Combinational Therapy Enhances the Effects of Anti-IGF-1R mAb Figitumumab to Target Small Cell Lung Cancer

Metformin: A Dual-Role Player in Cancer Treatment and Prevention

Cancer continues to pose a significant global health challenge, as evidenced by the increasing incidence rates and high mortality rates, despite the advancements made in chemotherapy. The emergence of chemoresistance further complicates the effectiveness of treatment. However, there is growing interest in the potential of metformin, a commonly prescribed drug for type 2 diabetes mellitus (T2DM), as an adjuvant chemotherapy agent in cancer treatment. Although the precise mechanism of action of metformin in cancer therapy is not fully understood, it has been found to have pleiotropic effects, including the modulation of metabolic pathways, reduction in inflammation, and the regulation of cellular proliferation. This comprehensive review examines the anticancer properties of metformin, drawing insights from various studies conducted in vitro and in vivo, as well as from clinical trials and observational research. This review discusses the mechanisms of action involving both insulin-dependent and independent pathways, shedding light on the potential of metformin as a therapeutic agent for different types of cancer. Despite promising findings, there are challenges that need to be addressed, such as conflicting outcomes in clinical trials, considerations regarding dosing, and the development of resistance. These challenges highlight the importance of further research to fully harness the therapeutic potential of metformin in cancer treatment. The aims of this review are to provide a contemporary understanding of the role of metformin in cancer therapy and identify areas for future exploration in the pursuit of effective anticancer strategies.

IGF-1R targeting in cancer - does sub-cellular localization matter?

The insulin-like growth factor receptor (IGF-1R) was among the most intensively pursued kinase targets in oncology. However, even after a slew of small-molecule and antibody therapeutics reached clinical trials for a range of solid tumors, the initial promise remains unfulfilled. Mechanisms of resistance to, and toxicities resulting from, IGF-1R-targeted drugs are well-catalogued, and there is general appreciation of the fact that a lack of biomarker-based patient stratification was a limitation of previous clinical trials. But no next-generation therapeutic strategies have yet successfully exploited this understanding in the clinic.Currently there is emerging interest in re-visiting IGF-1R targeted therapeutics in combination-treatment protocols with predictive biomarker-driven patient-stratification. One such biomarker that emerged from early clinical trials is the sub-cellular localization of IGF-1R. After providing some background on IGF-1R, its drugging history, and the trials that led to the termination of drug development for this target, we look more deeply into the correlation between sub-cellular localization of IGF-1R and susceptibility to various classes of IGF-1R - targeted agents.

Will We Unlock the Benefit of Metformin for Patients with Lung Cancer? Lessons from Current Evidence and New Hypotheses

Metformin has been under basic and clinical study as an oncological repurposing pharmacological agent for several years, stemming from observational studies which consistently evidenced that subjects who were treated with metformin had a reduced risk for development of cancer throughout their lives, as well as improved survival outcomes when diagnosed with neoplastic diseases. As a result, several basic science studies have attempted to dissect the relationship between metformin’s metabolic mechanism of action and antineoplastic cellular signaling pathways. Evidence in this regard was compelling enough that a myriad of randomized clinical trials was planned and conducted in order to establish the effect of metformin treatment for patients with diverse neoplasms, including lung cancer. As with most novel antineoplastic agents, early results from these studies have been mostly discouraging, though a recent analysis that incorporated body mass index may provide significant information regarding which patient subgroups might derive the most benefit from the addition of metformin to their anticancer treatment. Much in line with the current pipeline for anticancer agents, it appears that the benefit of metformin may be circumscribed to a specific patient subgroup. If so, addition of metformin to antineoplastic agents could prove one of the most cost-effective interventions proposed in the context of precision oncology. Currently published reviews mostly rely on a widely questioned mechanism of action by metformin, which fails to consider the differential effects of the drug in lean vs. obese subjects. In this review, we analyze the pre-clinical and clinical information available to date regarding the use of metformin in various subtypes of lung cancer and, further, we present evidence as to the differential metabolic effects of metformin in lean and obese subjects where, paradoxically, the obese subjects have reported more benefit with the addition of metformin treatment. The novel mechanisms of action described for this biguanide may explain the different results observed in clinical trials published in the last decade. Lastly, we present novel hypothesis regarding potential biomarkers to identify who might reap benefit from this intervention, including the role of prolyl hydroxylase domain 3 (PHD3) expression to modify metabolic phenotypes in malignant diseases.

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.

Progression and metastasis of small cell lung carcinoma: the role of the PI3K/Akt/mTOR pathway and metabolic alterations

Small cell lung carcinoma (SCLC) is characterized by high metastatic rate and poor prognosis. The platinum-based chemotherapy still represents the backbone of the therapy; however, acquired resistance develops almost in all patients. Although SCLC has been formerly considered a homogeneous disease, recent advances in SCLC research have highlighted the importance of inter- and intratumoral heterogeneity and have resulted in the subclassification of SCLC. The newly described SCLC subtypes are characterized by distinct biological behavior and vulnerabilities that can be therapeutically exploited. The PI3K/Akt/mTOR pathway is frequently affected in SCLC, and its activation represents a promising therapeutic target. Since the mTOR pathway is a master regulator of cellular metabolism, its alterations may also influence the bioenergetic processes of SCLC cells. Despite the encouraging preclinical results, both mTOR and metabolic inhibitors have met limited clinical success so far. Patient selection for personalized therapy, the development of rational drug combinations, and a better understanding of heterogeneity and spatiotemporal evolution of the tumor cells may improve efficacy and can help to overcome acquired resistance. Here we provide a summary of current investigations regarding the role of the mTOR pathway and metabolic alterations in the progression and metastasis formation of SCLC.

The Emerging Role of the Fetal Insulin Receptor in Hormone-refractory Breast Cancer

Type 1 insulin-like growth factor receptor (IGF-1R) is a transmembrane tyrosine kinase receptor and a mediator of the biologic effects of insulin-like growth factor (IGF)-I and -II. Inhibitors of IGF-1R signaling were tested in clinical cancer trials aiming to assess the utility of this receptor as a therapeutic target; essentially all IGF-1R inhibitors failed to provide an additional benefit compared with standard-of-care therapy. In this review, we will evaluate the role the insulin receptor (IR) plays in mediating IGF signaling and subsequent metabolic and mitogenic effects as 1 possible reason for these failures. IR is expressed as 2 isoforms, with the fetal isoform IR-A derived from alternative splicing and loss of exon 11, the adult isoform (IR-B) includes this exon. Cancer frequently re-expresses fetal proteins and this appears to be the case in cancer with a re-expression of the fetal isoform and an increased IR-A:IR-B ratio. The biological effects of IR isoform signaling are complex and not completely understood although it has been suggested that IR-A could stimulate mitogenic signaling pathways, play a role in cancer cell stemness, and mediate tolerance to cancer therapies. From a clinical perspective, the IR-A overexpression in cancer may explain why targeting IGF-1R alone was not successful. However, given the predominance of IR-A expression in cancer, it may also be possible to develop isoform specific inhibitors and avoid the metabolic consequences of inhibiting IR-B. If such inhibitors could be developed, then IR-A expression could serve as a predictive biomarker, and cotargeting IR-A and IGF-1R could provide a novel, more effective therapy method.

Future Options of Molecular-Targeted Therapy in Small Cell Lung Cancer

Lung cancer is the leading cause of cancer-related deaths worldwide. With a focus on histology, there are two major subtypes: Non-small cell lung cancer (NSCLC) (the more frequent subtype), and small cell lung cancer (SCLC) (the more aggressive one). Even though SCLC, in general, is a chemosensitive malignancy, relapses following induction therapy are frequent. The standard of care treatment of SCLC consists of platinum-based chemotherapy in combination with etoposide that is subsequently enhanced by PD-L1-inhibiting atezolizumab in the extensive-stage disease, as the addition of immune-checkpoint inhibition yielded improved overall survival. Although there are promising molecular pathways with potential therapeutic impacts, targeted therapies are still not an integral part of routine treatment. Against this background, we evaluated current literature for potential new molecular candidates such as surface markers (e.g., DLL3, TROP-2 or CD56), apoptotic factors (e.g., BCL-2, BET), genetic alterations (e.g., CREBBP, NOTCH or PTEN) or vascular markers (e.g., VEGF, FGFR1 or CD13). Apart from these factors, the application of so-called 'poly-(ADP)-ribose polymerases' (PARP) inhibitors can influence tumor repair mechanisms and thus offer new perspectives for future treatment. Another promising therapeutic concept is the inhibition of 'enhancer of zeste homolog 2' (EZH2) in the loss of function of tumor suppressors or amplification of (proto-) oncogenes. Considering the poor prognosis of SCLC patients, new molecular pathways require further investigation to augment our therapeutic armamentarium in the future.

Insulin Receptor Isoforms in Cancer

The insulin receptor (IR) mediates both metabolic and mitogenic effects especially when overexpressed or in clinical conditions with compensatory hyperinsulinemia, due to the metabolic pathway resistance, as obesity diabetes. In many cancers, IR is overexpressed preferentially as IR-A isoform, derived by alternative splicing of exon 11. The IR-A overexpression, and the increased IR-A:IR-B ratio, are mechanisms that promote the mitogenic response of cancer cells to insulin and IGF-2, which is produced locally by both epithelial and stromal cancer cells. In cancer IR-A, isoform predominance may occur for dysregulation at both mRNA transcription and post-transcription levels, including splicing factors, non-coding RNAs and protein degradation. The mechanisms that regulate IR isoform expression are complex and not fully understood. The IR isoform overexpression may play a role in cancer cell stemness, in tumor progression and in resistance to target therapies. From a clinical point of view, the IR-A overexpression in cancer may be a determinant factor for the resistance to IGF-1R target therapies for this issue. IR isoform expression in cancers may have the meaning of a predictive biomarker and co-targeting IGF-1R and IR-A may represent a new more efficacious treatment strategy.

Insulin-like growth factor-1 receptor knockdown enhances radiosensitivity via the HIF-1α pathway and attenuates ATM/H2AX/53BP1 DNA repair activation in human lung squamous carcinoma cells

Insulin-like growth factor-1 receptor (IGF-1R) is a cell membrane receptor involved in cell proliferation and apoptosis, which is highly expressed in lung squamous cell carcinoma (SCC). The present study aimed to observe the influence of IGF-1R silencing on the radiosensitivity of SCC and investigate the potential mechanisms involved. Human lung SCC H520 cells with relatively high expression of IGF-1R were used. IGF-1R expression was silenced using short hairpin RNA. The influence of IGF-1R silencing on radiosensitivity and apoptosis was assessed using a clone formation assay and flow cytometry. The expression levels of proteins relevant in DNA damage repair and hypoxic signaling pathways were analyzed using western blotting. Decreased expression of IGF-1R led to an increase in the sensitivity of H520 cells to irradiation. Molecular analysis showed that the reduced expression of IGF-1R decreased the protein expression of ataxia-telangiectasia mutated (ATM), H2A histone family member X (H2AX) and p53 binding protein 1 (53BP1), which are associated with the DNA repair pathway. Furthermore, 53BP1 is also known to be involved in apoptosis. Proteins involved in the hypoxic pathway, including hypoxia inducible factor 1 α (HIF-1α), matrix metallopeptidase 9 (MMP-9) and vascular endothelial growth factor A (VEGFA) were also involved in the radiosensitivity. In conclusion, decreased expression of IGF-1R leads to improved radiosensitivity of SCC cells, and the underlying mechanism may be associated with the decreased expression of proteins involved in ATM/H2AX/53BP1 DNA damage repair and the HIF-1α/MMP-9 hypoxic pathway, which results in the induction of apoptosis and increased radiosensitivity. These findings suggest that targeting of IGF-1R may represent a novel approach for lung SCC radiation treatment.

Metformin induces cell cycle arrest at the G1 phase through E2F8 suppression in lung cancer cells

A target molecule responsible for cell cycle arrest by metformin was discovered using a gene chip array in lung cancer cells and the effect of metformin on E2F8 was assessed. The siRNA-mediated knockdown of E2F8 significantly suppressed G1-S progression while ectopic expression of E2F8 relieved metformin-induced G1 arrest. The mRNA levels of p21 were found to be inversely related to those of E2F8 in lung cancer cells while siRNA-mediated knockdown of p21 partly rescued siE2F8-induced arrest of the cell cycle. Metformin had no effect on degradation of E2F8 mRNA. Activation and inhibition of AMPK by AICAR and Dorsomorphin, respectively, did not affect E2F8 suppression by metformin. The clinical significance of E2F8 was analyzed in The Cancer Genome Atlas (TCGA) data. One hundred six (13%) of 848 TCGA lung cancers overexpressed E2F8 mRNA. The overexpression of E2F8 was associated with poor overall survival (adjusted hazard ratio = 1.58, 95% confidence interval = 1.13-2.22; P = 0.008). The present study suggests that metformin may induce cell cycle arrest at the G1 phase by suppressing E2F8 expression in lung cancer cells. In addition, E2F8 may be associated with poor overall survival in lung cancer patients irrespective of histology.

Insulin-Like Growth Factor (IGF) Pathway Targeting in Cancer: Role of the IGF Axis and Opportunities for Future Combination Studies

Despite a strong preclinical rationale for targeting the insulin-like growth factor (IGF) axis in cancer, clinical studies of IGF-1 receptor (IGF-1R)-targeted monotherapies have been largely disappointing, and any potential success has been limited by the lack of validated predictive biomarkers for patient enrichment. A large body of preclinical evidence suggests that the key role of the IGF axis in cancer is in driving treatment resistance, via general proliferative/survival mechanisms, interactions with other mitogenic signaling networks, and class-specific mechanisms such as DNA damage repair. Consequently, combining IGF-targeted agents with standard cytotoxic agents, other targeted agents, endocrine therapies, or immunotherapies represents an attractive therapeutic approach. Anti-IGF-1R monoclonal antibodies (mAbs) do not inhibit IGF ligand 2 (IGF-2) activation of the insulin receptor isoform-A (INSR-A), which may limit their anti-proliferative activity. In addition, due to their lack of specificity, IGF-1R tyrosine kinase inhibitors are associated with hyperglycemia as a result of interference with signaling through the classical metabolic INSR-B isoform; this may preclude their use at clinically effective doses. Conversely, IGF-1/IGF-2 ligand-neutralizing mAbs inhibit proliferative/anti-apoptotic signaling via IGF-1R and INSR-A, without compromising the metabolic function of INSR-B. Therefore, combination regimens that include these agents may be more efficacious and tolerable versus IGF-1R-targeted combinations. Herein, we review the preclinical and clinical experience with IGF-targeted therapies to-date, and discuss the rationale for future combination approaches as a means to overcome treatment resistance.

MicroRNA-379 acts as a tumor suppressor in non-small cell lung cancer by targeting the IGF‑1R-mediated AKT and ERK pathways

Lung cancer is one of the most common types of malignancy in humans and is a leading cause of cancer-related deaths among men and women worldwide. Aberrantly expressed microRNAs in non-small cell lung cancer (NSCLC) contribute to tumor occurrence and development as either tumor suppressors or promoters. MicroRNA-379 (miR‑379) is dysregulated in several types of human cancer. However, its expression pattern, role and underlying mechanism in NSCLC progression and metastasis are poorly understood. In this study, assay of reverse transcription-quantitative polymerase chain reaction showed that miR‑379 was downregulated in both NSCLC tissue and cell lines. Low miR‑379 expression in NSCLC tissues was significantly correlated with TNM stage and lymph node metastasis. In addition, functional experiments revealed that restoring the expression of miR‑379 inhibited cell proliferation, migration and invasion of NSCLC. The insulin-like growth factor receptor-1 (IGF‑1R) was identified as a direct target of miR‑379 in NSCLC. IGF‑1R was highly expressed in NSCLC tissues and inversely correlated with miR‑379 expression. Downregulation of IGF‑1R had tumor suppressive roles similar to that of miR‑379 overexpression on NSCLC cell proliferation, migration and invasion. Moreover, the upregulation of IGF‑1R effectively rescued the tumor suppressive roles induced by miR‑379 overexpression in NSCLC. The resumption of the expression of miR‑379 inhibited the activation of AKT and ERK signaling pathways in NSCLC. These findings suggested that miR‑379 acts as a tumor suppressor in NSCLC by directly targeting IGF‑1R and indirectly regulating AKT and ERK signaling pathways. miR‑379 provides novel therapeutic targets for the treatment of patients with this disease.

Glypican-3 induces oncogenicity by preventing IGF-1R degradation, a process that can be blocked by Grb10

Hepatocellular carcinoma (HCC) is the most common primary liver malignancy and is a major cause of cancer-related death worldwide. Previously, we demonstrated that glypican-3 (GPC3) is highly expressed in HCC, and that GPC3 induces oncogenicity and promotes the growth of cancer cells through IGF-1 receptor (IGF-1R). In the present study, we investigated the mechanisms of GPC3-mediated enhancement of IGF-1R signaling. We demonstrated that GPC3 decreased IGF-1-induced IGF-1R ubiquitination and degradation and increased c-Myc protein levels. GPC3 bound to Grb10, a mediator of ligand-induced receptor ubiquitination, and the overexpression of Grb10 blocked GPC3-enhanced IGF-1-induced ERK phosphorylation. GPC3 promoted the growth of NIH3T3 and PLC-PRF-5 cells in serum-free medium but did not promote the growth of IGF-1R negative R- cells. Grb10 overexpression decreased GPC3-promoted cell growth. Therefore, the present study elucidates the mechanisms of GPC3-induced oncogenicity, which may highlight new strategies for the treatment of HCC.

Is the Canonical RAF/MEK/ERK Signaling Pathway a Therapeutic Target in SCLC?

The activity of the RAF/MEK/ERK signaling pathway is critical for the proliferation of normal and cancerous cells. Oncogenic mutations driving the development of lung adenocarcinoma often activate this signaling pathway. In contrast, pathway activity levels and their biological roles are not well established in small cell lung cancer (SCLC), a fast-growing neuroendocrine lung cancer subtype. Here we discuss the function of the RAF/MEK/ERK kinase pathway and the mechanisms leading to its activation in SCLC cells. In particular, we argue that activation of this pathway may be beneficial to the survival, proliferation, and spread of SCLC cells in response to multiple stimuli. We also consider evidence that high levels of RAF/MEK/ERK pathway activity may be detrimental to SCLC tumors, including in part by interfering with their neuroendocrine fate. On the basis of these observations, we examined when small molecules targeting kinases in the RAF/MEK/ERK pathway may be useful therapeutically in patients with SCLC, including in combination with other therapeutic agents.