Factors associated with blunt internal carotid artery injury in petrous temporal bone fractures

INTRODUCTION

Traumatic internal carotid artery (ICA) injuries are an uncommon complication of petrous temporal bone (PTB) fractures that can have devastating consequences of stroke, haemorrhage and death. Current guidelines suggest that all PTB fractures should be screened for blunt cerebrovascular injury, however clinical practice varies. The purpose of this study was to identify features associated with PTB fractures that increase the likelihood of ICA injury.

METHODS

A retrospective cohort study was performed on all patients with PTB fractures who were investigated with computed-tomography angiography (CTA) scan admitted to a Level One Trauma Service in Melbourne, Australia from 2015-2020. Patient demographic and injury data were obtained from The Royal Melbourne Hospital Trauma Registry and medical records. Multivariate binomial logistic regression was performed to identify features associated with ICA injury.

RESULTS

Out of 377 patients with 419 PTB fractures, 205 received a CTA scan and were included, identifying 22 ICA injuries (9.4%). The median age of ICA injuries was 33 (IQR 23-61), median Abbreviated Injury Scale (AIS) score for the head region was 5 (IQR 5-5) and the in-hospital mortality rate was 45.5%, mainly due to unsurvivable brain injury. Five patients (22.7%) developed ICA-specific complications of stroke or carotid-cavernous fistula. We identified five factors that were significantly associated with ICA injury. These included PTB fractures involving the carotid canal (OR 6.7, 95% CI 1.9-23.9, p=0.003), presenting with an initial GCS less than nine (OR 5.7, 95% CI 1.2-26.5, p=0.025) and increasing head AIS (OR 2.4, 95% CI 1.2-4.6, p=0.009). Mechanisms of injury that were associated with ICA injury were motor vehicle crash (OR 4.4, 95% CI 1.4-14.2, p=0.012) and motorbike crash (OR 4.6, 95% CI 1.2-18, p=0.029).

CONCLUSION

Patients with PTB fractures and an additional feature of carotid canal involvement, presenting GCS less than nine, increasing head AIS indicative of severe head trauma or mechanism of injury by motor vehicle or motorbike crash, are at an increased risk of ICA injury and should be screened with a CTA scan.

Eribulin Synergistically Increases Anti-Tumor Activity of an mTOR Inhibitor by Inhibiting pAKT/pS6K/pS6 in Triple Negative Breast Cancer

Unlike other breast cancer subtypes, patients with triple negative breast cancer (TNBC) have poor outcomes and no effective targeted therapies, leaving an unmet need for therapeutic targets. Efforts to profile these tumors have revealed the PI3K/AKT/mTOR pathway as a potential target. Activation of this pathway also contributes to resistance to anti-cancer agents, including microtubule-targeting agents. Eribulin is one such microtubule-targeting agent that is beneficial in treating taxane and anthracycline refractory breast cancer. In this study, we compared the effect of eribulin on the PI3K/AKT/mTOR pathway with other microtubule-targeting agents in TNBC. We found that the phosphorylation of AKT was suppressed by eribulin, a microtubule depolymerizing agent, but activated by paclitaxel, a microtubule stabilizing agent. The combination of eribulin and everolimus, an mTOR inhibitor, resulted in an increased reduction of p-S6K1 and p-S6, a synergistic inhibition of cell survival in vitro, and an enhanced suppression of tumor growth in two orthotopic mouse models. These findings provide a preclinical foundation for targeting both the microtubule cytoskeleton and the PI3K/AKT/mTOR pathway in the treatment of refractory TNBC.

Baicalein upregulates DDIT4 expression which mediates mTOR inhibition and growth inhibition in cancer cells

Baicalein is a natural flavone that exhibits anticancer properties. Using microarrays we found that DDIT4 was the highest transcript induced by baicalein in cancer cells. We confirmed in multiple cancer cell lines large, dose-related expression of DDIT4 by quantitative RT-PCR and immunoblot, which correlates with growth inhibition. Time course experiments demonstrate that DDIT4 is rapidly inducible, with high expression maintained for several days in vitro. Induction of DDIT4 expression is p53 independent based on evaluation of p53 knockout cells. Since DDIT4 is known to inhibit mTORC1 activity we confirmed that baicalein suppresses phosphorylation of mTORC1 targets. Using RNA interference we demonstrate that mTORC1 activity and growth inhibition by baicalein is attenuated by knockdown of DDIT4. We furthermore demonstrate suppression of established tumors by baicalein in a mouse model of breast cancer with increased DDIT4 expression in the tumors. Finally, we demonstrate that baicalein upregulates DDIT4 and causes mTORC1 and growth inhibition in platinum resistant cancer cells in marked contrast to platinum chemotherapy treatment. These studies demonstrate that baicalein inhibits mTORC1 through DDIT4 expression, and may be useful in cancer chemotherapy and chemoprevention.

Abstract P3-03-08: A comparison of PI3K inhibition by eribulin, other microtubule targeting agents and a DNA-damaging chemotherapeutic in triple negative and HER2 expressing breast cancer cell lines

Background. Eribulin is a microtubule-targeting agent with significant benefits in treating refractory metastatic breast cancer. Tumors from patients with Triple negative breast cancer (TNBC) have high levels of Akt expression and consistently show activation of the PI3K-mTOR pathway. Our objective was to compare Eribulin's ability to inhibit PI3K pathway activity and cell growth with two other microtubule targeting agents, Paclitaxel and Vinblastine, as well as a conventional DNA damaging chemotherapeutic Cisplatin.

Methods. MDA468 and BT549 TNBC cell lines and SKBR3 HER2 overexpressing breast cancer cell lines were used for this study. Western blot analysis was used to evaluate the expression of phosphorylated Akt-Ser473 (pAkt) and S6K1 (pS6K1) at different time points from 2 to 24 hours of treatment with Eribulin, Paclitaxel, Vinblastine, or Cisplatin. MTT assays were used to assess growth inhibition after 72 hours of treatment.

Results. Western blot analysis for MDA468 cells treated with Eribulin in varying concentrations confirm partial inhibition of pAkt expression as early as 4 hours at 100 pM concentration. Complete inhibition is reached at 50 nM. Partial inhibition of pS6K1 can be seen as early as 4 hours at 500 nM. Western analysis for MDA468 cells treated with Vinblastine in varying concentrations confirms inhibition of pAkt and pS6K1 beginning at 50 nM at 24 hours. Western analysis for MDA468 cells treated with Paclitaxel in varying concentrations showed increases in pAkt expression in a dose responsive fashion with significant increase in pAkt beginning at 5 nM concentration as well as increase in pS6K1 at 24 hours. Cisplatin markedly increases pAkt at 24 hours in a dose responsive fashion and decreases pS6K1 at 500 nM to 1000 nM concentration range in BT549. The IC50's for Eribulin ranged from 0.06 nM to 0.3 nM at 72 hours by MTT assay. The IC50's for Vinblastine ranged from 0.5 nM to 0.9 nM. Paclitaxel has reported IC50's in the 2 nM to 75 nM range in these cell lines, and Cisplatin has IC50's ranging from to ∼500 nM to ∼2000 nM at 72 hours in these cell lines.

Conclusion. Our study shows that for microtubule targeting agents such as Eribulin and Vinblastine that block polymerization of tubulin into microtubules, both pAkt and pS6K1 expression is suppressed. Growth inhibition is also confirmed, and is seen at doses when pAkt and pS6K1 are not suppressed. Eribulin inhibits pAkt and pS6K1 at lower concentrations than Vinblastine. With Paclitaxel, a microtubule-targeting agent that enhances polymerization of tubulin to microtubules, and Cisplatin, a conventional DNA damaging chemotherapeutic we observe an increase in pAkt expression, with variable effects on pS6K1. Enhancement of Akt activity is a likely survival response by cancer cells to chemotherapy, yet in the case of microtubule polymerization blockade as seen with Eribulin and Vinblastine, Akt activity is suppressed, along with downstream mTOR activity. The potential role of microtubule polymerization blockade in inhibition of the PI3K pathway needs further study. It may be a factor in the novel finding of pAkt and pS6K1 inhibition by Eribulin.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P3-03-08.

Abstract P3-03-07: Combination of eribulin and PI3K inhibitors in triple negative and HER2 expressing breast cancer cell lines results in synergistic growth inhibition and enhanced inhibition of the PI3K pathway

Background. Patients with triple negative breast cancer (TNBC) have high levels of pAkt expression and activation of the PI3K-mTOR pathway. Eribulin is a microtubule-targeting agent with benefits in treating taxane and anthracycline refractory breast cancer. Our objective was to evaluate its efficacy in inhibiting PI3K pathway activity and cell growth both alone and in combination with PI3K/MTOR inhibitors BEZ 235 and BKM 120.

Methods. TNBC cell lines MDA468, BT549, HS587T, MDA231, and HER2 expressing breast cancer cell line SKBR3 were used for this study. Both MDA468 and BT549 have PI3K- related mutations. The tetrazolium salt, 3-4,5 dimethylthiazol-2,5 diphenyl tetrazolium bromide (MTT) assays were used to assess growth inhibition after 72 hour treatment with eribulin, BEZ 235 and BKM 120 both alone and in combination. Combination indices (CI) generated by Chou-Talalay plots were used to quantify synergy. Western blots were used to evaluate the expression of phosphorylated Akt (pAkt), S6K1 (pS6K1) and S6 (pS6) from 30 min to 24 hours of treatment at different doses.

Results. Eribulin has IC50 ranging from 60 pM to 300 pM, BEZ 235 has IC50 ranging from 50 nM to 80 nM, and BKM has IC50 ranging from 500 nM or higher. Standard dilutions of eribulin in combination with BEZ 235 resulted in synergistic growth inhibition (CI<1) in both MDA468 and BT549 cells at all doses tested, but required higher concentrations (500 to 2000 nM) for BKM 120. Western blot analysis for all cell lines treated with eribulin showed pAkt inhibition by eribulin alone with doses as low as 1 nM and as early as 4 hours. PI3K inhibitor alone confirmed inhibition of pAkt, pS6K1 and pS6 at early time points with feedback increase in pAkt at 24h. While both BEZ 235 and BKM 120 treatment increased pAkt in a dose dependent fashion at 24 hours, combination treatment with eribulin showed a dose dependent decrease in pAkt.

Conclusion. Our study shows significant synergistic growth inhibition with the combination of eribulin and PI3K inhibitors. This may be related to inhibition by eribulin of the feedback increase in pAkt seen with PI3K inhibitors alone at later time points. These findings point to a potential role for combination therapy of both eribulin and PI3K inhibitors in treating refractory metastatic disease.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P3-03-07.

Effect of eribulin on cell growth and PI3K pathway activity with and without RAD001 in triple-negative and HER2-expressing breast cancer

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Background: Patients with triple-negative breast cancer have high levels of Akt expression and activation of the PI3K-mTOR pathway. Eribulin is a microtubule-targeting agent with benefits in treating refractory triple negative disease. Our objective was to evaluate its efficacy in inhibiting PI3K pathway activity and cell growth both alone and in combination with the mTOR inhibitor RAD001. Methods: MDA468, BT549 and SKBR3 breast cancer cell lines were used for this study. MTT assays were used to assess growth inhibition after 72 hour treatment with eribulin alone and in combination with RAD001. Combination indices (CI) generated by Chou-Talalay plots were used to quantify synergy. Western blots were used to evaluate the expression of phosphorylated Akt-Ser473 (pAkt) and S6K1 after 24 hours of treatment with both agents. Results: Both MDA468 and SKBR3 cells treated with eribulin in varying concentrations showed inhibition of pAkt expression. Standard dilutions of eribulin in combination with log dilutions of RAD001 resulted in marked synergistic growth inhibition (CI<<1) in both MDA468 and BT549 cells. Western blot analysis for MDA468 cells treated with the combination erubulin and RAD001 showed a dose related suppression of pAkt along with complete inhibition of pS6K1, while RAD001 alone increased pAkt. Conclusions: Our study shows dose related inhibition of Akt activation as well as inhibition of cell growth in triple negative breast cancer and HER2 cell lines treated with eribulin alone or combined with RAD001. We also show reversal of the pAkt feedback response seen with mTOR inactivation, and a significant synergistic growth inhibition with combination treatment. These findings point to a potential role for eribulin and RAD001 in the treatment of refractory triple-negative breast cancer. [Table: see text]

Evaluation of contrast densities in the diagnosis of carotid stenosis by CT angiography

OBJECTIVE

This study assesses intravascular density produced by ionic and nonionic contrast material and its effect on visualization of stenoses by CT angiography.

MATERIALS AND METHODS

CT angiography was performed using a 32-vessel phantom to study grades of luminal stenoses (0-100%), three lengths of stenoses (1, 3, and 5 mm), and two angles of inclination into the stenoses (45 degrees and 75 degrees). Scans were obtained with a slice thickness of 2 mm, a slice interval of 1.5 mm, a pitch of 1.0, a voltage of 120 kV, and a current of both 100 and 200 mA. Vessels were oriented parallel to the z-axis, and opacified with ionic and nonionic contrast material that had densities of 100, 150, 200, 250, 300, and 350 H. Cross-sectional luminal diameters were measured in and out of the stenoses. Edge definition and halo artifact for each vessel were graded by an investigator who was unaware of the contrast material density used.

RESULTS

A contrast density of 150 H as revealed by CT angiography yielded the most accurate stenosis measurements with ionic contrast material. For nonionic contrast material, attenuation values of 150 and 200 H produced the best results on CT angiography. A density of 100 H or greater than 250 H significantly increased the error of vessel measurement (p = .001) for both types of contrast material. For the two current levels tested (100 and 200 mA), no statistical difference was found.

CONCLUSION

The accuracy of CT angiography in measuring carotid stenosis depends on the luminal attenuation value. An optimum contrast density is 150 H for ionic contrast material; for nonionic contrast material, 150-200 H (at the window and level settings of 300 H and 40 H).