumulation, we elucidated whether GH effects on DNA damage are mediated through induced IGF-1. In nontumorous human colon cells, GH, but not IGF-1, increased DNA damage. Stably disrupted IGF-1 receptor (IGF-1R) by lentivirus-expressing short hairpin RNA in vitro or treatment with the IGF-1R phosphorylation inhibitor picropodophyllotoxin (PPP) in vitro and in vivo led to markedly induced GH receptor (GHR) abundance, rendering cells more responsive to GH actions. Suppressing IGF-1R triggered DNA damage in both normal human colon cells and three-dimensional human intestinal organoids. DNA damage was further increased when cells with disrupted IGF-1R were treated with GH. Because GH induction of DNA damage accumulation appeared to be mediated not by IGF-1R but probably by more abundant GH receptor expression, we injected athymic mice with GH-secreting xenografts and then treated them with PPP. In these mice, high circulating GH levels were associated with increased colon DNA damage despite disrupted IGF-1R activity (P < 0.01), whereas GHR levels were also induced. Further confirming that GH effects on DNA damage are directly mediated by GHR signaling, GHR-/- mice injected with PPP did not show increased DNA damage, whereas wild-type mice with intact GHR exhibited increased colon DNA damage in the face of IGF-1 signaling suppression. The results indicate that GH directly induces DNA damage independent of IGF-1.

Excess growth hormone suppresses DNA damage repair in epithelial cells

Growth hormone (GH) decreases with age, and GH therapy has been advocated by some to sustain lean muscle mass and vigor in aging patients and advocated by athletes to enhance performance. Environmental insults and aging lead to DNA damage, which - if unrepaired - results in chromosomal instability and tumorigenesis. We show that GH suppresses epithelial DNA damage repair and blocks ataxia telangiectasia mutated (ATM) kinase autophosphorylation with decreased activity. Decreased phosphorylation of ATM target proteins p53, checkpoint kinase 2 (Chk2), and histone 2A variant led to decreased DNA repair by nonhomologous end-joining. In vivo, prolonged high GH levels resulted in a 60% increase in unrepaired colon epithelial DNA damage. GH suppression of ATM was mediated by induced tripartite motif containing protein 29 (TRIM29) and attenuated tat interacting protein 60 kDa (Tip60). By contrast, DNA repair was increased in human nontumorous colon cells (hNCC) where GH receptor (GHR) was stably suppressed and in colon tissue derived from GHR-/- mice. hNCC treated with etoposide and GH showed enhanced transformation, as evidenced by increased growth in soft agar. In mice bearing human colon GH-secreting xenografts, metastatic lesions were increased. The results elucidate a mechanism underlying GH-activated epithelial cell transformation and highlight an adverse risk for inappropriate adult GH treatment.

The signaling pathways that mediate the anti-cancer effects of caloric restriction

Caloric restriction (CR) has been shown to promote longevity and ameliorate aging-associated diseases, including cancer. Extensive research over recent decades has revealed that CR reduces IGF-1/PI3K/AKT signaling and increases sirtuin signaling. We recently found that CR also enhances ALDOA/DNA-PK/p53 signaling. In the present review, we summarize the molecular mechanisms underlying the modulation of the IGF-1/PI3K/AKT pathway, sirtuin signaling, and the ALDOA/DNA-PK/p53 pathway by CR. We also summarize the evidence concerning the roles of these signaling pathways in carcinogenesis, and discuss how they are regulated by CR. Finally, we discuss the crosstalk between these signaling pathways.

Targeting DNA Double-Strand Break Repair Pathways to Improve Radiotherapy Response

More than half of cancer patients receive radiotherapy as a part of their cancer treatment. DNA double-strand breaks (DSBs) are considered as the most lethal form of DNA damage and a primary cause of cell death and are induced by ionizing radiation (IR) during radiotherapy. Many malignant cells carry multiple genetic and epigenetic aberrations that may interfere with essential DSB repair pathways. Additionally, exposure to IR induces the activation of a multicomponent signal transduction network known as DNA damage response (DDR). DDR initiates cell cycle checkpoints and induces DSB repair in the nucleus by non-homologous end joining (NHEJ) or homologous recombination (HR). The canonical DSB repair pathways function in both normal and tumor cells. Thus, normal-tissue toxicity may limit the targeting of the components of these two pathways as a therapeutic approach in combination with radiotherapy. The DSB repair pathways are also stimulated through cytoplasmic signaling pathways. These signaling cascades are often upregulated in tumor cells harboring mutations or the overexpression of certain cellular oncogenes, e.g., receptor tyrosine kinases, PIK3CA and RAS. Targeting such cytoplasmic signaling pathways seems to be a more specific approach to blocking DSB repair in tumor cells. In this review, a brief overview of cytoplasmic signaling pathways that have been reported to stimulate DSB repair is provided. The state of the art of targeting these pathways will be discussed. A greater understanding of the underlying signaling pathways involved in DSB repair may provide valuable insights that will help to design new strategies to improve treatment outcomes in combination with radiotherapy.

Inhibition of IGF1R enhances 2-deoxyglucose in the treatment of non-small cell lung cancer

OBJECTIVE

We previously postulated that 2-deoxyglucose (2-DG) activates multiple pro-survival pathways through IGF1R to negate its inhibitory effect on glycolysis. Here, we evaluated whether IGF1R inhibitor synergizes with 2-DG to impede the growth of non-small cell lung cancer (NSCLC).

MATERIALS AND METHODS

The activation of IGF1R signaling was assessed by the phosphorylation of IGF1R and its downstream target AKT using immunoblot. Drug dose response and combination index analyses were carried out according to the method of Chou and Talalay. Flow cytometry was used to evaluate cell cycle progression. Apoptosis was monitored by caspase-3/PARP cleavages or Annexin V staining. A subcutaneous xenograft model was used to assess this combination in vivo.

RESULTS

2-DG induces the phosphorylation of IGF1R in its kinase domain, which can be abolished by the IGF1R inhibitor BMS-754807. Furthermore, the combination of 2-DG and BMS-754807 synergistically inhibited the survival of several non-small cell lung cancer (NSCLC) cell lines both in vitro and in vivo. The mechanistic basis of this synergy was cell line-dependent, and LKB1-inactivated EKVX cells underwent apoptosis following treatment with a subtoxic dose of 2-DG and BMS-754807. For these cells, the restoration of LKB1 kinase activity suppressed apoptosis induced by this combination but enhanced G1 arrest. In H460 cells, the addition of 2-DG did not enhance the low level of apoptosis induced by BMS-754807. However, treatment with 0.75 μM of BMS-754807 resulted in the accumulation of H460 cells with 8n-DNA content without affecting cell density increases. Hence, H460 cells may escape BMS-754807-induced G2/M cell cycle arrest through polyploidy. The inclusion of 2-DG blocked formation of the 8n-DNA cell population and restored G2/M phase cell cycle arrest.

CONCLUSION

The combination of 2-DG and IGF1R inhibitor BMS-754807 may be used to suppress the proliferation of NSCLC tumors through different mechanisms.

Nuclear IGF1R Interacts with Regulatory Regions of Chromatin to Promote RNA Polymerase II Recruitment and Gene Expression Associated with Advanced Tumor Stage

Internalization of ligand-activated type I IGF receptor (IGF1R) is followed by recycling to the plasma membrane, degradation or nuclear translocation. Nuclear IGF1R reportedly associates with clinical response to IGF1R inhibitory drugs, yet its role in the nucleus is poorly characterized. Here, we investigated the significance of nuclear IGF1R in clinical cancers and cell line models. In prostate cancers, IGF1R was predominantly membrane localized in benign glands, while malignant epithelium contained prominent internalized (nuclear/cytoplasmic) IGF1R, and nuclear IGF1R associated significantly with advanced tumor stage. Using ChIP-seq to assess global chromatin occupancy, we identified IGF1R-binding sites at or near transcription start sites of genes including JUN and FAM21, most sites coinciding with occupancy by RNA polymerase II (RNAPol2) and histone marks of active enhancers/promoters. IGF1R was inducibly recruited to chromatin, directly binding DNA and interacting with RNAPol2 to upregulate expression of JUN and FAM21, shown to mediate tumor cell survival and IGF-induced migration. IGF1 also enriched RNAPol2 on promoters containing IGF1R-binding sites. These functions were inhibited by IGF1/II-neutralizing antibody xentuzumab (BI 836845), or by blocking receptor internalization. We detected IGF1R on JUN and FAM21 promoters in fresh prostate cancers that contained abundant nuclear IGF1R, with evidence of correlation between nuclear IGF1R content and JUN expression in malignant prostatic epithelium. Taken together, these data reveal previously unrecognized molecular mechanisms through which IGFs promote tumorigenesis, with implications for therapeutic evaluation of anti-IGF drugs.Significance: These findings reveal a noncanonical nuclear role for IGF1R in tumorigenesis, with implications for therapeutic evaluation of IGF inhibitory drugs. Cancer Res; 78(13); 3497-509. ©2018 AACR.

Genistein and AG1024 synergistically increase the radiosensitivity of prostate cancer cells

Radiosensitivity of prostate cancer (PCa) cells promotes the curative treatment for PCa. The present study was designed to investigate the synergistic effect of genistein and AG1024 on the radiosensitivity of PCa cells. The optimal X-irradiation dose (4 Gy) and genistein concentration (30 µM) were selected by using the CCK-8 assay. Before X-irradiation (4 Gy), PC3 and DU145 cells were treated with genistein (30 µM), AG1024 (10 µM) and their combination. All treatments significantly reduced cell proliferation and enhanced cell apoptosis. Using flow cytometric analysis, we found that genistein arrested the cell cycle at S phase and AG1024 arrested the cell cycle at G2/M phase. Genistein treatment suppressed the homologous recombination (HRR) and the non-homologous end joining (NHEJ) pathways by inhibiting the expression of Rad51 and Ku70, and AG1024 treatment only inhibited the NHEJ pathway via the inactivation of Ku70 as detected by western blot analysis. Moreover, the combination treatment with genistein and AG1024 more effectively radiosensitized PCa cells than single treatments by suppressing cell proliferation, enhancing cell apoptosis and inactivating the HRR and NHEJ pathways. In vivo experiments demonstrated that animals receiving the combination treatment with genistein and AG1024 displayed obviously decreased tumor volume compared with animals treated with single treatment with either genistein or AG1024. We conclude that the combination of genistein (30 µM) and AG1024 (10 µM) exhibited a synergistic effect on the radiosensitivity of PCa cells by suppressing the HRR and NHEJ pathways.

IGF-1R inhibition sensitizes breast cancer cells to ATM-related kinase (ATR) inhibitor and cisplatin

The complexity of the IGF-1 signalling axis is clearly a roadblock in targeting this receptor in cancer therapy. Here, we sought to identify mediators of resistance, and potential co-targets for IGF-1R inhibition. By using an siRNA functional screen with the IGF-1R tyrosine kinase inhibitor (TKI) BMS-754807 in MCF-7 cells we identified several genes encoding components of the DNA damage response (DDR) pathways as mediators of resistance to IGF-1R kinase inhibition. These included ATM and Ataxia Telangiectasia and RAD3-related kinase (ATR). We also observed a clear induction of DDR in cells that were exposed to IGF-1R TKIs (BMS-754807 and OSI-906) as indicated by accumulation of γ-H2AX, and phosphorylated Chk1. Combination of the IGF-1R/IR TKIs with an ATR kinase inhibitor VE-821 resulted in additive to synergistic cytotoxicity compared to either drug alone. In MCF-7 cells with stably acquired resistance to the IGF-1R TKI (MCF-7-R), DNA damage was also observed, and again, dual inhibition of the ATR kinase and IGF-1R/IR kinase resulted in synergistic cytotoxicity. Interestingly, dual inhibition of ATR and IGF-1R was more effective in MCF-7-R cells than parental cells. IGF-1R TKIs also potentiated the effects of cisplatin in a panel of breast cancer cell lines. Overall, our findings identify induction of DDR by IGF-1R kinase inhibition as a rationale for co-targeting the IGF-1R with ATR kinase inhibitors or cisplatin, particularly in cells with acquired resistance to TKIs.

Inactivation of DNA-PK by knockdown DNA-PKcs or NU7441 impairs non-homologous end-joining of radiation-induced double strand break repair

The DNA-dependent protein kinase (DNA-PK) complex plays a pivotal role in non-homologous end-joining (NHEJ) repair. We investigated the mechanism of NU7441, a highly selective DNA-PK inhibitor, in NHEJ-competent mouse embryonic fibroblast (MEF) cells and NHEJ-deficient cells and explored the feasibility of its application in radiosensitizing nasopharyngeal carcinoma (NPC) cells. We generated wild-type and DNA-PKcs^−/− MEF cells. Clonogenic survival assays, flow cytometry, and immunoblotting were performed to study the effect of NU7441 on survival, cell cycle, and DNA repair. NU7441 profoundly radiosensitized wild-type MEF cells and SUNE-1 cells, but not DNA-PKcs^−/− MEF cells. NU7441 significantly suppressed radiation-induced DSB repair post-irradiation through unrepaired and lethal DNA damage, the cell cycle arrest. The effect was associated with the activation of cell cycle checkpoints. The present study revealed a mechanism by which inhibition of DNA-PK sensitizes cells to irradiation suggesting that radiotherapy in combination with DNA-PK inhibitor is a promising paradigm for the management of NPC which merits further investigation.

The insulin-like growth factor system in multiple myeloma: diagnostic and therapeutic potential

Multiple myeloma (MM) is a highly heterogeneous plasma cell malignancy. The MM cells reside in the bone marrow (BM), where reciprocal interactions with the BM niche foster MM cell survival, proliferation, and drug resistance. As in most cancers, the insulin-like growth factor (IGF) system has been demonstrated to play a key role in the pathogenesis of MM. The IGF system consists of IGF ligands, IGF receptors, IGF binding proteins (IGFBPs), and IGFBP proteases and contributes not only to the survival, proliferation, and homing of MM cells, but also MM-associated angiogenesis and osteolysis. Furthermore, increased IGF-I receptor (IGF-IR) expression on MM cells correlates with a poor prognosis in MM patients. Despite the prominent role of the IGF system in MM, strategies targeting the IGF-IR using blocking antibodies or small molecule inhibitors have failed to translate into the clinic. However, increasing preclinical evidence indicates that IGF-I is also involved in the development of drug resistance against current standard-of-care agents against MM, including proteasome inhibitors, immunomodulatory agents, and corticoids. IGF-IR targeting has been able to overcome or revert this drug resistance in animal models, enhancing the efficacy of standard-of-care agents. This finding has generated renewed interest in the therapeutic potential of IGF-I targeting in MM. The present review provides an update of the impact of the different IGF system components in MM and discusses the diagnostic and therapeutic potentials.

Evolutionarily conserved serum microRNAs predict radiation-induced fatality in nonhuman primates

Effective planning for the medical response to a radiological or nuclear accident is complex. Because of limited resources for medical countermeasures, the key would be to accurately triage and identify victims most likely to benefit from treatment. We used a mouse model system to provide evidence that serum microRNAs (miRNAs) may effectively predict the impact of radiation on the long-term viability of animals. We had previously used nonhuman primates (NHPs) to demonstrate that this concept is conserved and serum miRNA signatures have the potential to serve as prediction biomarkers for radiation-induced fatality in a human population. We identified a signature of seven miRNAs that are altered by irradiation in both mice and NHPs. Genomic analysis of these conserved miRNAs revealed that there is a combination of seven transcription factors that are predicted to regulate these miRNAs in human, mice, and NHPs. Moreover, a combination of three miRNAs (miR-133b, miR-215, and miR-375) can identify, with nearly complete accuracy, NHPs exposed to radiation versus unexposed NHPs. Consistent with historical data, female macaques appeared to be more sensitive to radiation, but the difference was not significant. Sex-based stratification allowed us to identify an interaction between gender and miR-16-2 expression, which affected the outcome of radiation exposure. Moreover, we developed a classifier based on two miRNAs (miR-30a and miR-126) that can reproducibly predict radiation-induced mortality. Together, we have obtained a five-miRNA composite signature that can identify irradiated macaques and predict their probability of survival.

IGF-1R associates with adverse outcomes after radical radiotherapy for prostate cancer

BACKGROUND

Activated type 1 insulin-like growth factor receptors (IGF-1Rs) undergo internalisation and nuclear translocation, promoting cell survival. We previously reported that IGF-1R inhibition delays DNA damage repair, sensitising prostate cancer cells to ionising radiation. Here we tested the clinical relevance of these findings.

METHODS

We assessed associations between IGF-1R and clinical outcomes by immunohistochemistry in diagnostic biopsies of 136 men treated with 55-70 Gy external beam radiotherapy for prostate cancer, comparing results with publicly available transcriptional data in surgically treated patients.

RESULTS

Following radiotherapy, overall recurrence-free survival was shorter in patients whose tumours contained high total, cytoplasmic and internalised (nuclear/cytoplasmic) IGF-1R. High total IGF-1R associated with high primary Gleason grade and risk of metastasis, and cytoplasmic and internalised IGF-1R with biochemical recurrence, which includes patients experiencing local recurrence within the radiation field indicating radioresistance. In multivariate analysis, cytoplasmic, internalised and total IGF-1R were independently associated with risk of overall recurrence, and cytoplasmic IGF-1R was an independent predictor of biochemical recurrence post radiotherapy. Insulin-like growth factor receptors expression did not associate with biochemical recurrence after radical prostatectomy.

CONCLUSIONS

These data reveal increased risk of post-radiotherapy recurrence in men whose prostate cancers contain high levels of total or cytoplasmic IGF-1R.