Soumen Roy

Microbiota: a key orchestrator of cancer therapy

The microbiota is composed of commensal bacteria and other microorganisms that live on the epithelial barriers of the host. The commensal microbiota is important for the health and survival of the organism. Microbiota influences physiological functions from the maintenance of barrier homeostasis locally to the regulation of metabolism, haematopoiesis, inflammation, immunity and other functions systemically. The microbiota is also involved in the initiation, progression and dissemination of cancer both at epithelial barriers and in sterile tissues. Recently, it has become evident that microbiota, and particularly the gut microbiota, modulates the response to cancer therapy and susceptibility to toxic side effects. In this Review, we discuss the evidence for the ability of the microbiota to modulate chemotherapy, radiotherapy and immunotherapy with a focus on the microbial species involved, their mechanism of action and the possibility of targeting the microbiota to improve anticancer efficacy while preventing toxicity.

Inner ear supporting cells protect hair cells by secreting HSP70

Mechanosensory hair cells are the receptor cells of hearing and balance. Hair cells are sensitive to death from exposure to therapeutic drugs with ototoxic side effects, including aminoglycoside antibiotics and cisplatin. We recently showed that the induction of heat shock protein 70 (HSP70) inhibits ototoxic drug-induced hair cell death. Here, we examined the mechanisms underlying the protective effect of HSP70. In response to heat shock, HSP70 was induced in glia-like supporting cells but not in hair cells. Adenovirus-mediated infection of supporting cells with Hsp70 inhibited hair cell death. Coculture with heat-shocked utricles protected nonheat-shocked utricles against hair cell death. When heat-shocked utricles from Hsp70-/- mice were used in cocultures, protection was abolished in both the heat-shocked utricles and the nonheat-shocked utricles. HSP70 was detected by ELISA in the media surrounding heat-shocked utricles, and depletion of HSP70 from the media abolished the protective effect of heat shock, suggesting that HSP70 is secreted by supporting cells. Together our data indicate that supporting cells mediate the protective effect of HSP70 against hair cell death, and they suggest a major role for supporting cells in determining the fate of hair cells exposed to stress.

Sound preconditioning therapy inhibits ototoxic hearing loss in mice

Therapeutic drugs with ototoxic side effects cause significant hearing loss for thousands of patients annually. Two major classes of ototoxic drugs are cisplatin and the aminoglycoside antibiotics, both of which are toxic to mechanosensory hair cells, the receptor cells of the inner ear. A critical need exists for therapies that protect the inner ear without inhibiting the therapeutic efficacy of these drugs. The induction of heat shock proteins (HSPs) inhibits both aminoglycoside- and cisplatin-induced hair cell death and hearing loss. We hypothesized that exposure to sound that is titrated to stress the inner ear without causing permanent damage would induce HSPs in the cochlea and inhibit ototoxic drug–induced hearing loss. We developed a sound exposure protocol that induces HSPs without causing permanent hearing loss. We used this protocol in conjunction with a newly developed mouse model of cisplatin ototoxicity and found that preconditioning mouse inner ears with sound has a robust protective effect against cisplatin-induced hearing loss and hair cell death. Sound therapy also provided protection against aminoglycoside-induced hearing loss. These data indicate that sound preconditioning protects against both classes of ototoxic drugs, and they suggest that sound therapy holds promise for preventing hearing loss in patients receiving these drugs.

Microbes and Cancer

Commensal microorganisms (the microbiota) live on all the surface barriers of our body and are particularly abundant and diverse in the distal gut. The microbiota and its larger host represent a metaorganism in which the cross talk between microbes and host cells is necessary for health, survival, and regulation of physiological functions locally, at the barrier level, and systemically. The ancestral molecular and cellular mechanisms stemming from the earliest interactions between prokaryotes and eukaryotes have evolved to mediate microbe-dependent host physiology and tissue homeostasis, including innate and adaptive resistance to infections and tissue repair. Mostly because of its effects on metabolism, cellular proliferation, inflammation, and immunity, the microbiota regulates cancer at the level of predisposing conditions, initiation, genetic instability, susceptibility to host immune response, progression, comorbidity, and response to therapy. Here, we review the mechanisms underlying the interaction of the microbiota with cancer and the evidence suggesting that the microbiota could be targeted to improve therapy while attenuating adverse reactions.

Gene Therapy Restores Hair Cell Stereocilia Morphology in Inner Ears of Deaf Whirler Mice.

Hereditary deafness is one of the most common disabilities affecting newborns. Many forms of hereditary deafness are caused by morphological defects of the stereocilia bundles on the apical surfaces of inner ear hair cells, which are responsible for sound detection. We explored the effectiveness of gene therapy in restoring the hair cell stereocilia architecture in the whirlin mouse model of human deafness, which is deaf due to dysmorphic, short stereocilia. Wild-type whirlin cDNA was delivered via adeno-associated virus (AAV8) by injection through the round window of the cochleas in neonatal whirler mice. Subsequently, whirlin expression was detected in infected hair cells (IHCs), and normal stereocilia length and bundle architecture were restored. Whirlin gene therapy also increased inner hair cell survival in the treated ears compared to the contralateral nontreated ears. These results indicate that a form of inherited deafness due to structural defects in cochlear hair cells is amenable to restoration through gene therapy.

Gut microbiome–mediated bile acid metabolism regulates liver cancer via NKT cells

Bile acids and liver cancer Liver cancer is a leading cause of cancer-related deaths in the United States. The composition of the gut microbiome influences many human diseases, including liver inflammatory disorders. Ma et al. found that commensal gut bacteria can recruit the immune system to control the growth of liver tumors in mice (see the Perspective by Hartmann and Kronenberg). Clostridium species modified bile acids to signal liver sinusoidal endothelial cells to produce the chemokine CXCL16. This recruited natural killer T (NKT) immune cells to perform antitumor surveillance of the liver. Growth of both primary and metastatic cancer was reduced by NKT cell–driven killing. Science, this issue p. eaan5931; see also p. 858 Cross-talk between bacteria and bile acid promotes natural killer T cell antitumor immunity in the liver. INTRODUCTION Primary liver tumors and liver metastasis currently represent the leading cause of cancer-related deaths. The liver intimately cross-talks with the gut and performs many essential functions related to digestion, metabolism of nutrients, and clearance of bacterial metabolites. Diseased livers are often associated with altered gut bacterial composition, or dysbiosis, and it has been suggested that gut bacterial products contribute to malignant transformation of hepatocytes. The liver is exposed to the gut microbiome through the portal vein and is an immunological organ that is heavily populated by immune cells. Emerging studies have shown that gut commensal bacteria are important regulators of antitumor immunity. Although it has been established that the gut microbiome influences the efficacy of cancer immunotherapy, the role of gut bacteria in antitumor surveillance in the liver is poorly understood. RATIONALE The liver is exposed to gut bacterial metabolites and products by way of blood from the intestine, which comprises 70% of the whole liver blood supply. Changes in the gut microbiome may affect immune cell function in the liver, and commensal bacteria can mediate the metabolism of primary into secondary bile acids, which recirculate back into the liver through the enterohepatic circulation. Given that bile acids are known to be involved in liver cancer development, we focused on the role of bile acids in immunosurveillance of tumors growing in the liver. We altered gut bacteria and examined changes of hepatic immune cells and antitumor immunity directed against liver tumors. Uncovering how the gut microbiome uses bile acids to shape immunity to liver cancer may have future therapeutic applications. RESULTS Using one primary liver model and three liver metastasis models, we found that altering commensal gut bacteria induced a liver-selective antitumor effect. A selective increase of hepatic CXCR6+ natural killer T (NKT) cells was observed, independent of mouse strain, gender, or presence of liver tumors. The accumulated hepatic NKT cells showed an activated phenotype and produced more interferon-γ upon antigen stimulation. In vivo studies using both antibody-mediated cell depletion and NKT-deficient mice confirmed that NKT cells mediated the inhibition of tumor growth in the liver. Further investigation showed that NKT cell accumulation was regulated by the expression of CXCL16, the solo ligand for CXCR6, on liver sinusoidal endothelial cells, which form the lining of liver capillaries and the first barrier for the blood coming from the gut entering the liver. Primary bile acids increased CXCL16 expression, whereas secondary bile acids showed the opposite effect. Removing gram-positive bacteria by antibiotic treatment with vancomycin, which contains the bacteria mediating primary-to-secondary bile acid conversion, was sufficient to induce hepatic NKT cell accumulation and decrease liver tumor growth. Feeding secondary bile acids or colonization of bile acid–metabolizing bacteria, reversed both NKT cell accumulation and inhibition of liver tumor growth in mice with altered gut commensal bacteria. In nontumor liver tissue from human patients with primary liver cancer, primary bile acid chenodeoxycholic acid (CDCA) levels correlated with CXCL16 expression, whereas an inverse correlation was observed with secondary bile acid glycolithocholate (GLCA), suggesting that the finding may apply to humans. CONCLUSION We describe a mechanism by which the gut microbiome uses bile acids as messengers to control a chemokine-dependent accumulation of hepatic NKT cells and antitumor immunity in the liver, against both primary and metastatic liver tumors. These findings not only have possible implications for future cancer therapeutic studies but also provide a link between the gut microbiome, its metabolites, and immune responses in the liver. Gut microbiome modulates liver cancer through bile acid–regulated NKT cells. Gut microbiome uses bile acids as a messenger to regulate chemokine CXCL16 level on liver sinusoidal endothelial cells (LSEC) and thus controls the accumulation of CXCR6+ hepatic NKT cells. The accumulated NKT cells have an activated phenotype and inhibit liver tumor growth. Primary liver tumors and liver metastasis currently represent the leading cause of cancer-related death. Commensal bacteria are important regulators of antitumor immunity, and although the liver is exposed to gut bacteria, their role in antitumor surveillance of liver tumors is poorly understood. We found that altering commensal gut bacteria in mice induced a liver-selective antitumor effect, with an increase of hepatic CXCR6+ natural killer T (NKT) cells and heightened interferon-γ production upon antigen stimulation. In vivo functional studies showed that NKT cells mediated liver-selective tumor inhibition. NKT cell accumulation was regulated by CXCL16 expression of liver sinusoidal endothelial cells, which was controlled by gut microbiome-mediated primary-to-secondary bile acid conversion. Our study suggests a link between gut bacteria–controlled bile acid metabolism and liver antitumor immunosurveillance.

Cochlear gene transfer mediated by adeno-associated virus: Comparison of two surgical approaches

Gene therapy offers the possibility of delivering corrective genetic materials to the cochlea, potentially improving hearing. In animals, the most commonly used surgical methods for viral gene therapy delivery to the cochlea are the round window and the cochleostomy approaches. However, the patterns of viral infection and the effects on hearing have not been directly compared between these two approaches. In this study, we compare the patterns of cochlear infection and effects on hearing between these two surgical approaches using adeno‐associated virus serotype 2/8 (AAV8) as the gene delivery vehicle.

Heat Shock Protein-Mediated Protection Against Cisplatin-Induced Hair Cell Death

Cisplatin is a highly successful and widely used chemotherapy for the treatment of various solid malignancies in both adult and pediatric patients. Side effects of cisplatin treatment include nephrotoxicity and ototoxicity. Cisplatin ototoxicity results from damage to and death of cells in the inner ear, including sensory hair cells. We showed previously that heat shock inhibits cisplatin-induced hair cell death in whole-organ cultures of utricles from adult mice. Since heat shock protein 70 (HSP70) is the most upregulated HSP in response to heat shock, we investigated the role of HSP70 as a potential protectant against cisplatin-induced hair cell death. Our data using utricles from HSP70−/− mice indicate that HSP70 is necessary for the protective effect of heat shock against cisplatin-induced hair cell death. In addition, constitutive expression of inducible HSP70 offered modest protection against cisplatin-induced hair cell death. We also examined a second heat-inducible protein, heme oxygenase-1 (HO-1, also called HSP32). HO-1 is an enzyme responsible for the catabolism of free heme. We previously showed that induction of HO-1 using cobalt protoporphyrin IX (CoPPIX) inhibits aminoglycoside-induced hair cell death. Here, we show that HO-1 also offers significant protection against cisplatin-induced hair cell death. HO-1 induction occurred primarily in resident macrophages, with no detectable expression in hair cells or supporting cells. Depletion of macrophages from utricles abolished the protective effect of HO-1 induction. Together, our data indicate that HSP induction protects against cisplatin-induced hair cell death, and they suggest that resident macrophages mediate the protective effect of HO-1 induction.

Magnetic Nanoparticle Mediated Steroid Delivery Mitigates Cisplatin Induced Hearing Loss

Cisplatin (cis-diamminedichloroplatinum) is widely used as a chemotherapeutic drug for genitourinary, breast, lung and head and neck cancers. Though effective in inducing apoptosis in cancer cells, cisplatin treatment causes severe hearing loss among patients. Steroids have been shown to mitigate cisplatin-induced hearing loss. However, steroids may interfere with the anti-cancer properties of cisplatin if administered systemically, or are rapidly cleared from the middle and inner ear and hence lack effectiveness when administered intra-tympanically. In this work, we deliver prednisolone-loaded nanoparticles magnetically to the cochlea of cisplatin-treated mice. This magnetic delivery method substantially reduced hearing loss in treated animals at high frequency compared to control animals or animals that received intra-tympanic methylprednisolone. The method also protected the outer hair cells from cisplatin-mediated ototoxicity.

Abstract 4926: Gut microbiota regulates cisplatin mediated cachexia and systemic toxicity

Chemotherapy induced toxicity severely affect the cancer survivors and lowers the quality of life. By 2020, there will be more than 18 million of cancer survivors all over the world. Majority of them might develop long term nephrotoxicity, ototoxicity and gut toxicity. In addition, chemotherapy may also facilitate the initiation and progression of cachexia. Recent studies have shown that gut microbiota modulates the efficacy of anti-cancer chemotherapy, however very limited knowledge is available regarding the role of gut microbiota in regulating systemic toxicity and cachexia. We hypothesized that gut microbiota modulates cisplatin induced systemic toxicity as well as cachexia. Four groups (n=10 in each group) of 6-8 weeks old C57B/6 mice were treated with cisplatin, cisplatin+antibiotics cocktails (ABX), ABX only and control. ABX cocktail contained primaxin, vancomycin and neomycin. This experiment was validated using C57B/6 germ free mice. We performed anti-p-γ-H2AX based toxicity assay for DNA damage. In addition, we performed immunohistochemistry for studying cachexia. HE 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4926. doi:10.1158/1538-7445.AM2017-4926