Kinesin Facilitates Phenotypic Targeting of Therapeutic Resistance in Advanced Prostate Cancer

Understanding the mechanisms underlying resistance is critical to improving therapeutic outcomes in patients with metastatic castration-resistant prostate cancer (mCRPC). Previous work showed dynamic interconversions between epithelial-mesenchymal transition (EMT) to mesenchymal-epithelial transition (MET) defines the phenotypic landscape of prostate tumors, as a potential driver of emergence of therapeutic resistance. In this study, we use in vitro and in vivo preclinical MDA PCa PDX models of resistant human prostate cancer to determine molecular mechanisms of cross-resistance between anti-androgen therapy and taxane chemotherapy, underlying the therapeutically resistant phenotype. Transcriptomic profiling revealed that resistant and sensitive prostate cancer C4-2B cells have a unique differential gene signature response to cabazitaxel. Gene pathway analysis showed that sensitive cells exhibit increase in DNA damage, while resistant cells express genes associated with protein regulation in response to cabazitaxel. These PDX specimens are from patients who have metastatic lethal CRPC, treated with androgen-deprivation therapy (ADT), antiandrogens and chemotherapy including 2nd line taxane chemotherapy, cabazitaxel. Immunohistochemistry revealed high expression of E-cadherin and low expression of vimentin resulting in re-differentiation toward an epithelial phenotype. Furthermore, the mitotic kinesin-related protein (HSET) involved in microtubule binding and the SLCO1B3 transporter (implicated in cabazitaxel intracellular transport), associated with resistance in these prostate tumors. Combinational targeting of kinesins (ispinesib) with cabazitaxel was more effective than single monotherapies in inducing cell death in resistant prostate tumors. Implications: Our findings are of translational significance in identifying kinesin as a novel target of cross-resistance, towards enhancing therapeutic vulnerability and improved clinical outcomes in patients with advanced prostate cancer.

Activation of STING in Response to Partial-Tumor Radiation Exposure

PURPOSE

To determine the mechanisms involved in partial volume radiation therapy (RT)-induced tumor response.

METHODS AND MATERIALS

We investigated 67NR murine orthotopic breast tumors in Balb/c mice and Lewis lung carcinoma (LLC cells; WT, Crispr/Cas9 Sting KO, and Atm KO) injected in the flank of C57Bl/6, cGAS, or STING KO mice. RT was delivered to 50% or 100% of the tumor volume using a 2 × 2 cm collimator on a microirradiator allowing precise irradiation. Tumors and blood were collected at 6, 24, and 48 hours post-RT and assessed for cytokine measurements.

RESULTS

There is a significant activation of the cGAS/STING pathway in the hemi-irradiated tumors compared with control and to 100% exposed 67NR tumors. In the LLC model, we determined that an ATM-mediated noncanonical activation of STING is involved. We demonstrated that the partial exposure RT-mediated immune response is dependent on ATM activation in the tumor cells and on the STING activation in the host, and cGAS is dispensable. Our results also indicate that partial volume RT stimulates a proinflammatory cytokine response compared with the anti-inflammatory profile induced by 100% tumor volume exposure.

CONCLUSIONS

Partial volume RT induces an antitumor response by activating STING, which stimulates a specific cytokine signature as part of the immune response. However, the mechanism of this STING activation, via the canonical cGAS/STING pathway or a noncanonical ATM-driven pathway, depends on the tumor type. Identifying the upstream pathways responsible for STING activation in the partial RT-mediated immune response in different tumor types would improve this therapy and its potential combination with immune checkpoint blockade and other antitumor therapies.

Endothelial mechanisms for inactivation of inflammation-induced hyperpermeability

BACKGROUND

Microvascular hyperpermeability is a hallmark of inflammation. Many negative effects of hyperpermeability are due to its persistence beyond what is required for preserving organ function. Therefore, we propose that targeted therapeutic approaches focusing on mechanisms that terminate hyperpermeability would avoid the negative effects of prolonged hyperpermeability while retaining its short-term beneficial effects.

METHODS

We tested the hypothesis that inflammatory agonist signaling leads to hyperpermeability and initiates a delayed cascade of cAMP-dependent pathways that causes inactivation of hyperpermeability. We applied platelet-activating factor (PAF) and vascular endothelial growth factor (VEGF) to induce hyperpermeability. We used an Epac1 agonist to selectively stimulate exchange protein activated by cAMP (Epac1) and promote inactivation of hyperpermeability.

RESULTS

Stimulation of Epac1 inactivated agonist-induced hyperpermeability in the mouse cremaster muscle and in human microvascular endothelial cells (HMVEC). PAF induced nitric oxide (NO) production and hyperpermeability within one minute, and NO-dependent increased cAMP concentration in about 15-20 minutes in HMVEC. PAF triggered phosphorylation of vasodilator-stimulated phosphoprotein (VASP) in a NO-dependent manner. Epac1 stimulation promoted cytosol-to-membrane eNOS translocation in HMVEC and in myocardial microvascular endothelial (MyEnd) cells from wild-type mice, but not in MyEnd cells from VASP knockout mice.

CONCLUSIONS

We demonstrate that PAF and VEGF cause hyperpermeability and stimulate the cAMP/Epac1 pathway to inactivate agonist-induced endothelial/microvascular hyperpermeability. Inactivation involves VASP-assisted translocation of eNOS from the cytosol to the endothelial cell membrane. We demonstrate that hyperpermeability is a self-limiting process, whose timed inactivation is an intrinsic property of the microvascular endothelium that maintains vascular homeostasis in response to inflammation.

Anoikis in phenotypic reprogramming of the prostate tumor microenvironment

Prostate cancer is one of the most common malignancies in males wherein 1 in 8 men are diagnosed with this disease in their lifetime. The urgency to find novel therapeutic interventions is associated with high treatment resistance and mortality rates associated with castration-resistant prostate cancer. Anoikis is an apoptotic phenomenon for normal epithelial or endothelial cells that have lost their attachment to the extracellular matrix (ECM). Tumor cells that lose their connection to the ECM can die via apoptosis or survive via anoikis resistance and thus escaping to distant organs for metastatic progression. This review discusses the recent advances made in our understanding of the signaling effectors of anoikis in prostate cancer and the approaches to translate these mechanistic insights into therapeutic benefits for reducing lethal disease outcomes (by overcoming anoikis resistance). The prostate tumor microenvironment is a highly dynamic landscape wherein the balance between androgen signaling, cell lineage changes, epithelial-mesenchymal transition (EMT), extracellular matrix interactions, actin cytoskeleton remodeling as well as metabolic changes, confer anoikis resistance and metastatic spread. Thus, these mechanisms also offer unique molecular treatment signatures, exploitation of which can prime prostate tumors to anoikis induction with a high translational significance.

Abstract 6056: Activation of Sting in response to partial-tumor radiation exposure

Purpose: It has been shown that ionizing radiation can mediate antitumor immunity via the activation of the cytosolic DNA sensor cGAS/STING pathway. Therefore, the purpose of this study was to determine whether STING activation is involved in partial volume radiation therapy (RT).

Materials/Methods: We investigated 67NR murine orthotopic breast tumors in Balb/c mice and LLC cells injected in the flank of C57Bl/6, cGAS, or STING KO mice. RT was delivered to 50% or 100% of the tumor volume using a 2X2 cm collimator on a microirradiator allowing precise irradiation. Tumors were collected at different time points post-RT and assessed for different measurements.

Results: We previously showed that a single dose of radiation delivered to half of the tumor (50% RT) activated an anti-tumor immune response comparable to the response in a fully-irradiated tumor in the immunogenic 67NR murine breast carcinoma tumor model and in the less immunogenic and more radioresistant Lewis lung carcinoma (LLC) tumor model. We have also demonstrated that this immune response was due to the infiltration of CD8+ T cells along with an increased expression of ICAM adhesion molecules. Treatment with either anti-CD8 or anti-ICAM antibodies abrogated the hemi-RT response. Furthermore, a significant abscopal effect was observed after partial irradiation with a single dose of 10Gy in a bilateral 67NR tumors model. In this study, we tested whether the hemi-irradiation-mediated immune response involves the cGAS/STING canonical pathway, or a non-canonical activation of STING, in the 67NR or LLC tumor models. It has been reported that STING can be activated, independently of cGAS, via non-canonical activation of STING, involving ATM and TRAF6, among other factors. We found significant activation of the cGAS/STING pathway in the hemi-irradiated tumors as compared to control and to 100% exposed 67NR tumors. Interestingly, the increased expression of the cGAS/STING pathway was found in the hemi-irradiated tumor but, also in the non-irradiated part of this hemi-irradiated tumor. In the LLC model, a non-canonical activation of STING was involved. Using both cGAS and STING KO mice, we demonstrated that the partial exposure RT-mediated immune response is dependent on STING activation in the host while cGAS is dispensable.

Conclusions: Upstream pathways responsible for STING activation are tumor type-specific. Identifying the upstream pathways responsible for STING activation in the partial RT-mediated immune response in different tumor types would improve this therapy and its potential combination with immune checkpoint blockade.

Citation Format: Mickael Mathieu, Prerna R. Nepali, Sadna Budhu, Simon N. Powell, John Humm, Joseph Deasy, Adriana Haimovitz-Friedman. Activation of Sting in response to partial-tumor radiation exposure [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 6056.

Abstract 38: Radiation Exposure And Coronary Atherosclerosis: Differential Effect Of The Radiation Site

Background: Thoracic radiation is commonly used in breast cancer, Hodgkin’s lymphoma, head and neck and lung cancer patients. Accelerated coronary artery atherosclerosis is a common complication of thoracic radiation as a result of unintended cardiac radiation. It is unclear however whether specific areas of the heart are more susceptible to the effects of radiation (RT). In this study we hypothesize that accelerated development of lesions post RT is dependent upon differential sensitivity of specific areas of the heart to the effects of RT.

Methods: Male Apolipoprotein E knockout mice on a high fat diet received 16Gy cardiac RT targeted to the whole or partial (apical or basal) region of the heart at 9 or 16 weeks of age (n=5 per group). Atherosclerotic lesions in H&E stained slides and inflammatory infiltrates in the hearts by IHC were assessed 8 weeks following RT and compared to control unirradiated mice.

Results: Our studies show that: (1) Subendocardial atherosclerotic lesions at the base of heart in mice irradiated at 9 weeks of age after basal irradiation (7.8±2.49) were comparable to whole heart irradiation (12.2±3.29). (2) A greater number of atherosclerotic lesions were present in the basal coronary arteries (29.33±5.48 vs 9±2.70) and basal subendocardial vasculature (6.66±2.07 vs 0.2±0.2) after irradiation of the cardiac base as compared to unirradiated controls in mice irradiated at 16 weeks of age. (3) Apical or whole heart irradiation had no impact on the development of lesions in the basal region of the hearts of older mice. (4) IL-6 was significantly increased in the serum of mice 6 hours post basal cardiac irradiation (105.10±17.56 pg/ml) when compared to unirradiated controls (29.85±11.63 pg/ml), demonstrating an acute inflammatory response. (5) Infiltration of inflammatory cells (CD45 and CD3) and enhanced expression of endothelial adhesion molecules (CD31) were differentially and locally regulated based upon the site of irradiation.

Conclusion: Our results indicate that the base of the heart is more prone to development of RT induced atherosclerotic lesions likely due to acute and delayed inflammatory responses. Avoiding this area from direct radiation exposure may improve the quality of life for cancer patients receiving thoracic RT.

Abstract 1663: Activation of STING in response to partial-tumor radiation exposure

Purpose: To determine whether STING activation is involved in partial volume radiation therapy.

Background: The potential of radiotherapy (RT) to induce immune recognition of cancer cells is a growing topic of research. It has been suggested that partial volume irradiation used in GRID therapy/Lattice RT, a type of RT in which radiation does not cover the entire tumor intentionally but rather is spatially fractionated, sometimes induces an immune response. We previously showed that a single dose of radiation delivered to half of the tumor (50% RT) activated an anti-tumor immune response comparable to the response in a fully-irradiated tumor in the immunogenic 67NR murine tumor model (breast carcinoma) and in the less immunogenic and more radioresistant Lewis lung carcinoma (LLC) tumor model. We have also demonstrated that this immune response was due to the infiltration of CD8+ T cells along with an increased expression of ICAM adhesion molecules. Treatment with either anti-CD8 or anti-ICAM antibodies abrogated the hemi-RT response. Furthermore, a significant abscopal effect was observed after partial irradiation with a single dose of 10Gy in a bilateral 67NR tumors model. It has been shown that ionizing radiation can mediate antitumor immunity via the activation of the cytosolic DNA sensor cGAS/STING pathway. Therefore, in this study, we tested whether the hemi-irradiation-mediated immune response involves the cGAS/STING canonical pathway, or a non-canonical activation of STING, in the 67NR or LLC tumor models. It has been reported that STING can be activated, independently of cGAS, via non-canonical activation of STING, involving ATM and TRAF6, among other factors.

Brief methods: We investigated 67NR murine orthotopic breast tumors in Balb/c mice and LLC cells injected in the flank of C57Bl/6, cGAS or STING KO mice. RT was delivered to 50% or 100% of the tumor volume using a 2X2 cm collimator on a microirradiator allowing precise irradiation. Tumors were collected at different time points post-RT and assessed for different measurements.

Results: There is significant activation of the cGAS/STING pathway in the hemi-irradiated tumors as compared to control and to 100% exposed 67NR tumors. Interestingly, the increased expression of the cGAS/STING pathway was found in the hemi-irradiated tumor but, also in the non-irradiated part of the tumor. In the LLC model, a non-canonical activation of STING is involved. Using both cGAS and STING KO mice, we demonstrated that the partial exposure RT-mediated immune response is dependent on STING activation in the host while cGAS is dispensable.

Conclusions: Identifying the upstream pathways responsible for STING activation in the partial RT-mediated immune response in different tumor types would improve this therapy and its potential combination with immune checkpoint blockade.

Citation Format: Mickael Mathieu, Prerna R. Nepali, Sadna Budhu, Simon N. Powell, John L. Humm, Joseph O. Deasy, Adriana Haimovitz-Friedman. Activation of STING in response to partial-tumor radiation exposure [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 1663.

Abstract 3069: Radiation exposure of the base of the heart accelerates coronary atherosclerosis

Purpose: To determine the mechanisms associated with the development of atherosclerotic lesions in different areas of the heart exposed to radiation therapy (RT). We hypothesize that accelerated development of cardiovascular disease (CVD) post-RT is dependent upon the differential sensitivity of regions of the heart to radiation.

Experimental procedures: Male Apolipoprotein E knockout (ApoE-/-) mice on a high fat diet received 16Gy cardiac irradiation targeted to the whole or partial (apical or basal) region of the heart at 9 weeks or 16 weeks of age. Atherosclerotic lesions and inflammatory changes in the hearts as compared to control unirradiated mice were assessed eight weeks following radiation.

Results: Our studies demonstrate that atherosclerotic lesion formation is accelerated by cardiac RT. Our results show that (1) Subendocardial atherosclerotic lesions at the base of heart of 9 weeks old mice after basal irradiation are comparable to those formed post whole heart irradiation. (2) A greater number of atherosclerotic lesions were present in the basal coronary arteries and basal subendocardial vasculature after irradiating the cardiac base as compared to unirradiated controls in older mice at 8 weeks post-RT. (3) Apical or whole heart irradiation had no impact on the development or acceleration of lesions in the basal region of the hearts of 16 week old mice, thus demonstrating the adverse impact of basal irradiation. (4) Infiltration of inflammatory cells (CD45 and CD3) and enhanced expression of endothelial adhesion molecules (CD31) were differentially and locally regulated based upon the site of irradiation. This also demonstrates a long-term inflammatory response to RT which may be crucial in the development of RT-related CVD.

Conclusion: Our results indicate that the base of the heart is more prone to development of RT-induced atherosclerotic lesions that could lead to CVD and thus omitting this area from RT direct exposure may improve the quality of life for cancer patients receiving thoracic RT.

Citation Format: Prerna R. Nepali, Mickael Mathieu, Sarah Kitz, Chiharuko Nakauchi, James Russell, Sebastien Monette, Andreas Rimner, Fiona A. Stewart, Edgar A. Jaimes, Adriana Haimovitz-Friedman. Radiation exposure of the base of the heart accelerates coronary atherosclerosis [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 3069.

Endothelial cAMP deactivates ischemia-reperfusion-induced microvascular hyperpermeability via Rap1-mediated mechanisms

Approaches to reduce excessive edema due to the microvascular hyperpermeability that occurs during ischemia-reperfusion (I/R) are needed to prevent muscle compartment syndrome. We tested the hypothesis that cAMP-activated mechanisms actively restore barrier integrity in postischemic striated muscle. We found, using I/R in intact muscles and hypoxia-reoxygenation (H/R, an I/R mimic) in human microvascular endothelial cells (HMVECs), that hyperpermeability can be deactivated by increasing cAMP levels through application of forskolin. This effect was seen whether or not the hyperpermeability was accompanied by increased mRNA expression of VEGF, which occurred only after 4 h of ischemia. We found that cAMP increases in HMVECs after H/R, suggesting that cAMP-mediated restoration of barrier function is a physiological mechanism. We explored the mechanisms underlying this effect of cAMP. We found that exchange protein activated by cAMP 1 (Epac1), a downstream effector of cAMP that stimulates Rap1 to enhance cell adhesion, was activated only at or after reoxygenation. Thus, when Rap1 was depleted by small interfering RNA, H/R-induced hyperpermeability persisted even when forskolin was applied. We demonstrate that 1) VEGF mRNA expression is not involved in hyperpermeability after brief ischemia, 2) elevation of cAMP concentration at reperfusion deactivates hyperpermeability, and 3) cAMP activates the Epac1-Rap1 pathway to restore normal microvascular permeability. Our data support the novel concepts that 1) different hyperpermeability mechanisms operate after brief and prolonged ischemia and 2) cAMP concentration elevation during reperfusion contributes to deactivation of I/R-induced hyperpermeability through the Epac-Rap1 pathway. Endothelial cAMP management at reperfusion may be therapeutic in I/R injury.NEW & NOTEWORTHY Here, we demonstrate that 1) stimulation of cAMP production deactivates ischemia-reperfusion-induced hyperpermeability in muscle and endothelial cells; 2) VEGF mRNA expression is not enhanced by brief ischemia, suggesting that VEGF mechanisms do not activate immediate postischemic hyperpermeability; and 3) deactivation mechanisms operate via cAMP-exchange protein activated by cAMP 1-Rap1 to restore integrity of the endothelial barrier.