Denis C. Guttridge

Sarcomas are malignant heterogeneous tumors of mesenchymal derivation. Dedifferentiated liposarcoma (DDLPS) is aggressive with recurrence in 80% and metastasis in 20% of patients. We previously found that miR-133a was significantly underexpressed in liposarcoma tissues. As this miRNA has recently been shown to be a tumor suppressor in many cancers, the objective of this study was to characterize the biological and molecular consequences of miR-133a underexpression in DDLPS. Real-time PCR was used to evaluate expression levels of miR-133a in human DDLPS tissue, normal fat tissue, and human DDLPS cell lines. DDLPS cells were stably transduced with miR-133a vector to assess the effects in vitro on proliferation, cell cycle, cell death, migration, and metabolism. A Seahorse Bioanalyzer system was also used to assess metabolism in vivo by measuring glycolysis and oxidative phosphorylation (OXPHOS) in subcutaneous xenograft tumors from immunocompromised mice. miR-133a expression was significantly decreased in human DDLPS tissue and cell lines. Enforced expression of miR-133a decreased cell proliferation, impacted cell cycle progression kinetics, decreased glycolysis, and increased OXPHOS. There was no significant effect on cell death or migration. Using an in vivo xenograft mouse study, we showed that tumors with increased miR-133a expression had no difference in tumor growth compared to control, but did exhibit an increase in OXPHOS metabolic respiration. Based on our collective findings, we propose that in DDPLS, loss of miR-133a induces a metabolic shift due to a reduction in oxidative metabolism favoring a Warburg effect in DDLPS tumors, but this regulation on metabolism was not sufficient to affect DDPLS.

A compounding feature of greater than 50% of all cancers is the high incidence of the cachexia syndrome, a complex metabolic disorder characterized by extreme weight loss due mainly to the gross depletion of skeletal muscle tissue. Although studies into the cause of cancer cachexia has spanned over multiple decades, little is known about the effects of various cancer treatments themselves on cachexia. For example, chemotherapy agents induce side effects such as nausea and anorexia, but these symptoms do not fully account for the changes seen with cancer cachexia. In this study we examine the effects of chemotherapeutic compounds, specifically, cisplatin in the colon-26 adenocarcinoma model of cancer cachexia. We find that although cisplatin is able to reduce tumor burden as expected, muscle wasting in mice nevertheless persists. Strikingly, cisplatin alone was seen to regulate muscle atrophy, which was independent of the commonly implicated ubiquitin proteasome system. Finally, we show that cisplatin is able to induce NF-κB activity in both mouse muscles and myotube cultures, suggesting that an additional side effect of cancer treatment is the regulation of muscle wasting that may be mediated through activation of the NF-κB signaling pathway.

Background: Metabolic reprogramming has emerged as a cancer hallmark, and one of the well-known cancer-associated metabolic alterations is the increase in the rate of glycolysis. Recent reports have shown that both the classical and alternative signaling pathways of NF-κB play important roles in controlling the metabolic profiles of normal cells and cancer cells. However, how these signaling pathways affect the metabolism of sarcomas, specifically rhabdomyosarcoma and osteosarcoma, has not been characterized. Methods: Classical NF-κB activity was inhibited through overexpression of the IκBα super repressor of NF-κB in rhabdomyosarcoma and osteosarcoma cells. Global gene expression analysis was performed using Affymetrix GeneChip Human Transcriptome Array 2.0 and data were interpreted using Gene Set Enrichment Analysis. Seahorse Bioscience XFe24 was used to analyze oxygen consumption rate as a measure of aerobic respiration. Results: Inhibition of classical NF-κB activity in sarcoma cell lines restored alternative signaling as well as an increased oxidative respiratory metabolic phenotype in vitro. In addition, microarray analysis indicated that inhibition of NF-κB in sarcoma cells reduced glycolysis. We showed that a glycolytic gene, hexokinase 2, is a direct NF-κB transcriptional target. Knockdown of hexokinase 2 shifted the metabolic profile in sarcoma cells away from aerobic glycolysis, and re-expression of hexokinase 2 rescued the metabolic shift induced by inhibition of NF-κB activity in osteosarcoma cells. Conclusions: These findings suggest that classical signaling of NF-κB plays a crucial role in the metabolic profile of pediatric sarcomas potentially through the regulation of hexokinase 2.

Background: Cancer‐associated wasting, termed cancer cachexia, has a profound effect on the morbidity and mortality of cancer patients but remains difficult to recognize and diagnose. While increases in circulating levels of a number of inflammatory cytokines have been associated with cancer cachexia, these associations were generally made in patients with advanced disease and thus may be associated with disease progression rather than directly with the cachexia syndrome. Thus, we sought to assess potential biomarkers of cancer‐induced cachexia in patients with earlier stages of disease.Methods: A custom multiplex array was used to measure circulating levels of 25 soluble factors from 70 pancreatic cancer patients undergoing attempted tumour resections. A high‐sensitivity multiplex was used for increased sensitivity for nine cytokines.Results: Resectable pancreatic cancer patients with cachexia had low levels of canonical pro‐inflammatory cytokines including interleukin‐6 (IL‐6), interleukin‐1β (IL‐1β), interferon‐γ (IFN‐γ), and tumour necrosis factor (TNF). Even in our more sensitive analysis, these cytokines were not associated with cancer cachexia. Of the 25 circulating factors tested, only monocyte chemoattractant protein‐1 (MCP‐1) was increased in treatment‐naïve cachectic patients compared with weight stable patients and identified as a potential biomarker for cancer cachexia. Although circulating levels of leptin and granulocyte‐macrophage colony‐stimulating factor (GM‐CSF) were found to be decreased in the same cohort of treatment‐naïve cachectic patients, these factors were closely associated with body mass index, limiting their utility as cancer cachexia biomarkers.Conclusions: Unlike in advanced disease, it is possible that cachexia in patients with resectable pancreatic cancer is not associated with high levels of classical markers of systemic inflammation. However, cachectic, treatment‐naïve patients have higher levels of MCP‐1, suggesting that MCP‐1 may be useful as a biomarker of cancer cachexia.

Macrophages are attracted to developing tumors and can participate in immune surveillance to eliminate neoplastic cells. In response, neoplastic cells utilize NF-κB to suppress this killing activity, but the mechanisms underlying their self-protection remain unclear. Here, we report that this dynamic interaction between tumor cells and macrophages is integrally linked by a soluble factor identified as growth and differentiation factor 15 (GDF-15). In vitro, tumor-derived GDF-15 signals in macrophages to suppress their proapoptotic activity by inhibiting TNF and nitric oxide (NO) production. In vivo, depletion of GDF-15 in Ras-driven tumor xenografts and in an orthotopic model of pancreatic cancer delayed tumor development. This delay correlated with increased infiltrating antitumor macrophages. Further, production of GDF-15 is directly regulated by NF-κB, and the colocalization of activated NF-κB and GDF-15 in epithelial ducts of human pancreatic adenocarcinoma supports the importance of this observation. Mechanistically, we found that GDF-15 suppresses macrophage activity by inhibiting TGF-β–activated kinase (TAK1) signaling to NF-κB, thereby blocking synthesis of TNF and NO. Based on these results, we propose that the NF-κB/GDF-15 regulatory axis is important for tumor cells in evading macrophage immune surveillance during the early stages of tumorigenesis.

Alveolar rhabdomyosarcoma (aRMS) is a pediatric soft tissue cancer commonly associated with a chromosomal translocation that leads to the expression of a Pax3:Foxo1 or Pax7:Foxo1 fusion protein, the developmental underpinnings of which may give clues to its therapeutic approaches. In aRMS, the NFκB–YY1–miR-29 regulatory circuit is dysregulated, resulting in repression of miR-29 and loss of the associated tumor suppressor activity. To further elucidate the role of NFκB in aRMS, we first tested 55 unique sarcoma cell lines and primary cell cultures in a large-scale chemical screen targeting diverse molecular pathways. We found that pharmacological inhibition of NFκB activity resulted in decreased cell proliferation of many of the aRMS tumor cultures. Surprisingly, mice that were orthotopically allografted with aRMS tumor cells exhibited no difference in tumor growth when administered an NFκB inhibitor, compared to control. Furthermore, inhibition of NFκB by genetically ablating its activating kinase inhibitor, IKKβ, by conditional deletion in a mouse model harboring the Pax3:Foxo1 chimeric oncogene failed to abrogate spontaneous tumor growth. Genetically engineered mice with conditionally deleted IKKβ exhibited a paradoxical decrease in tumor latency compared with those with active NFκB. However, using a synthetic-lethal approach, primary cell cultures derived from tumors with inactivated NFκB showed sensitivity to the BCL-2 inhibitor navitoclax. When used in combination with an NFκB inhibitor, navitoclax was synergistic in decreasing the growth of both human and IKKβ wild-type mouse aRMS cells, indicating that inactivation of NFκB alone may not be sufficient for reducing tumor growth, but, when combined with another targeted therapeutic, may be clinically beneficial.

Involuntary weight loss, a part of the cachexia syndrome, is a debilitating comorbidity of cancer and currently has no treatment options. Results from a recent clinical trial at our institution showed that biliary tract cancer patients treated with a MEK inhibitor exhibited poor tumor responses but surprisingly gained weight and increased their skeletal muscle mass. This implied that MEK inhibition might be anticachectic. To test this potential effect of MEK inhibition, we utilized the established Colon-26 model of cancer cachexia and the MEK1/2 inhibitor MEK162. Results showed that MEK inhibition effectively prevented muscle wasting. Importantly, MEK162 retained its ability to spare muscle loss even in mice bearing a Colon-26 clone resistant to the MEK inhibitor, demonstrating that the effects of blocking MEK are at least in part independent of the tumor. Because single-agent MEK inhibitors have been limited as a first-line targeted therapy due to compensatory activation of other oncogenic signaling pathways, we combined MEK162 with the PI3K/Akt inhibitor buparlisib. Results showed that this combinatorial treatment significantly reduced tumor growth due to a direct activity on Colon-26 tumor cells in vitro and in vivo, while also preserving skeletal muscle mass. Together, our results suggest that as a monotherapy, MEK inhibition preserves muscle mass, but when combined with a PI3K/Akt inhibitor exhibits potent antitumor activity. Thus, combinatorial therapy might serve as a new approach for the treatment of cancer cachexia. Mol Cancer Ther; 16(2); 344–56. ©2016 AACR. See related article by Kobayashi et al., p. 357