Chaperonin containing TCP-1 (CCT/TRiC) is a novel therapeutic and diagnostic target for neuroblastoma

Chaperonin containing TCP1 (CCT/TRiC) is a multi-subunit protein folding complex that enables the cancer phenotype to emerge from the mutational landscape that drives oncogenesis. We and others linked increased expression of CCT subunits to advanced tumor stage and invasiveness that inversely correlates with cancer patient outcomes. In this study, we examined the expression of the second CCT subunit, CCT2, using genomic databases of adult and pediatric tumors and normal tissues, and found that it was highly expressed in pediatric cancers, showing a significant difference compared to normal tissues. Histologic staining confirmed that CCT subunits are highly expressed in tumor tissues, which was exemplified in neuroblastoma. Using two neuroblastoma cells, MYCN-amplified, IMR-32 cells, and non-amplified, SK-N-AS cells, we assessed baseline levels for CCT subunits and found expressions comparable to the highly invasive triple-negative breast cancer (TNBC) cell line, MDA-MB-231. Exogenous expression of CCT2 in both SK-N-AS and IMR-32 cells resulted in morphological changes, such as larger cell size and increased adherence, with significant increases in the CCT substrates, actin, and tubulin, as well as increased migration. Depletion of CCT2 reversed these effects and reduced cell viability. We evaluated CCT as a therapeutic target in IMR-32 cells by testing a novel peptide CCT inhibitor, CT20p. Treatment with CT20p induced cell death in these neuroblastoma cells. The use of CCT2 as a biological indicator for detection of neuroblastoma cells shed in blood was examined by spiking IMR-32 cells into human blood and using an anti-CCT2 antibody for the identification of spiked cancer cells with the CellSearch system. Results showed that using CCT2 for the detection of neuroblastoma cells in blood was more effective than the conventional approach of using epithelial markers like cytokeratins. CCT2 plays an essential role in promoting the invasive capacity of neuroblastoma cells and thus offers the potential to act as a molecular target in the development of novel therapeutics and diagnostics for pediatric cancers.

Identification of a novel IL-5 signaling pathway in chronic pancreatitis and crosstalk with pancreatic tumor cells

BACKGROUND

While inflammation is associated with pancreatic cancer, the underlying mechanisms leading to cancer initiation are still being delineated. Eosinophils may promote or inhibit tumor growth, although the specific role in pancreatic cancer has yet to be determined. Eosinophil-supporting cytokine interleukin-5 and receptor are likely to have a role, but the significance in the pancreatic cancer microenvironment is unknown.

METHODS

Genetically engineered Akt1^Myr/KRas^G12D and KRas^G12D mice were used to model changes induced by chronic inflammation. Tissue samples were collected to analyze the tumor microenvironment and infiltration of immune cells, whereas serum was collected to analyze cytokine and amylase activity in the inflammatory model. The expression of IL-5R and the effects of IL-5 were analyzed in human and murine tumor cells.

RESULTS

Compound Akt1^Myr/KRas^G12D mice, compared to single KRas^G12D or Akt1^Myr mice, exhibited increased tissue damage after repeat inductions of inflammation, and had accelerated tumor development and metastasis. M2 macrophages and newly identified eosinophils co-localized with fibrotic regions rather than infiltrating into tumors, consistent with immune cell privilege. The majority of eosinophils found in the pancreas of Akt1^Myr/KRas^G12D mice with chronic inflammation lacked the cytotoxic NKG2D marker. IL-5 expression was upregulated in pancreatic cells in response to inflammation, and then diminished in advanced lesions. Although not previously described in pancreatic tumors, IL-5Rα was increased during mouse pancreatic tumor progression and expressed in human pancreatic ductal adenocarcinomas (7 of 7 by immunohistochemistry). IL-5 stimulated tumor cell migration and activation through STAT5 signaling, thereby suggesting an unreported tumor-promoting role for IL-5Rα in pancreatic cancer.

CONCLUSIONS

Chronic inflammation induces increased pancreatic cancer progression and immune cells such as eosinophils are attracted to areas of fibrosis. Results suggest that IL-5 in the pancreatic compartment stimulates increased IL-5Rα on ductal tumor cells to increase pancreatic tumor motility. Collectively, IL-5/IL-5Rα signaling in the mouse and human pancreatic tumors microenvironment is a novel mechanism to facilitate tumor progression. Additional file 1: Video Abstract.

Targeting chaperonin containing TCP1 (CCT) as a molecular therapeutic for small cell lung cancer

Identifying new druggable targets is desired to meet the needs for effective cancer treatments. To this end, we previously reported the efficacy of a therapeutic peptide called CT20p that displays selective cytotoxicity through inhibition of a multi-subunit, protein-folding complex called Chaperonin-Containing TCP-1 (CCT). To investigate the role of CCT in cancer progression, we examined protein levels of CCT subunits in liver, prostate, and lung cancer using human tissue microarrays. We found that these cancers expressed higher levels of CCT2 as compared to normal tissues. Small cell lung cancer (SCLC) stood out as having statistically significant difference in CCT2. Higher levels of CCT2 in tumors from lung cancer patients were also associated with decreased survival. Using SCLC cell lines, we observed detectable amounts of CCT subunits and cells were susceptible to killing by CT20p. Treatment with CT20p, delivered to cells using polymeric nanoparticles, was cytotoxic to all SCLC cell lines, decreasing the levels of CCT client proteins like STAT3. In contrast, treatment with a STAT3 inhibitor was effective in one of the SCLC cell lines. While we found that CCT levels could vary in cell lines, normal tissues had low levels of CCT and minimal toxicity to liver or kidney function was observed in mice treated with CT20p. These results indicate that in SCLC, changes in CCT levels could be used as a biomarker for diagnosis and that targeting CCT for inhibition with CT20p is a promising treatment approach for those cancers such as SCLC that currently lack targeted therapeutics.

Abstract 4895: CT20p as a therapeutic for lung cancer with elevated chaperoning containing TCP1 (CCT) expression levels

Lung cancer is the leading cause of cancer related fatalities worldwide and although there is a substantial effort in the development of improved, more specific, and less debilitating therapies, very little progress has been made accomplishing this goal. We propose the use of CT20p, a therapeutic peptide developed by our laboratory, as novel therapy for lung cancer. We have previously demonstrated that CT20p has tumor specific cytotoxicity in breast cancer cells and it induces tumor regression in xenograft models of breast cancer. We have also determined Chaperonin containing T-complex (CCT) to be the intracellular target of CT20p and that susceptibility to CT20p correlates with its expression levels, with tumor cells expressing high levels of CCT being the most susceptible. CCT is a large macromolecular complex composed of 8 subunits (CCTα, CCTβ, CCTγ, CCTδ, CCTϵ, CCTζ, CCTη, CCTθ). Immunoblot probing against four relevant CCT subunits (CCTβ, CCTγ, CCTδ, CCTϵ) was used to determine their relative expression level in five small cell lung cancer (SCLC) cell lines when compared to normal lung cells. We determined that the expression levels of the four probed CCT subunits varied amongst the five SCLC cell lines, however, the four CCT subunits were always expressed at higher levels when compared to normal lung cells. Immunohistochemistry staining for CCTβ was used on tissue microarray (TMA) of lung cancer progression. Results were interpreted on a scale of 1 to 4 (with 4 being the strongest staining). We determined that CCTβ levels increase with cancer severity and identified a significant correlation between CCTβ levels and cancer progression in both small cell lung carcinoma (SCLC) and Squamous cell lung carcinoma (SqCLC). Using The Cancer Genome Atlas (TCGA) database, we have found CCT gene alterations in clinical lung cancer cases range from 10% to 43%, however, only CCT4 gene amplification in SqCLC cases correlated with decreased survival. Altogether, these results suggest that CT20p has the potential for being a therapeutic for multiple types of lung cancer due to increased target expression.

Citation Format: Ana C. Carr, Amr S. Khaled, Rania Bassiouni, Annette R. Khaled. CT20p as a therapeutic for lung cancer with elevated chaperoning containing TCP1 (CCT) expression levels [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 4895. doi:10.1158/1538-7445.AM2017-4895

PSMA-Targeted Theranostic Nanocarrier for Prostate Cancer

Herein, we report the use of a theranostic nanocarrier (Folate-HBPE(CT20p)) to deliver a therapeutic peptide to prostate cancer tumors that express PSMA (folate hydrolase 1). The therapeutic peptide (CT20p) targets and inhibits the chaperonin-containing TCP-1 (CCT) protein-folding complex, is selectively cytotoxic to cancer cells, and is non-toxic to normal tissue. With the delivery of CT20p to prostate cancer cells via PSMA, a dual level of cancer specificity is achieved: (1) selective targeting to PSMA-expressing prostate tumors, and (2) specific cytotoxicity to cancer cells with minimal toxicity to normal cells. The PSMA-targeting theranostic nanocarrier can image PSMA-expressing cells and tumors when a near infrared dye is used as cargo. Meanwhile, it can be used to treat PSMA-expressing tumors when a therapeutic, such as the CT20p peptide, is encapsulated within the nanocarrier. Even when these PSMA-targeting nanocarriers are taken up by macrophages, minimal cell death is observed in these cells, in contrast with doxorubicin-based therapeutics that result in significant macrophage death. Incubation of PSMA-expressing prostate cancer cells with the Folate-HBPE(CT20p) nanocarriers induces considerable changes in cell morphology, reduction in the levels of integrin β1, and lower cell adhesion, eventually resulting in cell death. These results are relevant as integrin β1 plays a key role in prostate cancer invasion and metastatic potential. In addition, the use of the developed PSMA-targeting nanocarrier facilitates the selective in vivo delivery of CT20p to PSMA-positive tumor, inducing significant reduction in tumor size.

Harnessing the immune response for the treatment of cancer by inducing immunogenic cell death through inhibition of a group II chaperonin

Immunotherapy is a promising treatment for cancer but lacks broad application. One way to enhance immunotherapy is by inducing immunogenic cell death (ICD). ICD is characterized by a unique molecular signature, involving the release of molecules that sensitize cancer cells to killing by the immune system. However, most ICD-inducing agents are not effective at clinically relevant doses. We developed a novel cytotoxic peptide, CT20p, that is delivered to cells using nanoparticles (NPs), which causes regression of tumors in mice at nanomolar concentrations. CT20p-treated cancer cells upregulated markers characteristic of ICD, such as calreticulin (Crt) and HSP70. The intracellular target of CT20p is a group II chaperonin called chaperonin containing-TCP-1 (CCT) that is essential for the folding of actin, tubulin and other proteins like STAT3. The CCT complex is composed of eight subunits (CCT1-8). That CT20p cytotoxicity is driven by CCT was proven by inhibiting or overexpressing CCT2 in susceptible or resistant cells, respectively. Disruption of CCT activity by CT20p caused endoplasmic reticulum (ER) stress that initiated intracellular pathways, such as PERK and IRE-1, generating danger signals associated with ICD. As a result, increased phagocytosis of dying cancer cells and enhanced NK cell killing was observed. Importantly, normal epithelial cells, macrophages or NK cells were unaffected. Using the CRISPR-CAS9 system, the genes for CCT were edited. Loss of CCT2 altered the levels of other CCT subunits as well as client proteins such as STAT3, while increasing membrane-exposed Crt. These studies revealed that inhibiting CCT induces ICD to stimulate immune functions essential for generating a robust anti-cancer immune response.

Abstract A30: Chronic inflammation induces severe stromal damage and early pancreatic tumors in mice with activated Akt1 and KRas

Inflammation and the immune environment is implicated as a risk for pancreatic ductal adenocarcinoma (PDAC), especially in chronic conditions. However, a mechanistic link is unknown. Recently, radiotherapy followed by immune checkpoint inhibitors are being tested and show promising results, thereby introducing immune modulation as a new investigational area for the treatment of pancreatic cancer. A potential barrier is that pancreatic fibrosis and desmoplastic reactivity are common characteristics of PDAC and makes therapeutic delivery difficult. To define how inflammation and desmoplasia effects the immune-pancreatic stromal environment and progression of PDAC, we have chronically injected caerulein into genetically engineered mice that we previously showed spontaneously develop PDAC through the cooperation of mutant active Akt1 and KRas. We show that injected Akt1Myr/KRasG12D mice have increased tissue remodeling, stellate cell activation, collagen production, and mucin production when compared to KRasG12D mice. They also have increased ductal proliferation, accelerated tumor formation, and increased immune cell infiltration in the pancreas ducts and stroma compared to control PBS- and caerulein-injected KRasG12D mice. Pro-inflammatory cytokines and macrophages likely activate stellate cells, which in turn facilitate additional cytokines to enhance a pro-tumor immune environment. Other than macrophages, the role that innate immune cells contribute to pancreatic cancer has not been well studied. Ongoing studies will delineate the immune cell infiltration, cytokine levels, and the effect on tumor formation in double mutant Akt1Myr/KRasG12D mice. Understanding the mechanisms by which inflammation affects tumor formation can lead to strategies to inhibit pro-tumor changes, impede PDAC development and improve overall patient survival.

Citation Format: Sarah B. Gitto, Kathryn A. Cline, Amr S. Khaled, Deborah A. Altomare.{Authors}. Chronic inflammation induces severe stromal damage and early pancreatic tumors in mice with activated Akt1 and KRas. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2016 May 12-15; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(24 Suppl):Abstract nr A30.

Abstract 4121: Chaperonin containing-TCP-1 protein level in breast cancer cells predicts therapeutic application of a cytotoxic peptide

Metastatic disease is a principal cause of death from breast cancer. This is due in part to the development of resistance to current therapeutics and the often debilitating side effects that impair quality of life. The challenge is to therapeutically target an essential physiological function of cancer cells not found in normal, non-transformed cells. To this end, we discovered CT20p, a therapeutic peptide that causes cancer-specific death in human breast tumor cells and tumor regression in xenograft models of breast cancer. Using a proteomics approach, we found that CT20p directly binds to multiple subunits of a type II chaperonin called chaperonin containing T-complex or CCT. CCT forms a large macromolecular complex composed of 8 subunits. Inhibition of CCT by CT20p depletes the pool of native actin and tubulin (obligate clients of CCT), impairing the polymerization of cytoskeletal elements needed to support cell adhesion and motility. As a result cancer cells lose the ability to migrate and die from loss of substrate survival signals. We found that expression levels of CCT varied among different triple negative breast cancer (TNBC) cell lines, with the highest expression occurring in those of the mesenchymal stem-like (MSL) subtype with metastatic potential. Lowest levels of CCT were found in normal breast epithelial cells. Sensitivity to killing by CT20p thus correlated with levels of CCT, with cancer cells expressing high amounts of CCT being the most susceptible. Using tissue microarrays (TMAs) of breast cancer progression, we developed an immunohistochemistry staining procedure for CCT. Results were interpreted on a scale of 1 to 4 (with 4 being the strongest staining). CCT expression was statistically higher in invasive ductal carcinoma (IDC) as compared to normal and cancer adjacent tissue (CAT) (p<0.0001). Within the types of IDC, CCT was highest in tumors that exceeded 5 cm across (T3), grew in chest wall or skin and in inflammatory breast cancer (T4) (p<0.05). Examining CCT levels in different molecular types showed little correlation with estrogen receptor (ER) positivity but strong correlation with ER and progesterone receptor (PR) positivity or PR alone (p>0.001). Statistical correlations were also observed with Her2 positivity (p>0.05). However, no statistically significant correlations were observed with TNBC tissues, with CCT staining ranging from the strongest staining (4) to lowest (1). These results are similar to that observed with the TNBC cell lines and indicate that CCT expression may reflect the heterogeneity of TNBC. These results suggest that CCT is a promising target for therapeutic intervention due to its increased expression in advanced stage breast cancer, independence of molecular identity and dependence by cancer cells to support essential cytoskeletal changes associated with the metastatic stem-like phenotype.

Citation Format: Annette R. Khaled, Amr S. Khaled, Rania Bassiouni, Priya Vishnubhotla. Chaperonin containing-TCP-1 protein level in breast cancer cells predicts therapeutic application of a cytotoxic peptide. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4121.

Chaperonin Containing TCP-1 Protein Level in Breast Cancer Cells Predicts Therapeutic Application of a Cytotoxic Peptide

PURPOSE

Metastatic disease is a leading cause of death for patients with breast cancer, driving the need for new therapies. CT20p is a peptide previously discovered by our group that displays cancer-specific cytotoxicity. To design the optimal therapeutic use of the peptide, we identified the intracellular target of CT20p in breast cancer cells, correlating expression patterns of the target with susceptibility to CT20p.

EXPERIMENTAL DESIGN

Using polymeric nanoparticles to deliver CT20p, we assessed cytoskeletal changes, cell migration, adhesion, and viability in cells treated with the peptide. Protein pull-down experiments, coupled to mass spectrometry, enabled identification of the peptide's intracellular target. Biochemical and histologic techniques validated target identity in human cell lines and breast cancer tissue microarrays and revealed susceptibility patterns to CT20p.

RESULTS

Chaperonin containing TCP-1 (CCT) was identified as the intracellular target of CT20p. Cancer cells susceptible to CT20p had increased CCT, and overexpression of CCTβ, a subunit of the CCT complex, enhanced susceptibility to CT20p. Susceptible cells displayed reduced tubulin, a substrate of CCT, and inhibition of migration upon CT20p treatment. CCTβ levels were higher in invasive ductal carcinomas than in cancer adjacent tissues and increased with breast cancer stage. Decreased breast cancer patient survival correlated with genomic alternations in CCTβ and higher levels of the chaperone.

CONCLUSIONS

Increased CCT protein in breast cancer cells underlies the cytotoxicity of CT20p. CCT is thus a potential target for therapeutic intervention and serves as a companion diagnostic to personalize the therapeutic use of CT20p for breast cancer treatment. Clin Cancer Res; 22(17); 4366-79. ©2016 AACR.

Abstract P5-03-02: The dynamic duo: A breast cancer-targeting nanoparticle loaded with a cytotoxic peptide as a treatment for metastatic disease

Metastatic breast cancer is a uniformly fatal disease with a 5-year survival rate of 15 percent. To date there are no effective approaches for targeted therapy. To develop a treatment for metastatic cancer, our group discovered a novel cytotoxic peptide, CT20p, and developed a nanotechnology-based platform to deliver and concentrate CT20p in breast tumors. CT20p was derived from Bax, a member of the Bcl-2 family. Unlike the parent protein, CT20p does not cause apoptosis and its cytotoxicity is independent of caspases and Bcl-2 overexpression. Rather, the intracellular target of CT20p is a protein called chaperonin-containing T-complex (CCT), which is required for the folding of actin and tubulin into their native forms. Inhibition of CCT activity by CT20p, indicated by decreased F-actin and tubulin, impaired the polymerization of microfilaments and microtubules, causing loss of cell migration and adhesion that promoted breast cancer cell death. In contrast, normal, non-transformed cells were resistant to the cytotoxicity of CT20p. On its own, CT20p is not membrane-permeable. To deliver the peptide to cells, we used nanoparticles formed with a novel aliphatic hyperbranched polyester polymer (HBPE-NPs). The surface of HBPE-NPs retains carboxylic acid groups for labeling of targeting ligands to enable accumulation in tumors. To concentrate on breast cancer, we functionalized the HBPE-NPs with either folate (FOL) or glutamate (GLU), which target the folate receptor (FR) or the metabotropic glutamate receptor (GRM-1) respectively. FR and GRM-2 are essential metabolic components that are highly expressed in solid tumors like breast cancer. In vitro targeting studies using triple negative breast cancer cell (TNBC) lines established that folate FOL or GLU-HBPE-NPs loaded with fluorescent dyes were readily up taken at high efficiency by TNBC cells. HBPE-NPs also contain unique hydrophobic cavities especially suited for encapsulating CT20p. We found that once the CT20p-HBPE-NPs were taken up by cancer cells, the peptide was released inside cells under acidic conditions (e.g. endosomes) and directly interacted with its intracellular target, CCT. Studies using primary cells derived from human breast tumors confirmed the targeted uptake of HBPE-NPs as well as demonstrated the cancer-specific cytotoxicity of CT20p. We treated a murine TNBC xenograft model with nanomolar amounts of FOL-CT20p-HBPE-NPs and achieved 100% regression of established tumors as well as prevented tumor growth. These studies indicated that CT20p is a potent and specific anti-cancer agent due to its inhibition of CCT, an essential molecular complex highly expressed in cancer cells, and that the peptide can be efficiently delivered to tumor sites using HBPE-NPs decorated with ligands to receptors, such FR or GRM-1, found on tumor cells.

Citation Format: Vishnubhotla P, Khaled AR, Khaled AS, Perez JM, Bassiouni R, Flores O, Nierenberg D. The dynamic duo: A breast cancer-targeting nanoparticle loaded with a cytotoxic peptide as a treatment for metastatic disease. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P5-03-02.

Abstract P5-04-04: Cutting the ties that bind: Targeting chaperonin-containing T-complex (CCT) for therapeutic intervention in the treatment of advanced stage breast cancer

Metastatic disease is a principal cause of death from breast cancer. This is due in part to the development of resistance to current therapeutics and the often debilitating side effects that impair quality of life. The challenge is to therapeutically target an essential physiological function of cancer cells not found in normal, non-transformed cells. To this end, we discovered CT20p, a therapeutic peptide that causes cancer-specific death in human breast tumor cells and tumor regression in xenograft models of breast cancer. Using a proteomics approach, we found that CT20p directly binds to multiple subunits of a type II chaperonin called chaperonin containing T-complex or CCT. CCT forms a large macromolecular complex composed of 8 subunits (CCTα, CCTβ, CCTγ, CCTδ, CCTϵ, CCTζ, CCTη, CCTω). Each subunit contains an ATP binding site as well as substrate binding sites. Inhibition of CCT by CT20p depletes the pool of native actin and tubulin (obligate clients of CCT), impairing the polymerization of cytoskeletal elements needed to support cell adhesion and motility. As a result cancer cells lose the ability to migrate and die from loss of substrate survival signals. We found that expression levels of CCT varied among different triple negative breast cancer (TNBC) cell lines, with the highest expression occurring in those of the mesenchymal stem-like (MSL) subtype with metastatic potential. Lowest levels of CCT were found in normal breast epithelial cells. Sensitivity to killing by CT20p thus correlated with levels of CCT, with cancer cells expressing high amounts of CCT being the most susceptible. Using tissue microarrays (TMAs) of breast cancer progression, we developed an immunohistochemistry staining procedure for CCTβ. Results were interpreted on a scale of 1 to 4 (with 4 being the strongest staining). CCTβ expression was statistically higher in invasive ductal carcinoma (IDC) as compared to normal and cancer adjacent tissue (CAT) (p<0.0001). Within the types of IDC, CCTβ was highest in tumors that exceeded 5 cm across (T3), grew in chest wall or skin and in inflammatory breast cancer (T4) (p<0.05). Examining CCTβ levels in different molecular types showed little correlation with estrogen receptor (ER) positivity but strong correlation with ER and progesterone receptor (PR) positivity or PR alone (p>0.001). Statistical correlations were also observed with Her2 positivity (p>0.05). However, no statistically significant correlations were observed with TNBC tissues, with CCTβ staining ranging from the strongest staining (4) to lowest (1). These results are similar to that observed with the TNBC cell lines and indicate that CCT expression may reflect the heterogeneity of TNBC. These results suggest that CCT is a promising target for therapeutic intervention due to its increased expression in advanced stage breast cancer, independence of molecular identity and dependence by cancer cells to support essential cytoskeletal changes associated with the metastatic stem-like phenotype.

Citation Format: Khaled AS, Vishnubhotla P, Khaled AR, Bassiouni R. Cutting the ties that bind: Targeting chaperonin-containing T-complex (CCT) for therapeutic intervention in the treatment of advanced stage breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P5-04-04.

Abstract P6-04-13: Preclinical testing using a novel CT20p peptide-nanoparticle combination in breast cancer

BACKGROUND: The marked difference in metabolism observed between tumor and normal cells could contribute to the development of invasive and metastatic forms of breast cancer. The problem is that while patients diagnosed with invasive forms of breast cancer may be initially responsive to treatment, a significant number develop relapsing and even metastatic disease. There is a critical unmet need to develop new therapeutic approaches for patients diagnosed with invasive forms of breast cancer that are effective given the unique metabolism of tumor cells. METHODS: We examined the cytotoxic properties of a novel peptide, CT20p, derived from the C-terminus of Bax. For delivery to cells, the amphipathic nature of CT20p allowed it to be encapsulated in polymeric nanoparticles (NPs). NPs were made using aliphatic hyperbranched polyester (HBPE) that incorporated surface carboxylic groups and interior hydrophobic cavities for encapsulation of CT20p. To examine the cytotoxic potential and targeting capacity of CT20p-HBPE-NPs, we treated MDA-MB-231 breast cancer cells and MCF-10A breast epithelial cells with the peptide-nanoparticle combination and measured changes in mitochondrial function, cell metabolism and induction of apoptotic and non-apoptotic cell death. The ability of CT20p-NP-HBPE to cause tumor regression was examined by subcutaneously implanting MDA-MB-231 cells in nude mice. RESULTS: Initial studies showed that CT20p caused the release of calcein from mitochondrial-like lipid vesicles, without disrupting vesicle integrity, and, when expressed as a fusion protein in cells, localized to mitochondria. While the peptide alone had little effect upon intact cells, likely not penetrating the plasma membrane, when encapsulated and delivered by nanoparticles, CT20p-HBPE-NPs proved an effective killer of breast cancer cells. CT20p-HBPE-NPs initiated non-apoptotic cell death within 3 hours of treatment by targeting mitochondria and deregulating cellular metabolism. Nanoparticles alone or nanoparticles encapsulating a control peptide had minimal effects. The cytotoxicity of CT20p-HPBE-NPs was most pronounced in breast cancer cells, sparing normal, epithelial cells. In implanted breast tumors, CT20p-HBPE-NPs accumulated in tumors within 24 hours and reduced tumor burden by 50-80%. CONCLUSION: These results reveal the innovative features of CT20p that allow nanoparticle-mediated delivery to tumors and the potential application in combination therapies that target the unique metabolism of cancer cells.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-04-13.

A comparison of DXA and CT based methods for estimating the strength of the femoral neck in post-menopausal women

The study goal was to compare simple two-dimensional (2D) analyses of bone strength using dual energy x-ray absorptiometry (DXA) data to more sophisticated three-dimensional (3D) finite element analyses using quantitative computed tomography (QCT) data. DXA- and QCT-derived femoral neck geometry, simple strength indices, and strength estimates were well correlated.

INTRODUCTION

Simple 2D analyses of bone strength can be done with DXA data and applied to large data sets. We compared 2D analyses to 3D finite element analyses (FEA) based on QCT data.

METHODS

Two hundred thirteen women participating in the Study of Women's Health Across the Nation (SWAN) received hip DXA and QCT scans. DXA BMD and femoral neck diameter and axis length were used to estimate geometry for composite bending (BSI) and compressive strength (CSI) indices. These and comparable indices computed by Hip Structure Analysis (HSA) on the same DXA data were compared to indices using QCT geometry. Simple 2D engineering simulations of a fall impacting on the greater trochanter were generated using HSA and QCT femoral neck geometry; these estimates were benchmarked to a 3D FEA of fall impact.

RESULTS

DXA-derived CSI and BSI computed from BMD and by HSA correlated well with each other (R=0.92 and 0.70) and with QCT-derived indices (R=0.83-0.85 and 0.65-0.72). The 2D strength estimate using HSA geometry correlated well with that from QCT (R=0.76) and with the 3D FEA estimate (R=0.56).

CONCLUSIONS

Femoral neck geometry computed by HSA from DXA data corresponds well enough to that from QCT for an analysis of load stress in the larger SWAN data set. Geometry derived from BMD data performed nearly as well. Proximal femur breaking strength estimated from 2D DXA data is not as well correlated with that derived by a 3D FEA using QCT data.

Apoptotic alkalinization induced by loss of a growth signal is mediated by phosphorylation of the Na+/H+ Exchanger isoform 1 at Ser726 and Ser729 (35.12)

Apoptosis is a complex process essential for cellular homeostasis. Early physiological changes that initiate cell death remain poorly understood. Previously, we observed that lymphocytes, undergoing apoptosis in response to loss of a growth factor experienced a rapid rise in cytosolic pH. We found that the protein responsible was the Na+/H+ Exchanger isoform 1 (NHE1), and that its activity was impeded by inhibition of p38 MAP kinase (MAPK). In the current study, we examined how NHE1 is activated during apoptosis. We identified the phosphorylation sites on NHE1 that regulate its alkalinizing activity in response to a death stimulus. Performing targeted mutagenesis, we observed that substitution of Ser726 and Ser729 for alanines produced a mutant form of NHE1 that did not alkalinize in response to apoptosis, and expression of which protected cells from serum-withdrawal induced death. In contrast, substitution of Ser726 and Ser729 for glutamic acids raised the basal pH and induced susceptibility to death. Serine phosphorylation of NHE1 during apoptosis decreased upon mutation of S726 and S729. Our findings thus confirm a necessary function for NHE1 during apoptosis and reveal the critical regulatory sites that when phosphorylated mediate the alkalinizing activity of NHE1 in the early stages of cell death.

Polyomavirus (BK virus) nephropathy in kidney transplant patients: a pathologic perspective

Reactivation of polyoma virus (BK virus) is a significant cause of morbidity in kidney transplant patients. This seemingly insignificant viral infection that affects the majority of population at a young age, once reactivated by immunosuppression, is a major factor contributing to graft loss. Screening techniques have been developed for early prediction of BK virus reactivation. These include plasma and urine assays for detection of BK virus DNA by PCR, urine cytology for detection of "decoy cells" and electron microscopy. Combining urine cytology and serology screening can be more effective for early detection of BK virus reactivation. Immunohistochemistry can be utilized as an additional tool to support the diagnosis. Once screening tests reveal a suspicious BK virus reactivation, tissue biopsy should be performed to confirm the diagnosis, rule out acute cellular rejection and plan treatment approaches. Treatment normally includes decreasing immunosuppression and the use of antiviral drug therapy. Unfortunately, disease outcome is often unfavorable and can culminate with eventual graft loss. Renal retransplantation has been performed with mixed results. As new data emerges, we will gain a better understanding of the disease caused by BK virus and respond with improved early diagnosis and treatment to preserve graft function.

Treatment of established recurrent hepatitis C in liver-transplant recipients with pegylated interferon-alfa-2b and ribavirin therapy

INTRODUCTION

The management issues of transplant patients with hepatitis C virus (HCV) are complex, and interferon therapy is often ineffective. We present data from a retrospective review in liver-transplant recipients suffering from HCV recurrence that were treated with pegylated alpha-2b interferon and ribavirin.

METHODS

A retrospective review of transplant recipients that received combination pegylated alpha-2b interferon (1.5 mcg/kg/wk) and ribavirin (400-600 mg/day) therapy intended for at least 48 weeks. Complications were recorded and included neutropenia (<750 cells), anemia (hemoglobin <8 g) with and without treatment consisting of blood transfusions, erythropoietin, or dose reduction of ribavirin, and depression. The diagnosis of HCV recurrence was determined by an increase in liver chemistries, histopathologic findings with inflammation along with viral recurrence using the COBAS AMPLICOR HCV test.

RESULTS

Fifty-seven liver-transplant recipients were included, 29 naive (group 1) to therapy and 28 nonresponders (group 2) to at least 6 months of interferon and ribavirin therapy. Eight (27.6%) patients in group 1 and six (21%) patients in group 2 were HCV nondetectable at the end of 48 weeks of therapy. Ribavirin therapy was decreased in 13 of 29 (45%) for group 1 and 11 of 28 (39%) in group 2. Therapeutic interventions were 4 of 57 (7%) blood transfusions, 23 of 57 (40%) erythropoietin, and 17 of 57 (30%) filgrastim.

CONCLUSION

Combination pegylated interferon with ribavirin appears to effective therapy in HCV recurrence and in HCV nonresponsive to interferon and ribavirin. This data reveals the difficulty and caution that must be taken when treating HCV-R liver-transplant recipients with combination pegylated alpha-2b interferon and ribavirin therapy.

Prediction of sustained virological response in liver transplant recipients with recurrent hepatitis C virus following combination pegylated interferon alfa-2b and ribavirin therapy using tissue hepatitis C virus reverse transcriptase polymerase chain reaction testing

The optimal duration of therapy for pegylated interferon combined with ribavirin in recurrent Hepatitis C virus (HCV) following liver transplantation is not known. We wanted to determine if testing for HCV in liver tissue by reverse transcriptase polymerase chain reaction (RT-PCR) was superior in predicting sustained virological response (SVR) in comparison to standard HCV ribonucleic acid (RNA) detection in the serum. All recipients received combination pegylated alpha-2b interferon (1.5 mcg/kg) and ribavirin (200-600 mg/d) therapy for at least 48 weeks of therapy and were found to have nondetectable HCV RNA by PCR serum testing at the end of therapy. Sustained virological response (SVR) was defined as nondetectable serum HCV RNA at 6 months post treatment withdrawal. Ten liver transplant recipients were included in the study; mean time from transplantation was 29.2 months. All had nondetectable serum HCV RNA by RT-PCR. In hepatic tissue 7/10 patients HCV RNA was found to be positive by RT-PCR while 3/10 had nondetectable HCV RNA in their liver by RT-PCR. SVR was attained in all 3/10 that were hepatic tissue HCV PCR negative after 12 months of combination therapy. In conclusion, direct detection of HCV RNA by RT-PCR of liver tissue appears to more effectively predict SVR following pegylated interferon and ribavirin therapy than the conventional use of serum.

Bax deficiency partially corrects interleukin-7 receptor alpha deficiency

The requirement for cytokines in hematopoiesis is partly attributable to the protection of cells from apoptosis. Since IL-7 is required for normal T cell development, we evaluated the role of Bax in vivo by generating mice deficient in both Bax and the IL-7 receptor alpha chain (IL-7R). Starting at birth, we observed complete recovery of all stages of alphabeta thymocyte development up to 4 weeks of age. However, by 12 weeks of age, thymic cellularity had reverted to that of mice deficient in IL-7R alone. The BH3 only proteins, Bad and Bim, were also part of the death pathway repressed by IL-7. Thus, in young mice, Bax emerges as an essential protein in the death pathway induced by IL-7 deficiency.