Traumatic brain injury imaging research roadmap

The past decade has seen impressive advances in the types of neuroimaging information that can be acquired in patients with traumatic brain injury. However, despite this increase in information, understanding of the contribution of this information to prognostic accuracy and treatment pathways for patients is limited. Available techniques often allow us to infer the presence of microscopic changes indicative of alterations in physiology and function in brain tissue. However, because histologic confirmation is typically lacking, conclusions reached by using these techniques remain solely inferential in almost all cases. Hence, a need exists for validation of these techniques by using data from large population samples that are obtained in a uniform manner, analyzed according to well-accepted procedures, and correlated with closely monitored clinical outcomes. At present, many of these approaches remain confined to population-based research rather than diagnosis at an individual level, particularly with regard to traumatic brain injury that is mild or moderate in degree. A need and a priority exist for patient-centered tools that will allow advanced neuroimaging tools to be brought into clinical settings. One barrier to developing these tools is a lack of an age-, sex-, and comorbidities-stratified, sequence-specific, reference imaging data base that could provide a clear understanding of normal variations across populations. Such a data base would provide researchers and clinicians with the information necessary to develop computational tools for the patient-based interpretation of advanced neuroimaging studies in the clinical setting. The recent "Joint ASNR-ACR HII-ASFNR TBI Workshop: Bringing Advanced Neuroimaging for Traumatic Brain Injury into the Clinic" on May 23, 2014, in Montreal, Quebec, Canada, brought together neuroradiologists, neurologists, psychiatrists, neuropsychologists, neuroimaging scientists, members of the National Institute of Neurologic Disorders and Stroke, industry representatives, and other traumatic brain injury stakeholders to attempt to reach consensus on issues related to and develop consensus recommendations in terms of creating both a well-characterized normative data base of comprehensive imaging and ancillary data to serve as a reference for tools that will allow interpretation of advanced neuroimaging tests at an individual level of a patient with traumatic brain injury. The workshop involved discussions concerning the following: 1) designation of the policies and infrastructure needed for a normative data base, 2) principles for characterizing normal control subjects, and 3) standardizing research neuroimaging protocols for traumatic brain injury. The present article summarizes these recommendations and examines practical steps to achieve them.

Phase II trial evaluating the feasibility of interdigitating folfox with chemoradiotherapy in locally advanced and metastatic rectal cancer

BACKGROUND

Patients (pts) with metastatic rectal cancer and symptomatic primary, require local and systemic control. Chemotherapy used during chemoradiotherapy (CRT) is adequate for radiosensitisation, but suboptimal for systemic control. The aim of this phase II study was to assess tolerability, local/systemic benefits, of a novel regimen delivering interdigitating intensive chemotherapy with radical CRT.

METHODS

Eligible pts had untreated synchronous symptomatic primary/metastatic rectal cancer. A total of 12 weeks of treatment with split-course pelvic CRT (total 50.4 Gy with concurrent oxaliplatin and 5-FU infusion) alternating with FOLFOX chemotherapy. All pts staged with CT, MRI and FDG-PET pre and post treatment.

RESULTS

Twenty-six pts were treated. Rectal primary MRI stage: T3 81% and T4 15%. Liver metastases in 81%. Twenty-four pts (92%) completed the 12-week regimen. All patients received planned RT dose, and for both agents over 88% of patients achieved a relative dose intensity of >75%. Grade 3 toxicities: neutropenia 23%, diarrhoea 15%, and radiation skin reaction 12%. Grade 4 toxicity: neutropenia 15%. FDG-PET metabolic response rate for rectal primary 96%, and for metastatic disease 60%.

CONCLUSIONS

Delivery of interdigitating chemotherapy with radical CRT was feasible to treat both primary and metastatic rectal cancer. High completion and response rates were encouraging.

Immune response to RB1-regulated senescence limits radiation-induced osteosarcoma formation

Ionizing radiation (IR) and germline mutations in the retinoblastoma tumor suppressor gene (RB1) are the strongest risk factors for developing osteosarcoma. Recapitulating the human predisposition, we found that Rb1+/- mice exhibited accelerated development of IR-induced osteosarcoma, with a latency of 39 weeks. Initial exposure of osteoblasts to carcinogenic doses of IR in vitro and in vivo induced RB1-dependent senescence and the expression of a panel of proteins known as senescence-associated secretory phenotype (SASP), dominated by IL-6. RB1 expression closely correlated with that of the SASP cassette in human osteosarcomas, and low expression of both RB1 and the SASP genes was associated with poor prognosis. In vivo, IL-6 was required for IR-induced senescence, which elicited NKT cell infiltration and a host inflammatory response. Mice lacking IL-6 or NKT cells had accelerated development of IR-induced osteosarcomas. These data elucidate an important link between senescence, which is a cell-autonomous tumor suppressor response, and the activation of host-dependent cancer immunosurveillance. Our findings indicate that overcoming the immune response to senescence is a rate-limiting step in the formation of IR-induced osteosarcoma.

Abstract 4735: Constitutively active RAS and MEK confer resistance to PLX4032 in BRAF-V600E human melanoma cells

Mutation of the BRAF gene occurs in 50-70% of melanomas. The most common of these encodes a V600E amino acid substitution that confers constitutive kinase activity. BRAF-V600E can act as a transforming oncogene and siRNAs to BRAF inhibit the proliferation and survival of melanoma cells. Therefore, BRAF-V600E represents an important novel drug target in these tumors. PLX4032 is a selective inhibitor of BRAF-V600E with a favorable safety profile and significant single agent response rate in clinical melanoma. However, acquired resistance to BRAF inhibitors represents a significant challenge in the development of these agents.

The current study shows that retrovirus-mediated expression of constitutively active MEK1-DD, KRAS-12D, HRAS-12V, or NRAS-61K in a panel of BRAF-V600E human melanoma cells promotes resistance to PLX4032. For example, expression of MEK1-DD in A375 cells resulted in a 13-fold increase in the PLX4032 IC50 concentration, while expression of any of the three RAS isoforms in these cells resulted in >15-fold increases in the PLX4032 IC50 concentration (determined by SRB assays). While PLX4032 potently inhibits ERK phosphorylation in A375 vector control cells, HRAS-12V and MEK1DD cells maintain ERK phosphorylation in the presence of PLX4032. Inhibition of clonogenicity, induction of G0/G1-phase arrest and apoptosis induction mediated by PLX4032 are also reversed by expression of MEK1-DD or RAS isoforms. For example, after treatment of A375 BRAF-V600E melanoma cells with 10 µM PLX4032 for 96 h, 30.2 ± 2.9% of vector control cells versus 9.3 ± 2.2% of MEK1-DD- and 8.3 ± 4.9% of HRAS-12V-expressing cells stained positive for Annexin-V-APC compared to 0.3 ± 0.2% of untreated cells. These findings indicate that activation of RAS or MEK could confer a proliferative and survival advantage in BRAF-V600E cells in the presence of PLX4032 and therefore, could contribute to acquired resistance to this drug.

Preliminary data also suggest that PLX4032 suppresses glycolysis in BRAF-V600E melanoma cells prior to changes in proliferation and viability. This corroborates recent clinical data from a cohort of patients with advanced metastatic melanoma participating in a phase I study of PLX4032. Baseline and day 15 FDG-PET data (indicating metabolic disease burden) from 27 patients treated with ≥ 320mg BID PLX4032 demonstrated a 100% partial metabolic response rate while 3 patients achieved a complete metabolic response after PLX4032 therapy. The current study demonstrates a 53.7% decrease in the rate of glucose uptake in A375 vector control cells treated with 10 µM PLX4032 for 24 h compared to a 4.0% decrease and 11.9% increase in the rate of glucose uptake in MEK1-DD and HRAS-12V expressing cells, respectively. These findings suggest that inhibition of glycolysis may be an important early response to PLX4032 therapy and that activation of RAS or MEK may reverse this effect.

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 4735. doi:10.1158/1538-7445.AM2011-4735

Abstract 3484: In vivo activity of combined PI3k/mTOR and MEK-inhibition in a K-RASG12D; PTEN deletion mouse model of ovarian cancer

The PI3K/Akt pathway is commonly deregulated in human cancer, making it an attractive target for novel anti-cancer therapeutics. We have utilized a mouse model of ovarian cancer generated by K-RASG12D activation and PTEN deletion in the ovarian surface epithelium (Dinulescu, et al, 2005) for the pre-clinical assessment of a novel PI3K/mTOR inhibitor (PF-04691502, Pfizer). To enable high throughput studies, we have transplanted primary tumours from these mice orthotopically into the ovarian bursa.

Tumour growth rates were monitored by small animal-Ultrasound, and when tumours reached an average of 200mm3, mice received vehicle or 10mg/kg PF-04691502 daily for 7 days. Ultrasound and FDG-PET scans were performed on day 0, day 2 and day 7 of therapy. PF-04691502 inhibited tumour growth at 7 days by 71.64%±8.93. Tumour weights measured post-mortem following 7 days treatment also showed a significant decrease in tumour mass in treated mice (0.78±0.13g in vehicle treated versus 0.38±0.06g in drug treated mice; p<0.05). FDG-PET imaging revealed that PF-04691502 reduced glucose metabolism dramatically at 48 hours, and this reduction was maintained for the 7 day treatment duration, suggesting FDG-PET may be exploited as a biomarker of response to PF-04691502. To confirm that the PI3K/mTOR pathway is successfully inhibited with PF-04691502, western blots and immunohistochemistry were performed on tumour samples harvested at 7 days post-treatment. These show that pAKT(S473) and pS6(S240/244) were dramatically inhibited following PF-04691502 treatment.

PF-04691502 was sufficient to inhibit PI3K/mTOR resulting in inhibition of tumour growth; however, we did not observe tumour regression in this model. Notably, tumours from PF-04691502 treated mice displayed activation of pERK, suggesting that activation of the MAPK pathway is a mechanism by which KRAS-mutant tumours can limit the efficacy of PI3K/mTOR inhibitors alone. To overcome the effects of RAS/MAPK signalling, we have performed studies evaluating PF-04691502 (7.5mg/kg, daily) in combination with an inhibitor of MEK (PD-0325901, Pfizer, 10mg/kg, daily). Ultrasound monitoring of tumour volume shows that over a 7 day treatment period, PF-04691502 led to tumour growth inhibition of 55%±10.27, PD-0325901 alone led to tumour regression (36.3%±20.45) and combined PD-0325901 and PF-04691502 led to a striking tumour regression of 80.7%±4.97. These data show that combined inhibition of PI3K/mTOR and MEK converts tumor growth delay with PI3K-inhibition alone to tumour regression in this KRAS and PTEN mutant mouse model of ovarian cancer. Therefore inhibition of MEK may enhance activity of PI3K/mTOR-inhibitors in tumours showing activation of the PI3K pathway by genomic changes such as mutation in KRAS combined with loss of PTEN.

Dinulescu D. M., et al. (2005) Nat. Med. 11:63-70.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3484.