Focal adhesion kinase-YAP signaling axis drives drug-tolerant persister cells and residual disease in lung cancer

Targeted therapy is effective in many tumor types including lung cancer, the leading cause of cancer mortality. Paradigm defining examples are targeted therapies directed against non-small cell lung cancer (NSCLC) subtypes with oncogenic alterations in EGFR, ALK and KRAS. The success of targeted therapy is limited by drug-tolerant persister cells (DTPs) which withstand and adapt to treatment and comprise the residual disease state that is typical during treatment with clinical targeted therapies. Here, we integrate studies in patient-derived and immunocompetent lung cancer models and clinical specimens obtained from patients on targeted therapy to uncover a focal adhesion kinase (FAK)-YAP signaling axis that promotes residual disease during oncogenic EGFR-, ALK-, and KRAS-targeted therapies. FAK-YAP signaling inhibition combined with the primary targeted therapy suppressed residual drug-tolerant cells and enhanced tumor responses. This study unveils a FAK-YAP signaling module that promotes residual disease in lung cancer and mechanism-based therapeutic strategies to improve tumor response.

3-Phosphoinositide-dependent kinase 1 drives acquired resistance to osimertinib

Osimertinib sensitive and resistant NSCLC NCI-H1975 clones are used to model osimertinib acquired resistance in humanized and non-humanized mice and delineate potential resistance mechanisms. No new EGFR mutations or loss of the EGFR T790M mutation are found in resistant clones. Resistant tumors grown under continuous osimertinib pressure both in humanized and non-humanized mice show aggressive tumor regrowth which is significantly less sensitive to osimertinib as compared with parental tumors. 3-phosphoinositide-dependent kinase 1 (PDK1) is identified as a potential driver of osimertinib acquired resistance, and its selective inhibition by BX795 and CRISPR gene knock out, sensitizes resistant clones. In-vivo inhibition of PDK1 enhances the osimertinib sensitivity against osimertinib resistant xenograft and a patient derived xenograft (PDX) tumors. PDK1 knock-out dysregulates PI3K/Akt/mTOR signaling, promotes cell cycle arrest at the G1 phase. Yes-associated protein (YAP) and active-YAP are upregulated in resistant tumors, and PDK1 knock-out inhibits nuclear translocation of YAP. Higher expression of PDK1 and an association between PDK1 and YAP are found in patients with progressive disease following osimertinib treatment. PDK1 is a central upstream regulator of two critical drug resistance pathways: PI3K/AKT/mTOR and YAP.

Abstract 5120: NPRL2 gene therapy induces effective antitumor immunity in KRAS/STK11 mutant anti-PD1 resistant metastatic human NSCLC in a humanized mouse model

NPRL2/TUSC4 is a potent tumor suppressor gene whose expression is reduced in many cancers including NSCLC. Restoration of NPRL2 expression in cancer cells induces DNA damages which leads to cell cycle arrest and apoptosis. We investigated the antitumor immune responses to NPRL2 gene therapy on anti-PD1 resistant KRAS/STK11 mutant NSCLC in a humanized mouse model. H1299 cells transfected with NPRL2 showed significant inhibition of colony formation after NPRL2 transfection. Humanized mice were generated by transplanting fresh human cord blood derived CD34 stem cells into sub-lethally irradiated NSG mice. The level of engraftment of human CD45, CD3 T, CD19 B, NK cells was verified before tumor implantation. Mice harboring > 25% human CD45 cells were considered humanized. KRAS/STK11 mutant anti-PD1 resistant A549 NSCLC cells were injected intravenously into humanized NSG mice and developed lung metastasis. Metastases were treated with intravenous injection of NPRL2 gene loaded cationic lipid nanoparticles with or without pembrolizumab (anti-PD1). A dramatic antitumor effect was mediated by NPRL2 treatment, whereas pembrolizumab was ineffective. A significant antitumor effect was also found in non-humanized NSG mice, although the effect was greater in humanized mice suggesting that the possible role of antitumor immunity. The antitumor effect of NPRL2 was associated with increased infiltration of human CD45, CD3 T, cytotoxic T, NK cells, and a decreased number of human regulatory T cells (Treg) in tumors. PD1 expressing exhausted CD8 T cells were downregulated in both the NPRL2 and pembrolizumab groups. The number of activated T cells (CD69+CD8+T), effector (EM) and central memory (CM) CD8 T cells were significantly increased by NPRL2 treatment. NPRL2 induced antigen presenting HLA-DR+ dendritic cells. When NPRL2 was combined with pembrolizumab, no synergistic antitumor effect was found in the KRAS/STK11 mutant anti-PD1 insensitive tumors. However, a robust and synergistic antitumor effect was observed in the KRAS wild type, anti-PD1 sensitive H1299 tumors grown in humanized mice treated with NPRL2 + pembrolizumab. Cytotoxic T cells, NK cells, and HLA-DR+ DC were associated with the antitumor effect. DOTAP-NPRL2 was tested in a syngeneic mouse model with LLC2 tumors that are KRAS mutant and anti-PD1 resistant. Consistent with the A549 humanized mouse model, NPRL2 showed a significantly strong antitumor effect whereas anti-PD1 was not effective in this model. The antitumor effect of NPRL2 was again correlated with the upregulation of HLA-DR+ DC, CD11c DC, TILs, NK and downregulation of Treg and myeloid cells in the tumor microenvironment. Taken together, these data suggest that NPRL2 gene therapy induces antitumor activity on KRAS/STK11 mutant anti-PD1 resistant tumors through DC mediated antigen presentation and cytotoxic immune cell activation.

Citation Format: Ismail M. Meraz, Mourad Majidi, Renduo Song, Feng Meng, Gao Lihui, Qi Wang, Jing Wang, Elizabeth Shpall, Jack A. Roth. NPRL2 gene therapy induces effective antitumor immunity in KRAS/STK11 mutant anti-PD1 resistant metastatic human NSCLC in a humanized mouse model. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5120.

Abstract 5354: 3-phosphoinositide-dependent kinase-1 (PDK1, PDPK1) is a driver of osimertinib acquired resistance in EGFR mutant NSCLC

Osimertinib, the only third-generation EGFR-TKI, showed incomplete responses to T790M-mutant NSCLC due to acquired resistance caused by activation of bypass pathways. We developed osimertinib-acquired resistant H1975-OSIR (T790M/L858R mutant) isogenic cells and TC386-OSIR isogenic PDXs. Neither H1975-OSIR nor TC386-OSIR PDXs developed additional mutations in EGFR. The H1975-OSIR clone showed 100 fold higher resistance to osimertinib compared with H1975 cells. TC386-OSIR PDX was developed through continuous in-vivo treatment for 8 months and the residual PDXs were passaged for several generations under continuous osimertinib treatment. TC386-OSIR fourth resistant generation (RG4) showed significantly higher resistance than initial generations (RG1). H1975-OSIR xenografts were developed in non-humanized and humanized NSG mice under osimertinib pressure. H1975-OsiR tumors were significantly less sensitive to osimertinib than their parental counterparts in both mouse models. Dose dependent antitumor activity of osimertinib (5mg/kg and 10mg/kg) was observed in H1975-parental tumors, whereas no treatment effect was observed for H1975-OsiR tumors with increasing doses. The tumor microenvironment was enriched with higher infiltration of tumor associated macrophages (TAM) and lower numbers of tumor infiltrating lymphocytes (TIL) in H1975-OSIR vs H1975 tumors. RPPA analysis of residual tumor tissues showed a distinct set of proteins upregulated in H1975-OsiR vs H1975-parental, among which PDK1 was the most upregulated. PDK1 was also significantly upregulated in H1975-OsiR tumors treated with osimertinib vs controls. PDK1 was not altered in any treatment groups in H1975-parental tumors. PDK1 and pPDK1 expression was many-fold higher in both H1975-OSIR cells and TC386-OSIR PDXs as compared to their parental counterparts by western blot and mass spec proteomics. Selective inhibition by the PDK inhibitor, BX 795, and CRISPR knock-out (KO) restored osimertinib sensitivity in resistant cells. Colony forming assays showed that the PDK1 KO clone was as sensitive as H1975-parental cells whereas a PDK overexpressing clone (OE) restored resistance. In-vivo inhibition of PDK1 by treating mice with BX-795 in both H1975-OSIR xenografts and TC386-OSIR PDXs significantly enhanced the antitumor activity of osimertinib. PDK1 KO dysregulated PI3K/Akt/mTOR signaling by downregulating Akt and mTOR phosphorylation and promoted cell cycle arrest at the G1 phase. NCI-H1975-OSIR and PDK1 OE cells showed a high level of nuclear localization of the activated Yes-associated protein pYAP(Y357). PDK1 KO cells significantly reduced nuclear localization of pYAP(Y357). The level of YAP and pYAP was upregulated in osimertinib resistant xenograft tumors and residual tumor biopsies. Taken together, we identified PDK1 as a drug able target to treat osimertinib acquired resistance.

Citation Format: Ismail M. Meraz, Mourad Majidi, Bingliang Fang, Feng Meng, Lihui Gao, RuPing Shao, Renduo Song, Feng Li, Min Jin Ha, Qi Wang, Jing Wang, Elizabeth Shpall, Sung Yun Jung, Franziska Haderk, Philippe Gui, Jonathan W. Riess, Victor Olivas, Trever G. Bivona, Jack A. Roth. 3-phosphoinositide-dependent kinase-1 (PDK1, PDPK1) is a driver of osimertinib acquired resistance in EGFR mutant NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5354.

TUSC2 immunogene enhances efficacy of chemo-immuno combination on KRAS/LKB1 mutant NSCLC in humanized mouse model

KRAS/LKB1 (STK11) NSCLC metastatic tumors are intrinsically resistant to anti-PD-1 or PD-L1 immunotherapy. In this study, we use a humanized mouse model to show that while carboplatin plus pembrolizumab reduce tumor growth moderately and transiently, the addition of the tumor suppressor gene TUSC2, delivered systemically in nanovesicles, to this combination, eradicates tumors in the majority of animals. Immunoprofiling of the tumor microenvironment shows the addition of TUSC2 mediates: (a) significant infiltration of reconstituted human functional cytotoxic T cells, natural killer cells, and dendritic cells; (b) induction of antigen-specific T cell responses; (c) enrichment of functional central and memory effector T cells; and (d) decreased levels of PD-1⁺ T cells, myeloid-derived suppressor cells, Tregs, and M2 tumor associated macrophages. Depletion studies show the presence of functional central and memory effector T cells are required for the efficacy. TUSC2 sensitizes KRAS/LKB1 tumors to carboplatin plus pembrolizumab through modulation of the immune contexture towards a pro-immune tumor microenvironment.

Meraz et al. explore the antitumor efficacy of TUSC2 tumor suppressor genetherapy via nanovisicles in combination with carboplatin and pembrolizumab against KRAS-LKB1 mutant NSCLC in humanized mouse model. They demonstrate a robust response and perform immune profiling studies, which show the development of a cytotoxic T cell effector response and effector memory cells.

Abstract 76: TUSC2 immunogene therapy enhances efficacy of chemo-immune combination therapy and induces robust antitumor immunity in KRAS-LKB1 mutant NSCLC in humanized mice

Oncogenic KRAS-LKB1 (KL)-mutant NSCLC lung cancers are resistant to immune checkpoint blockade (ICB) therapy due to impaired immunogenicity. Carboplatin plus ICB, the first line of treatment for NSCLC, showed limited efficacy on KL subtypes. TUSC2, a novel immunogene delivered systemically via nanovesicles, induces apoptosis in tumor cells and promotes a variety of innate and adaptive immune responses. We recently developed an improved humanized mouse that reconstitutes a human immune system in NSG mice by transplanting fresh human cord blood derived CD34+ stem cells (Hu-mice). In this study, we evaluated the antitumor immune response of a chemo-immunotherapy combination with TUSC2 on highly metastatic KL-mutant human lung cancer in Hu-mice. Hu-mice were challenged with A549 cells (Krasmt/LKB1-) and lung metastases were treated with TUSC2, nivolumab, or the combination. The results showed a synergistic antitumor effect with the combination. When TUSC2 was combined with pembrolizumab (pembro), a significant antitumor effect was also found, which was correlated with significantly higher levels of T, CD69+ active T, NK and CD69+ active NK and significantly lower levels of MDSC and Treg. Pembro alone significantly reduced tumor burden as compared with control whereas no antitumor effect was observed in non-Hu-mice. The chemo-immune (carbo+pembro) combination significantly reduced tumor burden over chemo or ICB alone. When TUSC2 was added to the chemo+immune combination, metastases regression was significantly greater than either TUSC2, TUSC2+pembro or carbo+pembro treatments. The triple combination in Hu-mice showed significant infiltration of cytotoxic T cells, NK cells and less infiltration of Treg into lung metastasis. The triple treatment also induced an antigen-specific T cell response, which was as shown by the presence of a significantly higher percentage of IFN-γ+ T cells in a co-culture with A549 cells. No IFN-γ+ T cells were found in a co-culture with control lung epithelial cells. Downregulation of PD-1 in TILs and upregulation of matured DC (MHCIIhi CD86+) was found in triple treatment. Significant enrichment of central memory (CM;CCR7+CD45RA-) and effector memory (EM;CCR7-CD45RA-) T cells in triple combination was observed. The EM and CM T cells were functionally active, and showed significantly higher capacity of releasing IFN-γ when stimulated with PMA. Similarly, TUSC2 also showed enhanced efficacy with carbo+aPD1 in highly metastatic KRASmt CMT167 in syngeneic mice. The antitumor effect was linked with increased infiltration of CD8+T, CD3+CD44+ and CD8+CD44+ memory T, NK cells and significantly less Treg cells in the tumor. In conclusion, the triple combination showed strong antitumor efficacy and induced robust antitumor immunity in KL-mutant NSCLC in clinically relevant Hu-mice supporting a clinical trial

Citation Format: Ismail M. Meraz, Mourad Majidi, RuPing Shao, Feng Meng, Min Jin Ha, Elizabeth Shpall, Jack A. Roth. TUSC2 immunogene therapy enhances efficacy of chemo-immune combination therapy and induces robust antitumor immunity in KRAS-LKB1 mutant NSCLC in humanized mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 76.

Abstract 4454: TUSC2 immunogene therapy enhances efficacy of immunotherapy and targeted drugs in human non-small cell lung cancer (NSCLC) in humanized mouse models

TUSC2 is a tumor suppressor gene, whose expression is reduced in almost all NSCLC. Systemic nanovesicle delivery of TUSC2 inhibits cancer cell growth through inhibition of a broad spectrum of kinases and mTOR downregulation as well as stimulation of the immune system through innate activation. We previously reported that TUSC2 downregulates PD-L1 expression in NSCLC and synergizes with anti-PD1 in inhibiting tumor growth in Kras mutant syngeneic mouse models through upregulation of NK and cytotoxic T cells. We developed an improved CD34-derived humanized mouse model (Hu-mice), with faster and higher human immune reconstitution than other available humanized mice, to evaluate immune responses in lung cancer. In this study, we tested whether TUSC2 immunogene therapy would enhance response to standard checkpoint blockade immunotherapy, chemotherapy and targeted therapies in humanized NSG mice implanted with highly metastatic Krasmt/LKB1− A549 cells. A significantly increased antitumor effect was found when TUSC2 was combined with pembrolizumab. Pembrolizumab alone reduced tumor burden as compared with an untreated control, whereas no antitumor effect was observed in non-Hu-mice implanted with A549 cells. The observed antitumor effect correlated with increased levels of CD8+ T and CD8+CD69+ active T, and decreased levels of MDSC and regulatory T cells in the combination group. A significantly higher percentages of CD56+ NK and CD56+CD69+ active NK cells were found in the TUSC2 alone and combination groups indicating TUSC2 related NK activation. Next, we tested whether TUSC2 enhances efficacy to carboplatin+pembrolizumab. The level of antitumor effect of carboplatin+pembrolizumab was similar to that of TUSC2 alone. However, when TUSC2 was combined with carboplatin+pembrolizumab, metastases regression was significantly greater than either TUSC2 alone or carboplatin+pembrolizumab treatments. Significantly fewer or no visible tumor nodules were found in dissected lungs in the TUSC2 combination as compared with other groups. Immune analysis of the triple combination in CMT167 syngeneic mice showed increased infiltration of CD3+ T, CD8+ T, NK cells and significantly less Treg cells into tumor, which was associated with significant tumor inhibition by the treatments. A higher percentage of CD3+CD44+ and CD8+CD44+ memory T cells were found in tumors after carbo+aPD1+TUSC2 treatment, as compared with either Carbo+aPD1 or control groups. The antitumor activity of Carbo+aPD1+TUSC2 was further enhanced when MEKi (Trametinib) was added. Moreover, we also combined TUSC2 with the anti-angiogenic agent, bevacizumab (anti-VEGF) to enhance efficacy in the highly angiogenic 786-O renal cell carcinoma. Synergistic antitumor activity was found with the combination, which was significantly stronger than either single agent. In conclusion, the addition of TUSC2 immunogene therapy with checkpoint blockade, chemotherapy, and targeted therapies showed enhanced antitumor efficacy.

Citation Format: Ismail M. Meraz, Mourad Majidi, Meng Feng, RuPing Shao, Min Jin Ha, Elizabeth J. Shpall, Jack A. Roth. TUSC2 immunogene therapy enhances efficacy of immunotherapy and targeted drugs in human non-small cell lung cancer (NSCLC) in humanized mouse models [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4454.

Abstract A75: Efficacy of novel immunogene combinations for Kras and LKB1 mutant NSCLC in a humanized mouse model

Due to lack of suitability of current preclinical models for immunotherapy research, we recently developed an improved humanized mouse by reconstituting a human immune system in NSG mice by transplanting fresh human cord blood-derived CD34+ stem cells (Hu-mice). The Hu-mice show functional representation of human T, B, natural killer (NK), dendritic cells (DC), myeloid-derived suppressor cells (MDSC), and responsiveness to checkpoint blockade. TUSC2 has recently been recognized as a novel immunogene that induces apoptosis in tumor cells and promotes a wide spectrum of tumor-specific innate and adaptive immune responses. We previously reported that TUSC2 delivered systemically by nanovesicles downregulates PD-L1 expression in NSCLC and synergizes with anti-PD1 in inhibiting tumor growth in Kras-mutant syngeneic mouse models through upregulating NK and cytotoxic T cells. In this study, we aimed to evaluate the antitumor efficacy of TUSC2 in combination with standard immunotherapy on highly metastatic Kras and LKB1 mutant human lung cancer in Hu-mice. Hu-mice were challenged with A549 cells (Krasmt/LKB1-) and lung metastases were treated with TUSC2, nivolumab, or the combination. The results showed a synergistic antitumor effect with the combination. A significantly increased antitumor effect was found when TUSC2 was combined with pembrolizumab in Hu-mice. Pembrolizumab alone significantly reduced tumor burden as compared with an untreated control, whereas no antitumor effect was observed in non-Hu-mice implanted with A549 cells. The antitumor effect was correlated with significantly higher levels of CD8+ T and CD8+CD69+ active T and significantly lower levels of MDSC and regulatory T cells in the combination group. A significantly higher percentage of CD56+ NK and CD56+CD59+ active NK cells was found in the TUSC2 alone and combination groups, indicating TUSC2 related NK activation. We tested whether TUSC2 enhances efficacy to carboplatin+pembrolizumab in Hu-mice implanted with A549-luc metastatic cells. The results showed that the level of antitumor effect of carboplatin+pembrolizumab was similar to that of TUSC2 alone, but when TUSC2 was combined with carboplatin+pembrolizumab, metastases regression was significantly greater than either TUSC2 alone or carboplatin+pembrolizumab treatments. Significantly fewer or no visible tumor nodules were found in dissected lungs in the TUSC2 combination as compared with other groups. In conclusion, TUSC2 immunogene therapy in combination with pembrolizumab and carboplatin+pembrolizumab showed strong antitumor efficacy in metastatic human NSCLC in a clinically relevant humanized mouse model, supporting a clinical trial.

Citation Format: Ismail M. Meraz, Mourad Majidi, Meng Feng, RuPing Shao, Min Jin Ha, Jeffrey Morris, Elizabeth J. Shpall, Jack A. Roth. Efficacy of novel immunogene combinations for Kras and LKB1 mutant NSCLC in a humanized mouse model [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr A75.

An Improved Patient-Derived Xenograft Humanized Mouse Model for Evaluation of Lung Cancer Immune Responses

Human tumor xenograft models do not replicate the human immune system and tumor microenvironment. We developed an improved humanized mouse model, derived from fresh cord blood CD34+ stem cells (CD34+ HSC), and combined it with lung cancer cell line-derived human xenografts or patient-derived xenografts (Hu-PDX). Fresh CD34+ HSCs could reconstitute detectable mature human leukocytes (hCD45+) in mice at four weeks without the onset of graft-versus-host disease (GVHD). Repopulated human T cells, B cells, natural killer (NK) cells, dendritic cells (DC), and myeloid-derived suppressor cells (MDSC) increased in peripheral blood, spleen, and bone marrow over time. Although cultured CD34+ HSCs labeled with luciferase could be detected in mice, the cultured HSCs did not develop into mature human immune cells by four weeks, unlike fresh CD34+ HSCs. Ex vivo, reconstituted T cells, obtained from the tumor-bearing humanized mice, secreted IFNγ upon treatment with phorbol myristate acetate (PMA) or exposure to human A549 lung tumor cells and mediated antigen-specific CTL responses, indicating functional activity. Growth of engrafted PDXs and tumor xenografts was not dependent on the human leukocyte antigen status of the donor. Treatment with the anti-PD-1 checkpoint inhibitors pembrolizumab or nivolumab inhibited tumor growth in humanized mice significantly, and correlated with an increased number of CTLs and decreased MDSCs, regardless of the donor HLA type. In conclusion, fresh CD34+HSCs are more effective than their expanded counterparts in humanizing mice, and do so in a shorter time. The Hu-PDX model provides an improved platform for evaluation of immunotherapy.

Abstract 4984: Development of an improved humanized patient-derived xenograft, Hu-PDX, mouse model for evaluation of antitumor immune response in lung cancer

Current preclinical models of non-small cell lung cancer (NSCLC) do not recapitulate the human tumor microenvironment. Mice reconstituted with a human immune system and bearing human patient derived xenografts may be advantageous in evaluating human anti-tumor immune response. We developed an improved NOD scid gamma (NSG) mouse model derived from non-expanded CD34+ stem cells, without CD3+ T cell contamination, to evaluate antitumor responses to immunotherapy in NSCLC. Using fresh CD34+ from umbilical cord blood reduced humanization time significantly. Human CD45+ cell reconstitution with increased functional human lymphoid (B, T, monocytes and NK cells) and myeloid (macrophages and MDSCs) lineage repopulation, without the onset of GvHD, was achieved as early as 4 weeks post-stem cell engraftment. Published studies using expanded CD34+ derived humanization reveal compromised purity of CD34+ stem cells with an increasing number of mononuclear cells. Reconstitution of CD8+ and CD4+T cells is not achieved until 12 to 15 weeks post-engraftment at much lower levels than fresh CD34+ humanization. Single cell suspension analysis shows levels of human reconstituted T, B, NK, DC and MDSC cells at 4 weeks, which increased significantly at 6 and 9 weeks in peripheral blood, spleen and bone marrow. Human repopulated T cells were functionally active in secretion of IFN-γ by mitogenic stimuli such as PMA and IL-2 and by allogenic human cancer cells. Antigen specific CTL responses were observed when reconstituted human T cells from PDX bearing humanized mice were challenged with PDX tumor. No non-antigen specific responses were observed when T cells were co-cultured with HLA-matched human bronchial epithelial cells (HBEC). To evaluate the applicability of the humanized mouse in lung cancer translational research, we combined it with Hu-PDX or Hu-xenograft tumors and analyzed tumor growth and treatment response to the anti-PD1 checkpoint inhibitor pembrolizumab. We found that efficient engraftment of PDXs and xenograft tumors were not dependent on donor HLA-status. Similar to the clinical outcome, treatment with pembrolizumab, inhibited tumor growth significantly in both Hu-PDX, and Hu-xenograft mice regardless of donor HLA-types, increasing cytotoxic T cells and decreasing MDSC levels. Pembrolizumab had no effect on the non-humanized NSG controls. In concordance with our previous study with a syngeneic mouse tumor, the antitumor effect of check point blockade was significantly enhanced when combined with nanoparticle systemically deliveredTUSC2, a tumor suppressor and immunomodulatory gene, in a KRAS mutant lung metastasis humanized mouse model. In conclusion, fresh CD34+ are more effective than their expanded counterparts in humanizing mice, do so in much reduced time, and recapitulate the immune response to cancer.

Citation Format: Ismail M. Meraz, Mourad Majidi, Feng Meng, RuPing Shao, Min Jin Ha, Shinya Neri, Bingliang Fang, Steven H. Lin, Peggy T. Tinkey, Elizabeth J. Shpall, Jeffrey Morris, Jack A. Roth. Development of an improved humanized patient-derived xenograft, Hu-PDX, mouse model for evaluation of antitumor immune response in lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4984.

Patient-derived tumor immune microenvironments in patient-derived xenografts of lung cancer

Background

Because patient-derived xenografts (PDXs) are grown in immunodeficient mouse strains, PDXs are regarded as lacking an immune microenvironment. However, whether patients’ immune cells co-exist in PDXs remains uncharacterized.

Methods

We cultured small pieces of lung PDX tissue in media containing human interleukin-2 and characterized the proliferated lymphocytes by flow cytometric assays with antibodies specific for human immune cell surface markers. Presence of immune cells in PDXs was also determined by immunohistochemical staining.

Results

Human tumor-infiltrating lymphocytes (TILs) were cultured from nine of 25 PDX samples (36%). The mean time of PDX growth in immunodeficient mice before obtaining TILs in culture was 113 days (range 63–292 days). The TILs detected in PDXs were predominantly human CD8⁺ T cells, CD4⁺ T cells, or CD19⁺ B cells, depending on cases. DNA fingerprint analysis showed that the TILs originated from the same patients as the PDXs. Further analysis of two PDX-derived CD8⁺ T cells showed that they were PD-1⁻, CD45RO⁺, and either CD62L⁺ or CD62L⁻, suggesting they were likely memory T cells. Immunohistochemical staining showed that human T cells (CD8⁺ or CD4⁺), B cells (CD19⁺), and macrophages (CD68⁺) were present in stroma or intraepithelial cancer structures and that human PD-L1 was expressed in stromal cells. Moreover, the patient-derived immune cells in PDX can be passaged to the F2 generation and may migrate to spleens of PDX-bearing mice.

Conclusions

Patient-derived immune cells co-exist in early passages of PDXs in some lung cancer PDX models. The CD8⁺ cells from PDXs were likely memory T cells. These results suggest that PDXs can be used for evaluating the functionality of immune components in tumor microenvironments.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1704-3) contains supplementary material, which is available to authorized users.

TUSC2 Immunogene Therapy Synergizes with Anti-PD-1 through Enhanced Proliferation and Infiltration of Natural Killer Cells in Syngeneic Kras-Mutant Mouse Lung Cancer Models

Expression of the multikinase inhibitor encoded by the tumor suppressor gene TUSC2 (also known as FUS1) is lost or decreased in non-small cell lung carcinoma (NSCLC). TUSC2 delivered systemically by nanovesicles has mediated tumor regression in clinical trials. Because of the role of TUSC2 in regulating immune cells, we assessed TUSC2 efficacy on antitumor immune responses alone and in combination with anti-PD-1 in two Kras-mutant syngeneic mouse lung cancer models. TUSC2 alone significantly reduced tumor growth and prolonged survival compared with anti-PD-1. When combined, this effect was significantly enhanced, and correlated with a pronounced increases in circulating and splenic natural killer (NK) cells and CD8⁺ T cells, and a decrease in regulatory T cells (Tregs), myeloid-derived suppressor cells (MDSCs), and T-cell checkpoint receptors PD-1, CTLA-4, and TIM-3. TUSC2 combined with anti-PD-1 induced tumor infiltrating more than NK and CD8⁺ T cells and fewer MDSCs and Tregs than each agent alone, both in subcutaneous tumor and in lung metastases. NK-cell depletion abrogated the antitumor effect and Th1-mediated immune response of this combination, indicating that NK cells mediate TUSC2/anti-PD-1 synergy. Release of IL15 and IL18 cytokines and expression of the IL15Rα chain and IL18R1 were associated with NK-cell activation by TUSC2. Immune response-related gene expression in the tumor microenvironment was altered by combination treatment. These data provide a rationale for immunogene therapy combined with immune checkpoint blockade in the treatment of NSCLC. Cancer Immunol Res; 6(2); 163-77. ©2018 AACR.

Overcoming resistance to anti-PD immunotherapy in a syngeneic mouse lung cancer model using locoregional virotherapy

Anti-PD-1 and anti-PD-L1 immunotherapy has provided a new therapeutic opportunity for treatment of advanced-stage non-small cell lung cancer (NSCLC). However, overall objective response rates are approximately 15%-25% in all NSCLC patients who receive anti-PD therapy. Therefore, strategies to overcome primary resistance to anti-PD immunotherapy are urgently needed. We hypothesized that the barrier to the success of anti-PD therapy in most NSCLC patients can be overcome by stimulating the lymphocyte infiltration at cancer sites through locoregional virotherapy. To this end, in this study, we determined combination effects of anti-PD immunotherapy and oncolytic adenoviral vector-mediated tumor necrosis factor-α-related apoptosis-inducing ligand (TRAIL) gene therapy (Ad/E1-TRAIL) or adenoviral-mediated TP53 (Ad/CMV-TP53) gene therapy in syngeneic mice bearing subcutaneous tumors derived from M109 lung cancer cells. Both anti-PD-1 and anti-PD-L1 antibodies failed to elicit obvious therapeutic effects in the M109 tumors. Intratumoral administration of Ad/E1-TRAIL or Ad/CMV-TP53 alone suppressed tumor growth in animals preexposed to an adenovector and bearing subcutaneous tumors derived from M109 cells. However, combining either anti-PD-1 or anti-PD-L1 antibody with these two adenoviral vectors elicited the strongest anticancer activity in mice with existing immunity to adenoviral vectors. Dramatically enhanced intratumoral immune response was detected in this group of combination therapy based on infiltrations of CD4+ and CD8+ lymphocytes and macrophages in tumors. Our results demonstrate that resistance to anti-PD-1 immunotherapy in syngeneic mouse lung cancer can be overcome by locoregional virotherapy.

Abstract 621: Tumor suppressor TUSC2 immunogene therapy is synergistic with anti-PD1 in lung cancer syngeneic mouse models

TUSC2, a pro-apoptotic tumor suppressor gene whose expression is lost or decreased in most lung cancers, activates the innate immune system through initiation of broad spectrum cytokine secretion and natural killer (NK) cell activation. TUSC2 delivered systemically by nanovesicles has mediated tumor regression in metastatic non-small cell lung cancer clinical trials. We studied the effect of TUSC2 on immune cell populations and the anti-tumor activity of TUSC2 in combination with anti-PD1 checkpoint blockade in two syngeneic mouse models: C57BL/6 mice subcutaneously injected with murine lung adenocarcinoma cell line CMT/167-luc cells (KrasG12V mutation) and 344SQ (KrasG12D allele and a knock-in Trp53R172HΔG allele) adenocarcinomas which metastasize to the lung in 129S2 mice. Tumor growth was monitored by scoring ex-vivo luminescence using the IVIS Imaging System 200. Multi-color flow cytometry was used for immune profiling of circulating immune cells after nanovesicle mediated TUSC2 intravenous injection. Cytokine gene expression in response to TUSC2 in sorted immune subpopulations was determined by real-time PCR. Tumor growth was significantly reduced with TUSC2 treatment compared with no treatment in both subcutaneous and metastatic mouse models. Synergistic anti-tumor activity was observed when TUSC2 was combined with anti-PD1 verified in five independent experiments. In the lung metastasis model, mice treated with TUSC2 + anti-PD1 lived significantly longer than with single agent treatment. Circulating NK cells increased three fold following TUSC2 nanovesicle intravenous injection both in tumor free and tumor bearing mice which correlated with tumor regression and survival. Cytotoxic T lymphocyte responses were increased whereas Tregs and MDSCs decreased with TUSC2 alone and TUSC2+anti-PD1 treatment. The levels of T cell checkpoint markers PD1, CTLA-4, LAG-3, and TIM-3 evaluated by flow cytometry were decreased after TUSC2 treatment. TUSC2 anti-tumor response was abolished when NK cells were depleted indicating NK cells are important mediators of the TUSC2 treatment effect. Single cell suspension analysis by flow cytometry showed high numbers of NK cells infiltrating lung tumor metastases after TUSC2 treatment. The number of tumor nodules in the lung was significantly less following treatment with TUSC2 nanovesicles compared with control. IL-15 gene expression which mediates NK cell proliferation, was increased by TUSC2. In conclusion, systemic TUSC2 nanovesicle immunogene therapy combined with checkpoint blockade showed synergistic anti-tumor efficacy and activated the immune system through upregulation of NK cells and CTL and downregulation of regulatory cells.

Citation Format: Ismail M. Meraz, Mourad Majidi, RuPing Shao, Meng Feng, Xiaobo Cao, David Rice, Boris Sepesi, Lin Ji, Jack Roth. Tumor suppressor TUSC2 immunogene therapy is synergistic with anti-PD1 in lung cancer syngeneic mouse models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 621. doi:10.1158/1538-7445.AM2017-621

Serine Proteases Enhance Immunogenic Antigen Presentation on Lung Cancer Cells

Immunotherapies targeting immune checkpoints have proven efficacious in reducing the burden of lung cancer in patients; however, the antigenic targets of these reinvigorated T cells remain poorly defined. Lung cancer tumors contain tumor-associated macrophages (TAM) and neutrophils, which release the serine proteases neutrophil elastase (NE) and proteinase 3 (P3) into the tumor microenvironment. NE and P3 shape the antitumor adaptive immune response in breast cancer and melanoma. In this report, we demonstrate that lung cancer cells cross-presented the tumor-associated antigen PR1, derived from NE and P3. Additionally, NE and P3 enhanced the expression of human leukocyte antigen (HLA) class I molecules on lung cancer cells and induced unique, endogenous peptides in the immunopeptidome, as detected with mass spectrometry sequencing. Lung cancer patient tissues with high intratumoral TAMs were enriched for MHC class I genes and T-cell markers, and patients with high TAM and cytotoxic T lymphocyte (CTL) infiltration had improved overall survival. We confirmed the immunogenicity of unique, endogenous peptides with cytotoxicity assays against lung cancer cell lines, using CTLs from healthy donors that had been expanded against select peptides. Finally, CTLs specific for serine proteases-induced endogenous peptides were detected in lung cancer patients using peptide/HLA-A2 tetramers and were elevated in tumor-infiltrating lymphocytes. Thus, serine proteases in the tumor microenvironment of lung cancers promote the presentation of HLA class I immunogenic peptides that are expressed by lung cancer cells, thereby increasing the antigen repertoire that can be targeted in lung cancer. Cancer Immunol Res; 5(4); 319-29. ©2017 AACR.

Reduced Cationic Nanoparticle Cytotoxicity Based on Serum Masking of Surface Potential

Functionalization of nanoparticles with cationic moieties, such as polyethyleneimine (PEI), enhances binding to the cell membrane; however, it also disrupts the integrity of the cell's plasma and vesicular membranes, leading to cell death. Primary fibroblasts were found to display high surface affinity for cationic iron oxide nanoparticles and greater sensitivity than their immortalized counterparts. Treatment of cells with cationic nanoparticles in the presence of incremental increases in serum led to a corresponding linear decrease in cell death. The surface potential of the nanoparticles also decreased linearly as serum increased and this was strongly and inversely correlated with cell death. While low doses of nanoparticles were rendered non-toxic in 25% serum, large doses overcame the toxic threshold. Serum did not reduce nanoparticle association with primary fibroblasts, indicating that the decrease in nanoparticle cytotoxicity was based on serum masking of the PEI surface, rather than decreased exposure. Primary endothelial cells were likewise more sensitive to the cytotoxic effects of cationic nanoparticles than their immortalized counterparts, and this held true for cellular responses to cationic microparticles despite the much lower toxicity of microparticles compared to nanoparticles.

A New Imaging Platform for Visualizing Biological Effects of Non-Invasive Radiofrequency Electric-Field Cancer Hyperthermia

Herein, we present a novel imaging platform to study the biological effects of non-invasive radiofrequency (RF) electric field cancer hyperthermia. This system allows for real-time in vivo intravital microscopy (IVM) imaging of radiofrequency-induced biological alterations such as changes in vessel structure and drug perfusion. Our results indicate that the IVM system is able to handle exposure to high-power electric-fields without inducing significant hardware damage or imaging artifacts. Furthermore, short durations of low-power (< 200 W) radiofrequency exposure increased transport and perfusion of fluorescent tracers into the tumors at temperatures below 41°C. Vessel deformations and blood coagulation were seen for tumor temperatures around 44°C. These results highlight the use of our integrated IVM-RF imaging platform as a powerful new tool to visualize the dynamics and interplay between radiofrequency energy and biological tissues, organs, and tumors.

Abstract 2594: Adjuvant cationic nanoliposomes induce anti-cancer immunity in a murine model of breast cancer

Nanoparticles, such as liposomes, provide opportunities to simultaneously present antigens and immune modulators. Using a 4T1 murine model of breast cancer, a cationic nanoliposomal formulation containing monophosphoryl lipid A and the cationic lipid 1,2-dioleoyl-3-trimethylammonium-propane induced anti-tumor activity following intratumoral administration. Addition of recombinant interleukin-12 (IL-12) further suppressed tumor growth and augmented T helper-1 cell (Th-1) polarization, with enhanced tumor infiltration by cytotoxic T cells, dendritic cells, and M1 macrophages, and amplification of interferon gamma secretion. Mice bearing dual tumors displayed arrest of tumor growth in treated tumors as well as distal, untreated tumors following combination therapy with adjuvant nanoliposomes and IL-12. In summary, adjuvant MPL-liposomes combined with localized IL-12 therapy block tumor growth, stimulate a Th-1 bias of the tumor microenvironment, and induce cancer-specific immune responses.

Citation Format: Ismail M. Meraz, David J. Savage, Jianhua Gu, Jessica Rhudy, Rita E. Serda. Adjuvant cationic nanoliposomes induce anti-cancer immunity in a murine model of breast cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2594. doi:10.1158/1538-7445.AM2014-2594

Adjuvant cationic liposomes presenting MPL and IL-12 induce cell death, suppress tumor growth, and alter the cellular phenotype of tumors in a murine model of breast cancer

Dendritic cells (DC) process and present antigens to T lymphocytes, inducing potent immune responses when encountered in association with activating signals, such as pathogen-associated molecular patterns. Using the 4T1 murine model of breast cancer, cationic liposomes containing monophosphoryl lipid A (MPL) and interleukin (IL)-12 were administered by intratumoral injection. Combination multivalent presentation of the Toll-like receptor-4 ligand MPL and cytotoxic 1,2-dioleoyl-3-trmethylammonium-propane lipids induced cell death, decreased cellular proliferation, and increased serum levels of IL-1β and tumor necrosis factor (TNF)-α. The addition of recombinant IL-12 further suppressed tumor growth and increased expression of IL-1β, TNF-α, and interferon-γ. IL-12 also increased the percentage of cytolytic T cells, DC, and F4/80(+) macrophages in the tumor. While single agent therapy elevated levels of nitric oxide synthase 3-fold above basal levels in the tumor, combination therapy with MPL cationic liposomes and IL-12 stimulated a 7-fold increase, supporting the observed cell cycle arrest (loss of Ki-67 expression) and apoptosis (TUNEL positive). In mice bearing dual tumors, the growth of distal, untreated tumors mirrored that of liposome-treated tumors, supporting the presence of a systemic immune response.

Characterization of Free and Porous Silicon-Encapsulated Superparamagnetic Iron Oxide Nanoparticles as Platforms for the Development of Theranostic Vaccines

Tracking vaccine components from the site of injection to their destination in lymphatic tissue, and simultaneously monitoring immune effects, sheds light on the influence of vaccine components on particle and immune cell trafficking and therapeutic efficacy. In this study, we create a hybrid particle vaccine platform comprised of porous silicon (pSi) and superparamagnetic iron oxide nanoparticles (SPIONs). The impact of nanoparticle size and mode of presentation on magnetic resonance contrast enhancement are examined. SPION-enhanced relaxivity increased as the core diameter of the nanoparticle increased, while encapsulation of SPIONs within a pSi matrix had only minor effects on T2 and no significant effect on T2* relaxation. Following intravenous injection of single and hybrid particles, there was an increase in negative contrast in the spleen, with changes in contrast being slightly greater for free compared to silicon encapsulated SPIONs. Incubation of bone marrow-derived dendritic cells (BMDC) with pSi microparticles loaded with SPIONs, SIINFEKL peptide, and lipopolysaccharide stimulated immune cell interactions and interferon gamma production in OT-1 TCR transgenic CD8⁺ T cells. Overall, the hybrid particle platform enabled presentation of a complex payload that was traceable, stimulated functional T cell and BMDC interactions, and resolved in cellular activation of T cells in response to a specific antigen.

Abstract B25: Porous silicon microparticles exhibit immunomodulatory effects leading to suppression of tumor growth

Nanoparticles, such as polymeric delivery platforms, can exhibit intrinsic immunostimulant properties, dependent on size, charge, surface modification, and composition. To function as effective adjuvants, a balance between immunostimulatory properties and biocompatibility is essential. We have demonstrated that porous silicon (pSi) microparticles are effective delivery vehicles, with uptake by target cell populations. A peritonitis mouse model was used to access early innate immune responses 24 hours following administration of pSi microparticles. C57BL/6 mice were injected intraperitoneally with microparticles of various shapes and sizes and cytokine production and cell infiltration were assessed. pSi microparticles were found to have proinflammatory effects. The microparticles induced significant leukocyte infiltration into the site of injection and elevated IL-1β levels in lavage fluid.

As cancer progresses, immune responses become more tolerant and cancer cells become more refractory to chemotherapies. Select chemotherapeutics, including cyclophosphamide, doxorubicin, and paclitaxel, have immunodulatory effects. Based on the immunopotentiating effects of pSi microparticles, and the ability of monophosphoryl lipid A (MPL) adsorbed pSi microparticles to activate antigen presenting cells, we sought to potentiate the doxorubicin-mediated immune response through co-delivery of MPL-pSi microparticles. When tumors in mice bearing intramammary 4T1-luc breast tumors reached a volume of 100 mm3, mice were injected with doxorubicin loaded liposomes (5 mg/kg) and MPL-pSi microparticles (5x108 microparticles; 10 µg MPL equivalent) by means of tail vein injection. Tumor growth was monitored by calipher measurements and luciferase expression using the IVIS Imaging System 200. While MPL-pSi microparticle-treated mice exhibited reduced tumor growth, mice receiving MPL-pSi microparticles and doxorubicin-loaded liposomes exhibited arrest of tumor growth. Thus pSi microparticles are an attractive immunopotentiating platform, with applications for both drug and antigen delivery.

Citation Format: Ismail M. Meraz, Laura Williams, Marie Yang, Edward C. Lavelle, Rita E. Serda. Porous silicon microparticles exhibit immunomodulatory effects leading to suppression of tumor growth. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology: Multidisciplinary Science Driving Basic and Clinical Advances; Dec 2-5, 2012; Miami, FL. Philadelphia (PA): AACR; Cancer Res 2013;73(1 Suppl):Abstract nr B25.

Activation of the inflammasome and enhanced migration of microparticle-stimulated dendritic cells to the draining lymph node

Porous silicon microparticles presenting pathogen-associated molecular patterns mimic pathogens, enhancing internalization of the microparticles and activation of antigen presenting dendritic cells. We demonstrate abundant uptake of microparticles bound by the TLR-4 ligands LPS and MPL by murine bone marrow-derived dendritic cells (BMDC). Labeled microparticles induce concentration-dependent production of IL-1β, with inhibition by the caspase inhibitor Z-VAD-FMK supporting activation of the NLRP3-dependent inflammasome. Inoculation of BALB/c mice with ligand-bound microparticles induces a significant increase in circulating levels of IL-1β, TNF-α, and IL-6. Stimulation of BMDC with ligand-bound microparticles increases surface expression of costimulatory and MHC molecules, and enhances migration of BMDC to the draining lymph node. LPS-microparticles stimulate in vivo C57BL/6 BMDC and OT-1 transgenic T cell interactions in the presence of OVA SIINFEKL peptide in lymph nodes, with intact nodes imaged using two-photon microscopy. Formation of in vivo and in vitro immunological synapses between BMDC, loaded with OVA peptide and LPS-microparticles, and OT-1 T cells are presented, as well as elevated intracellular interferon gamma levels in CD8(+) T cells stimulated by BMDC carrying peptide-loaded microparticles. In short, ligand-bound microparticles enhance (1) phagocytosis of microparticles; (2) BMDC inflammasome activation and upregulation of costimulatory and MHC molecules; (3) cellular migration of BMDC to lymphatic tissue; and (4) cellular interactions leading to T cell activation in the presence of antigen.

Abstract 1565: Mesoporous silicon particle mediated dendritic cell based vaccine formulation showed stronger immunoresponse for the presentation of tumor antigens and adjuvant

Dendritic cell (DC) based immunotherapy is being used for cancer therapy in various clinical trials. During evaluation of recent clinical studies, it became apparent that efficient DC-based immunotherapy is dependent on a number of factors, such as the mode of antigen presentation, maturation of DC, injection site, and vaccination dosing. Major limiting factors for DC-based vaccines are insufficient loading of antigens by DC and poor migratory capacity of DC to lymph nodes. Nanotechnology provides tools to load large payloads of antigens and adjuvants in particles for uptake by DC. Toll-like receptor (TLR) ligands have been proposed as vaccine adjuvants for boosting adaptive immunity in cancer therapy. TLR signaling induces DC activation that is characterized by enhanced expression of costimulatory molecules and increased secretion of cytokines necessary for activation and differentiation of naive T cells. In this study, we have used porous silicon (pSi) microparticles to create a novel vaccine. We have demonstrated that porous silicon particles can be decorated with TLR-ligands using lipopolysaccharide (LPS) or monophosphoryl lipid (MPL). This decorated particles are substrates for bone marrow-derived DC internalization, leading to cellular uptake and activation and enhanced migration of DC to lymph nodes. Confocal and scanning electron microscopy, as well as flow cytometry studies supported higher uptake of LPS and MPL conjugated particles as compared to unlabeled particles. TLR ligands induced morphological changes in GM-CSF-stimulated bone marrow cells during particle uptake consistent with classical DC dentron formation. Stimulated antigen presenting cells also expressed elevated levels of costimulatory (e.g. CD80, CD86) and major histocompatibility molecules (MHC), and secreted pro-inflammatory cytokines both in vitro and in vivo. Ex-vivo processed DC loaded with TLR ligand coated pSi showed enhanced migration to lymph node as compared with empty DC when injected mice subcutaneously. As expected, LPS conjugation to particles showed toxicity towards DC whereas MPL conjugated pSi showed little or no toxicity.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1565. doi:1538-7445.AM2012-1565

P1-01-12: Mesoporous Silicon Particles for the Presentation of Tumor Antigens and Adjuvant for Anti-Cancer Immunity

Custom-made vaccines based on personalized tumor antigens are realistic options for secondary therapy, with the patient's excised tumor providing antigens. Overlap in the personalized repertoire of tumor antigens among patients also provides insight into targets for preventative cancer vaccines. Nanotechnology provides carriers for shielded delivery of antigens and presentation of immunostimulatory molecules. Rapid uptake of particles by phagocytic immune cells and migration to lymphatic tissue for antigen presentation provides opportunities to elicit tumor specific immune responses. Dendritic cells (DC) are the master antigen presenting cells (APC) for efficient processing and presentation of antigens. We have tested the ability of mesoporous silicon particles (pSi) to function as substrates for DC and to activate cells via engagement of surface toll-like receptors (TLR). pSi particles, surface labeled with lipopolysaccharide (LPS) or monophosphoryl lipid (MPL), were presented to bone marrow-derived DC. This resulted in rapid uptake of particles, with an enormous capacity for number of particles internalized per cell. Confocal microscopy studies supported higher uptake of LPS and MPL conjugated as compared to unlabeled pSi. pSi particle uptake into DC was also supported by electron microscopy imaging. TLR ligands induced morphological changes in GM-CSF stimulated cells consistent with maturation towards a DC phenotype. As expected, LPS conjugation to particles resulted in significant toxicity. MPL conjugated pSi showed little or no toxicity to DC and showed improved particle uptake into DC with morphological changes consistent with maturation towards a mature DC phenotype.The impact of cytokine cocktail on DC maturation and its impact on particle uptake were also examined. Flow cytometry analysis supported greater uptake of pSi by DC stimulated with GM-CSF and IL-4 compared to GM-CSF alone, with reduced uptake in the presence of TNF-alpha. Consistent with findings reported by others, addition of TNF-alpha to the cell media also resulted in higher levels of expression of costimulatory molecules by DC, compared to cells stimulated with GM-CSF alone. Thus immature DC are better able to internalize particle-based vaccines, with cytokine or TLR-driven maturation enhancing expression of costimulatory molecules for more effective antigen presentation.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P1-01-12.

Enterotoxigenic Escherichia coli and diffusely adherent E. coli as likely causes of a proportion of pathogen-negative travelers' diarrhea--a PCR-based study

BACKGROUND

Enteropathogens cannot be identified in 40% to 50% of subjects with travelers' diarrhea (TD).

METHODS

We used polymerase chain reaction (PCR) methods to look for the presence of two bacterial causes of diarrhea in a large group of international travelers after failing to detect a pathogen by conventional tests. DNA was isolated from the diarrheal stool and subjected to PCR from 162 subjects from whom we earlier failed to identify a pathogen in a previous study and included 54 from Antigua, Guatemala, 39 from Guadalajara, Mexico, 29 from Kolkata, India, and 40 from Goa, India. Gene products for enterotoxigenic Escherichia coli (ETEC)--LT (heat-labile enterotoxin) and ST (heat-stable enterotoxin)--and diffusely adherent E. coli (DAEC), afa/dr (Afa fimbrial and Dr nonfimbrial family of adhesins), were used.

RESULTS

At least one gene product was identified in diarrhea stool samples of 47 of 162 (29%) subjects. ETEC virulence genes (LT, ST) were found in 34 (21%) samples studied, with rates of occurrence ranging from 8% in Goa to 39% for the samples from Guatemala (p = 0.0006). A large number of ST-only strains explained the high ETEC rate in Guatemala. DAEC afa/dr family of adhesions was identified in between 8 and 14% of the samples.

CONCLUSIONS

ETEC and DAEC were implicated in nearly one-third of the subjects initially diagnosed as pathogen negative. Direct PCR results from stools are consistent with the previous assumption that most undiagnosed TD is bacterial in nature and also highlights the potential value that PCR can add to studies designed to evaluate treatment and preventive interventions for TD, including vaccines.