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T S Ravikumar

Publications and source records attributed to T S Ravikumar.

At least 19 recordsLinked to original sources
PubMed2005

Induction of p21WAF1 expression protects HT29 colon cancer cells from apoptosis induced by cryoinjury.

BACKGROUND: Cryotherapy is a method of in situ destruction of tumors by freeze/thaw mechanisms. Cancer cells located in the peripheral zone of the tumor undergoing cryotherapy can die by apoptosis. We hypothesized that p21WAF1 is involved in the mediation of cryotherapy-induced apoptosis. METHODS: HT29 cells grown on a plate were subjected to -10 degrees C and returned to 37 degrees C for various periods of time. Cells were analyzed by flow cytometry, Western blot, and reverse transcriptase-polymerase chain reaction for determining cell-cycle distribution, p21WAF1 protein expression, and messenger RNA levels, respectively. The p21WAF1 expression in nude mouse tumor xenografts after cryotherapy was examined by immunofluorescence staining. A series of the p21WAF1 promoter cloned into a luciferase reporter vector were transfected into HT29 cells for identifying the response element to cryoinjury. Antisense oligodeoxynucleotide (ODN) was applied to examine the effect of p21WAF1 expression on cryotherapy-induced apoptosis. RESULTS: Both protein and messenger RNA of p21WAF1 were induced by cryoinjury in cultured cells and tumor xenografts. Deletion analysis of the p21WAF1 promoter revealed that a region from -121 to -95 base pairs was responsible for the activation and that this activation was p53 independent. HT29 cells arrested at the G1 phase after cryoinjury. The cryotherapy-induced apoptotic rate in HT29 cells was increased in the presence of antisense p21WAF1 ODN in comparison to the random ODN. CONCLUSIONS: Induction of p21WAF1 increases tumor cell survival and may result in recurrences at treated sites after cryotherapy. Combining antisense ODN targeted against p21WAF1 and cryotherapy may improve clinical outcomes in the treatment of colorectal cancer.

Apoptosis↗
PubMed2004

Heat shock protein 70 is induced in mouse human colon tumor xenografts after sublethal radiofrequency ablation.

BACKGROUND: Radiofrequency ablation (RFA) destroys tumor cells by generating high temperatures through ionic vibration. Tumor recurrence may be a direct function of sublethal temperature. Further, a set of proteins called heat shock proteins (HSPs) can be synthesized under heat stress to facilitate recovery of tumor cells from heat damage. METHODS: Subcutaneous xenografts were induced in nude mice by injection with HT29 human colon cancer cells. The tumors were exposed surgically and subjected to RFA. The tumors were randomly assigned to achieve a target tumor temperature of 42 degrees C, 45 degrees C, or 50 degrees C. Total RNA and cell lysates were isolated from tumor tissues and subjected to reverse transcription-polymerase chain reaction and Western blot analyses, respectively, at various time points after treatments for assessing HSP expression. For in vitro experiments, HT29 cells were subjected to variable temperatures, and HSP expression was assayed. RESULTS: During a 50-day follow-up, the recurrence rates were 0% at 50 degrees C, 30% at 45 degrees C, and 100% at 42 degrees C. The messenger RNA and protein levels of HSP90 and HSP27 remained unchanged after RFA at 45 degrees C; however, HSP70 was induced at 4 and 10 hours after RFA. In vitro HT29 culture cells subjected to a heated water bath exhibited a cellular sensitivity to heat and change of HSP expression similar to those in tumor xenografts subjected to RFA. CONCLUSIONS: Our data establish the requisite heat parameters during RFA for human colon tumors in vitro and in vivo. Because HSP70 plays an important role in protecting cell death from a variety of stresses, HSP70 could be a potential target for enhancing the efficacy of RFA.

Adenocarcinoma↗
PubMed2003

Development of cross-resistance between heat and cisplatin or hydroxyurea treatments in FaDu squamous carcinoma cells.

BACKGROUND: Induction of hyperthermia by radiofrequency ablation is gaining popularity in treating a variety of solid tumors. This study examined an impact of sublethal heat treatment interacted with chemotherapeutic drugs on the survival of head and neck squamous carcinoma cells using in vitro model. MATERIALS AND METHODS: FaDu cells were subjected to heat treatment at 42 degrees C or 45 degrees C for 15 min either before or after exposure to cisplatin or hydroxyurea. The survival of cells was determined by 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide assay. The RNA and protein levels of various heat shock proteins were examined by reverse transcription polymerase chain reaction and Western blot analysis, respectively. Cell cycle progression was analyzed by flow cytometry with propidium iodide staining. RESULTS: FaDu cells preheated to 45 degrees C exhibited an increased resistance to hydroxyurea but not to cisplatin. The heat treatment resulted in induction of HSP70 expression at transcript and protein levels, but there was no change in expression of HSP90beta and HSP27. After heat treatment, cells accumulated in S-phase at 3 h and proceeded to G(2)/M phase at 24 h. When cells pre-exposed to drugs for 24 h, the cisplatin-treated cells exhibited a higher thermotolerance than the hydroxyurea-treated cells at heat treatment of 45 degrees C. Cisplatin and hydroxyurea caused cells to accumulate in S-phase and increased the protein expression of HSP27 but not HSP90beta and HSP70. CONCLUSION: FaDu cells surviving the heat treatment expressed HSP70 and disrupted cell cycle progression, which resulted in developing a resistance to subsequent hydroxyurea treatment. However, the heat treatment did not have an effect on the sensitivity to cisplatin. In the reversed procedure, pre-exposure to hydroxyurea and cisplatin resulted in developing a thermotolerance.

Antineoplastic Agents↗
PubMed2003

Apoptosis induced by cryo-injury in human colorectal cancer cells is associated with mitochondrial dysfunction.

Cryotherapy, a method of in situ ablation, is used in the treatment of colorectal liver metastases with variable results. During the treatment, the central area of treated tumor undergoes necrotic destruction by lethal cryo-injury; however, the cellular response of tumor exposed to sublethal cryo-injury at the peripheral zone is unclear. In our study, we have identified the induction of apoptosis by cryo-injury at -10 degrees C in 4 colorectal cancer cell lines (HT29, HCT116, KM12C and KM12SM). The apoptosis was characterized by chromatin condensation, transferase-mediated dUTP nick end-labeling (TUNEL) staining, proteolytic cleavage of poly(ADP-ribose) polymerase (PARP) and cytokeratin 18, and activation of caspase-3. The occurrence and intensity of cryo-induced apoptosis did not correlate with the functional status of p53 in the cell lines studied. The expression of anti-apoptotic proteins (Bcl-2, Bcl-X(L)) and pro-apoptotic proteins (Bax, Bcl-X(S), Bad, and Bak) in response to cryo-injury varied in this cell line panel. The basal level of Bcl-2/Bax protein ratio correlated inversely to the apoptotic rate. We further demonstrated that Bax level decreased in cytosol and increased in mitochondria, followed by a loss of mitochondrial membrane potential after cryo-injury in HT29 cells. These findings indicate that cryo-injury induces apoptosis in colorectal cancer cells via disruption of mitochondrial integrity. The cryo-induced apoptosis was also identified in a nude mouse tumor xenograft model. Our elucidation of the apoptosis pathway induced by cryo-injury implies that synergistic combination of cryosurgery with pharmacological agents that augment of apoptosis induction may have clinical relevance in treating colorectal liver metastasis.

Animals↗
PubMed2002

Resection of liver metastases: state of the art.

In this article, we present current surgical perspectives on the management of liver metastases, with a focus on state-of-the-art resection, by drawing on clinical data provided in the medical literature. Metastases from colorectal cancer are the most amenable to resection, when considering long-term benefits. To highlight the evidence-based rationalefor surgical resection, a succinct comparison of all treatment modalities for liver metastasis from colorectal cancer is provided. Special emphasis has been placed on the current status of perioperative patient evaluation, durability of results, prognosticators, technical advances, and alternative treatment strategies. In various areas, we have attempted to delineate any improvements on the horizon. The role of surgical resection in noncolorectal metastases is also discussed.

Clinical Trials as Topic↗
PubMed2001

Induction of apoptosis in human colon carcinoma cells HT29 by sublethal cryo-injury: mediation by cytochrome c release.

Cryosurgery is an emerging treatment for human solid tumors, notably colorectal liver metastasis. Cryosurgical procedures generate a thermal gradient of from at least -50 degrees C at the center of the tumor being treated to about 0 degrees C at the periphery. Cell death occurs by necrosis in the center, while the peripheral zone of frozen tumor harbors a mix of viable and dead tissue. In order to understand the mechanisms of cell death and survival in this peripheral area at risk for tumor recurrence, we have established an in vitro freezing system that mimics in vivo conditions of sublethal injury. HT29 colon cancer cells were subjected to freezing temperatures from -6 degrees C to -36 degrees C, thawed at room temperature for 30 min and rewarmed at 37 degrees C for a period of time. Post-freeze-thaw, cryolytic cells were evaluated by trypan blue exclusive assay. We also identified apoptotic cells after rewarming by cell shrinkage, nucleic condensation, TUNEL assay, DNA fragmentation and PARP degradation. The intensity of cryolysis and apoptosis was increased by lowering the freezing temperature. At -36 degrees C, all cells were dead immediately after freeze-thaw. A kinetic analysis of cryo-induced apoptosis showed that the commitment to enter apoptosis occurred right after the freeze-thaw period and lasted less than 8 hr after rewarming. We further demonstrated that freezing triggers one of the caspase cascade involved in apoptosis: release of cytochrome c from mitochondria to cytosol, followed by activation of caspase-9 and degradation of PARP. These results indicate the death of cancer cells under cryo-treatment at sublethal freezing temperature can be attributed 2 different modes, cryolysis as well as apoptosis. HT29 cells carrying p53 mutant have very quick response for induction of apoptosis by cryo-treatment and contain an intact pathway of caspase cascade. Further studies will address if mechanisms in cells with wild-type p53 will differ.

Apoptosis↗
PubMed2000

Total pelvic exenteration and reconstruction for locally invasive recurrent sarcoma of the perineum.

Extensive primary tumors and locally recurrent tumors of the pelvis or perineum are difficult to manage. We describe the techniques necessary to perform total pelvic exenteration with en bloc resection of the perineum and genitalia for treatment of recurrent sarcoma of the perineum. Wide excision of the sarcoma with negative margins can be achieved by resecting the inferior portion of the pubic symphysis. An absorbable mesh sling may be used to suspend the small bowel above the pelvis, facilitating postoperative radiation. A catheterizable continent urinary reservoir avoids the necessity of two stomas and improves quality of life. Adequate tissue coverage can be attained by myocutaneous gracilis flaps that promote wound healing.

Adult↗
PubMed1998

Experimental basis for hepatic cryotherapy.

Hepatic cryotherapy has emerged as a viable therapeutic option in the treatment of liver tumors, both primary and secondary. We will provide the experimental basis for its application in the liver with particular reference to safety and efficacy issues. Also discussed are experiments with the use of hepatic cryotherapy in animals that have demonstrated the effectiveness of the technique, and improvements in technology that have enabled better delivery. The future of this modality looks bright with increasing advances in technology to enable better application. Its use in combination with other treatment modalities could offer improved success in treating liver tumors.

Animals↗
PubMed1998

Minimally invasive staging of patients with melanoma: sentinel lymphadenectomy and detection of the melanoma-specific proteins MART-1 and tyrosinase by reverse transcriptase polymerase chain reaction.

BACKGROUND: A minimally invasive standard has yet to be developed for sentinel lymphadenectomy, and many patients undergo this procedure in the main operating room under general anesthesia. These patients often have microscopic metastases in sentinel nodes that could be missed by histopathologic examination. Techniques of reverse transcriptase polymerase chain reaction (RT-PCR) could detect these metastases if the nodes could be preserved intraoperatively. STUDY DESIGN: Fifty patients with melanoma > or = mm thick underwent sentinel lymphadenectomy under local anesthesia in an outpatient surgical unit. Sentinel nodes were identified using blue dye and technetium-99 sulfur colloid and a hand-held gamma probe. Each node was sectioned, with half sent for routine histopathologic study and half preserved in liquid nitrogen. We used RT-PCR to detect mRNA for tyrosinase and Melanoma Antigen Recognized by T cells-1 (MART-1). RESULTS: All patients were able to tolerate sentinel lymph node biopsy under local anesthesia. Sentinel lymph nodes were obtained in 100% of our patients, and usable mRNA was harvested from all but five. Ten patients had positive sentinel node(s) by standard histopathologic examination, and all of these nodes were also positive for MART-1 and tyrosinase. Three patients with negative results by histopathology had positive results by RT-PCR analysis. The average cost of these outpatient operations was 38% less than the same operations performed in the main operating room under general anesthesia. CONCLUSIONS: Sentinel lymphadenectomy under local anesthesia in an outpatient setting and intraoperative lymph node preservation in liquid nitrogen are both feasible. Both tyrosinase and MART-1 are promising markers in the detection of occult melanoma in lymph nodes.

Actins↗
PubMed1997

Chemotherapy for metastatic melanoma during pregnancy.

Melanoma during pregnancy represents a difficult problem. Although surgery is a definitive therapy for early-stage disease, rapidly progressive metastatic disease in pregnancy requires a series of more difficult decisions. We report the use of combination chemotherapy with tamoxifen, carmustine, dacarbazine, and cisplatin in a patient with metastatic melanoma during the second trimester of pregnancy. The patient received 2 cycles of chemotherapy prior to delivery of a healthy 1520-g baby girl at 30 weeks gestation. Placental pathology, however, revealed malignant melanoma in the intervillous space and melanin pigment granules in villous Hofbauer cells and synctial trophoblasts. This report also reviews the literature, assessing the importance of pregnancy as a prognostic factor, the effects of metastasis on the products of conception, and the use of chemotherapy in pregnancy. We conclude that combination chemotherapy can be administered in the second trimester of pregnancy for the treatment of rapidly progressive melanoma without interfering with the successful maturation and delivery of an infant of 30 weeks gestation.

Adult↗
PubMed1996

Expression of 32-kDa laminin-binding protein mRNA in colon cancer tissues.

Colorectal cancer initiation and progression are associated with stepwise genetic alterations. We and others have shown that a gene encoding for a 32-kDa putative laminin-binding protein (LBP-32) is overexpressed during colorectal cancer progression by Northern blots analysis. Northern blots cannot indicate the heterogeneity of expression from cell to cell and the distribution pattern of gene expression within a given tumor. In order to overcome these problems, we examined the LBP-32 mRNA expression in colorectal carcinomas by in situ hybridization. LBP-32 mRNA expression in 30 cases of primary and metastatic colorectal cancers and their respective adjacent normal tissues were detected by in situ hybridization using 35S-UTP radiolabeled antisense riboprobes. The results showed that LBP-32 mRNA was expressed at a low level in the normal colonic mucosa adjacent to the tumor compared with colon cancer tissues. Its expression in poorly differentiated colorectal cancer was much higher than that in well- and moderately differentiated colorectal cancer. More importantly, the LBP-32 mRNA was expressed more highly in the invasive lesions of the cancer and liver metastases compared with the cancer lesions in situ. Our results imply that in situ hybridization is a powerful tool in evaluating the changes in gene expression in the cancer cells and LBP-32 mRNA expression is related to progression, invasion, and metastasis of colorectal cancer.

Carcinoma↗
PubMed1996

Laparoscopic staging and intraoperative ultrasonography for liver tumor management.

Intraoperative ultrasonography has become an invaluable tool for programs that perform large volume, complex liver operations. Together with laparoscopy, intraoperative ultrasonography helps in appropriate staging, aids in decision-making, and tailors operations so as to minimize short-term morbidity and optimize long-term benefit.

Decision Making↗
PubMed1996

Interstitial therapies for liver tumors.

A variety of tumor-directed "interstitial" treatments based on physical, chemical, and radiobiologic antineoplastic principles have been investigated for the management of patients with unresectable tumors confined to the liver. Cryosurgery, ethanol injection, and laser photocoagulation are reviewed.

Animals↗
PubMed1996

Isolated liver perfusion for liver metastases: pharmacokinetic advantage?

The pharmacokinetic advantage of a novel system to noninvasively isolate the hepatic venous outflow and infuse high doses of chemotherapy (doxorubicin or 5-FU) is discussed and compared with intravenous infusion and intra-arterial infusion without hepatic venous detoxification. This dose intensification schema may provide new pharmacokinetic and pharmacodynamic principles for the treatment of a variety of tumors metastasizing the liver, including melanoma, sarcoma, and adenocarcinoma.

Adenocarcinoma↗
PubMed1995

Biochemical modulation of 5-fluorouracil with brequinar: results of a phase I study.

Biochemical modulation can increase the efficacy of 5-fluorouracil (5-FU). Pizzorno et al. have previously shown that brequinar, a de novo pyrimidine synthesis inhibitor, enhances the antitumor effect of 5-FU in vivo [Cancer Res 52: 1660-1665, 1992]. On the basis of their data, we conducted a phase I study of brequinar in combination with 5-FU in patients with refractory solid tumors. The initial dose (100 mg/m2) of brequinar was raised in 100-mg/m2 increments in cohorts of three assessable patients. The initial dose of 5-FU was 500 mg/m2, but escalation was allowed in patients who showed no significant toxic reaction. Brequinar was administered over 1 h and 5-FU over 2 h starting 18-20 h after the initiation of infusion of brequinar. Treatments were repeated weekly. Responses were evaluated after 4 weeks (one course) and then every 8 weeks thereafter. Pharmacokinetics of brequinar and determination of plasma uridine levels were performed in at least three patients at each dose level. Of the 25 patients registered in the study, 21 were assessable for toxicity studies. The dose of brequinar was escalated up to 600 mg/m2. In addition, the dose of 5-FU was increased to 600 mg/m2 as a result of a lack of a significant toxic reaction in the first nine patients. No objective responses were observed. One patient developed grade 3 stomatitis, and one developed grade 3 esophagitis at the 400 and 600 mg/m2 dose of brequinar, respectively. Brequinar produced a dose-dependent decrease in plasma uridine levels at doses up to 500 mg/m2. No additional decrease in plasma uridine occurred with higher doses of brequinar, thus suggesting a plateau effect. This observation prompted us to terminate the study before reaching the maximum tolerated dose of brequinar. Our data indicate that brequinar in doses > or = 400 mg/m2 results in significant biochemical modulation. The lack of toxicity seen at these doses of brequinar suggests that the initial dose of the effector agent 5-FU should be increased in future studies.

Adult↗
PubMed1995

Metachronous small-bowel adenocarcinoma in celiac sprue.

Celiac sprue, or nontropical sprue, is associated with an increased incidence of digestive tract malignancy. We report a patient with celiac sprue who developed two primary adenocarcinomas of the jejunum > 2 years apart. The second cancer was asymptomatic and detected by surveillance computed tomography. Small-bowel cancers are unusual, and frequency of follow-up has not been established, so that it is important to have a high index of suspicion for these malignancies in celiac patients with vague gastrointestinal symptoms.

Adenocarcinoma↗