Glutamine metabolism and radiosensitivity: Beyond the Warburg effect.

Mounting data suggest that cancer cell metabolism can be utilized therapeutically to halt cell proliferation, metastasis and disease progression. Radiation therapy is a critical component of cancer treatment in curative and palliative settings. The use of metabolism-based therapeutics has become increasingly popular in combination with radiotherapy to overcome radioresistance. Over the past year, a focus on glutamine metabolism in the setting of cancer therapy has emerged. In this mini-review, we discuss several important ways (DNA damage repair, oxidative stress, epigenetic modification and immune modulation) glutamine metabolism drives cancer growth and progression, and present data that inhibition of glutamine utilization can lead to radiosensitization in preclinical models. Future research is needed in the clinical realm to determine whether glutamine antagonism is a feasible synergistic therapy that can be combined with radiotherapy.

A Pilot Trial Using Telemedicine in Radiation Oncology: The Future of Health Care Is Virtual.

Background: Social determinants of health directly affect cancer survival. Driven by advances in technology and recent demands due to COVID-19, telemedicine has the ability to improve patient access to care, lower health care costs, and increase workflow efficiency. The role of telemedicine in radiation oncology is not established. Materials and Methods: We conducted an IRB-approved pilot trial using a telehealth platform for the first post-radiation visit in patients with any cancer diagnosis. The primary endpoint was feasibility of using telehealth defined by completion of five telehealth visits per month in a single department. Secondary endpoints included the ability to assess patients appropriately, patient and physician satisfaction. Physicians were surveyed again during the pandemic to determine whether viewpoints changed. Results: Between May 27, 2016 and August 1, 2018, 37 patients were enrolled in the Telehealth in Post-operative Radiation Therapy (TelePORT) trial, with 24 evaluable patients who completed their scheduled telehealth visit. On average, 1.4 patients were accrued per month. All patients were satisfied with their care, had enough time with their physician and 85.7% believed the telehealth communication was excellent. All physicians were able to accurately assess the patient's symptoms via telehealth, whereas 82.3% felt they could accurately assess treatment-related toxicity. Physicians assessing skin toxicity from breast radiation were those who did not feel they were able to assess toxicity. Discussion and Conclusions: Both health care providers and patients have identified telemedicine as a suitable platform for radiation oncology visits. Although there are limitations, telemedicine has significant potential for increasing access of cancer care delivery in radiation oncology.

The Incorporation of Immunotherapy and Targeted Therapy Into Chemoradiation for Cervical Cancer: A Focused Review.

In 2011 the Food and Drug Administration (FDA) approved anti-vascular endothelial growth factor (VEGF) therapy, bevacizumab, for intractable melanoma. Within the year, immunotherapy modulators inhibiting cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed cell death protein 1 (PD-1) were approved in addition to programmed death-ligand 1 (PD-L1) antibodies in 2012. Since then, research showing the effectiveness of targeted therapies in a wide range of solid tumors has prompted studies incorporating their inclusion as part of upfront management as well as refractory or relapsed disease. For treatment of cervical cancer, which arises from known virus-driven oncogenic pathways, the incorporation of targeted therapy is a particularly attractive prospect. The current standard of care for locally advanced cervical cancer includes concurrent platinum-based chemotherapy with radiation therapy (CRT) including external beam radiation therapy (EBRT) and brachytherapy. Building upon encouraging results from trials testing bevacizumab or immunotherapy in recurrent cervical cancer, these agents have begun to be incorporated into upfront CRT strategies for prospective study. This article will review background data establishing efficacy of angiogenesis inhibitors and immunotherapy in the treatment of cervical cancer as well as results of prospective studies combining targeted therapies with standard CRT with the aim of improving outcomes. In addition, the role of immunotherapy and radiation on the tumor microenvironment (TME) will be discussed.

Advantages of real-time transabdominal ultrasound guidance in combined interstitial/intracavitary cervical brachytherapy: a case-based review.

Sub-optimal placement of both intracavitary devices and interstitial needles is a relatively common occurrence in cervical brachytherapy, which may reduce the accuracy of dose distribution and contribute to adverse toxicities. To mitigate complications, improve target dose coverage, and verify proper device placement, implants may be placed under real-time image guidance. Traditionally, transrectal ultrasound has been used for needle guidance. However, we have utilized transabdominal ultrasound (TA-US) in our brachytherapy center. The purpose of this pictorial essay was to provide a pictorial description of TA-US technique, present a retrospective review of our preliminary outcomes adopting TA-US into routine practice, and to discuss the advantages of real-time ultrasound image guidance for placement of intrauterine tandem and interstitial needles.

MicroRNA-21 is Required for Hematopoietic Cell Viability After Radiation Exposure.

PURPOSE: Radiation therapy is an essential intervention used in the treatment of more than half of cancer patients. With the increasing use of hypofractionated radiation regimens, concurrent use of radiation and chemotherapy, targeted agents and immunotherapy, the risk of radiation-induced toxicities is increased. However, much remains unknown about the molecular underpinnings responsible for radiation-induced toxicity. MicroRNA (miRNA) are small, non-coding RNA involved in post-transcriptional regulation of gene expression. miR-21 is an oncomiR that is dysregulated in a significant fraction of human malignancies, and its overexpression is linked to poor overall survival, chemoresistance, and radioresistance in several human cancers. However, the contribution of miR-21 in governing radiation sensitivity in normal, untransformed cells, and the impact of silencing this miRNA in normal tissues remains largely unexplored. MATERIALS AND METHODS: miR-21 levels were evaluated in tissues by qRT-PCR without and after total body irradiation (TBI). Mice lacking miR-21 were genetically engineered, subjected to TBI, and monitored for survival. Hematopoietic stem and progenitor cell (HSPC) numbers and function were assessed using flow cytometry, histology, complete blood cell counts, and bone marrow transplantation. RESULTS: miR-21 expression was increased in radiosensitive tissues, but not in radioinsensitive tissues following TBI in wild-type mice, suggesting it may have a critical function in the normal tissue response to irradiation. Compared to wild-type mice, mice lacking one or both alleles of miR-21 showed reduced numbers of HSPCs and increased sensitivity to an LD50/30 dose of TBI with evidence of bone marrow failure. Transplantation of wild-type bone marrow into irradiated miR-21-deficient mice rescued the mice from death. CONCLUSIONS: Our data identify miR-21 as a critical component of HSPC viability and essential for bone marrow recovery following irradiation. Further investigation is warranted to determine whether miR-21 can be used to stratify patients at risk for hematopoietic toxicity following irradiation.

Onco-metabolism: defining the prognostic significance of obesity and diabetes in women with brain metastases from breast cancer.

PURPOSE: Metabolic dysregulation has been implicated as a molecular driver of breast cancer in preclinical studies, especially with respect to metastases. We hypothesized that abnormalities in patient metabolism, such as obesity and diabetes, may drive outcomes in breast cancer patients with brain metastases. METHODS: We retrospectively identified 84 consecutive patients with brain metastases from breast cancer treated with intracranial radiation therapy. Radiation was delivered as whole-brain radiation to a median dose of 3000 cGy or stereotactic radiosurgery to a median dose of 2100 cGy. Kaplan Meier curves were generated for overall survival (OS) data and Mantel-Cox regression was performed to detect differences in groups. RESULTS: At analysis, 81 survival events had occurred and the median OS for the entire cohort was 21.7 months. Despite similar modified graded prognostic assessments, resection rates, and receptor status, BMI ≥ 25 kg/m2 (n = 45) was associated with decreased median OS (13.7 vs. 30.6 months; p < 0.001) and median intracranial progression-free survival (PFS) (7.4 vs. 10.9 months; p = 0.04) compared to patients with BMI < 25 kg/m2 (n = 39). Similar trends were observed among all three types of breast cancer. Patients with diabetes (n = 17) had decreased median OS (11.8 vs. 26.2 months; p < 0.001) and median intracranial PFS (4.5 vs. 10.3 months; p = 0.001) compared to non-diabetics (n = 67). On multivariate analysis, both BMI ≥ 25 kg/m2 [HR 2.35 (1.39-3.98); p = 0.002] and diabetes [HR 2.77 (1.454-5.274); p = 0.002] were associated with increased mortality. CONCLUSIONS: Elevated BMI or diabetes may negatively impact both overall survival and local control in patients with brain metastases from breast cancer, highlighting the importance of the translational development of therapeutic metabolic interventions. Given its prognostic significance, BMI should be used as a stratification in future clinical trial design in this patient population.

Caloric restriction counteracts chemotherapy-induced inflammation and increases response to therapy in a triple negative breast cancer model.

Triple negative breast cancer (TNBC) is a heterogeneous disease that has no available targeted therapies. Previously, we have shown that caloric restriction (CR) can augment the effects of radiation therapy in a TNBC mouse model. To build upon this, we now present data regarding the combination of chemotherapy and CR in the same 4T1 model. Chemotherapy can induce inflammation that breeds resistance to therapy. We propose CR as a mechanism to decrease chemotherapy-induced inflammation and increase efficacy of therapy. 12-week old Balb/c mice were orthotopically injected with a syngeneic triple negative breast cancer cell line (4T1) and were treated in one of six cohorts: ad lib fed (AL), 30% reduction in calorie intake (CR), cisplatin or docetaxol alone or a combination CR+cisplatin/docetaxol. Mice in the cohorts receiving chemotherapy+CR had longer overall survival (12 ± 2 days) as compared to the AL group. These mice also demonstrated less lung metastases at the final time point of in vivo imaging. In addition, downregulation of the IGF-1R and IRS signaling pathways were noted most significantly in those mice receiving combination therapy. Lastly, serum from these mice demonstrated an increase in inflammatory cytokines TNF-α and IL-1ß in response to chemotherapy alone. This increase was dampened by the addition of CR. Taken together, these data suggest that while chemotherapy is effective in TNBC, it can cause inflammation, which can be a driver of resistance to therapy. This chemotherapy-induced inflammation can be reversed with the use of CR as a nontoxic adjunct to treatment.

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

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.

microRNA alterations driving acute and late stages of radiation-induced fibrosis in a murine skin model.

PURPOSE: Although ionizing radiation is critical in treating cancer, radiation-induced fibrosis (RIF) can have a devastating impact on patients' quality of life. The molecular changes leading to radiation-induced fibrosis must be elucidated so that novel treatments can be designed. METHODS AND MATERIALS: To determine whether microRNAs (miRs) could be responsible for RIF, the fibrotic process was induced in the right hind legs of 9-week old CH3 mice by a single-fraction dose of irradiation to 35 Gy, and the left leg served as an unirradiated control. Fibrosis was quantified by measurements of leg length compared with control leg length. By 120 days after irradiation, the irradiated legs were 20% (P=.013) shorter on average than were the control legs. RESULTS: Tissue analysis was done on muscle, skin, and subcutaneous tissue from irradiated and control legs. Fibrosis was noted on both gross and histologic examination by use of a pentachrome stain. Microarrays were performed at various times after irradiation, including 7 days, 14 days, 50 days, 90 days, and 120 days after irradiation. miR-15a, miR-21, miR-30a, and miR-34a were the miRs with the most significant alteration by array with miR-34a, proving most significant on confirmation by reverse transcriptase polymerase chain reaction, c-Met, a known effector of fibrosis and downstream molecule of miR-34a, was evaluated by use of 2 cell lines: HCT116 and 1522. The cell lines were exposed to various stressors to induce miR changes, specifically ionizing radiation. Additionally, in vitro transfections with pre-miRs and anti-miRs confirmed the relationship of miR-34a and c-Met. CONCLUSIONS: Our data demonstrate an inverse relationship with miR-34a and c-Met; the upregulation of miR-34a in RIF causes inhibition of c-Met production. miRs may play a role in RIF; in particular, miR-34a should be investigated as a potential target to prevent or treat this devastating side effect of irradiation.

MicroRNA expression altered by diet: can food be medicinal?

As the link between metabolism and major disease processes becomes more well-defined, the identification of key molecular targets is leading to new therapeutic strategies. As a result, small non-coding RNA molecules that regulate gene expression via epigenetic alterations, microRNAs have been identified as regulators of these metabolic processes. In the last decade, dietary interventions have been used to change metabolism and to potentially alter disease progression and clinical outcomes. These interventions have been linked, at a molecular level, to microRNAs. This review will summarize the role of various dietary strategies on the expression of several microRNA families.

The metastatic potential of triple-negative breast cancer is decreased via caloric restriction-mediated reduction of the miR-17~92 cluster.

Caloric restriction (CR) has been shown to cause tumor regression in models of triple-negative breast cancer (TNBC), and the regression is augmented when coupled with ionizing radiation (IR). In this study, we sought to determine if the molecular interaction between CR and IR could be mediated by microRNA (miR). miR arrays revealed 3 miRs in the miR-17~92 cluster as most significantly down regulated when CR is combined with IR. In vivo, CR and IR down regulated miR-17/20 in 2 TNBC models. To elucidate the mechanism by which this cluster regulates the response to CR, cDNA arrays were performed and the top 5 statistically significant gene ontology terms with high fold changes were all associated with extracellular matrix (ECM) and metastases. In silico analysis revealed 4 potential targets of the miR-17~92 cluster related to ECM: collagen 4 alpha 3, laminin alpha 3, and metallopeptidase inhibitors 2 and 3, which were confirmed by luciferase assays. The overexpression or silencing of miR-17/20a demonstrated that those miRs directly affected the ECM proteins. Furthermore, we found that CR-mediated inhibition of miR-17/20a can regulate the expression of ECM proteins. Functionally, we demonstrate that CR decreases the metastatic potential of cells which further demonstrates the importance of the ECM. In conclusion, CR can be used as a potential treatment for cancer because it may alter many molecular targets concurrently and decrease metastatic potential for TNBC.

Selectively starving cancer cells through dietary manipulation: methods and clinical implications.

As the link between obesity and metabolic syndrome and cancer becomes clearer, the need to determine the optimal way to incorporate dietary manipulation in the treatment of cancer patients becomes increasingly important. Metabolic-based therapies, such as caloric restriction, intermittent fasting and a ketogenic diet, have the ability to decrease the incidence of spontaneous tumors and slow the growth of primary tumors, and may have an effect on distant metastases in animal models. Despite the abundance of preclinical data demonstrating the benefit of dietary modification for cancer, to date there are few clinical trials targeting diet as an intervention for cancer patients. We hypothesize that this may be due, in part, to the fact that several different types of diet modification exist with no clear recommendations regarding the optimal method. This article will delineate three commonly used methods of dietary manipulation to assess the potential of each as a regimen for cancer therapy.

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.