Glioblastoma stem cell metabolism and immunity

Despite enormous efforts being invested in the development of novel therapies for brain malignancies, there remains a dire need for effective treatments, particularly for pediatric glioblastomas. Their poor prognosis has been attributed to the fact that conventional therapies target tumoral cells, but not glioblastoma stem cells (GSCs). GSCs are characterized by self-renewal, tumorigenicity, poor differentiation, and resistance to therapy. These characteristics represent the fundamental tools needed to recapitulate the tumor and result in a relapse. The mechanisms by which GSCs alter metabolic cues and escape elimination by immune cells are discussed in this article, along with potential strategies to harness effector immune cells against GSCs. As cellular immunotherapy is making significant advances in a variety of cancers, leveraging this underexplored reservoir may result in significant improvements in the treatment options for brain malignancies.

Similarities and divergences in the metabolism of immune cells in cancer and helminthic infections

Energetic and nutritional requirements play a crucial role in shaping the immune cells that infiltrate tumor and parasite infection sites. The dynamic interaction between immune cells and the microenvironment, whether in the context of tumor or helminth infection, is essential for understanding the mechanisms of immunological polarization and developing strategies to manipulate them in order to promote a functional and efficient immune response that could aid in the treatment of these conditions. In this review, we present an overview of the immune response triggered during tumorigenesis and establishment of helminth infections, highlighting the transition to chronicity in both cases. We discuss the energetic demands of immune cells under normal conditions and in the presence of tumors and helminths. Additionally, we compare the metabolic changes that occur in the tumor microenvironment and the infection site, emphasizing the alterations that are induced to redirect the immune response, thereby promoting the survival of cancer cells or helminths. This emerging discipline provides valuable insights into disease pathogenesis. We also provide examples of novel strategies to enhance immune activity by targeting metabolic pathways that shape immune phenotypes, with the aim of achieving positive outcomes in cancer and helminth infections.

Glycogen synthase kinase (GSK-3) synergizes with PD-1/PDL1 blockade to generate super-armed CD8 killers against tumors

Immune checkpoint blockade (ICB) of negative co-receptors on T-cells such as programmed cell death-1 (PD-1) is promising for the treatment of cancer. Despite success, the poor prognosis for most patients highlights the need for novel clinical interventions. We have shown that the kinase, glycogen synthase kinase-3 (GSK-3) negatively regulates T-cell activation due to altered PD-1 and LAG-3 expression (Taylor et al., 2016 Immunity; Rudd et al., 2019 Cell Reports). GSK-3 inhibition (GSK-3i) is as effective as anti-PD-1 in controlling the growth of melanoma (Taylor et al., 2017 Can Res; Krueger and Rudd, Immunity 2017; Stelle et al., 2021 iScience). GSK-3i increases Tbet (Tbx21) transcription, which inhibits PD-1/LAG-3 transcription, while increasing granzyme B (GZMB) and interferon gamma (IFNγ). Here, we show that Gsk3−/− mice and small molecule inhibitors (SMIs) synergize with anti-PD-1 to eliminate melanomas that are resistant to anti-PD-1 monotherapy. Transcriptomic profiling showed that GSK-3 × PD-1 cooperativity was characterized by a specific increase in a family of different granzymes (7/12 GZM genes out of a data base of 20,500 potential genes). Some GZMs have been characterized and others not, but as a family, this increased armory of GZMs in CD8+ T-cells is expected to greatly enhance tumor killing. Overall, our data shows the PD-1 × GSK-3 synergy in limiting tumor growth is due to a specific set of cytolysis mediators needed for tumor killing.

Structure-Activity Relationships of Withanolides as Antiproliferative Agents for Multiple Myeloma: Comparison of Activity in 2D Models and a 3D Coculture Model

Multiple myeloma (MM) is a hematological cancer in which relapse and resistance are highly frequent. Therefore, alternatives to conventional treatments are necessary. Withaferin A, a withanolide isolated from Withania somnifera, has previously shown promising activity against various MM models. In the present study, structure-activity relationships (SARs) were evaluated using 56 withanolides. The antiproliferative activity was assessed in three MM cell lines and in a 3D MM coculture model to understand the in vitro activity of compounds in models of various complexity. While the results obtained in 2D allowed a quick and simple evaluation of cytotoxicity used for a first selection, the use of the 3D MM coculture model allowed filtering compounds that perform better in a more complex setup. This study shows the importance of the last model as a bridge between 2D and in vivo studies to select the most active compounds and ultimately lead to a reduction of animal use for more sustained in vivo studies. NF-κB inhibition was determined to evaluate if this could be one of the targeted pathways. The most active compounds, withanolide D (2) and 38, should be further evaluated in vivo.

Hydroxychloroquine (HCQ) decreases the benefit of anti-PD-1 immune checkpoint blockade in tumor immunotherapy

Immunotherapy using checkpoint blockade (ICB) with antibodies such as anti-PD-1 has revolutionised the treatment of many cancers. Despite its use to treat COVID-19 patients and autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis, the effect of hydroxychloroquine (HCQ) on cancer immunotherapy has not been examined. In this study, remarkably, we find that HCQ alone, or in combination with azithromycin (AZ), at doses used to treat patients, decreased the therapeutic benefit of anti-PD-1 in cancer immunotherapy. No deleterious effect was seen on untreated tumors. Mechanistically, HCQ and HCQ/AZ inhibited PD-L1 expression on tumor cells, while specifically targeting the anti-PD-1 induced increase in progenitor CD8+CD44+PD-1+TCF1+ tumor infiltrating T cells (TILs) and the generation of CD8+CD44+PD-1+ effectors. Surprisingly, it also impaired the appearance of a subset of terminally exhausted CD8+ TILs. No effect was seen on the presence of CD4+ T cells, FoxP3+ regulatory T cells (Tregs), thymic subsets, B cells, antibody production, myeloid cells, or the vasculature of mice. This study indicates for the first time that HCQ and HCQ/AZ negatively impact the ability of anti-PD-1 checkpoint blockade to promote tumor rejection.

Inhibiting the MNK1/2-eIF4E axis impairs melanoma phenotype switching and potentiates antitumor immune responses

Melanomas commonly undergo a phenotype switch, from a proliferative to an invasive state. Such tumor cell plasticity contributes to immunotherapy resistance; however, the mechanisms are not completely understood and thus are therapeutically unexploited. Using melanoma mouse models, we demonstrated that blocking the MNK1/2-eIF4E axis inhibited melanoma phenotype switching and sensitized melanoma to anti-PD-1 immunotherapy. We showed that phospho-eIF4E-deficient murine melanomas expressed high levels of melanocytic antigens, with similar results verified in patient melanomas. Mechanistically, we identified phospho-eIF4E-mediated translational control of NGFR, a critical effector of phenotype switching. Genetic ablation of phospho-eIF4E reprogrammed the immunosuppressive microenvironment, exemplified by lowered production of inflammatory factors, decreased PD-L1 expression on dendritic cells and myeloid-derived suppressor cells, and increased CD8+ T cell infiltrates. Finally, dual blockade of the MNK1/2-eIF4E axis and the PD-1/PD-L1 immune checkpoint demonstrated efficacy in multiple melanoma models regardless of their genomic classification. An increase in the presence of intratumoral stem-like TCF1+PD-1+CD8+ T cells, a characteristic essential for durable antitumor immunity, was detected in mice given a MNK1/2 inhibitor and anti-PD-1 therapy. Using MNK1/2 inhibitors to repress phospho-eIF4E thus offers a strategy to inhibit melanoma plasticity and improve response to anti-PD-1 immunotherapy.

Withanolide D Exhibits Similar Cytostatic Effect in Drug-Resistant and Drug-Sensitive Multiple Myeloma Cells

In spite of recent therapeutic advances, multiple myeloma (MM) remains a malignancy with very low curability. This has been partly attributed to the existence of a drug-resistant subpopulation known as cancer stem cells (CSCs). MM-CSCs are equipped with the necessary tools that render them highly resistant to virtually all conventional therapies. In this study, the growth inhibitory effects of withanolide D (WND), a steroidal lactone isolated from Withania somnifera, on drug-sensitive tumoral plasma cells and drug-resistant MM cells have been investigated. In MTT/XTT assays, WND exhibited similar cytostatic effects between drug-resistant and drug-sensitive cell lines in the nM range. WND also induced cell death and apoptosis in MM-CSCs and RPMI 8226 cells, as examined by the calcein/ethidium homodimer and annexin V/propidium iodide stainings, respectively. To determine whether P-glycoprotein (P-gp) efflux affected the cytostatic activity of WND, P-gp was inhibited with verapamil and results indicated that the WND cytostatic effect in MM-CSCs was independent of P-gp efflux. Furthermore, WND did not increase the accumulation of the fluorescent P-gp substrate rhodamine 123 in MM-CSCs, suggesting that WND may not inhibit P-gp at the tested relevant doses. Therefore, the WND-induced cytostatic effect may be independent of P-gp efflux. These findings warrant further investigation of WND in MM-CSC animal models.

Targeting Multiple Myeloma Cancer Stem Cells with Natural Products - Lessons from Other Hematological Malignancies

Multiple myeloma is characterized by the accumulation of malignant plasma cells in the bone marrow. Multiple myeloma is the second most frequently diagnosed hematological malignancy, predominantly affecting the elderly. Despite recent advances in the development of novel therapies, multiple myeloma remains an incurable malignancy where the majority of patients relapse, develop resistance, and eventually die from the disease. This has been attributed to the fact that conventional therapy currently in use targets mainly the bulk of tumor cells, but not the tumor-initiating cancer stem cells. Cancer stem cells are a highly resistant subpopulation of cells believed to be responsible for the initiation, progression, metastasis, and relapse of cancer. Enormous efforts have been invested in the characterization of cancer stem cells. These efforts led to the characterization of key cellular signaling pathways responsible for conferring stem cell characteristics including self-renewal, differentiation, migratory, survival, and intracellular detoxification capabilities. Targeting these protective mechanisms offers a valuable strategy that may help combat a major driving force behind cancers. The use of natural products offers a promising therapeutic approach for targeting cancer stem cells. In this review, recent advances achieved in the characterization of cancer stem cells derived from hematological malignancies, with a particular focus on multiple myeloma, are discussed and major natural products that target cancer stem cells are presented. As natural products remain an essential source of novel chemical structures and medicinal leads, the exploitation of this immense reservoir is used to draw lessons in targeting multiple myeloma-cancer stem cells.

Epigenetic strategies to reverse drug resistance in heterogeneous multiple myeloma

Multiple myeloma (MM) is a hematological malignancy, which remains incurable because most patients eventually relapse or become refractory to current treatments. Due to heterogeneity within the cancer cell microenvironment, cancer cell populations employ a dynamic survival strategy to chemotherapeutic treatments, which frequently results in a rapid acquisition of therapy resistance. Besides resistance-conferring genetic alterations within a tumor cell population selected during drug treatment, recent findings also reveal non-mutational mechanisms of drug resistance, involving a small population of "cancer stem cells" (CSCs) which are intrinsically more refractory to the effects of a variety of anticancer drugs. Other studies have implicated epigenetic mechanisms in reversible drug tolerance to protect the population from eradication by potentially lethal exposures, suggesting that acquired drug resistance does not necessarily require a stable heritable genetic alteration. Clonal evolution of MM cells and the bone marrow microenvironment changes contribute to drug resistance. MM-CSCs may not be a static population and survive as phenotypically and functionally different cell types via the transition between stem-like and non-stem-like states in local microenvironments, as observed in other types of cancers. Targeting MM-CSCs is clinically relevant, and different approaches have been suggested to target molecular, metabolic and epigenetic signatures, and the self-renewal signaling characteristic of MM CSC-like cells. Here, we summarize epigenetic strategies to reverse drug resistance in heterogeneous multiple myeloma.

Withaferin A induces cell death and differentiation in multiple myeloma cancer stem cells

Multiple myeloma (MM) remains an incurable malignancy despite the development of novel therapeutics. This is believed to be due to a subset of rare chemotherapy-resistant cancer stem cells (CSCs). Differentiation therapy represents one strategy aimed at reducing the stemness of CSCs. The anticancer effect of withaferin A (WFA) was studied in MM-CSCs and RPMI 8226 MM tumoral plasma cells (RPMIs). WFA exhibited growth inhibitory effects in both MM-CSCs and RPMIs, with IC₅₀ values of 649 and 224 nM, respectively. WFA also induced a G₂ cell cycle arrest, as well as cell death and apoptosis. Although, WFA did not exhibit a direct anti-migratory effect, a remarkable morphological change was observed in MM-CSCs in response to WFA treatment. Using qPCR gene expression analyses, WFA caused a reduction in stemness markers, and a promotion of differentiation markers in MM-CSCs. These results warrant further investigation of WFA in relevant MM animal models.

Bruceantin inhibits multiple myeloma cancer stem cell proliferation

Multiple myeloma (MM) continues to claim the lives of a majority of patients. MM cancer stem cells (CSCs) have been demonstrated to sustain tumor growth. Due to their ability to self-renew and to express detoxifying enzymes and efflux transporters, MM-CSCs are rendered highly resistant to conventional therapies. Therefore, managing MM-CSCs characteristics could have profound clinical implications. Bruceantin (BCT) is a natural product previously demonstrated to inhibit the growth of MM in RPMI 8226 cells-inoculated mouse xenograft models, and to cause regression in already established tumors. The objectives of the present study were to test the inhibitory effects of BCT on MM-CSCs growth derived from a human primary tumor, and to explore a mechanism of action underlying these effects. BCT exhibited potent antiproliferative activity in MM-CSCs starting at 25 nM. BCT induced cell cycle arrest, cell death and apoptosis in MM-CSCs as well as inhibited cell migration and angiogenesis in vitro. Using a qPCR screen, it was found that the gene expression of a number of Notch pathway members was altered. Pretreatment of MM-CSCs with the γ-secretase inhibitor RO4929097, a Notch pathway inhibitor, reversed BCT-induced effects on MM-CSCs proliferation. In this study, BCT was shown to be an effective agent in controlling the proliferation, viability and migration of MM-CSCs as well as angiogenesis in vitro. The effect on MM-CSCs proliferation may be mediated by the Notch pathway. These results warrant further investigation of BCT in a broader set of human-derived MM-CSCs and with in vivo models representative of MM.

Chemokine-like receptor 1 regulates skeletal muscle cell myogenesis

The chemokine-like receptor-1 (CMKLR1) is a G protein-coupled receptor that is activated by chemerin, a secreted plasma leukocyte attractant and adipokine. Previous studies identified that CMKLR1 is expressed in skeletal muscle in a stage-specific fashion during embryogenesis and in adult mice; however, its function in skeletal muscle remains unclear. Based on the established function of CMKLR1 in cell migration and differentiation, we investigated the hypothesis that CMKLR1 regulates the differentiation of myoblasts into myotubes. In C(2)C(12) mouse myoblasts, CMKLR1 expression increased threefold with differentiation into multinucleated myotubes. Decreasing CMKLR1 expression by adenoviral-delivered small-hairpin RNA (shRNA) impaired the differentiation of C(2)C(12) myoblasts into mature myotubes and reduced the mRNA expression of myogenic regulatory factors myogenin and MyoD while increasing Myf5 and Mrf4. At embryonic day 12.5 (E12.5), CMKLR1 knockout (CMKLR1(-/-)) mice appeared developmentally delayed and displayed significantly lower wet weights and a considerably diminished myotomal component of somites as revealed by immunolocalization of myosin heavy chain protein compared with wild-type (CMKLR1(+/+)) mouse embryos. These changes were associated with increased Myf5 and decreased MyoD protein expression in the somites of E12.5 CMKLR1(-/-) mouse embryos. Adult male CMKLR1(-/-) mice had significantly reduced bone-free lean mass and weighed less than the CMKLR1(+/+) mice. We conclude that CMKLR1 is essential for myogenic differentiation of C(2)C(12) cells in vitro, and the CMKLR1 null mice have a subtle skeletal muscle deficit beginning from embryonic life that persists during postnatal life.

Fixity of ports to the abdominal wall during laparoscopic surgery: a randomized comparison of cutting versus blunt trocars

BACKGROUND

Dislodgement of ports from the abdominal wall is a common problem during laparoscopic surgery. The aim of this study was to evaluate port stability using either cutting or blunt-tipped trocars.

METHODS

Patients undergoing laparoscopic surgery were randomized to have the secondary ports inserted using either cutting or blunt-tipped trocars. The fixity of ports to the abdominal wall was evaluated at the start and completion of surgery by measuring the total traction force required to displace the ports. Similarly, the friction forces required to displace instruments within the ports were measured.

RESULTS

Thirty patients were randomized into two groups (15 patients in each group), and a total of 114 ports (cutting, n = 51; blunt, n = 63) were evaluated. The groups were comparable in age, gender, body mass index, and operating time. The total traction forces needed to displace the 5-mm and 10-mm ports were significantly lower when cutting trocars were used at both the beginning (2.6 vs. 11.8 N, p < 0.001, and 6.3 vs. 15.5 N, p = 0.014, respectively) and completion of surgery (1.3 vs. 6.7 N, p < 0.001, and 1.1 vs. 12.0 N, p = 0.001, respectively). The declines in the total traction forces from the start to the completion of surgery were significant for the 5-mm and 10-mm cutting-trocar ports (p = 0.031 and p = 0.043, respectively) but not for the blunt-trocar ports (p = 0.088 and p = 0.152, respectively). While no significant differences between the instruments' friction forces and the traction forces of the cutting-trocar ports were observed, the former were significantly lower than the traction force needed to displace the blunt-trocar ports. This explains the significantly greater frequency of spontaneous port dislodgements when cutting ports were employed (25.5% vs. 1.6%, p < 0.001). Port-site bleeding was encountered only in patients (n = 2, 13%) where cutting trocars were used.

CONCLUSIONS

Port fixity to the abdominal wall during laparoscopic surgery declines with time. The insertion of ports using a blunt-tipped trocar is associated with significantly greater stability and fixity of the port to the abdominal wall. The use of blunt-tipped trocars is recommended for routine practice in laparoscopic surgery.