Operative Approach Does Not Impact Radial Margin Positivity in Distal Rectal Cancer.

BACKGROUND: Robotic surgery is attractive for resection of low rectal cancer due to greater dexterity and visualization, but its benefit is poorly understood. We aimed to determine if operative approach impacts radial margin positivity (RMP) and postoperative outcomes among patients undergoing abdominoperineal resection (APR). METHODS: This was a retrospective cohort study of patients from the National Surgical Quality Improvement Program who underwent APR for low rectal cancer from 2016 to 2019. Patients were stratified by operative approach: robotic, laparoscopic, and open APR (R-APR, L-APR, and O-APR). Emergent cases were excluded. The primary outcome was RMP. 30-day postoperative outcomes were also evaluated, using logistic regression analysis. RESULTS: Among 1,807 patients, 452 (25.0%) underwent R-APR, 474 (26.2%) L-APR, and 881 (48.8%) O-APR. No differences regarding RMP (13.5% R-APR vs. 10.8% L-APR vs. 12.3% O-APR, p = 0.44), distal margin positivity, positive nodes, readmission, or operative time were observed between operative approaches. Adjusted analysis confirmed that operative approach did not predict RMP (p > 0.05 for all). Risk factors for RMP included American Society of Anesthesiologists (ASA) classification III (ASA I-II ref; OR 1.46, p = 0.039), pT3-4 stage (T0-2 ref, OR 4.02, p < 0.001), pN2 stage (OR 1.98, p = 0.004), disseminated cancer (OR 1.90, p = 0.002), and lack of preoperative radiation (OR 1.98, p < 0.01). CONCLUSIONS: No difference in RMP was observed among R-APR, L-APR, and O-APR. Postoperatively, R-APR yielded greater benefit when compared to O-APR, but was comparable to that of L-APR. Minimally invasive surgery may be an appropriate option and worthy consideration for patients with distal rectal cancer requiring APR.

Correlates of poor adherence to a healthy lifestyle among a diverse group of colorectal cancer survivors.

PURPOSE: Lifestyle factors may have a synergistic effect on health. We evaluated the correlates of poor adherence to a healthy lifestyle among a diverse sample of colorectal cancer (CRC) survivors to inform future lifestyle promotion programs. METHODS: Lifestyle questions from a cross-sectional survey were completed by 283 CRC survivors (41% Hispanic, 40% rural, 33% low income). Adherence to recommendations (yes/no) for physical activity, fruit and vegetable servings/day, avoiding tobacco, and healthy weight was summed to create an overall lifestyle quality score. Polytomous logistic regression was used to evaluate correlates of good (reference group), moderate, and poor overall lifestyle quality. Potential correlates included sociodemographic characteristics, cancer-related factors, and indicators of health and well-being. RESULTS: CRC survivors with poor adherence were 2- to 3.4-fold significantly more likely to report multiple comorbidities, poor physical functioning, fatigue, anxiety/depressive symptoms, and poor social participation. In multivariable analyses, poor physical functioning was the only significant correlate of poor adherence to lifestyle recommendations, compared to good adherence [OR (95% CI) 3.4 (1.8-6.4)]. The majority of survivors, 71% and 78%, indicated interest in receiving information on exercise and eating a healthy diet, respectively. CONCLUSION: Future lifestyle promotion programs for CRC survivors should carefully consider indicators of physical and psychosocial health and well-being, especially poor physical functioning, in the design, recruitment, and implementation of these health programs.

Phase II Trial Using a Combination of Oxaliplatin, Capecitabine, and Celecoxib with Concurrent Radiation for Newly Diagnosed Resectable Rectal Cancer.

LESSONS LEARNED: Colorectal cancers exhibit a high level of cyclooxygenase-2 (COX-2) expression with strong preclinical rationale for improved clinical outcomes with COX-2 inhibition. Celecoxib is a COX-2 inhibitor and we have shown that it can be safely combined with capecitabine and oxaliplatin as part of neoadjuvant treatment with radiation therapy (RT) in rectal cancer.There was a significant improvement in skin toxicity with this combination as compared with historical data. Considering the field has moved on to single-agent capecitabine, we believe future trials with capecitabine and celecoxib hold potential. BACKGROUND: Improved survival is seen among patients with rectal cancer who achieve pathologic complete response (pCR) after neoadjuvant therapy. Cyclooxygenase-2 (COX-2) expression is increased in gastrointestinal malignancies and it may serve as a target to enhance pathologic response. A trial combining chemoradiation and COX-2 inhibition was conducted to evaluate the pCR rate, surgical outcomes, survival, and treatment toxicity. METHODS: Patients with resectable (T3-4, N1-2) rectal cancer within 12 cm of the anal verge were included in this phase II clinical trial. The neoadjuvant treatment consisted of capecitabine 850 mg/m2 b.i.d. Monday through Friday for 5 weeks, weekly oxaliplatin 50 mg/m2 intravenous (IV), celecoxib 200 mg b.i.d. daily, along with concurrent 45 gray radiation therapy in 25 fractions. RESULTS: Thirty-two patients were included in the final analysis. The primary endpoint was pCR: 31% (95% confidence interval [CI]: 16%-50%). Secondary endpoints were surgical downstaging (SD): 75% (95% CI: 57%-89%) and sphincter-sparing surgery (SSS): 56% (95% CI: 38%-74%). Common grade >3 toxicities were diarrhea and abnormal liver function tests (9% each). Grade 0 and 1 toxicities included radiation dermatitis (59% and 34%, respectively) and proctitis (63% and 28%, respectively). At 3 years, disease-free survival and overall survival (OS) were 84% (95% CI: 65%-93%) and 94% (95% CI: 77%-98%), respectively. CONCLUSION: Chemoradiation with celecoxib in rectal cancer was well tolerated and demonstrated high rates of pCR, SD, and SSS. Improvement in skin toxicity (34% grade 1 and no grade 3/4) as compared with historical results (43%-78% grade 3/4) seems to be a significant improvement with addition of celecoxib to neoadjuvant chemotherapy.

Restoration of PTEN activity decreases metastases in an orthotopic model of colon cancer.

BACKGROUND: Mutational loss of tumor suppressor phosphatase and tensin homologue deleted on chromosome ten (PTEN) is associated with malignant progression in many cancers, including colorectal cancer (CRC). PTEN is involved in negatively regulating the phosphatidylinositol 3-kinase/AKT oncogenic signaling pathway and has been implicated in the metastatic colonization process. Few in vivo models are available to study CRC metastasis. The purpose of this study was to determine the effect of restoring PTEN activity on metastases in an orthotopic murine model. METHODS: Green fluorescent protein labeled TENN, a highly metastatic human colon cancer cell line with mutational loss of PTEN gene and TENN clones (with restoration of PTEN gene) tumors were orthotopically implanted onto the colons of BALB/c nude mice and allowed to develop primary and metastatic tumors. Seven weeks post-implantation, mice were euthanized and organs extracted for examination. RESULTS: Both TENN and TENN clone cell lines demonstrated 100% primary invasion. However, compared with the parental TENN cells, which demonstrated 62% metastases to both lungs and liver, TENN clone cells showed an approximately 50% reduction in metastasis, with only 31.6% liver metastasis and no metastasis to the lungs (P = 0.02). CONCLUSIONS: Our study shows that reactivation of PTEN tumor suppressor pathway leads to a 50% reduction in CRC metastasis without affecting primary tumor formation. Importantly, PTEN restoration also changed the organotropic homing from liver and lung metastasis to liver metastasis only. This in vivo study demonstrates that PTEN might act specifically as a metastasis suppressor and, thus, efforts to target the phosphatidylinositol 3-kinase/PTEN pathway are legitimate.

WITHDRAWN: Restoration of transforming growth factor-beta receptor II expression in colon cancer cells with microsatellite instability increases metastatic potential in vivo.

Microsatellite instability (MSI), which occurs in 15% of colorectal cancer, has been shown to have a lower incidence of metastasis and better patient survival rates compared with microsatellite stable colorectal cancer. However, a mechanistic understanding of the basis for this difference is very limited. Here, we show that restoration of TGFß signaling by re-expression of TGFß receptor II in MSI colon cancer cells increased PI3K/AKT activation, conferred resistance to growth factor deprivation stress-induced apoptosis, and promoted cell motility in vitro. Treatment with a potent PI3K inhibitor (LY294002) blocked the prosurvival and promotility effects of TGFß, indicating that TGFß-mediated promotion of cell survival and motility is dependent upon activation of the PI3K/AKT pathway. Analysis of apoptotic effectors that are affected by TGFß signaling indicated that Bim is an effector of TGFß-mediated survival. In addition, TGFß-induced down-regulation of E-cadherin contributed to the prosurvival effect of TGFß, and restoration of TGFß signaling in MSI colon cancer cells increased liver metastasis in an orthotopic model in vivo. Taken together, our results demonstrate that restoration of TGFß signaling promotes cell survival, motility, and metastatic progression in MSI colon cancer cells and indicate that TGFß receptor II mutations contribute to the favorable outcomes in colon cancer patients with MSI.

Transforming growth factor-ß suppresses metastasis in a subset of human colon carcinoma cells.

BACKGROUND: TGFß signaling has typically been associated with suppression of tumor initiation while the role it plays in metastasis is generally associated with progression of malignancy. However, we present evidence here for an anti-metastatic role of TGFß signaling. METHODS: To test the importance of TGFß signaling to cell survival and metastasis we compared human colon carcinoma cell lines that are either non-tumorigenic with TGFß response (FET), or tumorigenic with TGFß response (FETα) or tumorigenic with abrogated TGFß response via introduction of dominant negative TGFßRII (FETα/DN) and their ability to metastasize. Metastatic competency was assessed by orthotopic transplantation. Metastatic colony formation was assessed histologically and by imaging. RESULTS: Abrogation of TGFß signaling through introduction of a dominant negative TGFß receptor II (TGFßRII) in non-metastatic FETα human colon cancer cells permits metastasis to distal organs, but importantly does not reduce invasive behavior at the primary site. Loss of TGFß signaling in FETα-DN cells generated enhanced cell survival capabilities in response to cellular stress in vitro. We show that enhanced cellular survival is associated with increased AKT phosphorylation and cytoplasmic expression of inhibitor of apoptosis (IAP) family members (survivin and XIAP) that elicit a cytoprotective effect through inhibition of caspases in response to stress. To confirm that TGFß signaling is a metastasis suppressor, we rescued TGFß signaling in CBS metastatic colon cancer cells that had lost TGFß receptor expression due to epigenetic repression. Restoration of TGFß signaling resulted in the inhibition of metastatic colony formation in distal organs by these cells. These results indicate that TGFß signaling has an important role in the suppression of metastatic potential in tumors that have already progressed to the stage of an invasive carcinoma. CONCLUSIONS: The observations presented here indicate a metastasis suppressor role for TGFß signaling in human colon cancer cells. This raises the concern that therapies targeting inhibition of TGFß signaling may be imprudent in some patient populations with residual TGFß tumor suppressor activity.

Colorectal Cancer Survivors' Receptivity toward Genomic Testing and Targeted Use of Non-Steroidal Anti-Inflammatory Drugs to Prevent Cancer Recurrence.

Genomic testing and targeted use of non-steroidal anti-inflammatory drugs (NSAIDs) may mitigate cancer recurrence risks. This study examines colorectal cancer (CRC) survivors' interest and receptivity to these strategies. Patients diagnosed with stage I-III CRC in 2004-2012 were recruited through the New Mexico Cancer Registry to complete a cancer survivorship experiences survey. We assessed interest in genomic testing, daily aspirin (ASA) and NSAID use, and receptivity to future daily ASA/NSAIDs. Descriptive statistics and multivariable logistic regression models estimated factors associated with genomic testing interest. Receptivity to future ASA/NSAIDs use was estimated for non-users of ASA/NSAIDs. Among CRC survivors (n = 273), 83% endorsed interest in genomic testing, 25% were ASA users and 47% ASA/NSAIDs users. In our final model, genomic testing interest was associated with being uncoupled [OR = 4.11; 95% CI = 1.49-11.35], low income [OR = 0.35, 95% CI: 0.14-0.88], smoking history [OR = 0.35, 95% CI: 0.14-0.90], low [OR: 0.33, 95% CI: 0.07-1.43] and moderate [OR: 0.26, 95% CI: 0.11-0.61] health literacy, and personal CRC risk worry [OR: 2.86, 95% CI: 1.63-5.02, p = 0.0002]. In our final model, ASA use was associated with age [OR: 1.05, 95% CI: 1.01-1.10] and cardiovascular disease history [OR: 2.42, 95% CI: 1.23-4.73, p = 0.010]. Among non-users ASA/NSAIDs, 83% reported receptivity to ASA/NSAIDs to reduce cancer risks, and no significant correlates were identified. The majority of survivors' expressed genomic testing interest and endorsed receptivity toward ASA/NSAIDs use for cancer risk management. Further research to optimize ASA/NSAIDs use guided by genomic testing is warranted.

The Impact of Surgical Delays on Short- and Long-Term Survival Among Colon Cancer Patients.

BACKGROUND: The purpose of this study was to assess the impact of surgical delays on short- and long-term survival among colon cancer patients. METHODS: Adult patients undergoing surgery for stage I, II, or III colon cancer were identified from the National Cancer Database (2010-2016). After categorization by wait times from diagnosis to surgery (<1 week, 1-3 weeks, 3-6 weeks, 6-9 weeks, 9-12 weeks, and >12 weeks), 30-day mortality, 90-day mortality, and 5-year overall survival were compared between patients both overall and after stratification by pathological disease stage. RESULTS: Among 187 394 colon cancer patients, 24.2% waited <1 week, 30.5% waited 1-3 weeks, 29.0% waited 3-6 weeks, 9.7% waited 6-9 weeks, 3.3% waited 9-12 weeks, and 3.3% waited >12 weeks for surgery. Patients undergoing surgery 3-6 weeks after colon cancer diagnosis exhibited the best 30-day mortality (1.3%), 90-day mortality (2.3%), and 5-year overall survival (71.8%) (P < .001 for all). After risk-adjusting for confounders, all wait times beyond 6 weeks were associated with worse 5-year overall survival (6-9 weeks: HR 1.10, 95% CI 1.06-1.15; 9-12 weeks: HR 1.25, 95% CI 1.18-1.33; >12 weeks: HR 1.43, 95% CI 1.35-1.52; P < .001 for all). Subgroup analysis after stratification by disease stage demonstrated that patients with stage III colon cancer were able to wait up to 9 weeks before exhibiting worse 5-year overall survival, compared to 6 weeks for patients with stage I or II disease. CONCLUSIONS: Colon cancer patients should undergo surgery 3-6 weeks after diagnosis, as all surgical delays beyond 6 weeks were associated with worse 30-day mortality, 90-day mortality, and 5-year overall survival.

Impact of Treatment Coordination on Overall Survival in Rectal Cancer.

BACKGROUND: Rectal cancer treatment is often multimodal, comprising of surgery, chemotherapy, and radiotherapy. However, the impact of coordination between these modalities is currently unknown. We aimed to assess whether delivery of nonsurgical therapy within same facility as surgery impacts survival in patients with rectal cancer. METHODS: A patient cohort with rectal cancer stages II to IV who received multimodal treatment between 2004 and 2016 from National Cancer Database was retrospectively analyzed. Patients were categorized into three groups: (A) surgery + chemotherapy + radiotherapy at same facility (surgery + 2); (B) surgery + chemotherapy or radiotherapy at same facility (surgery + 1); or (C) only surgery at reporting facility (chemotherapy + radiotherapy elsewhere; surgery + 0). The primary outcome was 5-year overall survival (OS), analyzed using Kaplan-Meier curves, log-rank tests, and Cox proportional-hazards models. RESULTS: A total of 44,716 patients (16,985 [37.98%] surgery + 2, 12,317 [27.54%] surgery + 1, and 15,414 [34.47%] surgery + 0) were included. In univariate analysis, we observed that surgery+2 patients had significantly greater 5-year OS compared to surgery + 1 or surgery + 0 patients (5-year OS: 63.46% vs 62.50% vs 61.41%, respectively; P= .002). We observed similar results in multivariable Cox proportional-hazards analysis, with surgery + 0 group demonstrating increased hazard of mortality when compared to surgery + 2 group (HR: 1.09; P< .001). These results held true after stratification by stage for stage II (HR 1.10; P= .022) and stage III (HR 1.12; P< .001) but not for stage IV (P= .474). CONCLUSION: Greater degree of care coordination within the same facility is associated with greater OS in patients with stage II to III rectal cancer. This finding illustrates the importance of interdisciplinary collaboration in multimodal rectal cancer therapy.

EGFR transactivates RON to drive oncogenic crosstalk.

Crosstalk between different receptor tyrosine kinases (RTKs) is thought to drive oncogenic signaling and allow therapeutic escape. EGFR and RON are two such RTKs from different subfamilies, which engage in crosstalk through unknown mechanisms. We combined high-resolution imaging with biochemical and mutational studies to ask how EGFR and RON communicate. EGF stimulation promotes EGFR-dependent phosphorylation of RON, but ligand stimulation of RON does not trigger EGFR phosphorylation - arguing that crosstalk is unidirectional. Nanoscale imaging reveals association of EGFR and RON in common plasma membrane microdomains. Two-color single particle tracking captured formation of complexes between RON and EGF-bound EGFR. Our results further show that RON is a substrate for EGFR kinase, and that transactivation of RON requires formation of a signaling competent EGFR dimer. These results support a role for direct EGFR/RON interactions in propagating crosstalk, such that EGF-stimulated EGFR phosphorylates RON to activate RON-directed signaling.

Inhibition of hyaluronan synthase-3 decreases subcutaneous colon cancer growth in mice.

PURPOSE: Hyaluronan and hyaluronan synthases have been implicated in cancer progression. Hyaluronan synthase-3 is up-regulated in metastatic colon cancer cells (SW620), and its expression mediates cellular growth in vitro. We hypothesized that inhibition of hyaluronan synthase-3 would decrease tumor formation and/or alter the pattern of metastasis in mouse models of colon cancer growth. METHODS: Hyaluronan synthase-3 was inhibited in SW620 cells by transfection with small interfering RNA (silenced cells); a scrambled sequence served as a negative control. To study primary tumor growth, transfected cells were injected into the flanks of BALB/c nude mice. To study metastasis, an orthotopic model was used. Metastases were confirmed histologically. Student t test and Fisher exact probability test were used for statistical analysis. RESULTS: Inhibition of hyaluronan synthase-3 significantly decreased subcutaneous tumor growth; tumor weight was 0.94 +/- 0.17 g in the hyaluronan synthase-3-silenced group vs 1.70 +/- 0.26 g in the control scrambled group (P < .01). In contrast, metastases were similar in both groups: liver metastases were present in 22% of the silenced group vs 11% of the scrambled group; lung metastases were present in 6% of the silenced group vs 0% of the scrambled group (P = not significant). CONCLUSION: Inhibition of hyaluronan synthase-3 expression in SW620 colon cancer cells decreases subcutaneous tumor growth in mice, but has less of an effect on lung and liver metastases. This observation suggests that hyaluronan synthase-3 may enhance primary colon cancer growth.

The role of transforming growth factor-beta in suppression of hepatic metastasis from colon cancer.

BACKGROUND: The role of transforming growth factor-beta (TGF-beta) in the development of hepatic metastasis from colon cancer is not clearly elucidated. The aim of this study was to determine the role of TGF-beta in the development of such metastasis. METHODS: Two human colon cancer cell lines were utilized: FET-alpha cells (intact TGF-beta inhibitory response), and CBS cells (defects in TGF-beta inhibitory response caused by a deficiency in type II receptor activity). The ability of these cell lines to metastasize was analysed in an orthotopic colon cancer mouse model. RESULTS: FET-alpha cells did not metastasize to the liver, but showed lung metastasis in 10% of the animals, whereas CBS cells gave rise to metastasis in 65%. Following the elimination of TGF-beta activity by transfection and overexpression of dominant negative type II receptor, FET-alpha cells demonstrated liver and lung metastasis in 70% of the animals. Similarly, after the restoration of type II receptor activity by ectopic expression, CBS cells formed metastasis in fewer (10%) animals. CONCLUSIONS: The results of our study demonstrate for the first time that TGF-beta displays selective metastasis suppressor activity. These abnormal pathways can serve as selective targets for future development of targeted therapies.

Mechanisms of Immunosuppression in Colorectal Cancer.

CRC is the third most diagnosed cancer in the US with the second-highest mortality rate. A multi-modality approach with surgery/chemotherapy is used in patients with early stages of colon cancer. Radiation therapy is added to the armamentarium in patients with locally advanced rectal cancer. While some patients with metastatic CRC are cured, the majority remain incurable and receive palliative chemotherapy as the standard of care. Recently, immune checkpoint blockade has emerged as a promising treatment for many solid tumors, including CRC with microsatellite instability. However, it has not been effective for microsatellite stable CRC. Here, main mechanisms of immunosuppression in CRC will be discussed, aiming to provide some insights for restoring immunosurveillance to improve treatment efficacy in CRC.

Retrorectal cyst: proteus in the backyard-case series and literature review.

Retrorectal cysts are cystic lesions located in the retrorectal space and are a distinct subset of retrorectal tumours, which are often misdiagnosed due to their rarity and mimicry of symptoms caused by common diseases. We have described the presentation and management of four patients who were diagnosed with retrorectal cysts from a 10-year retrospective chart review at our institute, a tertiary care centre. In middle-aged women, the following should raise suspicion of retrorectal cyst: gastrointestinal or urinary obstructive features, mass or fullness palpable on the posterior wall on digital rectal examination, presacral dimple, perianal fistula and/or recurrent disease. Such features should prompt an MRI evaluation of the pelvis for definitive diagnosis.

Should total number of lymph nodes be used as a quality of care measure for stage III colon cancer?

OBJECTIVE: To assess whether TNODS is an independent prognostic factor after adjusting for the lymph node ratio (LNR). SUMMARY BACKGROUND DATA: The medical literature has suggested that the TNODS is associated with better survival in stage II and III colon cancer. Thus TNODS was endorsed as a quality measure for patient care by American College of Surgeons, National Quality Forum. There is, however, little biologic rationale to support this linkage. METHODS: : A total of 24,477 stage III colon cancer patients were identified from Surveillance, Epidemiology, and End Results cancer registry and categorized into 4 groups, LNR1 to LNR4, according to LNR interval: <0.07, 0.07 to 0.25, 0.25 to 0.50, and >0.50. Patients were also stratified according to TNODS into high TNODS (> or = 12) and low TNODS (<12) groups. The method of Kaplan-Meier was used to estimate the 5-year survival and the log-rank test was used to test the survival difference among the different groups. RESULTS: Patients with high TNODS have better survival compared with those with low TNODS (5-year survival 51.0% vs. 45.0%, P < 0.0001). However, after stratifying by LNR status, there was no significant survival difference between patients with high TNODS and those with low TNODS within strata LNR2 (5-year survival 56.3% vs. 56.0%, P = 0.26). Ironically, patients with high TNODS had significantly worse survival than those with low TNODS within strata LNR3 (5-year survival 41.2% vs. 47.4%, P = 0.0009) and LNR 4 (5-year survival 22.0% vs. 32.1%, P < 0.0001). CONCLUSIONS: The previously reported prognostic effect of TNODS on node-positive colon cancer was confounded by LNR. This observation calls into question the use of TNODS as a quality measure for colon cancer patients' care.

Factors associated with sphincter-preserving surgery for rectal cancer at national comprehensive cancer network centers.

OBJECTIVE: To determine rate and predictors of sphincter-preserving surgery (SPS) for rectal cancer patients treated at specialty institutions. SUMMARY BACKGROUND DATA: SPS has been considered a surrogate for surgical quality, and sphincter preservation is tremendously important to patients. Evidence of association between case volume and SPS rate has prompted recommendations that all rectal cancer patients undergo surgery at specialty institutions. However, rates of SPS, and the factors associated with ability to perform SPS, have not been well-characterized. METHODS: A prospective registry of all colorectal cancer patients treated at 7 National Comprehensive Cancer Network institutions was used to identify patients with clinical stage I-III rectal cancer undergoing surgery (n = 674) between September 2005 and October 2007. Patient, tumor and treatment factors were abstracted; patients' clinical characteristics with and without SPS were compared using descriptive statistics and multivariable logistic regression. RESULTS: Of 674 identified patients (median age, 58.2; 60% male), 520 (77%) had SPS. Of these, 240 had low anterior resection with coloanal anastomosis, 268 low anterior resection without coloanal anastomosis; 12 had other SPS procedures. Sixty-two percent had a temporary diverting stoma. On multivariable analyses, independent predictors of SPS included younger age at diagnosis, proximal location in the rectum, nonfixed tumor, and institution. CONCLUSIONS: SPS rates at National Comprehensive Cancer Network institutions exceed those seen in population-based samples and clinical trials. In addition to expected variation in SPS rates based on patient and tumor characteristics, we identified variation among institutions. Although the optimal rate of SPS remains unknown, this provides areas for further research and potential performance improvement.

The effects of epidermal growth factor receptor activation and attenuation of the TGFbeta pathway in an orthotopic model of colon cancer.

BACKGROUND: Colorectal cancer is the second leading cause of cancer related mortality, with a majority of deaths resulting from metastases. Few in vivo models allow for the study of the complex process of metastasis. The purpose of this study was to determine the effects of epidermal growth factor receptor activation and TGFbeta pathway attenuation in FET, a weakly tumorigenic human colon cancer cell line, in an orthotopic model. METHODS AND RESULTS: Using FET, FETalpha, FETalphaDNRII, and FETDNRII cells were constructed. Tumors were orthotopically implanted onto the colons of BALB/c nude mice. After 7 wk, the mice were euthanized and organs extracted for examination. All cell lines demonstrated primary invasion. FETalpha was weakly metastatic compared with FETalphaDNRII and FETDNRII, which demonstrated metastases to the lung and liver, respectively. CONCLUSION: Epidermal growth factor receptor (EGFR) activation transforms a nontumorigenic cell line into a tumorigenic but not metastatic one. The tumorigenic line becomes metastatic with the attenuation of TGFbeta signaling. Loss of EGFR activation in the TGFbeta inhibited line results in a decreased metastatic burden, but importantly, changes the organotropic homing from lung to liver. Thus, these in vivo studies demonstrate that EGFR activation and TGFbeta signaling pathways play a role in tumorigenicity and in pattern of metastases.

A novel mechanism of resistance to epidermal growth factor receptor antagonism in vivo.

Epidermal growth factor receptor (EGFR) is widely expressed in a number of solid tumors including colorectal cancers. Overexpression of this receptor is one means by which a cell can achieve positive signals for survival and proliferation; another effective means is by constitutive activation of EGFR. We have elucidated the role of constitutive EGFR signaling in malignant progression by stably transfecting colon cancer cells with a human transforming growth factor-alpha cDNA (a ligand for EGFR) under repressible control by tetracycline. We show that constitutive expression of transforming growth factor-alpha and its subsequent constitutive activation of EGFR allows for cancer cell survival in response to environmental stress in vitro and in vivo as well. The reversal of constitutive EGFR activation results in the loss of downstream mitogen-activated protein kinase and Akt activation, and a reduction in xenograft size that is associated with decreased proliferation and increased apoptosis. We used CI-1033, a small molecule antagonist of EGFR, to dissect an activation pathway that shows the ability of ERBb2 to activate Akt, but not Erk in the face of EGFR antagonism. This novel escape mechanism is a possible explanation of why anti-EGFR therapies have shown disappointing results in clinical trials.

Mutant PIK3CA-bearing colon cancer cells display increased metastasis in an orthotopic model.

Mutations in the PIK3CA gene are common in human cancers, including colon cancer. We compared two pairs of colon cancer cells (HCT116 and DLD1) bearing only the wild-type (WT) or mutant (MUT) PIK3CA allele for their survival capacity under stress conditions in vitro as well as their metastatic properties in an in vivo orthotopic model. When subjected to growth factor deprivation stress (GFDS), the MUT PIK3CA cells displayed resistance to GFDS-induced apoptosis relative to the WT cells. Phosphatidylinositol 3-kinase (PI3K) and its downstream effector AKT were constitutively activated during stress conditions in the MUT PIK3CA cells but not in the WT cells. The MUT cells showed hypersensitivity to PI3K inhibition. Moreover, the proapoptotic protein Bax was expressed at a very high level in the WT PIK3CA cells, whereas it was almost undetectable in the MUT cells. Inhibition of Bax expression by small interfering RNA protected the WT PIK3CA cells from GFDS-induced apoptosis, suggesting an important role of Bax in GFDS-induced apoptosis. These results indicated that the MUT PI3K confers resistance to GFDS-induced apoptosis and that the MUT cells are more dependent on the PI3K pathway for survival. In vivo studies showed that the MUT PIK3CA-bearing cells were more metastatic than the WT cells in an orthotopic model of colon cancer. Taken together, these results suggest that MUT PI3K imparts a more aggressive phenotype in colon cancer cells and could be a potential therapeutic target for treatment of colon cancer patients bearing PIK3CA mutations.