Telemedicine Use in Disasters: A Scoping Review.

Disasters have many deleterious effects and are becoming more frequent. From a health-care perspective, disasters may cause periods of stress for hospitals and health-care systems. Telemedicine is a rapidly growing technology that has been used to improve access to health-care during disasters. Telemedicine applied in disasters is referred to as disaster telemedicine. Our objective was to conduct a scoping literature review on current use of disaster telemedicine to develop recommendations addressing the most common barriers to implementation of a telemedicine system for regional disaster health response in the United States. Publications on telemedicine in disasters were collected from online databases. This included both publications in English and those translated into English. Predesigned inclusion/exclusion criteria and a PRISMA flow diagram were applied. The PRISMA flow diagram was used on the basis that it would help streamline the available literature. Literature that met the criteria was scored by 2 reviewers who rated relevance to commonly identified disaster telemedicine implementation barriers, as well as how disaster telemedicine systems were implemented. We also identified other frequently mentioned themes and briefly summarized recommendations for those topics. Literature scoring resulted in the following topics: telemedicine usage (42 publications), system design and operating models (43 publications), as well as difficulties with credentialing (5 publications), licensure (6 publications), liability (4 publications), reimbursement (5 publications), and technology (24 publications). Recommendations from each category were qualitatively summarized.

Context is key: Understanding the regulation, functional control, and activities of the p53 tumour suppressor.

The p53 tumour suppressor is considered one of the most critical genes in cancer biology. By upregulating apoptosis, cell cycle arrest, and DNA damage repair in normal cells, p53 prevents the propagation of cells with tumorigenic potential; therefore, mutations in p53 are associated with carcinogenic transformation and can be accompanied by the accumulation of a novel gain-of-function oncogenic protein, mutant p53. Although p53 is most often understood to utilize context-dependent post-translational modifications to achieve regulation of its many target genes, recent research has also sought to define other mechanisms of regulating p53 gene expression prior to translation and to understand how this alternative regulation of p53 may influence target gene expression and cellular outcome. This review attempts to summarize what is known about p53 regulation at the transcriptional, post-transcriptional, and post-translational levels while paying special attention to the ways in which context may influence p53 regulation and subsequent regulation of its target genes.

The Design and Implementation of a Professional Development Program for Physician Assistants in an Academic Emergency Department.

Physician assistants (PAs) are expanding their role in academic emergency departments (EDs). There are no published models for how to integrate PAs into departmental educational activities, scholarship, and operations outside of a PA residency approach. We created a professional development program for PAs that would provide them with opportunities to integrate into all aspects of our department mission and provide them with a forum for personal growth and ongoing education. The program provides PAs with resources including protected time and mentorship to become a content expert in an academic area of interest. We review our 5-year experience creating and implementing this program, which has grown from six PAs in 2013 to 24 PAs in 2018. These PAs now have formal roles in five of our eight divisions, participating in education, administrative, and research activities. The retention rate for PAs in this program is 90.2% versus 85.7% for PAs at our department who are not in the program. Our experience and results demonstrate the value of investing in the professional development and continued education of PAs at an academic ED versus the traditional model of service and the potential for integration into all aspects of an academic ED's mission.

Association of two BRM promoter polymorphisms and smoking status with malignant pleural mesothelioma risk and prognosis.

Brahma (BRM), of the SWI/SNF complex, has two 6 to 7 bp insertion promoter polymorphisms (BRM-741/BRM-1321) that cause epigenetic BRM suppression, and are associated with risk of multiple cancers. BRM polymorphisms were genotyped in malignant pleural mesothelioma (MPM) cases and asbestos-exposed controls. Multivariable logistic regression (risk) and Cox regression (prognosis) were performed, including stratified analyses by smoking status to investigate the effect of polymorphisms on MPM risk and prognosis. Although there was no significant association overall between BRM-741/BRM-1321 and risk in patients with MPM, a differential effect by smoking status was observed (P-interaction < .001), where homozygous variants were protective (aOR of 0.18-0.28) in ever smokers, while never smokers had increased risk when carrying homozygous variants (aOR of 2.7-4.4). While there was no association between BRM polymorphisms and OS in ever-smokers, the aHR of carrying homozygous-variants of BRM-741, BRM-1321 or both were 4.0 to 8.6 in never-smokers when compared to wild-type carriers. Mechanistically, lower mRNA expression of BRM was associated with poorer general cancer prognosis. Electrophoretic mobility shift assays and chromatin immunoprecipitation experiments (ChIP) revealed high BRM insertion variant homology to MEF2 regulatory binding sites. ChIP experimentation confirmed MEF2 binding only occurs in the presence of insertion variants. DNA-affinity purification assays revealed YWHA scaffold proteins as vital to BRM mRNA expression. Never-smokers who carry BRM homozygous variants have an increased chance of developing MPM, which results in worse prognosis. In contrast, in ever-smokers, there may be a protective effect, with no difference in overall survival. Mechanisms for the interaction between BRM and smoking require further study.

HER2 Overexpression Triggers an IL1α Proinflammatory Circuit to Drive Tumorigenesis and Promote Chemotherapy Resistance.

Systemic inflammation in breast cancer correlates with poor prognosis, but the molecular underpinnings of this connection are not well understood. In this study, we explored the relationship between HER2 overexpression, inflammation, and expansion of the mammary stem/progenitor and cancer stem-like cell (CSC) population in breast cancer. HER2-positive epithelial cells initiated and sustained an inflammatory milieu needed to promote tumorigenesis. HER2 induced a feedforward activation loop of IL1α and IL6 that stimulated NFκB and STAT3 pathways for generation and maintenance of breast CSC. In mice, Il1a genetic deficiency delayed MMTV-Her2-induced tumorigenesis and reduced inflammatory cytokine expression as well as CSC in primary tumors. In clinical specimens of human breast tumor tissues, tissue microarray analysis revealed a strong positive correlation between IL1α/IL6 expression and CSC-positive phenotype. Pharmacologic blockade of IL1α signaling reduced the CSC population and improved chemotherapeutic efficacy. Our findings suggest new therapeutic or prevention strategies for HER2-positive breast cancers.Significance: IL1α signaling driven by HER2 promotes chronic inflammation needed to support cancer stem-like cell maintenance in HER2-positive breast cancers. Cancer Res; 78(8); 2040-51. ©2018 AACR.

Current Emergency Preparedness Resources and Capabilities Among Academic Health Systems in the United States.

OBJECTIVE: Although hospital emergency preparedness efforts have been recognized as important, there has been growing pressure on cost containment, as well as consolidation within the US health care system. There is little data looking at what health care emergency preparedness functions have been, could be, or should be centrally coordinated at a system level. METHODS: We developed a questionnaire for academic health systems and asked about program funding, resources provided, governance, and activities. The questionnaire also queried managers' opinions regarding the appropriate role for the system-level resources in emergency response, as well as about what is most helpful at the system-level supporting preparedness. RESULTS: Fifty-two of 97 systems (54%) responded. The most frequently occurring system-wide activities included: creating trainings or exercise templates (75%), promoting preparedness for employees in the system (75%), providing access to specific subject matter experts (73%), and developing specific plans for individual member entities within their system (73%). The top resources provided included a common mass notification system (71%), arranging for centralized contracts for goods and services (71%), and providing subject matter expertise (69%). CONCLUSIONS: Currently, there is wide variation in the resources, capabilities, and programs used to support and coordinate system-level emergency preparedness among academic health systems. (Disaster Med Public Health Preparedness. 2018;12:574-577).

Two BRM promoter polymorphisms predict poor survival in patients with hepatocellular carcinoma.

Polymorphisms in the promoter of the BRM gene, a critical subunit of the chromatin remodeling SWI/SNF complex, have previously been implicated in risk and prognosis in Caucasian-predominant lung, head and neck, esophageal, and pancreatic cancers, and in hepatocellular cancers in Asians. We investigated the role of these polymorphisms in hepatocellular carcinoma (HCC) risk and prognosis. HCC cases were recruited in a comprehensive cancer center while the matched controls were recruited from family practice units from the same catchment area. For risk analyses, unconditional logistic regression analyses were performed in HCC patients and matched healthy controls. Overall survival analyses were performed using Cox proportional hazard models, Kaplan-Meier curves, and log-rank tests. In 266 HCC cases and 536 controls, no association between either BRM promoter polymorphism (BRM-741 or BRM-1321) and risk of HCC was identified (P > 0.10 for all comparisons). There was significant worsening of overall survival as the number of variant alleles increased: BRM-741 per variant allele adjusted hazards ratio (aHR) 5.77, 95% confidence interval (CI) 2.89-11.54 and BRM-1321 per variant allele aHR 4.09, 95%CI 2.22-7.51. The effects of these two polymorphisms were at least additive, where individuals who were double homozygotes for the variant alleles had a 45-fold increase in risk of death when compared to those who were double wild-type for the two polymorphisms. Two BRM promoter polymorphisms were strongly associated with HCC prognosis but were not associated with increased HCC susceptibility. The association was strongest in double homozygotes for the allele variants.

Palliative treatment of patients with inoperable locally advanced, recurrent or metastatic head and neck squamous cell cancer, using a low-dose and personalized chemotherapeutic regimen.

Inoperable or metastatic head and neck squamous cell cancer (HNSCC) is known to be associated with a poor patient prognosis. First line therapies include a Taxol, platinum-based antineoplastic and fluorouracil (FU) treatment regimen (TPF) or a platinum-based antineoplastic, FU and EGFR inhibitor treatment regimen (PFE). The toxicity of these regimens is one of the major limiting factors, particularly for palliative treatment. The present study is a retrospective study of 15 patients with HNSCC, where the treatment goal was palliative. Of the 15 patients, 8 received a TPF, while 7 received a PFE. A total of 129 treatment cycles were administered with a median of 9 cycles (range, 3-14). Chemotherapy began with low doses and was subsequently titrated up based on tolerance and response. Positive responses were noted with the lower doses compared with the conventional doses, and maximal doses were not required. The median dose of cisplatin, paclitaxel and 5-FU administered was 40 mg/m2, 80 mg/m2 and 360 mg/m2/day for 5 days, respectively. Cetuximab was used at a standard dose. At the initial follow-up (mean, 64 days; 3 cycles), a 100% disease control rate (DCR) and 80% overall response rate (ORR) was achieved. A positive response, 60% DCR and 60% ORR, was maintained until the late stages of the study (mean, 217 days; 9 cycles). Following termination of chemotherapy after >9 cycles, 4 patients remained disease free for ~1 year. A total of 3 patients exhibited a pathologic complete response despite radiologically exhibiting residual disease. The median progression-free survival time was 10.03 months and the overall survival time was 15.77 months. The only grade 3 hematologic toxicity noted was neutropenia in 3 (20%) patients. Grade 3 vomiting was noted in 1 (6.67%) patient and grade 3 stomatitis was noted in 1 (6.67%) patient. Due to low toxicity patients exhibited improved tolerance to this approach, particularly in terms of palliative care. Furthermore, these results are in contrast to the axiom that increased doses are more effective.

Association of BRM promoter polymorphisms and esophageal adenocarcinoma outcome.

PURPOSE: Brahma (BRM) is a critical catalytic subunit of the SWI/SNF chromatin remodeling complex; expression of BRM is commonly lost in various cancer types. BRM promoter polymorphisms (BRM-741; BRM-1321) are associated with loss of BRM expression, and with cancer risk/survival. We evaluated these two polymorphisms in the overall survival (OS) of esophageal adenocarcinoma (EAC) patients. RESULTS: Of 270 patients, 37% were stage IV. Minor allele frequencies were 47-49%; 15% were double-homozygotes. When compared to the wild-type genotype, the homozygous variant of BRM-741 carried an adjusted OS hazard ratio (aHR) of 1.64 (95% CI:1.1-2.4); for BRM-1321, the aHR was 2.09 (95% CI:1.4-3.0). Compared to the double wild-type, carrying homozygous variants of both promoter polymorphisms (double-homozygote) yielded an aHR of 2.21 (95% CI:1.4-3.6). Directions/magnitudes of associations were similar in subsets by age, gender, smoking status, use of platinum agents, and disease stage, and for progression-free survival. MATERIALS AND METHODS: In a cohort of EAC patients of all stages (84% male; median age of 64 years), two BRM polymorphisms were genotyped. Cox proportional hazards models, adjusted for known prognostic variables, estimated the association of polymorphisms with OS. CONCLUSIONS: BRM polymorphisms were associated with OS in EAC in this study. Validation studies are warranted.

BRM Promoter Polymorphisms and Survival of Advanced Non-Small Cell Lung Cancer Patients in the Princess Margaret Cohort and CCTG BR.24 Trial.

Introduction: BRM, a key catalytic subunit of the SWI/SNF chromatin remodeling complex, is a putative tumor susceptibility gene that is silenced in 15% of non-small cell lung cancer (NSCLC). Two novel BRM promoter polymorphisms (BRM-741 and BRM-1321) are associated with reversible epigenetic silencing of BRM protein expression.Experimental Design: Advanced NSCLC patients from the Princess Margaret (PM) cohort study and from the CCTG BR.24 clinical trial were genotyped for BRM promoter polymorphisms. Associations of BRM variants with survival were assessed using log-rank tests, the method of Kaplan and Meier, and Cox proportional hazards models. Promoter swap, luciferase assays, and chromatin immunoprecipitation (ChIP) experiments evaluated polymorphism function. In silico analysis of publicly available gene expression datasets with outcome were performed.Results: Carrying the homozygous variants of both polymorphisms ("double homozygotes", DH) when compared with those carrying the double wild-type was associated with worse overall survival, with an adjusted hazard ratios (aHR) of 2.74 (95% CI, 1.9-4.0). This was confirmed in the BR.24 trial (aHR, 8.97; 95% CI, 3.3-18.5). Lower BRM gene expression (by RNA-Seq or microarray) was associated with worse outcome (P < 0.04). ChIP and promoter swap experiments confirmed binding of MEF2D and HDAC9 only to homozygotes of each polymorphism, associated with reduced promoter activity in the DH.Conclusions: Epigenetic regulatory molecules bind to two BRM promoter sequence variants but not to their wild-type sequences. These variants are associated with adverse overall and progression-free survival. Decreased BRM gene expression, seen with these variants, is also associated with worse overall survival. Clin Cancer Res; 23(10); 2460-70. ©2016 AACR.

An alternative approach with a low dose and prolonged chemotherapy for palliative treatment of locally advanced, metastatic or recurrent squamous cell head and neck cancer

Background: It is expected that about 65,000 new patients will be diagnosed with head and neck cancer in 2017 in the United States. Patients with recurrent or advanced or metastatic head and neck do not have good survival due to aggressive and recurrent nature of this cancer. Moreover, cumulative and residual toxicities from previous and ongoing treatments significantly impede quality of remaining part of their life. Currently available chemotherapeutic regimens for this group are derived from the treatments used for the potentially curable disease. These regimens and associated toxicity are obviously not the best matches for the treatment with palliative intent. We here present a retrospective study where we used dose-adjusted chemotherapy specifically for palliative treatment this sub-group of head and neck cancer patients. Methods: Study population was identified from the University of Florida, and IRB approval was obtained. We used currently available and approved chemotherapeutic agents (including Taxols, Platins, 5-Fluorouracil and Epidermal Growth Factor Receptor inhibitors) for treatment of head and neck cancer but dose-adjusted at approximate 50% dose of currently recommended doses. We then gave personalized doses for a prolonged period by titrating doses based on response and tolerability of each patient. Data was collected for treatment, response, side effects, and outcomes. KM analysis was performed for survival data. Results: Total of 32 patients were included in this study with a median age of 65.2 years and a median follow-up of 10.1 months. 62.5% (n = 20) had locally advanced disease and rest had metastatic disease. 37.5% (n = 12) had new disease while rest had recurrent cancer. Of 32 patients, 14 patients received TPF based while 18 patients received PFE based chemotherapy. Total of 270 chemotherapy cycles were delivered among these 32 patients. They received a median of 9 cycles (range 3­14) over a median of 6.2 months (range 1.8­21.1). With this treatment approach, we noted median progression-free survival of 14.0 months and median overall survival of 15.7 months. Notable grade 3 toxicities were generalized fatigue in 12.5% (n = 4), nausea/vomiting in 6.3% (n = 2), diarrhea in in 6.3% (n = 2), mouth soreness in 6.3% (n = 2), rash in 3.1% (n = 1), neutropenia in 18% (n = 6) and anemia in 15.6% (n = 5) while notable grade 4 toxicities were neutropenia and anaphylaxis in 3.1% (n = 1) patient each (AU)

Mechanism of BRG1 silencing in primary cancers.

BRG1 (SMARCA4) is a documented tumor suppressor and a key subunit of the SWI/SNF chromatin remodeling complex that is silenced in many cancer types. Studies have shown that BRG1 is mutated in cancer-derived cell lines, which led to the assertion that BRG1 is also mutated in primary human tumors. However, the sequencing of BRG1-deficient tumors has revealed a paucity of mutations; hence, the cause of BRG1 silencing in tumors remains an enigma. We conducted immunohistochemistry (IHC) on a number of tumor microarrays to characterize the frequency of BRG1 loss in different tumor types. We also analyzed BRG1-deficient tumors by sequencing the genomic DNA and the mRNA. We then tested if BRG1 expression could be induced in BRG1-negative cell lines (i.e., that lack mutations in BRG1) after the application of several different epigenetic agents, including drugs that inhibit the AKT pathway. We found that a subset of BRG1-negative cell lines also demonstrated aberrant splicing of BRG1, and in at least 30% of BRG1-deficient tumors, BRG1 expression appeared to be suppressed due to aberrant BRG1 splicing. As the majority of BRG1-deficient tumors lack mutations or splicing defects that could drive BRG1 loss of expression, this suggests that other mechanisms underlie BRG1 silencing. To this end, we analyzed 3 BRG1-deficient nonmutated cancer cell lines and found that BRG1 was inducible in these cell lines upon inhibition of the AKT pathway. We show that the loss of BRG1 is associated with the loss of E-cadherin and up-regulation of Vimentin in primary tumors, which explains why BRG1 loss is associated with a poor prognosis in multiple tumor types.

BRM polymorphisms, pancreatic cancer risk and survival.

Variant alleles of two promoter polymorphisms in the BRM gene (BRM-741, BRM-1321), create MEF2D transcription binding sites that lead to epigenetic silencing of BRM, the key catalytic component of the SWI/SNF chromatin remodeling complex. BRM suppression can be reversed pharmacologically.(1) Our group and others have reported associations with lung, head and neck, hepatocellular cancer risk,(1-3) and with lung and esophageal cancer prognosis (ASCO 2013; abstract 11057 & 4077). Herein, we assessed risk and survival associations with pancreatic cancer. A provincial population-based case-control study was conducted with 623 histologically confirmed pancreatic adenocarcinoma cases and 1,192 age/gender distribution-matched controls.(4) Survival of cases was obtained through the Ontario Cancer Registry. Logistic and Cox proportional hazard regression models were fitted, adjusting for relevant covariates. Median age was 65 y; 52% were male; Stage I (8%), II (55%), III (14%), IV (23%); 53% after curative resection, 79% after chemotherapy; and 83% had died. In the risk analysis, adjusted odds ratios (aOR) were 1.01 (95% CI: 0.1-2.0) and 0.96 (95% CI: 0.7-1.3) for the homozygotes of BRM-741 and BRM-1321, respectively; aOR of double-homozygotes was 1.11 (95% CI: 0.80-1.53), compared to the double-wildtype. For the survival analysis, adjusted hazard ratios (aHR) were 2.19 (95% CI: 1.9-2.5) for BRM-741 and 1.94 (95% CI: 1.7-2.2) for BRM-1321, per unit increase in variant alleles. Compared with the double-wildtype, aHR for carrying no, one, and two double-homozygotes were 2.14 (95% CI: 1.6-2.8), 4.17 (95% CI: 3.0-5.7), 8.03 (95% CI: 5.7-11.4), respectively. In conclusion, two functional promoter BRM polymorphisms were not associated with pancreatic adenocarcinoma risk, but are strongly associated with survival.

MOF Acetylates the Histone Demethylase LSD1 to Suppress Epithelial-to-Mesenchymal Transition.

The histone demethylase LSD1 facilitates epithelial-to-mesenchymal transition (EMT) and tumor progression by repressing epithelial marker expression. However, little is known about how its function may be modulated. Here, we report that LSD1 is acetylated in epithelial but not mesenchymal cells. Acetylation of LSD1 reduces its association with nucleosomes, thus increasing histone H3K4 methylation at its target genes and activating transcription. The MOF acetyltransferase interacts with LSD1 and is responsible for its acetylation. MOF is preferentially expressed in epithelial cells and is downregulated by EMT-inducing signals. Expression of exogenous MOF impedes LSD1 binding to epithelial gene promoters and histone demethylation, thereby suppressing EMT and tumor invasion. Conversely, MOF depletion enhances EMT and tumor metastasis. In human cancer, high MOF expression correlates with epithelial markers and a favorable prognosis. These findings provide insight into the regulation of LSD1 and EMT and identify MOF as a critical suppressor of EMT and tumor progression.

A novel double-negative feedback loop between miR-489 and the HER2-SHP2-MAPK signaling axis regulates breast cancer cell proliferation and tumor growth.

Human epidermal growth factor receptor 2 (HER2 or ErBb2) is a receptor tyrosine kinase overexpressed in 20-30% of breast cancers and associated with poor prognosis and outcome. Dysregulation of several microRNAs (miRNAs) plays a key role in breast cancer progression and metastasis. In this study, we screened and identified miRNAs dysregualted in HER2-positive breast cancer cells. Our molecular study demonstrated that miR-489 was specifically downregulated by the HER2-downstream signaling, especially through the MAPK pathway. Restoration or overexpression of miR-489 in HER2-positive breast cancer cells significantly inhibited cell growth in vitro and decreased the tumorigenecity and tumor growth in xenograft mice. Mechanistically, we found that overexpression of miR-489 led to the decreased levels of HER2 and SHP2 and thus attenuated HER2-downstream signaling. Furthermore, we for the first time demonstrated that HER2 is a direct target of miR-489 and therefore HER2-SHP2-MAPK and miR-489 signaling pathways form a mutually inhibitory loop. Using quantitative real-time PCR analysis and Fluorescent in situ hybridization technique (FISH), we found that miR-489 was expressed at significantly lower level in tumor tissues compared to the adjacent normal tissues. Downregulation of miR-489 in breast cancers was associated with aggressive tumor phenotypes. Overall, our results define a double-negative feedback loop involving miR-489 and the HER2-SHP2-MAPK signaling axis that can regulate breast cancer cell proliferation and tumor progression and might have therapeutic relevance for HER2-positive breast cancer.

Base of tongue squamous cell carcinoma with infiltrative bone marrow carcinomatosis after definitive chemoradiation: A case report.

BACKGROUND: Oropharyngeal squamous cell carcinoma (SCC) is known for its propensity for aggressive local progression and regional lymphatic spread. Distant metastases are relatively uncommon and the likelihood of hematogenous dissemination is primarily related to the extent and location of cervical lymph node metastases. Common sites of distant metastasis include the liver and lung. METHODS: We report an unusual case of base of tongue SCC with infiltrative bone marrow carcinomatosis presenting months after definitive chemoradiation despite locoregional control. RESULTS: Our patient exhibited an unusual pattern of distant dissemination after definitive chemoradiation had resulted in locoregional control. CONCLUSION: Patients who present with bone marrow failure after definitive treatment with apparent disease control should be monitored for bone marrow infiltration by the tumor and, if such infiltration is present, should be evaluated for palliative chemotherapy. Unfortunately, the prognosis for such patients is poor. © 2016 Wiley Periodicals, Inc. Head Neck 38: E2449-E2453, 2016.

Loss of the SWI/SNF ATPase subunits BRM and BRG1 drives lung cancer development.

Inactivation of Brg1 and Brm accelerated lung tumor development, shortened tumor latency, and caused a loss of differentiation. Tumors with Brg1 and/or Brm loss recapitulated the evolution of human lung cancer as observed by the development of local tumor invasion as well as distal tumor metastasis, thereby making this model useful in lung cancer studies. Brg1 loss contributed to metastasis in part by driving E-cadherin loss and Vimentin up-regulation. By changing more than 6% of the murine genome with the down-regulation of tumor suppressors, DNA repair, differentiation and cell adhesion genes, and the concomitant up-regulation of oncogenes, angiogenesis, metastasis and antiapoptosis genes, caused by the dual loss of Brg1/Brm further accelerated tumor development. Additionally, this Brg1/Brm-driven change in gene expression resulted in a nearly two-fold increase in tumorigenicity in Brg1/Brm knockout mice compared with wild type mice. Most importantly, Brg1/Brm-driven lung cancer development histologically and clinically reflects human lung cancer development thereby making this GEMM model potentially useful.

BRG1 and BRM loss selectively impacts RB and P53, respectively: BRG1 and BRM have differential functions in vivo.

The SWI/SNF complex is an important regulator of gene expression that functions by interacting with a diverse array of cellular proteins. The catalytic subunits of SWI/SNF, BRG1 and BRM, are frequently lost alone or concomitantly in a range of different cancer types. This loss abrogates SWI/SNF complex function as well as the functions of proteins that are required for SWI/SNF function, such as RB1 and TP53. Yet while both proteins are known to be dependent on SWI/SNF, we found that BRG1, but not BRM, is functionally linked to RB1, such that loss of BRG1 can directly or indirectly inactivate the RB1 pathway. This newly discovered dependence of RB1 on BRG1 is important because it explains why BRG1 loss can blunt the growth-inhibitory effect of tyrosine kinase inhibitors (TKIs). We also observed that selection for Trp53 mutations occurred in Brm-positive tumors but did not occur in Brm-negative tumors. Hence, these data indicate that, during cancer development, Trp53 is functionally dependent on Brm but not Brg1. Our findings show for the first time the key differences in Brm- and Brg1-specific SWI/SNF complexes and help explain why concomitant loss of Brg1 and Brm frequently occurs in cancer, as well as how their loss impacts cancer development.