Associative learning contributes to the persistence of fatigue-like behavior in male mice in a model of cancer survivorship

Persistent fatigue is a debilitating side effect that impacts a significant proportion of cancer survivors for which there is not yet an FDA-approved treatment. While certainly a multi-factorial problem, persistent fatigue could be due, in part, to associations learned during treatment. Therefore, we sought to investigate the role of associative learning in the persistence of fatigue using a preclinical model of cancer survivorship. For this purpose, we used a murine model of human papilloma virus-related head and neck cancer paired with a curative regimen of cisplatin-based chemoradiation in male C57BL/6J mice. Fatigue-like behavior was assessed by measuring variations in voluntary wheel running using a longitudinal design. Treatment robustly decreased voluntary wheel running, and this effect persisted for more than a month posttreatment. However, when wheels were removed during treatment, to minimize treatment-related fatigue, mice showed a more rapid return to baseline running levels. We confirmed that the delayed recovery observed in mice with continual wheel access was not due to increased treatment-related toxicity, in fact running attenuated cisplatin-induced kidney toxicity. Finally, we demonstrated that re-exposure to a treatment-related olfactory cue acutely re-instated fatigue. These data provide the first demonstration that associative processes can modulate the persistence of cancer-related fatigue-like behavior.

Stromal HIF2 Regulates Immune Suppression in the Pancreatic Cancer Microenvironment

BACKGROUND & AIMS

Pancreatic ductal adenocarcinoma (PDAC) has a hypoxic, immunosuppressive stroma that contributes to its resistance to immune checkpoint blockade therapies. The hypoxia-inducible factors (HIFs) mediate the cellular response to hypoxia, but their role within the PDAC tumor microenvironment remains unknown.

METHODS

We used a dual recombinase mouse model to delete Hif1α or Hif2α in α-smooth muscle actin-expressing cancer-associated fibroblasts (CAFs) arising within spontaneous pancreatic tumors. The effects of CAF HIF2α expression on tumor progression and composition of the tumor microenvironment were evaluated by Kaplan-Meier analysis, reverse transcription quantitative real-time polymerase chain reaction, histology, immunostaining, and by both bulk and single-cell RNA sequencing. CAF-macrophage crosstalk was modeled ex vivo using conditioned media from CAFs after treatment with hypoxia and PT2399, an HIF2 inhibitor currently in clinical trials. Syngeneic flank and orthotopic PDAC models were used to assess whether HIF2 inhibition improves response to immune checkpoint blockade.

RESULTS

CAF-specific deletion of Hif2α, but not Hif1α, suppressed PDAC tumor progression and growth, and improved survival of mice by 50% (n = 21-23 mice/group, Log-rank P = .0009). Deletion of CAF-HIF2 modestly reduced tumor fibrosis and significantly decreased the intratumoral recruitment of immunosuppressive M2 macrophages and regulatory T cells. Treatment with the clinical HIF2 inhibitor PT2399 significantly reduced in vitro macrophage chemotaxis and M2 polarization, and improved tumor responses to immunotherapy in both syngeneic PDAC mouse models.

CONCLUSIONS

Together, these data suggest that stromal HIF2 is an essential component of PDAC pathobiology and is a druggable therapeutic target that could relieve tumor microenvironment immunosuppression and enhance immune responses in this disease.

p16 Represses DNA Damage Repair via a Novel Ubiquitin-Dependent Signaling Cascade

Squamous cell carcinoma driven by human papillomavirus (HPV) is more sensitive to DNA-damaging therapies than its HPV-negative counterpart. Here, we show that p16, the clinically used surrogate for HPV positivity, renders cells more sensitive to radiotherapy via a ubiquitin-dependent signaling pathway, linking high levels of this protein to increased activity of the transcription factor SP1, increased HUWE1 transcription, and degradation of ubiquitin-specific protease 7 (USP7) and TRIP12. Activation of this pathway in HPV-positive disease led to decreased homologous recombination and improved response to radiotherapy, a phenomenon that can be recapitulated in HPV-negative disease using USP7 inhibitors in clinical development. This p16-driven axis induced sensitivity to PARP inhibition and potentially leads to "BRCAness" in head and neck squamous cell carcinoma (HNSCC) cells. Thus, these findings support a functional role for p16 in HPV-positive tumors in driving response to DNA damage, which can be exploited to improve outcomes in both patients with HPV-positive and HPV-negative HNSCC.

SIGNIFICANCE

In HPV-positive tumors, a previously undiscovered pathway directly links p16 to DNA damage repair and sensitivity to radiotherapy via a clinically relevant and pharmacologically targetable ubiquitin-mediated degradation pathway.

Targeting DNA damage response in head and neck cancers through abrogation of cell cycle checkpoints

PURPOSE

Head and neck cancers (HNSCC) are routinely treated with radiotherapy; however, normal tissue toxicity remains a concern. Therefore, it is important to validate treatment modalities combining molecularly targeted agents with radiotherapy to improve the therapeutic ratio. The aim of this study was to assess the ability of the PARP inhibitor niraparib (MK-4827) alone, or in combination with cell cycle checkpoint abrogating drugs targeting Chk1 (MK-8776) or Wee1 (MK-1775), to radiosensitize HNSCCs in the context of HPV status.

MATERIALS AND METHODS

PARP1, PARP2, Chk1 or Wee1 shRNA constructs were analyzed from an in vivo shRNA screen of HNSCC xenografts comparing radiosensitization differences between HPV(+) and HPV(-) tumors. Radiosensitization by niraparib alone or in combination with MK-8776 or MK-1775 was assessed by clonogenic survival in HPV(-) and HPV(+) cells; and the role of p16 in determining response was explored. Relative expressions of DNA repair genes were compared by PCR array in HPV(+) and HPV(-) cells, and following siRNA-mediated knockdown of TRIP12 in HPV(-) cells.

RESULTS

In vivo shRNA screening showed a modest preferential radiosensitization by Wee1 and PARP2 in HPV(-) and Chk1 in HPV(+) tumor models. Niraparib alone enhanced the radiosensitivity of all HNSCC cell lines tested. However, HPV(-) cells were sensitized to a greater degree, as suggested by the shRNA screen. When combined with MK-8776 or MK-1775, radiosensitization was further enhanced in an HPV dependent manner with HPV(+) cells enhanced by MK-8776 and HPV(-) cells enhanced by MK-1775. A PCR array for DNA repair genes showed PARP and HR proteins BRCA1 and RAD51 were much lower in HPV(+) cells than in HPV(-). Similarly, directly knocking down p16-dependent TRIP12 decreased expression of these same genes. Overexpressing p16 decreased TRIP12 expression and increased radiosensitivity in HPV(-) HN5. However, while PARP inhibition led to significant radiosensitization in the control, it led to no further significant radiosensitization in p16 overexpressing cells. Forced p16 expression in HPV(-) HN5 increased accumulation in G1 and subG1 and limited progression to S phase, thus reducing effectiveness of PARP inhibition.

CONCLUSIONS

Niraparib effectively radiosensitizes HNSCCs with a greater benefit seen in HPV(-). HPV status also plays a role in response to MK-8776 or MK-1775 when combined with niraparib due to differences in DNA repair mechanisms. This study suggests that using cell cycle abrogators in combination with PARP inhibitors may be a beneficial treatment option in HNSCC, but also emphasizes the importance of HPV status when considering effective treatment strategies.

Mitochondrial fusion exploits a therapeutic vulnerability of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) requires mitochondrial oxidative phosphorylation (OXPHOS) to fuel its growth, however, broadly inhibiting this pathway might also disrupt essential mitochondrial functions in normal tissues. PDAC cells exhibit abnormally fragmented mitochondria that are essential to its oncogenicity, but it was unclear if this mitochondrial feature was a valid therapeutic target. Here, we present evidence that normalizing the fragmented mitochondria of pancreatic cancer via the process of mitochondrial fusion reduces OXPHOS, which correlates with suppressed tumor growth and improved survival in preclinical models. Mitochondrial fusion was achieved by genetic or pharmacologic inhibition of dynamin related protein-1 (Drp1) or through overexpression of mitofusin-2 (Mfn2). Notably, we found that oral leflunomide, an FDA-approved arthritis drug, promoted a two-fold increase in Mfn2 expression in tumors and was repurposed as a chemotherapeutic agent, improving the median survival of mice with spontaneous tumors by 50% compared to vehicle. We found that the chief tumor suppressive mechanism of mitochondrial fusion was enhanced mitophagy, which proportionally reduced mitochondrial mass and ATP production. These data suggest that mitochondrial fusion is a specific and druggable regulator of pancreatic cancer growth that could be rapidly translated to the clinic.

Selective EGLN Inhibition Enables Ablative Radiotherapy and Improves Survival in Unresectable Pancreatic Cancer

When pancreatic cancer cannot be removed surgically, patients frequently experience morbidity and death from progression of their primary tumor. Radiation therapy (RT) cannot yet substitute for an operation because radiation causes fatal bleeding and ulceration of the nearby stomach and intestines before achieving tumor control. There are no FDA-approved medications that prevent or reduce radiation-induced gastrointestinal injury. Here, we overcome this fundamental problem of anatomy and biology with the use of the oral EGLN inhibitor FG-4592, which selectively protects the intestinal tract from radiation toxicity without protecting tumors. A total of 70 KPC mice with autochthonous pancreatic tumors received oral FG-4592 or vehicle control ± ablative RT to a cumulative 75 Gy administered in 15 daily fractions to a limited tumor field. Although ablative RT reduced complications from local tumor progression, fatal gastrointestinal bleeding was observed in 56% of mice that received high-dose RT with vehicle control. However, radiation-induced bleeding was completely ameliorated in mice that received high-dose RT with FG-4592 (0% bleeding, P < 0.0001 compared with vehicle). Furthermore, FG-4592 reduced epithelial apoptosis by half (P = 0.002) and increased intestinal microvessel density by 80% compared with vehicle controls. EGLN inhibition did not stimulate cancer growth, as treatment with FG-4592 alone, or overexpression of HIF2 within KPC tumors independently improved survival. Thus, we provide a proof of concept for the selective protection of the intestinal tract by the EGLN inhibition to enable ablative doses of cytotoxic therapy in unresectable pancreatic cancer by reducing untoward morbidity and death from radiation-induced gastrointestinal bleeding. SIGNIFICANCE: Selective protection of the intestinal tract by EGLN inhibition enables potentially definitive doses of radiation therapy. This might allow radiation to be a surgical surrogate for unresectable pancreatic cancer.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/79/9/2327/F1.large.jpg.

Enteral Activation of WR-2721 Mediates Radioprotection and Improved Survival from Lethal Fractionated Radiation

Unresectable pancreatic cancer is almost universally lethal because chemotherapy and radiation cannot completely stop the growth of the cancer. The major problem with using radiation to approximate surgery in unresectable disease is that the radiation dose required to ablate pancreatic cancer exceeds the tolerance of the nearby duodenum. WR-2721, also known as amifostine, is a well-known radioprotector, but has significant clinical toxicities when given systemically. WR-2721 is a prodrug and is converted to its active metabolite, WR-1065, by alkaline phosphatases in normal tissues. The small intestine is highly enriched in these activating enzymes, and thus we reasoned that oral administration of WR-2721 just before radiation would result in localized production of the radioprotective WR-1065 in the small intestine, providing protective benefits without the significant systemic side effects. Here, we show that oral WR-2721 is as effective as intraperitoneal WR-2721 in promoting survival of intestinal crypt clonogens after morbid irradiation. Furthermore, oral WR-2721 confers full radioprotection and survival after lethal upper abdominal irradiation of 12.5 Gy × 5 fractions (total of 62.5 Gy, EQD2 = 140.6 Gy). This radioprotection enables ablative radiation therapy in a mouse model of pancreatic cancer and nearly triples the median survival compared to controls. We find that the efficacy of oral WR-2721 stems from its selective accumulation in the intestine, but not in tumors or other normal tissues, as determined by in vivo mass spectrometry analysis. Thus, we demonstrate that oral WR-2721 is a well-tolerated, and quantitatively selective, radioprotector of the intestinal tract that is capable of enabling clinically relevant ablative doses of radiation to the upper abdomen without unacceptable gastrointestinal toxicity.

Abstract 4164: Fasting protects mice from lethal radiation by promoting small intestinal stem cell survival

Pancreatic cancer is the fourth leading cause of cancer-related deaths in the US. Surgical resection is the only potentially curative treatment; however, only 15%-20% of patients present with tumors that can be resected. There is no consensus regarding standard of care in unresectable cases, however many academic centers use stereotactic body radiotherapy (SBRT) to give tumor-directed radiotherapy (RT). Unfortunately, even this conformal technique can still cause severe gastrointestinal (GI) toxic effects caused by the proximity of the pancreatic head to the duodenum. Protecting the intestine from the toxic effects of radiation may enable dose escalation that could achieve more effective local control of disease. We and others have previously shown that a prolonged fast of 24 hours protects mice from lethal doses of etoposide. In this study, we extend and build on our previous finding to demonstrate that a similar 24 hour fast also protects from lethal doses of total abdominal radiation. Histologic analyses, using the Withers-Elkind microcolony assay, show that fasting protected small intestinal (SI) stem cells from radiation damage and promoted early regeneration. To show a proof-of-principle for the use of this radioporotective maneuver in cancer therapy, we developed an orthotopic model of pancreatic cancer using KPC tumor cells syngeneic to C57BL/6. Here, we show that fasting-mediated intestinal protection enabled dose escalated SBRT for treatment of these orthotopic tumors. RT with fasting radioprotection delayed tumor growth and improved survival compared to controls. Given this robust phenotype, we developed a 3D culture ex vivo assay using intestinal stem cell enriched epithelial spheroid cultures. We modified these intestinal spheroids with a bioluminescent reporter and used these cells to develop a modified clonogenic assay for 3D culture that can be used to identify novel radioprotectors, such as a fasting mimetic. Taken together, these results suggest that fasting protects small intestinal stem cells sufficiently to allow animals to receive potentially curative doses of abdominal radiation that would other wise be lethal. Future work will aim to identifying the mechanism by which fasting confers intestinal protection and drug candidates that can be used to mimic this fasting-mediated protection.

Citation Format: Marimar de la Cruz Bonilla, Kristina M. Stemler, Tara N. Fujimoto, Sabrina Jeter-Jones, Jessica M. Molkentine, Gabriela M. Asencio Torres, Cullen M. Taniguchi, Helen Piwnica-Worms. Fasting protects mice from lethal radiation by promoting small intestinal stem cell survival [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4164.

Tumor-Associated Fatigue in Cancer Patients Develops Independently of IL1 Signaling

Fatigue is the most common symptom of cancer at diagnosis, yet causes and effective treatments remain elusive. As tumors can be highly inflammatory, it is generally accepted that inflammation mediates cancer-related fatigue. However, evidence to support this assertion is mostly correlational. In this study, we directly tested the hypothesis that fatigue results from propagation of tumor-induced inflammation to the brain and activation of the central proinflammatory cytokine, IL1. The heterotopic syngeneic murine head and neck cancer model (mEER) caused systemic inflammation and increased expression of Il1b in the brain while inducing fatigue-like behaviors characterized by decreased voluntary wheel running and exploratory activity. Expression of Il1b in the brain was not associated with any alterations in motivation, measured by responding in a progressive ratio schedule of food reinforcement, depression-like behaviors, or energy balance. Decreased wheel running occurred prior to Il1b detection in the brain, when systemic inflammation was minimal. Furthermore, mice null for two components of IL1β signaling, the type 1 IL1 receptor or the receptor adapter protein MyD88, were not protected from tumor-induced decreases in wheel running, despite attenuated cytokine action and expression. Behavioral and inflammatory analysis of four additional syngeneic tumor models revealed that tumors can induce fatigue regardless of their systemic or central nervous system inflammatory potential. Together, our results show that brain IL1 signaling is not necessary for tumor-related fatigue, dissociating this type of cancer sequela from systemic cytokine expression.Significance: These findings challenge the current understanding of fatigue in cancer patients, the most common and debilitating sequela associated with malignancy. Cancer Res; 78(3); 695-705. ©2017 AACR.

Neuroimmune mechanisms of behavioral alterations in a syngeneic murine model of human papilloma virus-related head and neck cancer

Patients with cancer often experience a high symptom burden prior to the start of treatment. As disease- and treatment-related neurotoxicities appear to be additive, targeting disease-related symptoms may attenuate overall symptom burden for cancer patients and improve the tolerability of treatment. It has been hypothesized that disease-related symptoms are a consequence of tumor-induced inflammation. We tested this hypothesis using a syngeneic heterotopic murine model of human papilloma virus (HPV)-related head and neck cancer. This model has the advantage of being mildly aggressive and not causing cachexia or weight loss. We previously showed that this tumor leads to increased IL-6, IL-1β, and TNF-α expression in the liver and increased IL-1β expression in the brain. The current study confirmed these features and demonstrated that the tumor itself exhibits high inflammatory cytokine expression (e.g., IL-6, IL-1β, and TNF-α) compared to healthy tissue. While there is a clear relationship between cytokine levels and behavioral deficits in this model, the behavioral changes are surprisingly mild. Therefore, we sought to confirm the relationship between behavior and inflammation by amplifying the effect using a low dose of lipopolysaccharide (LPS, 0.1mg/kg). In tumor-bearing mice LPS induced deficits in nest building, tail suspension, and locomotor activity approximately 24h after LPS. However, these mice did not display an exacerbation of LPS-induced weight loss, anorexia, or anhedonia. Further, while heightened serum IL-6 was observed there was minimal priming of liver or brain cytokine expression. Next we sought to inhibit tumor-induced burrowing deficits by reducing inflammation using minocycline. Minocycline (∼50mg/kg/day in drinking water) was able to attenuate tumor-induced inflammation and burrowing deficits. These data provide evidence in favor of an inflammatory-like mechanism for the behavioral alterations associated with tumor growth in a syngeneic murine model of HPV-related head and neck cancer. However, the inflammatory state and behavioral changes induced by this tumor clearly differ from other forms of inflammation-induced sickness behavior.

TRIP12 as a mediator of human papillomavirus/p16-related radiation enhancement effects

Patients with human papillomavirus (HPV)-positive head and neck squamous cell carcinoma (HNSCC) have better responses to radiotherapy and higher overall survival rates than do patients with HPV-negative HNSCC, but the mechanisms underlying this phenomenon are unknown. p16 is used as a surrogate marker for HPV infection. Our goal was to examine the role of p16 in HPV-related favorable treatment outcomes and to investigate the mechanisms by which p16 may regulate radiosensitivity. HNSCC cells and xenografts (HPV/p16-positive and -negative) were used. p16-overexpressing and small hairpin RNA-knockdown cells were generated, and the effect of p16 on radiosensitivity was determined by clonogenic cell survival and tumor growth delay assays. DNA double-strand breaks (DSBs) were assessed by immunofluorescence analysis of 53BP1 foci; DSB levels were determined by neutral comet assay; western blotting was used to evaluate protein changes; changes in protein half-life were tested with a cycloheximide assay; gene expression was examined by real-time polymerase chain reaction; and data from The Cancer Genome Atlas HNSCC project were analyzed. p16 overexpression led to downregulation of TRIP12, which in turn led to increased RNF168 levels, repressed DNA damage repair (DDR), increased 53BP1 foci and enhanced radioresponsiveness. Inhibition of TRIP12 expression further led to radiosensitization, and overexpression of TRIP12 was associated with poor survival in patients with HPV-positive HNSCC. These findings reveal that p16 participates in radiosensitization through influencing DDR and support the rationale of blocking TRIP12 to improve radiotherapy outcomes.

Sickness behavior induced by cisplatin chemotherapy and radiotherapy in a murine head and neck cancer model is associated with altered mitochondrial gene expression

The present study was undertaken to explore the possible mechanisms of the behavioral alterations that develop in response to cancer and to cancer therapy. For this purpose we used a syngeneic heterotopic mouse model of human papilloma virus (HPV)-related head and neck cancer in which cancer therapy is curative. Mice implanted or not with HPV+ tumor cells were exposed to sham treatment or a regimen of cisplatin and radiotherapy (chemoradiation). Sickness was measured by body weight loss and reduced food intake. Motivation was measured by burrowing, a highly prevalent species specific behavior. Tumor-bearing mice showed a gradual decrease in burrowing over time and increased brain and liver inflammatory cytokine mRNA expression by 28 days post tumor implantation. Chemoradiation administered to healthy mice resulted in a mild decrease in burrowing, body weight, and food intake. Chemoradiation in tumor-bearing mice decreased tumor growth and abrogated liver and brain inflammation, but failed to attenuate burrowing deficits. PCR array analysis of selected hypoxia and mitochondrial genes revealed that both the tumor and chemoradiation altered the expression of genes involved in mitochondrial energy metabolism within the liver and brain and increased expression of genes related to HIF-1α signaling within the brain. The most prominent changes in brain mitochondrial genes were noted in tumor-bearing mice treated with chemoradiation. These findings indicate that targeting mitochondrial dysfunction following cancer and cancer therapy may be a strategy for prevention of cancer-related symptoms.

Inhibition of P-TEFb by DRB suppresses SIRT1/CK2α pathway and enhances radiosensitivity of human cancer cells

BACKGROUND

Positive transcription elongation factor-b (P-TEFb) is a complex containing CDK9 and a cyclin (T1, T2 or K). The effect of inhibition of P-TEFb by 5,6-dichloro-l-β-D-ribofuranosyl benzimidazole (DRB) on cell radiosensitivity and the underlying mechanisms were investigated.

MATERIALS AND METHODS

Six human cancer cell lines were subjected to (3)H-uridine incorporation, cell viability and clonogenic cell survival assays; cell-cycle redistribution and apoptosis assay; western blots and nuclear 53BP1 foci analysis after exposing the cells to DRB with/without γ-radiation.

RESULTS

DRB suppressed colony formation and enhanced radiosensitivity of all cell lines. DRB caused a further increase in radiation-induced apoptosis and cell-cycle redistribution depending on p53 status. DRB prolonged the presence of radiation-induced nuclear p53 binding protein-1 (53BP1) foci and suppressed the expression of sirtuin-1 (SIRT1) and casein kinase 2-alpha (CK2α), suggesting an inhibition of DNA repair processes.

CONCLUSION

Our findings indicate that DRB has the potential to increase the efficacy of radiotherapy and warrants further investigation using in vivo tumor models.

Abstract 4895: P16INK4A, a surrogate marker of HPV infection and prognosis for head and neck cancer, delays DNA damage repair and enhances radiation response

Human papillomavirus (HPV) type 16 is a major cause of oropharyngeal carcinoma (OPC). P16INK4A has been suggested to be a reliable surrogate marker of HPV-associated OPC with 100% sensitivity and about 80% specificity. Increasing data showed tumor HPV positivity or p16 expression was strongly associated with significantly better prognosis in patients with OPC. As a tumor suppressor gene, p16 has biological functions including regulation of cell cycle progression at the G1/S boundary, angiogenesis, cell senescence, tumor invasion, cell spreading, apoptosis and anoikis. The present study was undertaken to assess the role of p16 in regulating tumor radioresponse and the underlying mechanisms in OPC cell lines.

OPC cell lines HN-5 (HPV and p16 negative) and UMSCC-47 (HPV and p16 positive) were used. P16 overexpressing HN-5 cells and shRNA p16 knockdown UMSCC-47 cells were generated using lentivirus vectors. Treatment endpoint was clonogenic cell survival (CSA) determined 10-12 days (for HN5) or 17-20 days (for UMSCC-47) after exposing the cells to 2-10 Gy single doses of γ-radiation (IR). Compared with the control (scramble) cells, p16-overexpressing HN5 cells had significantly higher radiosensitivity (by a factor of 1.56 at 0.1 cell survival fraction); whereas, p16-knockingdown UMSCC-47 cells had less radiosensitivity (by a factor of 1.23 at 0.1 cell survival fraction). Overexpressing P16 in HN-5 cells significantly prolonged the presence of radiation-induced double-strand breaks detected on the basis of 53BP1 foci at 24h after 4 Gy IR. To directly gauge damaged DNA, an alkaline comet assay to detect both single- and double-strand DNA breaks was performed. P16 overexpressing HN-5 cells exhibited a 2.09-fold increase in the comet ‘tail moment’ 48 hours after IR. This finding was supported by increased expression of 53BP1 analyzed by Western blot.

In conclusion, other than being a robust surrogate marker for tumor control and survival outcome, our findings demonstrated that p16 also functions as a potent radiation sensitizer. The major underlying mechanism of p16 regulating radiosensitivity is by inhibition of DNA damage repair.

Citation Format: Li Wang, Peijing Zhang, David P Molkentine, Hailong Piao, Chunyan Chen, Jessica M Molkentine, Jinsong Zhang, David R Valdecanas, Heath Skinner, Thomas A Buchholz, Junjie Chen, Li Ma, Kathy A Mason, Kie-kian Ang, Raymond E Meyn. P16INK4A, a surrogate marker of HPV infection and prognosis for head and neck cancer, delays DNA damage repair and enhances radiation response. [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 4895. doi:10.1158/1538-7445.AM2014-4895

Abstract 4435: Targeting Met signaling to overcome human cancer cell resistance to radiation

Purpose: Targeting signaling pathways that are implicated in cancer cell resistance to therapy are being investigated to improve therapy outcome. One of the receptor tyrosine kinases, c-Met (Met) is frequently overexpressed in many cancer types including non small cell lung cancers (NSCLCs) and head and neck squamous cell carcinomas (HNSCCs) and is associated with resistance to radiation. EMD1214063 is a small molecule inhibitor that suppresses the kinase activity of Met. The current study investigated the potential of EMD1214063 (provided by EMD Serono Merck Inc) in enhancing cancer cell sensitivity to radiation.

Materials and Methods: Three NSCLC lines (A549, H460 and H1993) and three HNSCC lines (FaDu, HN-5 and UMSCC-1) with different levels of Met protein were used for the study. The effects of EMD1214063 on Met expression, cell viability, migration and cell radiosensitivity were assessed. Various scheduling effect on the magnitude of increased cell radiosensitivity was evaluated. 53BP1 foci formation was assayed for DNA repair kinetics. In vivo tumor growth delay assays on two NSCLCs and two HNSCCs generated in mice were performed to test the efficacy of EMD1214063 on tumor growth and tumor response to radiation.

Results: NSCLC lines expressed higher levels of Met than HNSCC lines. EMD1214063 reduced survival of NSCLC lines markedly and had a minimal effect on HNSCC lines in vitro. Western blots showed three major Met protein bands with molecular weights of about 145 kDa, 60 kDa and 45 kDa. Radiation increased the expression levels of the 145 kDa and 60 kDa fragments of Met in a dose dependent manner. EMD1214063 suppressed the radiation-induced expression of Met and prolonged the presence of 53BP1 foci. It potently enhanced the radiosensitivity of A549, H1993, HN-5 and FaDu but not that of H460 and UMSCC-1. The enhancement factors at the survival fraction of 0.5 ranged from 1.11 to 2.24, with H1993 being the most responsive cell line. In vivo data showed lack of single agent activity of EMD1214063 on the growth of tumor xenografts tested (A549, H460 and FaDu). However, it showed a schedule dependent effect in enhancing A549 tumor xenograft response to radiation: a marked enhancement was observed only when EMD1214063 was given concurrently with fractionated doses of radiation. In vivo studies on other tumor types are ongoing.

Conclusions: This study demonstrated that EMD1214063 reduced viability and migration of NSCLC cells and it selectively enhanced radiosensitivity of cells that express higher levels of basal or induced Met and the underlying mechanism may be inhibition of DNA repair. In vivo study data showed EMD1214063 induced a schedule dependent enhancement of tumor response to radiation in a NSCLC line. These data warrant further in vivo investigations aiming at taking best regimens to the clinic testing.

This study is being supported by EMD Serono Merck via an independent medical grant.

Citation Format: Uma Raju, David P. Molkentine, Jessica M. Molkentine, David N. Valdecanas, K Kian Ang. Targeting Met signaling to overcome human cancer cell resistance to radiation. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4435. doi:10.1158/1538-7445.AM2013-4435

MK-1775, a novel Wee1 kinase inhibitor, radiosensitizes p53-defective human tumor cells

PURPOSE

Radiotherapy is commonly used to treat a variety of solid tumors. However, improvements in the therapeutic ratio for several disease sites are sorely needed, leading us to assess molecularly targeted therapeutics as radiosensitizers. The aim of this study was to assess the wee1 kinase inhibitor, MK-1775, for its ability to radiosensitize human tumor cells.

EXPERIMENTAL DESIGN

Human tumor cells derived from lung, breast, and prostate cancers were tested for radiosensitization by MK-1775 using clonogenic survival assays. Both p53 wild-type and p53-defective lines were included. The ability of MK-1775 to abrogate the radiation-induced G₂ block, thereby allowing cells harboring DNA lesions to prematurely progress into mitosis, was determined using flow cytometry and detection of γ-H2AX foci. The in vivo efficacy of the combination of MK-1775 and radiation was assessed by tumor growth delay experiments using a human lung cancer cell line growing as a xenograft tumor in nude mice.

RESULTS

Clonogenic survival analyses indicated that nanomolar concentrations of MK-1775 radiosensitized p53-defective human lung, breast, and prostate cancer cells but not similar lines with wild-type p53. Consistent with its ability to radiosensitize, MK-1775 abrogated the radiation-induced G₂ block in p53-defective cells but not in p53 wild-type lines. MK-1775 also significantly enhanced the antitumor efficacy of radiation in vivo as shown in tumor growth delay studies, again for p53-defective tumors.

CONCLUSIONS

These results indicate that p53-defective human tumor cells are significantly radiosensitized by the potent and selective wee1 kinase inhibitor, MK-1775, in both the in vitro and in vivo settings. Taken together, our findings strongly support the clinical evaluation of MK-1775 in combination with radiation.

Abstract 2488: Co-targeting EGFR and IGF-1R to sensitize or overcome induced resistance of head and neck cancer models to radiation

Purpose: Emerging data show crosstalk among receptor tyrosine kinases (RTK), e.g., epidermal growth factor receptor (EGFR) and insulin-like growth factor receptor (IGF-1R). Higher IGF-1R expression was associated with resistance to EGFR inhibitors and ionizing radiation (IR). We investigated the effects of cetuximab (EGFR antibody) and A12 (IGF-1R antibody) on the response of head and neck squamous cell carcinoma (HNSCC) to IR, escape mechanisms from EGFR blockade leading to radioresistance, and strategies to overcome it.

Methods: Three HNSCC models (HN-5, FaDu, and UMSCC-1) expressing different levels of EGFR and IGF-1R were studied. The effects of cetuximab and A12 (from Imclone) on cell viability (MTS assay) and radiosensitivity (clonogenic survival assay) were determined. Various scheduling of drugs were examined. Alterations in target signaling were analyzed by Western blots.

Results: Cetuximab inhibited viability of cells (14 to 53%) in a cell type dependent manner. The highest EGFR expressing HN-5 was the most responsive to cetuximab. A12 had no effect on cell viability but elicited a moderate radiosensitization of all three cell lines (enhancement factors, EFs, ranged from 1.11 to 1.67). Cetuximab, given 6 h before till 66 h after IR, significantly enhanced the radiosensitivity of HN-5 (EF, 2.55) and FaDu (EF, 1.46), but no effect on UMSCC-1. A 48 h exposure to cetuximab before IR, however, increased radioresistance of HN-5 and FaDu without affecting UMSCC-1. Continuing with cetuximab for 72 h after IR resulted in a net radiation sensitization in HN-5, partially reversed radioresistance in FaDu, and enhanced the radiosensitivity of UMSCC-1. Western blots revealed that cetuximab (48 h) upregulated IGF-1R in FaDu (2.28 fold) and UMSCC-1 (1.26 fold) but, not in HN-5; however, EGFR was upregulated in HN-5. IGF-1R inhibition had no effect on HN-5, reverted the radiation response partially in FaDu, and increased the net radiosensitivity of UMSCC-1. Compared to EGFR inhibition alone, co-targeting of both pathways did not yield a better effect on HN-5, reverted radiosensitivity to the baseline level in FaDu, but further increased UMSCC-1 radiosensitivity.

Conclusion: This study showed that tumors responded to prolonged EGFR inhibition by upregulating other pro-survival RTK signaling, e.g. IGF-1R. In HN-5, EGFR was a main pro-survival signaling as EGFR inhibition yielded consistent sensitization that was not enhanced by IGF-1R blockade. UMSCC-1 seemed to rely on EGFR and IGF-1R signaling as dual inhibition yielded better sensitization than single pathway blockade. In FaDu, IGF-1R could become a major pro-survival signaling as it was associated with increased resistance that was only reverted by co-targeting IGF-1R. Taken together our data suggest that therapeutic benefit would result from combining cetuximab and A12 with IR in some HNSCC.

Supported by P0-1 CA-06294

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2488. doi:10.1158/1538-7445.AM2011-2488