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Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:06.77,0:00:10.98,Default,,0000,0000,0000,,The onset of cancer usually begins as\Na solitary tumor
Dialogue: 0,0:00:10.98,0:00:13.56,Default,,0000,0000,0000,,in a specific area of the body.
Dialogue: 0,0:00:13.56,0:00:15.42,Default,,0000,0000,0000,,If the tumor is not removed,
Dialogue: 0,0:00:15.42,0:00:18.53,Default,,0000,0000,0000,,cancer has the ability to \Nspread to nearby organs,
Dialogue: 0,0:00:18.53,0:00:23.27,Default,,0000,0000,0000,,as well as places far away\Nfrom the origin, such as the brain.
Dialogue: 0,0:00:23.27,0:00:25.61,Default,,0000,0000,0000,,So how does cancer move to new areas,
Dialogue: 0,0:00:25.61,0:00:29.80,Default,,0000,0000,0000,,and why are some organs more likely\Nto get infected than others?
Dialogue: 0,0:00:29.80,0:00:34.54,Default,,0000,0000,0000,,The process of cancer spreading across the\Nbody is known as metastasis.
Dialogue: 0,0:00:34.54,0:00:40.15,Default,,0000,0000,0000,,It begins when cancer cells from an initial\Ntumor invade nearby normal tissue.
Dialogue: 0,0:00:40.15,0:00:41.72,Default,,0000,0000,0000,,As the cells proliferate,
Dialogue: 0,0:00:41.72,0:00:45.80,Default,,0000,0000,0000,,they spread via one of the three \Ncommon routes of metastasis:
Dialogue: 0,0:00:45.80,0:00:49.66,Default,,0000,0000,0000,,transcoelomic, lymphatic, \Nor hematogenous spread.
Dialogue: 0,0:00:49.66,0:00:54.100,Default,,0000,0000,0000,,In transcoelomic spread, malignant cells\Npenetrate the covering surfaces
Dialogue: 0,0:00:54.100,0:00:57.28,Default,,0000,0000,0000,,of cavities in our body.
Dialogue: 0,0:00:57.28,0:00:59.79,Default,,0000,0000,0000,,These surfaces are known as \Nperitoneum
Dialogue: 0,0:00:59.79,0:01:03.29,Default,,0000,0000,0000,,and serve as walls to segment \Nthe body cavity.
Dialogue: 0,0:01:03.29,0:01:06.02,Default,,0000,0000,0000,,Malignant cells in ovarian cancer, \Nfor example,
Dialogue: 0,0:01:06.02,0:01:09.71,Default,,0000,0000,0000,,spread through peritoneum, \Nwhich connects the ovary to the liver,
Dialogue: 0,0:01:09.71,0:01:13.24,Default,,0000,0000,0000,,resulting in metastasis on \Nthe liver surface.
Dialogue: 0,0:01:13.24,0:01:19.00,Default,,0000,0000,0000,,Next, cancerous cells invade blood vessels\Nwhen they undergo hematogenous spread.
Dialogue: 0,0:01:19.00,0:01:21.84,Default,,0000,0000,0000,,As there are blood vessels almost \Neverywhere in the body,
Dialogue: 0,0:01:21.84,0:01:26.48,Default,,0000,0000,0000,,malignant cells utilize this to reach\Nmore distant parts of the body.
Dialogue: 0,0:01:26.48,0:01:30.95,Default,,0000,0000,0000,,Finally, lymphatic spread occurs\Nwhen the cancer invades the lymph nodes,
Dialogue: 0,0:01:30.95,0:01:35.26,Default,,0000,0000,0000,,and travels to other parts of the body\Nvia the lymphatic system.
Dialogue: 0,0:01:35.26,0:01:37.59,Default,,0000,0000,0000,,As this system drains many\Nparts of the body,
Dialogue: 0,0:01:37.59,0:01:40.99,Default,,0000,0000,0000,,it also provides a large network\Nfor the cancer.
Dialogue: 0,0:01:40.99,0:01:44.89,Default,,0000,0000,0000,,In addition, the lymphatic vessels empty\Ninto the blood circulation,
Dialogue: 0,0:01:44.89,0:01:48.70,Default,,0000,0000,0000,,allowing the malignant cells to undergo\Nhematogenous spread.
Dialogue: 0,0:01:48.70,0:01:52.80,Default,,0000,0000,0000,,Once at a new site, the cells once again\Nundergo proliferation,
Dialogue: 0,0:01:52.80,0:01:56.71,Default,,0000,0000,0000,,and form small tumors known as\Nmicrometastases.
Dialogue: 0,0:01:56.71,0:01:59.82,Default,,0000,0000,0000,,These small tumors then grow \Ninto full-fledged tumors,
Dialogue: 0,0:01:59.82,0:02:02.84,Default,,0000,0000,0000,,and complete the metastatic process.
Dialogue: 0,0:02:02.84,0:02:06.98,Default,,0000,0000,0000,,Different cancers have been known to have\Nspecific sites of metastasis.
Dialogue: 0,0:02:06.98,0:02:11.04,Default,,0000,0000,0000,,For example, prostate cancer commonly\Nmetastasizes to the bone,
Dialogue: 0,0:02:11.04,0:02:14.43,Default,,0000,0000,0000,,while colon cancer metastasizes \Nto the liver.
Dialogue: 0,0:02:14.43,0:02:17.89,Default,,0000,0000,0000,,Various theories have been proposed to\Nexplain the migration pattern
Dialogue: 0,0:02:17.89,0:02:19.73,Default,,0000,0000,0000,,of malignant cells.
Dialogue: 0,0:02:19.73,0:02:23.07,Default,,0000,0000,0000,,Of particular interest are \Ntwo conflicting theories.
Dialogue: 0,0:02:23.07,0:02:25.04,Default,,0000,0000,0000,,Stephen Paget, an English surgeon,
Dialogue: 0,0:02:25.04,0:02:28.71,Default,,0000,0000,0000,,came up with the seed and soil\Ntheory of metastasis.
Dialogue: 0,0:02:28.71,0:02:32.46,Default,,0000,0000,0000,,The seed and soil theory stated that\Ncancer cells die easily
Dialogue: 0,0:02:32.46,0:02:34.38,Default,,0000,0000,0000,,in the wrong microenvironment,
Dialogue: 0,0:02:34.38,0:02:39.04,Default,,0000,0000,0000,,hence they only metastasize to a location\Nwith similar characteristics.
Dialogue: 0,0:02:39.04,0:02:43.84,Default,,0000,0000,0000,,However, James Ewing, the first professor\Nof pathology at Cornell University,
Dialogue: 0,0:02:43.84,0:02:46.07,Default,,0000,0000,0000,,challenged the seed and soil theory,
Dialogue: 0,0:02:46.07,0:02:50.39,Default,,0000,0000,0000,,and proposed that the site of metastasis\Nwas determined by the location
Dialogue: 0,0:02:50.39,0:02:55.55,Default,,0000,0000,0000,,of the vascular and lymphatic channels\Nwhich drain the primary tumor.
Dialogue: 0,0:02:55.55,0:02:59.84,Default,,0000,0000,0000,,Patients with primary tumors that were\Ndrained by vessels leading to the lung
Dialogue: 0,0:02:59.84,0:03:02.83,Default,,0000,0000,0000,,would eventually develop lung metastases.
Dialogue: 0,0:03:02.83,0:03:06.69,Default,,0000,0000,0000,,Today, we know that both theories contain\Nvaluable truths.
Dialogue: 0,0:03:06.69,0:03:10.45,Default,,0000,0000,0000,,Yet the full stories of metastasis is much\Nmore complicated
Dialogue: 0,0:03:10.45,0:03:12.81,Default,,0000,0000,0000,,than either of the two proposed theories.
Dialogue: 0,0:03:12.81,0:03:14.88,Default,,0000,0000,0000,,Factors like the cancer cell's properties,
Dialogue: 0,0:03:14.88,0:03:18.58,Default,,0000,0000,0000,,and the effectiveness of the immune system\Nin eliminating the cancer cells,
Dialogue: 0,0:03:18.58,0:03:22.83,Default,,0000,0000,0000,,also play a role in determining\Nthe success of metastasis.
Dialogue: 0,0:03:22.83,0:03:28.10,Default,,0000,0000,0000,,Unfortunately, many questions about \Nmetastasis remain unanswered until today.
Dialogue: 0,0:03:28.10,0:03:30.88,Default,,0000,0000,0000,,Understanding the exact mechanism holds\Nan important key
Dialogue: 0,0:03:30.88,0:03:34.21,Default,,0000,0000,0000,,to finding a cure for\Nadvanced stage cancers.
Dialogue: 0,0:03:34.21,0:03:37.09,Default,,0000,0000,0000,,By studying both the genetic and\Nenvironmental factors,
Dialogue: 0,0:03:37.09,0:03:39.71,Default,,0000,0000,0000,,which contribute to successful metastasis,\N
Dialogue: 0,0:03:39.71,0:03:43.14,Default,,0000,0000,0000,,we can pinpoint ways to shut down\Nthe process.
Dialogue: 0,0:03:43.14,0:03:45.83,Default,,0000,0000,0000,,The war against cancer is \Na constant struggle,
Dialogue: 0,0:03:45.83,0:03:50.55,Default,,0000,0000,0000,,and scientists are hard at work developing\Nnew methods against metastasis.
Dialogue: 0,0:03:50.55,0:03:53.24,Default,,0000,0000,0000,,Of recent interest is immunotherapy,
Dialogue: 0,0:03:53.24,0:03:56.83,Default,,0000,0000,0000,,a modality which involves harnessing the\Npower of the immune system
Dialogue: 0,0:03:56.83,0:03:59.51,Default,,0000,0000,0000,,to destroy the migrating cells.
Dialogue: 0,0:03:59.51,0:04:01.23,Default,,0000,0000,0000,,This can be done in different ways,
Dialogue: 0,0:04:01.23,0:04:06.77,Default,,0000,0000,0000,,such as training immune cells to recognize\Ncancerous cells via vaccines.
Dialogue: 0,0:04:06.77,0:04:08.82,Default,,0000,0000,0000,,The growth and activity\Nof the immune cells
Dialogue: 0,0:04:08.82,0:04:12.91,Default,,0000,0000,0000,,can also be stimulated by injecting\Nman-made interleukins,
Dialogue: 0,0:04:12.91,0:04:16.86,Default,,0000,0000,0000,,chemicals which are usually secreted by\Nthe immune cells of the body.
Dialogue: 0,0:04:16.86,0:04:19.72,Default,,0000,0000,0000,,These two treatments are only the\Ntip of the iceberg.
Dialogue: 0,0:04:19.72,0:04:23.74,Default,,0000,0000,0000,,With the collaborated research efforts of \Ngovernments, companies and scientists,
Dialogue: 0,0:04:23.74,0:04:27.64,Default,,0000,0000,0000,,perhaps the process of metastasis will\Nbe stopped for good.