Gil Redelman-Sidi

The mechanism of action of BCG therapy for bladder cancer—a current perspective

Bacillus Calmette–Guérin (BCG) has been used to treat non-muscle-invasive bladder cancer for more than 30 years. It is one of the most successful biotherapies for cancer in use. Despite long clinical experience with BCG, the mechanism of its therapeutic effect is still under investigation. Available evidence suggests that urothelial cells (including bladder cancer cells themselves) and cells of the immune system both have crucial roles in the therapeutic antitumour effect of BCG. The possible involvement of bladder cancer cells includes attachment and internalization of BCG, secretion of cytokines and chemokines, and presentation of BCG and/or cancer cell antigens to cells of the immune system. Immune system cell subsets that have potential roles in BCG therapy include CD4+ and CD8+ lymphocytes, natural killer cells, granulocytes, macrophages, and dendritic cells. Bladder cancer cells are killed through direct cytotoxicity by these cells, by secretion of soluble factors such as TRAIL (tumour necrosis factor-related apoptosis-inducing ligand), and, to some degree, by the direct action of BCG. Several gaps still exist in our knowledge that should be addressed in future efforts to understand this biotherapy of cancer.

2009 H1N1 influenza infection in cancer patients and hematopoietic stem cell transplant recipients

OBJECTIVES Although usually mild, 2009 H1N1 Influenza has caused up to 6000 deaths in the US. To determine outcome in patients with cancer and/or hematopoietic stem cell transplant (HSCT), we reviewed our recent experience at Memorial Sloan-Kettering Cancer Center (MSKCC). METHODS During the initial NYC outbreak (May 19-June 30, 2009), all respiratory samples at MSKCC were tested for 2009 H1N1 influenza by DFA, culture, and RT-PCR. Medical records were reviewed for all cases. RESULTS During the 6-week period, 45(11%) of 394 tested patients were diagnosed with 2009 H1N1 Influenza. These included 29(17%) of 167 patients with hematologic conditions compared to 16(7%) of 226 with solid tumors (P < 0.01). 21(22%) of 96 tested HSCT recipients were positive. Cough (93%) and fever (91%) were common. Of 29 patients who were radiographically assessed, 8(27%) had lower airway disease. 17(37%) were hospitalized. None required mechanical ventilation. No deaths were attributed to influenza. All treated patients tolerated antiviral medication. CONCLUSIONS 2009 H1N1 Influenza caused mild symptoms in most patients with cancer and/or HSCT. None died or required mechanical ventilation. Immunosuppression from cancer or its treatment including HSCT may not be a substantial risk for poor outcome, however further studies are needed to validate our results.

Mycobacteria exploit three genetically distinct DNA double-strand break repair pathways

Bacterial pathogens rely on their DNA repair pathways to resist genomic damage inflicted by the host. DNA double‐strand breaks (DSBs) are especially threatening to bacterial viability. DSB repair by homologous recombination (HR) requires nucleases that resect DSB ends and a strand exchange protein that facilitates homology search. RecBCD and RecA perform these functions in Escherichia coli and constitute the major pathway of error‐free DSB repair. Mycobacteria, including the human pathogen M. tuberculosis, elaborate an additional error‐prone pathway of DSB repair via non‐homologous end‐joining (NHEJ) catalysed by Ku and DNA ligase D (LigD). Little is known about the relative contributions of HR and NHEJ to mycobacterial chromosome repair, the factors that dictate pathway choice, or the existence of additional DSB repair pathways. Here we demonstrate that Mycobacterium smegmatis has three DSB repair pathway options: HR, NHEJ and a novel mechanism of single‐strand annealing (SSA). Inactivation of NHEJ or SSA is compensated by elevated HR. We find that mycobacterial RecBCD does not participate in HR or confer resistance to ionizing radiation (IR), but is required for the RecA‐independent SSA pathway. In contrast, the mycobacterial helicase–nuclease AdnAB participates in the RecA‐dependent HR pathway, and is a major determinant of resistance to IR and oxidative DNA damage. These findings reveal distinctive features of mycobacterial DSB repair, most notably the dedication of the RecBCD and AdnAB helicase–nuclease machines to distinct repair pathways.

Oncogenic activation of Pak1-dependent pathway of macropinocytosis determines BCG entry into bladder cancer cells

Bacille Calmette-Guerin (BCG) is an attenuated strain of Mycobacterium bovis that is used widely as a vaccine for tuberculosis and is used as an effective treatment for superficial bladder carcinoma. Despite being the most successful cancer biotherapy, its mechanism of action and response determinants remain obscure. Here, we establish a model system to analyze BCG interaction with bladder cancer cells, using it to show that these cells vary dramatically in their susceptibility to BCG infection. Unexpectedly, the uptake of BCG by bladder cancer cells occurs by macropinocytosis rather than phagocytosis. BCG entry into bladder cancer cells relied upon Rac1, Cdc42, and their effector kinase Pak1. The difference in susceptibility between BCG-permissive and -resistant bladder cancer cells was due to oncogenic activation of signaling pathways that activate macropinocytosis, with phosphoinositide 3-kinase inhibitor activation stimulating BCG uptake independently of Akt. Similarly, activated Ras strongly activated Pak1-dependent uptake of BCG. These results reveal that oncogenic activation of macropinocytosis determines BCG uptake by bladder cancer cells, implying that tumor responsiveness to BCG may be governed by the specific mutations present in the treated cancer cell.

IFN-γ Release Assays in the Diagnosis of Latent Tuberculosis Infection among Immunocompromised Adults

Immunocompromised persons with latent tuberculosis infection (LTBI) are at increased risk for tuberculosis reactivation compared with the general population. The tuberculin skin test, the traditional assay for diagnosing LTBI, has reduced accuracy in immunocompromised patients. IFN-γ release assays (IGRAs) are in vitro blood tests that measure T-cell release of IFN-γ after stimulation with antigens unique to Mycobacterium tuberculosis. Here we review the data for the use of QuantiFERON-TB Gold In-Tube and T-SPOT.TB, the two currently available IGRAs, in immunocompromised adults, including persons infected with HIV, patients with immune-mediated inflammatory disorders, candidates for treatment with tumor necrosis factor-α inhibitors, patients receiving hemodialysis, solid-organ transplant recipients, and patients with cancer. On the basis of the available data, IGRAs have advantages over the tuberculin skin test in specific patient populations and in certain situations. Further studies are needed to more accurately define the usefulness of IGRAs in immunocompromised patients.

Rapidly Growing Mycobacteria Infection in Patients with Cancer

BACKGROUND Rapidly growing mycobacteria (RGM) have been associated with various clinical syndromes in immunocompetent and immunocompromised hosts. The risk factors and outcomes of RGM infection in patients with cancer have not been clearly defined. METHODS Data were derived from 2 distinct sources. Demographic and clinical data were collected for all patients with cancer at Memorial Sloan-Kettering Cancer Center with a culture positive for RGM from January 1999 through December 2008. We also reviewed the literature for studies describing RGM infection in patients with cancer. RESULTS During the 10-year period, 28 patients with cancer at Memorial Sloan-Kettering Cancer Center had cultures positive for RGM. Most cases occurred in patients with solid tumors and were confined to the lung. A review of the literature identified 313 additional patients with cancer and RGM infection. Combining our series data with cases from the literature, we defined 3 distinct syndromes: pulmonary disease, which occurred in 158 patients (47%); bloodstream infection, occurring in 151 patients (45%); and disseminated infection involving at least 1 end organ, affecting 26 persons (8%). The syndromes differed by age of onset, underlying cancer, main RGM species, and outcome. Persons with bloodstream infection typically were young and had an excellent outcome; those with disseminated infection were older, had pronounced immunosuppression, and had a very poor prognosis. CONCLUSIONS RGM infections in patients with cancer comprise 3 distinct disorders with different risk factors, predominant mycobacterial species, and prognoses. In turn, the approach to management, including number and duration of antimycobacterial drugs, may be fundamentally different for various patients with cancer who receive a diagnosis of RGM infection.

Inhibition of Mycobacterial Infection by the Tumor Suppressor PTEN

Background: PTEN tumor suppressor is a master cellular regulator but was not previously implicated in pathogenic infection. Results: PTEN expression or pharmacological inhibition of PI3K-Akt-mTOR pathway decreases mycobacterial infection. Conclusion: The lipid phosphatase activity of PTEN suppresses mycobacterial infection by inhibiting PI3K signaling. Significance: Understanding how the genetic context of cells influences their susceptibility to pathogens is important for cancer patient care and for treating pathogenic infection. The tumor suppressor PTEN is a lipid phosphatase that is frequently mutated in various human cancers. PTEN suppresses tumor cell proliferation, survival, and growth mainly by inhibiting the PI3K-Akt signaling pathway through dephosphorylation of phosphatidylinositol 3,4,5-triphosphate. In addition to it role in tumor suppression, the PTEN-PI3K pathway controls many cellular functions, some of which may be important for cellular resistance to infection. Currently, the intersection between tumorigenic signaling pathways and cellular susceptibility to infection is not well defined. In this study we report that PTEN signaling regulates infection of both noncancerous and cancerous cells by multiple intracellular mycobacterial pathogens and that pharmacological modulation of PTEN signaling can affect mycobacterial infection. We found that PTEN deficiency renders multiple types of cells hyper-susceptible to infection by Mycoplasma and Mycobacterium bovis Bacillus Calmette-Guérin (BCG). The lipid phosphatase activity of PTEN is required for attenuating infection. Furthermore, we found mycobacterial infection activates host cell Akt phosphorylation, and pharmacological inhibition of Akt or PI3K activity reduced levels of intracellular infection. Intriguingly, inhibition of mTOR, one of the downstream components of the Akt signaling and a promising cancer therapeutic target, also lowered intracellular Bacillus Calmette-Guérin levels in mammary epithelial cancer MCF-7 cells. These findings demonstrate a critical role of PTEN-regulated pathways in pathogen infection. The relationship of PTEN-PI3K-Akt mTOR status and susceptibility to mycobacterial infection suggests that the interaction of mycobacterial pathogens with cancer cells may be influenced by genetic alterations in the tumor cells.

Kitten-transmitted Bordetella bronchiseptica infection in a patient receiving temozolomide for glioblastoma

Bordetella bronchiseptica is a gram negative coccobacillus that can be transmitted from domestic animals and cause severe infections in immunocompromised patients. A 56-year-old man with a left parietal glioblastoma was treated with resection, radiation and concomitant and adjuvant temozolomide chemotherapy. He received bevacizumab for progression, and dose dense metronomic temozolomide was added for additional progression. He developed chronic cough and was diagnosed with B. bronchiseptica infection. This is the first reported case of B. bronchiseptica infection in a patient receiving temozolomide. The infection was likely acquired from an infected kitten. Patients receiving temozolomide should be counseled on the risks of acquiring zoonotic infections, including B. bronchiseptica, from their pets.

Influenza in patients with hematologic disease: an ounce of prevention is worth a pound of cure.

The article by Wei et al. in this issue of Leukemia and Lymphoma describes severe outcomes among 11 hospitalized patients with hematologic disease infected with novel influenza A (H1N1) [1]. These included lower respiratory tract involvement in nine patients, need for mechanical ventilation in three patients, and death in five patients. Severe disease and poor outcome in patients with hematologic conditions infected with novel influenza A (H1N1) has been documented in other recent reports [2,3]. These findings parallel the experience with seasonal influenza in this population, with high proportions of poor outcomes including lower respiratory tract involvement [4,5] and mortality [6,7]. Outcomes may remain poor despite appropriate treatment with antivirals, as is described in the article by Wei et al. Given the potentially grave consequences of influenza infection in this population, it is paramount to prevent it. There are currently three main strategies to prevent influenza infection: infection control measures including isolation of symptomatic patients and prevention of disease transmission from their contacts; vaccination of patients and their close contacts; and use of antivirals for prophylaxis (Table I). Among the 11 patients described by Wei et al., seven acquired the infection while hospitalized [1]. These cases might have been prevented by strict adherence to infection control measures. In a recent Cochrane review, the main intervention shown to be effective in prevention of transmission of respiratory viruses was frequent hand-washing [8]. This intervention appears to be particularly efficacious when applied to children in the same household as the patient. In the same review, use of barriers, including masks, gloves, and gowns, in inpatient settings was also found to be effective [8]. Special care should be taken to prevent transmission of influenza from healthcare professionals to patients; hospital employees should be vaccinated against the circulating influenza strains, and any healthcare worker experiencing respiratory symptoms should not be allowed to come to work. When a patient with a hematologic condition is hospitalized with influenza, isolation precautions should be strictly maintained until symptoms resolve and repeat virologic studies are negative; it is well documented that viral shedding in this population can be prolonged, even in the absence of symptoms [9]. The second strategy is vaccination. The main concern in vaccinating this population against influenza is whether they are able to mount an adequate immune response to the vaccine. Several studies have documented low rates of humoral response to the influenza vaccine in this population, with a response rate as low as 19% in patients with multiple myeloma. However, the response rate is highly variable and depends on the underlying malignancy, chemotherapy used, and the assay used to assess immunologic response [10]. Patients within 6 months of hematopoietic stem cell transplant (HSCT) have poor rates of response to influenza vaccination [11], as do patients within 1 week of receiving standard chemotherapy [12]. Although response rates may be low, inactivated influenza vaccine should be recommended for all patients with hematologic conditions. In recipients of HSCT and

Lysis-independent potentiation of immune checkpoint blockade by oncolytic virus

Intratumoral therapy with oncolytic viruses is increasingly being explored as a strategy to potentiate an immune response against cancer, but it remains unknown whether such therapy should be restricted to cancers sensitive to virus-mediated lysis. Using Newcastle Disease Virus (NDV) as a model, we explore immunogenic potential of an oncolytic virus in bladder cancer, where existing immunotherapy with PD-1 and PD-L1-targeting antibodies to date has shown suboptimal response rates. Infection of human and mouse bladder cancer cells with NDV resulted in immunogenic cell death, activation of innate immune pathways, and upregulation of MHC and PD-L1 in all tested cell lines, including the cell lines completely resistant to NDV-mediated lysis. In a bilateral flank NDV-lysis-resistant syngeneic murine bladder cancer model, intratumoral therapy with NDV led to an increase of immune infiltration in both treated and distant tumors and a shift from an inhibitory to effector T cell phenotype. Consequently, combination of intratumoral NDV with systemic PD-1 or CTLA-4 blockade led to improved local and abscopal tumor control and overall survival. These findings encourage future clinical trials combining intratumoral NDV therapy with systemic immunomodulatory agents and underscore the rationale for such treatments irrespective of tumor cell sensitivity to NDV-mediated lysis.