Tu Dan

Caloric restriction augments radiation efficacy in breast cancer

Dietary modification such as caloric restriction (CR) has been shown to decrease tumor initiation and progression. We sought to determine if nutrient restriction could be used as a novel therapeutic intervention to enhance cytotoxic therapies such as radiation (IR) and alter the molecular profile of triple-negative breast cancer (TNBC), which displays a poor prognosis. In two murine models of TNBC, significant tumor regression is noted with IR or diet modification, and a greater regression is observed combining diet modification with IR. Two methods of diet modification were compared, and it was found that a daily 30% reduction in total calories provided more significant tumor regression than alternate day feeding. At the molecular level, tumors treated with CR and IR showed less proliferation and more apoptosis. cDNA array analysis demonstrated the IGF-1R pathway plays a key role in achieving this physiologic response, and multiple members of the IGF-1R pathway including IGF-1R, IRS, PIK3ca and mTOR were found to be downregulated. The innovative use of CR as a novel therapeutic option has the potential to change the biology of tumors and enhance the opportunity for clinical benefit in the treatment of patients with TNBC.

Caloric restriction coupled with radiation decreases metastatic burden in triple negative breast cancer

ABSTRACT Purpose: Metastatic breast cancer is devastating and triple negative breast cancers (TNBC) have a higher propensity for metastasis. Improved local control upfront in this aggressive cancer could potentially decrease its propensity toward metastasis. We sought to determine if using caloric restriction (CR) as a systemic therapy, combined with radiation therapy (IR) to the primary tumor, may impact metastatic disease. Methods: An orthotopic mouse model using a highly metastatic, luciferase-tagged TNBC cell line (4T1), was used to generate palpable tumors. Mice were then treated with CR, IR, and a combination of the two. In vivo imaging was performed for metastatic evaluation. Molecular evaluation of the tumors was performed, generating a mechanistic hypothesis for CR, which was then tested with pertinent pathway inhibition in the model. Results: CR significantly increased the time to developing metastases, decreased the overall number and volume of lung metastases, and increased survival. CR decreased proliferation, increased apoptosis and globally downregulated the IGF-1R signaling pathway. Adding an IGF-1R/INSR inhibitor to local IR in vivo accomplished a decrease in metastases similar to CR plus IR, demonstrating the importance of the IGF-1R signaling pathway, and underscoring it as a possible mechanism for CR. Conclusions: CR decreased metastatic burden and therefore may complement cytotoxic therapies being used in the clinical setting for metastatic disease. Downregulation of the IGF-1R pathway, is in part responsible for this response and modulating IGF-1R directly resulted in similar improved progression-free survival. The novel use of CR has the potential to enhance clinical outcomes for patients with metastatic breast cancer.

microRNAs: the short link between cancer and RT-induced DNA damage response

DNA damage response (DDR) networks have long been noted to be implicated in cell death induced via ionizing radiation (1). These DNA damage sensing and signaling pathways establish control through cell cycle checkpoints, cellular senescence, and apoptosis (2). When functioning properly, DDR networks act as a barrier against tumor growth while maintaining genome integrity. New discoveries have unveiled specific roles of proteins in DDR networks, which may serve as potential therapeutic targets and sensitizers to ionizing radiation (3). Unfortunately, although a clear connection has been established between dysfunctional DDR networks and malignancy, clinical trials targeting these pathways in the oncology realm have shown limited efficacy to date (4, 5). Lapsed regulation of DDR pathways in malignancy allows cells to bypass cellular checkpoints and progress through the cell cycle with stalled replication forks, incomplete DNA replication, and other forms of DNA damage (6). This genomic instability is propagated through cellular generations resulting in a neoplastic phenotype. A number of specific pathognomonic DDR defects have been identified in a number of cancers, including the mismatch repair protein MSH2 in colorectal cancer and the homologous recombination proteins BRCA1 and BRCA2 in breast and ovarian cancers (7, 8). Recent evidence suggests DDR mishaps may occur at an early stage in some precancerous lesions, double-strand break (DSB) markers such as nuclear gamma-H2AX are significantly elevated (9). To further understand the role of DDR in malignancy, attention can be turned to the investigation of microRNAs (miRs), as another component of the DDR machinery in post-transcriptional gene regulation (10). miRs are small, non-coding RNA molecules that are complementary to one or more messenger RNA molecules (mRNA) (11). This specific pairing leads to the translational inhibition and degradation of the target mRNA. Global dysregulation of miRNAs is frequently observed in malignancy and patterns of dysregulation seem to be dependent on cancer type (12). More recently, it has been demonstrated that miR expression is regulated by DNA lesions and DDR proteins (13). It is suggested that miRs may play a regulatory role in an intermediary timeframe, in between rapid post-translational protein modifications and delayed transcriptional activation of target genes (14). Our laboratory has previously shown that normal human fibroblasts exhibit unique miRNA signatures when exposed to exogenous agents that induce oxidative or genotoxic stress (15). A time course after exposure showed changes in 17 miR species following exposure to radiation, 23 after H2O2 treatment, and 45 after etoposide treatment. The miR signatures varied with direct (etoposide) and indirect (H2O2) effects (Figure ​(Figure1).1). Eight miRs were altered specifically by radiation and etoposide, suggesting these might be used to discern direct DNA damage due to radiation. Alternatively, two miRs were altered with radiation and H2O2, suggesting these could comprise a signature of indirect DNA damage. These arrays did not demonstrate any significantly altered miRs that were unique to radiation alone. Interestingly, production of reactive oxygen species (ROS) increased with increasing doses of radiation. Additionally, pre-treatment with the thiol antioxidant cysteine decreased both ROS production and reversed the changes in the miRNA signature in response to irradiation. Figure 1 Effects of cytotoxic stressors on microRNAs and protein expression interplay. DNA damage may occur following exposure to genotoxic agents including ionizing radiation, etoposide, and hydrogen peroxide (H2O2) exposure. Ionizing radiation causes DNA damage ... The miRs affected in our study are reflective of more recent literature investigating individual miRs that are altered in response to DDR (16). In fact, they are implicated in more mechanistic studies dealing with homologous recombination, non-homologous end joining, and base excision repair (17, 18). Post-transcriptional regulation of mRNAs mediated by miRs plays a fundamental role in adjusting DDR machinery. miR-421 in neuroblastoma and HeLa cells downregulates ATM kinase, which is a crucial integrator of DNA DSBs repair machinery (19). Ectopic expression of miR-421 leads to S-phase cell cycle checkpoint changes and an increase in radiosensitivity. Although it has not been clearly demonstrated that miRs directly mediate the choice between homologous recombination and NHEJ-mediated repair of a DSB, evidence suggests that miRs are at least intimately involved by targeting factors that belong to a specific pathway. Expression of miR-182 directly downregulates BRCA1 and defers from homologous recombination (20). Alternatively, the expression of miR-101 and miR-34a would downregulate DNA-PKcs and p53 binding protein 1, respectively, impeding the NHEJ repair pathway (21, 22). Other miRNAs, such as miR-34, miR-521, miR-21, have been shown to regulate the expression of important DDR network proteins BCL2, manganese superoxide dismutase (MnSOD), and MSH2, respectively (23–25). Due to the miRNA regulation of DDR machinery and to the clear connection between DDR dysregulation and a neoplastic phenotype, we believe miRs could define the relationship between cancer and DDR. Our laboratory’s studies suggest that miRs serve as integrators of the cellular response to ROS and DNA strand breaks, both of which are results of ionizing radiation. It is our opinion that further investigation of miR impact on cellular sensitivity to DNA-damaging agents could elucidate therapeutic targets to combat cancer, as miRs may provide the link between DDR and malignancy.

Abstract 5189: Caloric restriction augments the chemotherapeutic response in a murine triple negative breast cancer model

Purpose: Triple negative breast cancers (TNBC) are a highly aggressive subtype of breast cancer, linked with a poor prognosis. TNBC tumors have a higher propensity for metastasis and unfortunately have fewer treatment options due to their lack of estrogen, progesterone or Her-2/neu receptors. We sought to determine if caloric restriction (CR) could augment the response of chemotherapy including docetaxel and cisplatin in a TNBC model and improve survival. Methods: An orthotopic mouse model using a highly metastatic, luciferase-tagged TNBC cell line (4T1), was used to generate palpable tumors. Mice were then treated with CR, cisplatin alone, docetaxel alone or a combination of CR and chemotherapy. Three times a week, primary tumors were measured with calipers and in vivo imaging was performed to evaluate the metastatic burden of disease. Molecular evaluation of the tumors was performed, generating a mechanistic hypothesis for increased sensitivity to chemotherapy. Results: Combining either docetaxel or cisplatin with CR, significantly decreased the rate of primary tumor growth (p Conclusions: CR augments the effect of systemic chemotherapy in an aggressive TNBC mouse model, in part by decreasing the inflammatory response. The novel use of CR in combination with systemic chemotherapy has the potential to enhance clinical outcomes for patients with triple negative breast cancer and should be tested in the clinical setting. Citation Format: Brittany Simone, Tu Dan, Ajay Palagani, Meredith LaRose, Jason E. Savage, Nicole Simone. Caloric restriction augments the chemotherapeutic response in a murine triple negative breast cancer model. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5189.

Correction to: Salvage fractionated stereotactic re-irradiation (FSRT) for patients with recurrent high grade gliomas progressed after bevacizumab treatment

The fourth author’s name was incorrect in the initial online publication. The original article has been corrected.

Prognostic value of CD44s in the NCI randomized trial on breast conservation with 25-year follow-up.

634 Background: Prognostic markers can be used in the management of early breast cancer to help determine which patients may benefit from either conservative or aggressive management. Breast tumor tissue from patients enrolled on the NCI randomized trial of Breast Conservation was analyzed to determine if a good prognostic marker could be identified. CD44s is a transmembrane glycoprotein typically bound to hyaluronan in the stroma that has been identified in the literature as having an association with tumor progression and metastasis because of its function as a cell adhesion molecule. Methods: 237 early stage breast cancer patients were randomized between 1979 and 1989 at the National Cancer Institute to receive mastectomy or lumpectomy followed by definitive radiation. Formalin- fixed paraffin embedded tumor specimens from 63 of these patients were available for study. Immunohistochemical staining was performed using a monoclonal antibody to the CD44s isoform of CD44, and was scored as negative or posi...

Abstract P4-10-01: Twenty-Five Year Results in the Treatment of Early Breast Carcinoma with Mastectomy Versus Breast Conservation Therapy: The National Cancer Institute Randomized Trial

Background: Breast conservation therapy (BCT) has become an accepted treatment in women with early stage breast cancer due to multiple randomized trials showing equivalent mortality rates when compared to modified radical mastectomy (MRM). Results of the National Cancer Institute9s prospective randomized trial comparing MRM to BCT are now reported at a median follow up of 25.4 years. Methods: Between 1979 and 1987, 237 evaluable patients with biopsy proven clinical Stage I or Stage II primary breast cancer were randomized to receive a MRM or a lumpectomy followed by definitive radiation to the entire breast followed by a boost to the tumor bed. An axillary dissection was performed in both arms. Negative margins were not required. Patients with node positive disease in either arm were treated with adriamycin and cytoxan. The primary endpoints were overall survival and disease-free survival. Results: At a median follow-up of 25.4 years, there was no statistical difference in overall survival between either arm, with 45.7% of patients alive in the MRM group and 38.0% alive in the BCT group (p=0.43). Although disease-free survival was significantly worse in patients randomized to BCT (57% vs 82%, P Conclusion: The 25 year survival rate among women receiving BCT vs MRM in the National Cancer Institute randomized trial appears to be equivalent and is consistent with findings across multiple trials. In patients receiving BCT there is an increased incidence of IBTR9s. Despite a higher risk of local failure in the BCT group, there is no increased risk of distant failure or mortality. The risk of local failure however, should be discussed when counseling patients regarding their treatment options. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P4-10-01.