Reversing immunosuppression in the tumor microenvironment of fibrolamellar carcinoma via PD-1 and IL-10 blockade

Fibrolamellar carcinoma (FLC) is a rare liver tumor driven by the DNAJ-PKAc fusion protein that affects healthy young patients. Little is known about the immune response to FLC, limiting rational design of immunotherapy. Multiplex immunohistochemistry and gene expression profiling were performed to characterize the FLC tumor immune microenvironment and adjacent non-tumor liver (NTL). Flow cytometry and T cell receptor (TCR) sequencing were performed to determine the phenotype of tumor-infiltrating immune cells and the extent of T cell clonal expansion. Fresh human FLC tumor slice cultures (TSCs) were treated with antibodies blocking programmed cell death protein-1 (PD-1) and interleukin-10 (IL-10), with results measured by cleaved caspase-3 immunohistochemistry. Immune cells were concentrated in fibrous stromal bands, rather than in the carcinoma cell compartment. In FLC, T cells demonstrated decreased activation and regulatory T cells in FLC had more frequent expression of PD-1 and CTLA-4 than in NTL. Furthermore, T cells had relatively low levels of clonal expansion despite high TCR conservation across individuals. Combination PD-1 and IL-10 blockade signficantly increased cell death in human FLC TSCs. Immunosuppresion in the FLC tumor microenvironment is characterized by T cell exclusion and exhaustion, which may be reversible with combination immunotherapy.

Hypoxia as a barrier to immunotherapy in pancreatic adenocarcinoma

Pancreatic ductal adenocarcinoma (PDA) is a lethal disease with limited response to cytotoxic chemoradiotherapy, as well as newer immunotherapies. The PDA tumor microenvironment contains infiltrating immune cells including cytotoxic T cells; however, there is an overall immunosuppressive milieu. Hypoxia is a known element of the solid tumor microenvironment and may promote tumor survival. Through various mechanisms including, but not limited to, those mediated by HIF-1α, hypoxia also leads to increased tumor proliferation and metabolic changes. Furthermore, epithelial to mesenchymal transition is promoted through several pathways, including NOTCH and c-MET, regulated by hypoxia. Hypoxia-promoted changes also contribute to the immunosuppressive phenotype seen in many different cell types within the microenvironment and thereby may inhibit an effective immune system response to PDA. Pancreatic stellate cells (PSCs) and myofibroblasts appear to contribute to the recruitment of myeloid derived suppressor cells (MDSCs) and B cells in PDA via cytokines increased due to hypoxia. PSCs also increase collagen secretion in response to HIF-1α, which promotes a fibrotic stroma that alters T cell homing and migration. In hypoxic environments, B cells contribute to cytotoxic T cell exhaustion and produce chemokines to attract more immunosuppressive regulatory T cells. MDSCs inhibit T cell metabolism by hoarding key amino acids, modulate T cell homing by cleaving L-selectin, and prevent T cell activation by increasing PD-L1 expression. Immunosuppressive M2 phenotype macrophages promote T cell anergy via increased nitric oxide (NO) and decreased arginine in hypoxia. Increased numbers of regulatory T cells are seen in hypoxia which prevent effector T cell activation through cytokine production and increased CTLA-4. Effective immunotherapy for pancreatic adenocarcinoma and other solid tumors will need to help counteract the immunosuppressive nature of hypoxia-induced changes in the tumor microenvironment. Promising studies will look at combination therapies involving checkpoint inhibitors, chemokine inhibitors, and possible targeting of hypoxia. While no model is perfect, assuring that models incorporate the effects of hypoxia on cancer cells, stromal cells, and effector immune cells will be crucial in developing successful therapies.

T-cell programming in pancreatic adenocarcinoma: a review

Despite recent advancements in multimodal therapy, pancreatic ductal adenocarcinoma (PDA) continues to have a dismal prognosis. In the era of burgeoning immune therapies against previously difficult-to-treat malignancies, there has been growing interest in activating the immune system against PDA; however, unlike in other cancers such as melanoma and lymphoma, immunotherapy has not yielded many clinically significant results. To harness these mechanisms for therapeutic use, an in-depth understanding of T-cell programming in the immune microenvironment of PDA must be achieved. The outcome of T-cell programming against pathogens or cancer depends on the uptake and presentation of foreign antigens by dendritic cells and macrophages to T cells, and the expression of various co-stimulatory molecules and cytokines. Subsequent immune responses are kept in check via regulatory mechanisms such as immune checkpoints (for example, programmed cell death protein 1 (PD-1) and cytotoxic T lymphocyte-associated protein 4 (CTLA-4)), as well as other immunosuppressive cell types such as regulatory T cells (Treg) and M2 macrophages. PDA presents a challenge from the perspective of immune therapy because of many immunosuppressive mechanisms at play in its microenvironment. The tumor itself produces IL-10 and transforming growth factor beta (TGF-β) that downregulate T-cell activation as well as the activity of antigen-presenting cells. At the same time, PDA also appears to recruit more regulatory elements into its milieu; higher infiltration of Treg, for instance, has been associated with poorer prognosis in PDA patients. M2 macrophages and myeloid-derived suppressive cells are also highly prevalent in the tumor microenvironment. T cells in PDA have high expression of PD-1, whereas the tumor has high expression of PD-L1, which likely inhibits activation of tumor antigen-specific T cells. Many of these immunosuppressive mechanisms have been targeted as potential immune therapies of PDA. Immune checkpoint inhibitors, which target PD-1 and CTLA-4, have been shown to be effective in other cancers such as melanoma; however, they have not demonstrated outcome benefits in PDA so far. Other novel investigational approaches under study currently include inhibiting the homing of immunosuppressive cell types to the tumor milieu, as well as vaccines designed to boost the adaptive response to PDA antigens. As our understanding of the nuanced and complex interactions of the immune microenvironment expands, more targeted approaches can be taken toward achieving therapeutic success in immune therapy against PDA.

Development of an infection-resistant LVAD driveline: a novel approach to the prevention of device-related infections

BACKGROUND

Infection remains the single most important challenge to extended left ventricular assist device (LVAD) use and often arises from the percutaneous driveline exit site. We evaluated the ability of an LVAD driveline prototype impregnated with chlorhexidine, triclosan, and silver sulfadiazine to resist bacterial and fungal colonization.

METHODS

The spectrum and duration of antimicrobial activity were evaluated in vitro by daily transfer of driveline segments embedded on agar plates inoculated with 10(8) colony-forming units (CFU) of Staphylococcus aureus (S. aureus), Staphlococcus epidermidis, Enterobacter aerogenes, Psuedomonas aeruginosa, and Candida albicans, and then measuring zones of inhibition around the sample subsequent to 24 hours of incubation at 37 degrees C. Antimicrobial activity was demonstrated against all organisms for greater than 14 days, and for over 21 days for gram-positive bacteria. To demonstrate in vivo efficacy of the treated driveline, 3-cm segments of driveline were implanted in the dorsal and ventral surface of rats. The exit site was inoculated with 10(6) CFU of S. aureus. After 7 days, driveline segments were aseptically explanted and assayed for bacterial colonization and retention of antimicrobial activity. One hundred percent of control segments were colonized (10(5) CFU S. aureus/cm) as against 13% of the test explants (< or = 330 CFU/cm; p < 0.0001).

RESULTS

Subcultures of the insertion site and driveline pocket tissue resulted in 10(3) to 10(5) CFU per swab culture for control rats and 0 to 10(2) CFU/swab for test animals. Test drivelines retained 80% of anti-S. aureus activity. Gross and histological examination of the driveline and surrounding pocket revealed minimal tissue reactivity with positive signs of tissue ingrowth.

CONCLUSION

An antimicrobial driveline may prevent early infections and facilitate ingrowth of tissue to provide long-term stability and protection against late infection.