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Today, The Visible Embryo is linked to over 600 educational institutions and is viewed by more than 1 million visitors each month. The field of early embryology has grown to include the identification of the stem cell as not only critical to organogenesis in the embryo, but equally critical to organ function and repair in the adult human. The identification and understanding of genetic malfunction, inflammatory responses, and the progression in chronic disease, begins with a grounding in primary cellular and systemic functions manifested in the study of the early embryo.

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Pregnancy Timeline by SemestersFetal liver is producing blood cellsHead may position into pelvisBrain convolutions beginFull TermWhite fat begins to be madeWhite fat begins to be madeHead may position into pelvisImmune system beginningImmune system beginningPeriod of rapid brain growthBrain convolutions beginLungs begin to produce surfactantSensory brain waves begin to activateSensory brain waves begin to activateInner Ear Bones HardenBone marrow starts making blood cellsBone marrow starts making blood cellsBrown fat surrounds lymphatic systemFetal sexual organs visibleFinger and toe prints appearFinger and toe prints appearHeartbeat can be detectedHeartbeat can be detectedBasic Brain Structure in PlaceThe Appearance of SomitesFirst Detectable Brain WavesA Four Chambered HeartBeginning Cerebral HemispheresFemale Reproductive SystemEnd of Embryonic PeriodEnd of Embryonic PeriodFirst Thin Layer of Skin AppearsThird TrimesterSecond TrimesterFirst TrimesterFertilizationDevelopmental Timeline
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Home | Pregnancy Timeline | News Alerts |News Archive Sep 18, 2013

 

Catharanthus is a genus of flowering plants in the dogbane family, Apocynaceae.
Like genus Vinca, they are known commonly as periwinkles.
The name Catharanthus comes from the Greek for "pure flower." These are perennial herbs.

C. roseus, known formerly as Vinca rosea, is a main source of vinca alkaloids, now sometimes called catharanthus alkaloids. There are about 130 of these compounds, including vinblastine, a common drug used to treat cancers.

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Potent, improved new derivatives of anticancer drug

One of the most successful chemotherapy drugs of the past few decades, vinblastine, has been improved and similar modifications are expected to boost the effectiveness of vincristine, a closely related drug commonly used against childhood leukemias and Hodgkin’s disease.

Scientists at The Scripps Research Institute (TSRI) have found a way to make dramatic improvements to the cancer cell-killing power of vinblastine.

The team’s modified versions of vinblastine showed 10 to 200 times greater potency than the clinical drug. Even more significantly, these new compounds overcome the drug resistance that emerges upon treatment relapse, which renders continued or subsequent vinblastine treatment ineffective in some patients.

“These new compounds should improve on what are already superb anticancer drugs,” said Dale L. Boger, who is the Richard and Alice Cramer Professor and Chair of the Department of Chemistry at TSRI. Boger and members of his laboratory reported the discovery in a paper recently published online ahead of print by the journal ACS Medicinal Chemistry Letters.

Anticancer Agents


Vinblastine and vincristine are natural products of a pink-flowered herb known as the Madagascar periwinkle.

Although the leaves of the plant had been used in traditional medicines for a range of other conditions, from diabetes to hemorrhoids, drug researchers at Eli Lilly found in the 1960s that the two compounds showed excellent potential as anticancer agents.


Both were found to selectively kill cancer cells by a mechanism that many other cancer drugs, including taxol, epothilones, and colchicine, have followed since—they bind a cellular protein called tubulin in a way that interferes with the buildup and breakdown of tubulin-containing chains called microtubules—structural elements of cells that play a key role in cell division. When the normal dynamics of their microtubules are disrupted, fast-dividing cancer cells stop dividing and die.

Since the 1960s, vinblastine has been used successfully in combination with other chemotherapy drugs against lymphomas as well as testicular, ovarian, breast, bladder and lung cancers. Vincristine is routinely used in combination regimes against childhood acute lymphoblastic leukemia and non-Hodgkin lymphomas.

Both compounds are presently isolated from cultivated fields of the plants that make them naturally, but in trace amounts (0.0001% of the dry leaf weight). Since they are plant-derived natural products, they cannot be accessed using existing biotechnology or genetic engineering methods and, prior to the TSRI efforts, they were viewed as far too complex to be prepare by laboratory organic chemistry techniques.


The authors developed a remarkable three-step preparation from commercially available chemicals using chemistry that they invented specifically for this purpose.


A significant limitation of vinblastine and vincristine is that, with extended treatment, they may evoke a powerful form of drug resistance. This resistance comes from a doorkeeper-type molecule called P-glycoprotein (Pgp), which transports infiltrating drug molecules out of the cancer cells. As cancer cells evolve to produce more and more Pgp, drugs fail to reach effective concentrations in cells and cancerous growth resumes. For years, medicinal chemists have tried to find modified versions—“analogues”—of these drugs that would overcome Pgp-mediated resistance, but without success.

Developing Extraordinary Potency

Last year, however, in a landmark paper in Organic Letters, Boger and his colleagues described a broad new method for modifying organic compounds like vinblastine, and demonstrated the method by making previously inaccessible variants of the drug.

“Although it is a versatile method, we developed it specifically so that we could start making these vinblastine analogues that couldn’t be made before,” Boger added.

As his team used the method to make more new vinblastine analogues, the scientists discovered a type of modification to the drug that limits its usual drop in potency against resistant, Pgp-overproducing cancer cells as compared to non-resistant cancer cells. For the new study, the team explored variations of that modification and eventually found several analogues that were as good at killing resistant cells as ordinary vinblastine is at killing non-resistant cancer cells.

These new analogues were also many times more potent than vinblastine against non-resistant cells—which are the kinds of cancer cells almost all patients have at diagnosis. The laboratory of a major drug company, Bristol-Myers Squibb, was able to repeat these results in a larger set of clinically important human tumor cell lines, and Boger’s team confirmed that the new analogues’ greater potency corresponds to their greater ability to bind to tubulin.


“The potency of these analogues is extraordinary—they show activity down at the 100 picomolar level [100 trillionths of a mole] against some cell lines. So we have something here that’s really unique, and we discovered it only because of the novel chemistry we developed.”

Dale L. Boger, Richard and Alice Cramer Professor and Chair of the Department of Chemistry at The Scripps Research Institute (TSRI)


Abstract
A series of disubstituted C20′-urea derivatives of vinblastine were prepared from 20′-aminovinblastine that was made accessible through a unique Fe(III)/NaBH4-mediated alkene functionalization reaction of anhydrovinblastine. Three analogues were examined across a panel of 15 human tumor cell lines, displaying remarkably potent cell growth inhibition activity (avg. IC50 = 200–300 pM), being 10–200-fold more potent than vinblastine (avg. IC50 = 6.1 nM). Significantly, the analogues also display further improved activity against the vinblastine-resistant HCT116/VM46 cell line that bears the clinically relevant overexpression of Pgp, exhibiting IC50 values on par with that of vinblastine against the sensitive HCT116 cell line, 100–200-fold greater than the activity of vinblastine against the resistant HCT116/VM46 cell line, and display a reduced 10–20-fold activity differential between the matched sensitive and resistant cell lines (vs 100-fold for vinblastine).

The other contributors to the paper, “Potent Vinblastine C20’ Ureas Displaying Additionally Improved Activity Against a Vinblastine-Resistant Cancer Cell Line,” were the lead author Timothy J. Barker, and Katharine K. Duncan and Katerina Otrubova, all of TSRI at the time of the study.

Funding for the study came in part from the National Institutes of Health (grants CA042056, CA115526, CA165303).

About The Scripps Research Institute
The Scripps Research Institute (TSRI) is one of the world's largest independent, not-for-profit organizations focusing on research in the biomedical sciences. TSRI is internationally recognized for its contributions to science and health, including its role in laying the foundation for new treatments for cancer, rheumatoid arthritis, hemophilia, and other diseases. An institution that evolved from the Scripps Metabolic Clinic founded by philanthropist Ellen Browning Scripps in 1924, the institute now employs about 3,000 people on its campuses in La Jolla, CA, and Jupiter, FL, where its renowned scientists—including three Nobel laureates—work toward their next discoveries. The institute's graduate program, which awards PhD degrees in biology and chemistry, ranks among the top ten of its kind in the nation. For more information, see www.scripps.edu.

Original press releas: http://www.scripps.edu/news/press/2013/20130916boger.html