Multicenter phase II trial of Motexafin gadolinium and pemetrexed for second-line treatment in patients with non-small cell lung cancer

Thioredoxin reductase selenoproteins from different organisms as potential drug targets for treatment of human diseases

Human thioredoxin reductase (TrxR) is a selenoprotein with a central role in cellular redox homeostasis, utilizing a highly reactive and solvent-exposed selenocysteine (Sec) residue in its active site. Pharmacological modulation of TrxR can be obtained with several classes of small compounds showing different mechanisms of action, but most often dependent upon interactions with its Sec residue. The clinical implications of TrxR modulation as mediated by small compounds have been studied in diverse diseases, from rheumatoid arthritis and ischemia to cancer and parasitic infections. The possible involvement of TrxR in these diseases was in some cases serendipitously discovered, by finding that existing clinically used drugs are also TrxR inhibitors. Inhibiting isoforms of human TrxR is, however, not the only strategy for human disease treatment, as some pathogenic parasites also depend upon Sec-containing TrxR variants, including S. mansoni, B. malayi or O. volvulus. Inhibiting parasite TrxR has been shown to selectively kill parasites and can thus become a promising treatment strategy, especially in the context of quickly emerging resistance towards other drugs. Here we have summarized the basis for the targeting of selenoprotein TrxR variants with small molecules for therapeutic purposes in different human disease contexts. We discuss how Sec engagement appears to be an indispensable part of treatment efficacy and how some therapeutically promising compounds have been evaluated in preclinical or clinical studies. Several research questions remain before a wider application of selenoprotein TrxR inhibition as a first-line treatment strategy might be developed. These include further mechanistic studies of downstream effects that may mediate treatment efficacy, identification of isoform-specific enzyme inhibition patterns for some given therapeutic compounds, and the further elucidation of cell-specific effects in disease contexts such as in the tumor microenvironment or in host-parasite interactions, and which of these effects may be dependent upon the specific targeting of Sec in distinct TrxR isoforms.

Inhibitors of the Cancer Target Ribonucleotide Reductase, Past and Present

Ribonucleotide reductase (RR) is an essential multi-subunit enzyme found in all living organisms; it catalyzes the rate-limiting step in dNTP synthesis, namely, the conversion of ribonucleoside diphosphates to deoxyribonucleoside diphosphates. As expression levels of human RR (hRR) are high during cell replication, hRR has long been considered an attractive drug target for a range of proliferative diseases, including cancer. While there are many excellent reviews regarding the structure, function, and clinical importance of hRR, recent years have seen an increase in novel approaches to inhibiting hRR that merit an updated discussion of the existing inhibitors and strategies to target this enzyme. In this review, we discuss the mechanisms and clinical applications of classic nucleoside analog inhibitors of hRRM1 (large catalytic subunit), including gemcitabine and clofarabine, as well as inhibitors of the hRRM2 (free radical housing small subunit), including triapine and hydroxyurea. Additionally, we discuss novel approaches to targeting RR and the discovery of new classes of hRR inhibitors.

The use of radiosensitizing agents in the therapy of glioblastoma multiforme-a comprehensive review

BACKGROUND

Glioblastoma is the most common malignant brain tumor in human adults. Despite several improvements in resective as well as adjuvant therapy over the last decades, its overall prognosis remains poor. As a means of improving patient outcome, the possibility of enhancing radiation response by using radiosensitizing agents has been tested in an array of studies.

METHODS

A comprehensive review of clinical trials involving radiation therapy in combination with radiosensitizing agents on patients diagnosed with glioblastoma was performed in the National Center for Biotechnology Information's PubMed database.

RESULTS

A total of 96 papers addressing this matter were published between 1976 and 2021, of which 63 matched the subject of this paper. All papers were reviewed, and their findings discussed in the context of their underlining mechanisms of radiosensitization.

CONCLUSION

In the history of glioblastoma treatment, several approaches of optimizing radiation-effectiveness using radiosensitizers have been made. Even though several different strategies and agents have been explored, clear evidence of improved patient outcome is still missing. Tissue-selectiveness and penetration of the blood-brain barrier seem to be major roadblocks; nevertheless, modern strategies try to circumvent these obstacles, using novel sensitizers based on preclinical data or alternative ways of delivery.

Clinical pharmacology and clinical trials of ribonucleotide reductase inhibitors: is it a viable cancer therapy?

PURPOSE

Ribonucleotide reductase (RR) enzymes (RR1 and RR2) play an important role in the reduction of ribonucleotides to deoxyribonucleotides which is involved in DNA replication and repair. Augmented RR activity has been ascribed to uncontrolled cell growth and tumorigenic transformation.

METHODS

This review mainly focuses on several biological and chemical RR inhibitors (e.g., siRNA, GTI-2040, GTI-2501, triapine, gemcitabine, and clofarabine) that have been evaluated in clinical trials with promising anticancer activity from 1960's till 2016. A summary on whether their monotherapy or combination is still effective for further use is discussed.

RESULTS

Among the RR2 inhibitors evaluated, GTI-2040, siRNA, gallium nitrate and didox were more efficacious as a monotherapy, whereas triapine was found to be more efficacious as combination agent. Hydroxyurea is currently used more in combination therapy, even though it is efficacious as a monotherapy. Gallium nitrate showed mixed results in combination therapy, while the combination activity of didox is yet to be evaluated. RR1 inhibitors that have long been used in chemotherapy such as gemcitabine, cladribine, fludarabine and clofarabine are currently used mostly as a combination therapy, but are equally efficacious as a monotherapy, except tezacitabine which did not progress beyond phase I trials.

CONCLUSIONS

Based on the results of clinical trials, we conclude that RR inhibitors are viable treatment options, either as a monotherapy or as a combination in cancer chemotherapy. With the recent advances made in cancer biology, further development of RR inhibitors with improved efficacy and reduced toxicity is possible for treatment of variety of cancers.

Gadolinium chloride elicits apoptosis in human osteosarcoma U-2 OS cells through extrinsic signaling, intrinsic pathway and endoplasmic reticulum stress

Gadolinium (Gd) compounds are important as magnetic resonance imaging (MRI) contrast agents, and are potential anticancer agents. However, no report has shown the effect of gadolinium chloride (GdCl3) on osteosarcoma in vitro. The present study investigated the apoptotic mechanism of GdCl3 on human osteosarcoma U-2 OS cells. Our results indicated that GdCl3 significantly reduced cell viability of U-2 OS cells in a concentration-dependent manner. GdCl3 led to apoptotic cell shrinkage and DNA fragmentation in U-2 OS cells as revealed by morphologic changes and TUNEL staining. Colorimetric assay analyses also showed that activities of caspase-3, caspase-8, caspase-9 and caspase-4 occurred in GdCl3-treated U-2 OS cells. Pretreatment of cells with pan-caspase inhibitor (Z-VAD-FMK) and specific inhibitors of caspase-3/-8/-9 significantly reduced cell death caused by GdCl3. The increase of cytoplasmic Ca2+ level, ROS production and the decrease of mitochondria membrane potential (ΔΨm) were observed by flow cytometric analysis in U-2 OS cells after GdCl3 exposure. Western blot analyses demonstrated that the levels of Fas, FasL, cytochrome c, Apaf-1, GADD153 and GRP78 were upregulated in GdCl3-treated U-2 OS cells. In conclusion, death receptor, mitochondria-dependent and endoplasmic reticulum (ER) stress pathways contribute to GdCl3-induced apoptosis in U-2 OS cells. GdCl3 might have potential to be used in treatment of osteosarcoma patients.

Pemetrexed for advanced stage nonsquamous non-small cell lung cancer: latest evidence about its extended use and outcomes

Non-small cell lung cancer (NSCLC) is still the leading cause of cancer-related death, and the treatment of advanced NSCLC relies on systemic treatments. During the last decade, pemetrexed, an antifolate agent, gradually became a key component of the treatment for patients with advanced nonsquamous NSCLC. It has indeed been shown to be efficient for first-line, maintenance and second- or third-line treatment in this subgroup of NSCLC. Moreover, it is usually well tolerated, with few grade 3 and 4 toxicities. Several studies have tried to identify predictive biomarkers of pemetrexed efficacy. Due to pemetrexed's mechanism of action, thymidilate synthase expression predictive value was investigated but could not be demonstrated. Currently, more than 400 trials of pemetrexed for the treatment of nonsquamous NSCLC are ongoing.

Systemic therapies in the treatment of non-small-cell lung cancer brain metastases

Non-small-cell lung cancer (NSCLC) brain metastases are common. Even though there are various subsets of NSCLC with molecular alterations, there is a common theme of brain metastases. Current treatment modalities are suboptimal. Systemic therapies for the treatment of NSCLC brain metastases have been explored and recent advances may pave the way for their successful employment in this patient population. While no specific agents have been associated with a marked benefit, stability of disease as well as radiographic responses have been noted in some patients. Biological activity of systemic therapies in some patients with NSCLC brain metastases raises hope for future advances and supports further investigation for this patient population with limited treatment options.

The place of pemetrexed in the management of non-small-cell lung cancer patients

Non-small cell lung cancer (NSCLC) remains the leading cause of cancer death worldwide. Chemotherapy is included in the management of the majority of NSCLC patients either in addition to a local treatment (surgery/radiotherapy) or alone. In this setting, pemetrexed has become one of the most important partners of current chemotherapy regimens for nonsquamous NSCLC patients. Indeed, pemetrexed demonstrated a comparable efficacy to other previously available drugs in NSCLC, with however a better safety profile and an easier schedule of administration. In addition, pemetrexed demonstrated a greater efficacy in nonsquamous NSCLC that lead to an exploration of the underlying potential biological background. It is now suggested that the tumor thymidylate synthase level may act as a predictor of pemetrexed efficacy, therefore potentially providing clinicians in the future with a predictor of efficacy, which it is usually lacking with standard chemotherapies.

Revisiting cutaneous adverse reactions to pemetrexed

Pemetrexed (Alimta®) is a multitargeted antifolate drug approved as a single agent or in combination with cisplatin for the treatment of a small number of malignancies including advanced and metastatic non-squamous non-small cell lung cancer (NSCLC), and malignant pleural mesothelioma. This review reports the recent peer-reviewed publications and original findings regarding cutaneous adverse reactions (CARs) to pemetrexed. Pemetrexed-related CARs are frequently reported under the unspecific term 'skin rash'. However, more specific diseases were tentatively identified as alopecias, urticarial vasculitis, acute generalized exanthematous pustulosis, toxic epidermal necrolysis, radiation recall dermatitis and pityriasis lichenoides. Most of the skin reactions occur shortly after pemetrexed administration. As with methotrexate-related CARs, the cell cycle arrest in the S phase may be regarded as a direct and major cause of the cytotoxic pathobiology. An adverse immune reaction is unlikely. In conclusion, pemetrexed is responsible for CARs exhibiting a variety of clinical presentations. Their origin is likely attributed to direct cytotoxicity following the cell cycle arrest in the S phase and cell necrosis.