No description available.

When breast tumor cells encounter stress due to cancer therapies, they may enter a dormant state, escaping from treatment-induced apoptosis. Dormant cells may eventually regain proliferative capabilities and cause recurrent metastatic disease, which is the leading cause of mortality in breast cancer patients. We sought to determine if a high dose of radiation therapy (RT) or combined chemo-immunotherapy, with and without the blockade of autophagy by chloroquine (CQ), could overcome treatment-induced tumor dormancy or relapse. We found that autophagy contributes in part to treatment-induced tumor dormancy. We also found that three therapeutic strategies were successful in inhibiting or preventing tumor relapse. These include: 18Gy/day RT, chemotherapy combined with the blockade of autophagy, and combined chemo-immunotherapy. Follow-up studies are needed to determine the feasibility of preventing tumor relapse by prolonging tumor dormancy versus eliminating dormant tumor cells.

No description available.

abstract: Relapse after tumor dormancy is one of the leading causes of cancer recurrence that ultimately leads to patient mortality. Upon relapse, cancer manifests as metastases that are linked to almost 90% cancer related deaths. Capture of the dormant and relapsed tumor phenotypes in high-throughput will allow for rapid targeted drug discovery, development and validation. Ablation of dormant cancer will not only completely remove the cancer disease, but also will prevent any future recurrence. A novel hydrogel, Amikagel, was developed by crosslinking of aminoglycoside amikacin with a polyethylene glycol crosslinker. Aminoglycosides contain abundant amount of easily conjugable groups such as amino and hydroxyl moieties that were crosslinked to generate the hydrogel. Cancer cells formed 3D spheroidal structures that underwent near complete dormancy on Amikagel high-throughput drug discovery platform. Due to their dormant status, conventional anticancer drugs such as mitoxantrone and docetaxel that target the actively dividing tumor phenotype were found to be ineffective. Hypothesis driven rational drug discovery approaches were used to identify novel pathways that could sensitize dormant cancer cells to death. Strategies were used to further accelerate the dormant cancer cell death to save time required for the therapeutic outcome. Amikagel’s properties were chemo-mechanically tunable and directly impacted the outcome of tumor dormancy or relapse. Exposure of dormant spheroids to weakly stiff and adhesive formulation of Amikagel resulted in significant relapse, mimicking the response to changes in extracellular matrix around dormant tumors. Relapsed cells showed significant differences in their metastatic potential compared to the cells that remained dormant after the induction of relapse. Further, the dissertation discusses the use of Amikagels as novel pDNA binding resins in microbead and monolithic formats for potential use in chromatographic purifications. High abundance of amino groups allowed their utilization as novel anion-exchange pDNA binding resins. This dissertation discusses Amikagel formulations for pDNA binding, metastatic cancer cell separation and novel drug discovery against tumor dormancy and relapse. / Dissertation/Thesis / Doctoral Dissertation Bioengineering 2016

Breast cancer mortality is mainly due to distant recurrence of the disease arising from dormant tumor cells established by cancer therapies. Patients who initially respond to cancer therapies often succumb to distant recurrence of the disease. It is not clear why people with the same type of breast cancer respond to treatments differently; some escape from dormancy and relapse earlier than others. In addition, some tumor clones respond to immunotherapy while others do not. We investigated how autophagy plays a role in accelerating or delaying recurrence of neu overexpressing mouse mammary carcinoma (MMC) following adriamycin (ADR) treatment, and in affecting response to immunotherapy. We explored two strategies: 1) transient blockade of autophagy with chloroquine (CQ), which blocks fusion of autophagosomes and lysosomes during ADR treatment, and 2) permanent inhibition of autophagy by a stable knockdown of ATG5 (ATG5KD), which inhibits the formation of autophagosomes in MMC during and after ADR treatment. We found that while CQ prolonged tumor dormancy, but that stable knockdown of autophagy resulted in early escape from dormancy and recurrence. Interestingly, ATG5KD MMC contained an increased frequency of ADR-induced polyploid-like cells and rendered MMC resistant to immunotherapy. On the other hand, a transient blockade of autophagy did not affect the sensitivity of MMC to immunotherapy. Our observations suggest that while chemotherapy-induced autophagy may facilitate tumor relapse, cell-intrinsic autophagy delays tumor relapse, in part, by inhibiting the formation of polyploid-like tumor dormancy. Although immunotherapy of breast cancer by means of anti-HER2 antibodies prolongs survival of breast cancer patients, disease recurrence remains a major challenge. On the other hand administration of human vaccines against infectious disease in a preventive setting or during latency/dormancy has been successful in offering a cure. Here, we sought to use adoptive immunotherapy (AIT) at the time of tumor dormancy in order to prevent progression of breast cancer. We used a low dose immunogenic chemotherapy by means of 5-FU, Adriamycin, and Cyclophosphamide (FAC) in order to stabilize tumor progression prior to AIT using autologous tumor-reactive lymphocytes. Low dose FAC established local tumor dormancy, inhibited distant tumor dormancy occurring long before distant metastasis, and induced predominate a Ki67- quiescent type of tumor dormancy, which is less susceptible to tumor immunoediting. Dormant tumor cells expressed the cell survival pathways, including the endothelin receptor/ligand (ETRA, ETRB and ET-1) and PD-L1, thereby protecting them from elimination by AIT. In addition, tumor-reactive CD8+ T cells also produced ET-1 as a survival ligand for ETRA positive tumor cells. A combination of AIT with the blockade of tumor cell survival pathways resulted in a significant improvement of AIT against tumor dormancy. We also showed that the inhibition Bcl-xL downstream of the tumor cell survival pathways is specifically effective against dormant tumor cells, suggesting a combination of AIT with small molecules inhibitors of Bcl-xL. Altogether, we showed that distant tumor dormancy is established long before distant recurrence of breast cancer, and that the expression of several tumor cell survival pathways in dormant cells protects them from immunotherapy. Our results suggest that immunotherapeutic targeting of tumor dormancy combined with the blockade of a common downstream cell survival pathway could prevent tumor progression and recurrence of the disease.

Background & Aims: Despite advances in surgical care and chemotherapeutic regimens, the five-year survival rate for Stage IV Hepatoblastoma (HB), the predominant pediatric liver tumor, remains at 27%. YAP1 and β-Catenin co-activation occurs in 80% of children’s HB; however, a lack of conditional genetic models precludes exploration of tumor maintenance and therapeutic targets. Thus, the clinical need for a targeted therapy remains unmet. Given the predominance of YAP1 and β-catenin activation in children’s tumors, I sought to evaluate YAP1 as a therapeutic target in HB. Approach & Results: Herein, I engineered the first conditional murine model of HB using hydrodynamic injection to deliver transposon plasmids encoding inducible YAP1S127A, constitutive β-CateninDelN90, and a luciferase reporter to murine liver. Tumor regression was evaluated using in vivo bioluminescent imaging, and tumor landscape characterized using RNA sequencing, ATAC sequencing and DNA foot-printing. Here I show that YAP1 withdrawal in mice mediates >90% tumor regression with survival for 230+ days. Mechanistically, YAP1 withdrawal promotes apoptosis in a subset of tumor cells and in remaining cells induces a cell fate switch driving therapeutic differentiation of HB tumors into Ki-67 negative “hbHep cells.” hbHep cells have hepatocyte-like morphology and partially restored mature hepatocyte gene expression. YAP1 withdrawal drives formation of hbHeps by modulating liver differentiation transcription factor (TF) occupancy. Indeed, tumor-derived hbHeps, consistent with their reprogrammed transcriptional landscape, regain partial hepatocyte function and can rescue liver damage in mice. Conclusions: YAP1 withdrawal, without modulation of oncogenic β-Catenin, significantly regresses hepatoblastoma, providing the first in vivo data to support YAP1 as a therapeutic target for HB. Modulating YAP1 expression alone is sufficient to drive long-term regression in hepatoblastoma because it promotes cell death in a subset of tumor cells and modulates transcription factor occupancy to reverse the fate of residual tumor cells to mimic functional hepatocytes.